ARUSHA TECHNICAL COLLEGE

JUNCTION OF MOSHI-ARUSHA AND NAIROBI ROADS

P.O. BOX 296, ARUSHA-TANZANIA

TELEPHONE: +255-27-2503040/2502076, FAX: +255-27-2548337

WEBSITE: http://www.atc.ac.tz E-MAIL: principal@atc.ac.tz

CIVIL ENGINEERING DEPARTMENT

BACHELORS DEGREE IN CIVIL & IRRIGATION ENGINEERING

PROJECTTITTLE: DESIGN OF LINED IRRIGATION CANALS NETWORK

AT CHEJU IRRIGATION SCHEME ZANZIBAR

FINAL YEAR PROJECT - 2014/2015

PRESENTED BY: SALUM M. JUMA

ADMISSION NUMBER: B120021

SUPERVISORS NAME: 1. Dr SENZIA M.A

2. Dr NURU R.M.
 CERTIFICATION

The undersigned certifies that they have read and hereby recommend for acceptance by the
Arusha Technical College a project entitled: Design of Lined Irrigation Canal Network at
Cheju Irrigation Scheme in partial fulfillment of the requirements for the award of the Bachelor
Degree in Civil and Irrigation Engineering of the Arusha Technical College.

Date: .../.../.. Supervisor(s): 1. Dr SENZIA M.A Signature; .................

2. Dr NURU R.M. Signature: .................

1
 DECLARATION

I, SALUM M. JUMA hereby declare that the contents of this dissertation is a result of my own
efforts in observations, investigations and findings, and to the best level of my knowledge and
experience gained through consultation to different experts/supervisors and various literatures. It
has never been presented and submitted to any other College, higher learning institution or a
similar of any other degree award.

SALUM M. JUMA

2
 DEDICATION

This project is dedicated to my beloved parents Mohammad J. Mussa and Asha J. Khamis who
raised me throughout my childhood and their positive and enthusiastic encouragements and for
their mutual and objective cooperation during my studies. Also lovingly dedicated to my true
treasures in life, my lovely fianc Halima Amour for her love, patience, wise words, prayers and
encouragement throughout my studies.

ACKNOWLEDGEMENT

First and foremost, I would like to extend my unshared thanks to Almighty God, for
obvious reasons, but especially for the countless blessings that He has

3
poured upon me in the completion of the project with strength,
determination and discipline.

A special vote of thanks goes to my supervisors, Dr. Senzia M.A and Dr Nuru R.M for their
patience, guidance, constructive comments, wisdom suggestions, courage, critical comments and
advice throughout my project work; I wish the best successful in all over their life. Also, special
thanks to all teaching staff of Civil Engineering Department for giving me such an enjoyable and
noble education and career.

Special thanks should also be to ATC Materials laboratory technicians namely; Mr. Bakari
Saliungu and Mr. Doto Charles. Additionally my heart thanks to my fellow students in Civil and
Irrigation Engineering for their valuable comments, suggestion, support and encouragements
during my study time.

My cordial thanks spread out to my brothers, sisters and lovely parents Mohammad J. Mussa and
Asha J. Khamis for their love, support and guidance throughout my life and for inculcating in me
the passion for knowledge. Out of the ordinary, I thank my lifelong best friend, companion and
my lovely fianc Halima Amour for her love and patience so exceedingly appreciated during the
period of three years of studies.

My special thanks are due to Ministry of Agriculture and Natural Resources for giving me
permission to attend this course of three years. Additionally, I sincerely appreciate the degree of
thoughtfulness and kindness to all staff of Department of Irrigation Mbweni Zanzibar for their
courage and support especially Chief Irrigation Engineer Juma A. Foum (Eng) together with Eng
Rashid S. Hamad for donating generously the enormous amount of time and providing some
relevant data and information required to carry out this project.

A debt of gratitude is to all people who in one way or another contributed idea directly or
indirectly. Because it would end up into long list to mention all the people I am indebted to, I
gratefully thank all of them collectively.

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 ABSTRACT

The focus of this project is on designing of lined irrigation canals network at Cheju scheme
located at Cheju village within south eastern part of Zanzibar main Island (Unguja Island). This
design is due to the fact that most of the area of Cheju scheme (about more than 1000ha) is not
developed under irrigation system, only about 90ha has so far been developed for irrigated
agriculture by using tubular wells as a source of water of this scheme.

The scheme area was found to have a total area of 1200ha but this project cover only 75ha which
will be irrigated by using two tubular wells and each tubular well has capacity of 35l/sec which
can cover the area of 38ha, reference being made on yield of the existing boreholes in Cheju
(average of 35 l/s) and crop water requirement.

The topographical survey was conducted in a study area was conducted for the purpose of
obtaining the topographical map of the study area. From that map, farm layout and profile of
main and secondary irrigation canals were produced.

Soil investigation was conducted in the project area by taking soil sample in a several point in a
study area by using augering method. The soil samples are taken in a depth of 0 to 30cm and 30
to 60cm in a several auger holes in a project area. The purpose of taking these soil samples was
for identifying different soil types whose characteristics serve as basis for the design decision
particularly on the type and method of irrigation system to be employed.

The collected samples were submitted to ATC Soil and Bitumen Laboratory laboratories for
grain size distribution (wet sieve analysis), permeability with specific gravity of soil and
Atterberg limits i.e Liquid limit, Plastic limit. The results of this investigation indicate that soil of
sample 1 in Cheju irrigation scheme contains the liquid limit of 46.25% and plastic limit 19.92%
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plastic index 26.33% and permeability of 2.71053 10 . Also investigation result indicates

that the soil of sample 21 in Cheju irrigation scheme contains the liquid limit of 71% and plastic
6
limit 28% plastic index 42% and permeability of 8.66964 10 . These results indicate that

the soil in Cheju scheme is clay soil which indicate high potential swell. Since swell potential
and swell pressure are key properties of expansive soils, so that the designed foundation during

5
construction should be strong enough to resist the effect of expansion and contraction which can
break the concrete of the canals.
The designed farm layout is comprised with primary farmland, secondary farmland and tertiary
farmland with dimension of 150m x 300m (4.5ha), 100m x 150m (1.5ha) and 100m x 50m
(0.5ha) respectively. The scale of the primary farmland section looks inefficient, but it can be
overcome through the managerial methodology of water supply into the farmland.

Surface irrigation farm layout is also comprised by designed main and secondary canals
as per objectives, while others structures have been proposed from standard drawing. The
proposed canals network comprises of two main canals with length of 610m and 570m and
eight secondary canals of different lengths. SC1=299m, SC2=292m, SC3=323, SC4=282m,
SC5=360m, SC6=272, SC7=343m and SC8=275m and they are located at interval distance of
150m apart.

Finally, in order to make sustainable irrigation scheme, this project recommended that for future
project the more effort should be put forward in a designing of drainage canals which will be
used to drain water from the field and to direct that water to the supplementary water sources and
the drainage water collected within supplementary water sources will be recycled back to the
scheme.

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 Table of Contents
CERTIFICATION..................................................................................................i

DECLARATION...................................................................................................ii

DEDICATION.....................................................................................................iii

ACKNOWLEDGEMENT......................................................................................iv

ABSTRACT........................................................................................................v

LIST OF TABLES AND FIGURES...........................................................................xi

LIST OF ABBREVIATIONS..................................................................................xii

CHAPTER ONE...................................................................................................1

1.0 INTRODUCTION.....................................................................................1
1.1 GENERAL OVERVIEW.............................................................................1
1.2 BACKGROUND INFORMATION......................................................................1
1.3 PROBLEM STATEMENT...........................................................................2
1.4 PROJECT OBJECTIVES............................................................................2
1.4.1 Main objectives......................................................................................2
1.4.2 Specific objectives...............................................................................2
1.5 SCOPE OF THE PROJECT.........................................................................3
1.6 SIGNIFICANCE OF THE PROJECT.............................................................3
CHAPTER TWO..................................................................................................4

2.0 LITERATURE REVIEW.............................................................................4

2.1 INTRODUCTION.....................................................................................4
2.2 CROP WATER REQUIREMENTS................................................................5
2.3 METHODS OF ESTIMATING CROP WATER REQUIREMENT..........................5
2.3.1 Direct Methods...................................................................................5
2.3.2 Indirect Methods.................................................................................6

7
 2.3.2.1 Pan Evaporation Method........................................................................6
2.3.2.2 Blaney-Criddle Method.........................................................................6
2.3.2.3 Penman-Monteith method......................................................................7
2.4 REFERENCE EVAPOTRANSPIRATION.......................................................7
2.5 IRRIGATION REQUIREMENTS..................................................................8
2.6 IRRIGATION CANALS.............................................................................9
2.6.1 Main canal.........................................................................................9
2.6.2 Field canals for small irrigation schemes....................................................9
2.6.3 Secondary canals...............................................................................10
2.6.4 Tertiary canals...................................................................................10
2.6.5 Design command area.........................................................................10
2.7 PLANNING OF AN IRRIGATION CANAL SYSTEM.....................................11
2.7.1 Alignment of irrigation canals...............................................................11
2.7.2 Curves in canals................................................................................12
2.7.3 Duty of water....................................................................................13
2.7.4 Irrigation-canal losses.........................................................................13
2.8 DESIGN OF LINED CANAL.....................................................................14
2.8.1 General Descriptions..........................................................................14
2.9 HYDRAULIC DESIGN............................................................................14
2.9.1 Chezys Equation...............................................................................15
2.9.2 Manning formula...............................................................................15
2.9.3 Most Efficient Hydraulic Section...........................................................17
2.9.4 Design discharge of a canal..................................................................18
2.9.5 Maximum Permissible Velocities...........................................................19
2.9.6 Minimum Velocity.............................................................................20
2.9.7 Canal Cross-Section...........................................................................20
2.9.8 Longitudinal canal sections..................................................................20
2.9.9 Side Slope........................................................................................21
2.9.10 Bank Width......................................................................................21
2.9.11 Bed Width and Depth ratio...................................................................22

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 2.9.12 Canal shape......................................................................................22
2.9.13 Berms.............................................................................................23
2.9.14 Freeboard........................................................................................23
2.9.15 Canal Curvature................................................................................24
2.10 WATER CONTROL AND DIVERSION STRUCTURES...................................24
2.10.1 Turnouts..........................................................................................24
2.10.2 Division boxes..............................................................................25
2.10.3 Check gates......................................................................................25
2.10.4 Drop Structures.................................................................................25
CHAPTER THREE.............................................................................................27

3.0 METHODOLOGY..................................................................................27
3.1 Description of the Study Area.....................................................................27
3.1.1 Location..........................................................................................27
3.1.2 Climate...........................................................................................27
3.1.2.1 Rainfall...........................................................................................27
3.1.2.2 Evaporation......................................................................................27
3.1.2.4 Wind..............................................................................................28
3.1.2.5 Relative humidity..............................................................................28
3.1.2.6 Soils...............................................................................................28
3.2 Site Visits..............................................................................................29
3.3 Consultation...........................................................................................30
3.4 Design..................................................................................................30
CHAPTER FOUR...............................................................................................31

4.0 DATA COLLECTION AND ANALYSIS.......................................................31

4.1 Data collection........................................................................................31
4.1.1 Topographical Survey data...................................................................31
4.1.2 Water sources...................................................................................31
4.1.3 Meteorological data............................................................................31
4.1.4 Soil data..........................................................................................32
4.1.5 Laboratory Soil Test...........................................................................33

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 4.2 DATA ANALYSIS...................................................................................33
4.2.1 Crop water requirement analysis............................................................33
4.2.2 Soil data analysis...............................................................................35
4.2.3 Topographical map.............................................................................35
4.2.3.1 Land Consolidation............................................................................36
4.2.3.1.1 Farmland......................................................................................36
4.2.3.1.2 Irrigation Canal..............................................................................36
4.2.4 Canals Hydraulic Design and consideration:.............................................36
4.2.5 Water Control Structures......................................................................37
CHAPTER FIVE................................................................................................38

5.0 CONCLUSION AND RECOMMENDATION................................................38

5.1 CONCLUSION.......................................................................................38
5.2 RECOMMENDATION.............................................................................38
REFERENCES:..................................................................................................40

APPENDICES...................................................................................................42

LIST OF TABLES AND FIGURES

10
Table 2.1: Values of minimum radii of channel curves for different channel capacities..12

Table 2.2: Conveyance losses in canals.....14

Table 2.3: Manning roughness coefficient values.16

Table 2.4: Best Hydraulic Sections17

Table 2.5: Maximum Permissible Velocities.19

Table 2.6: Side Slopes for Lined Canal.21

Table 2.7: Minimum Embankment Width for Lined Canal...21

Table 2.8: Assumed values of water depth for canal.....22

Table 2.9: Freeboard of irrigation channels as suggested by CWC.......23

Table 2.10: Freeboard in irrigation channels.................................................................................23

Table 4.1: Average meteorological data from 2004 to 2013....................................................................32

Table 4.2: Summary of soil laboratory test results........................................................................35

Figure 1: Trapezoidal section.18

Figure 2: Map of project area.28

Figure 3: The analysis of irrigation requirement of rice for actual project area............................34

Figure 4: Summary crop water analysis of rice crop for actual project area.................................35

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 LIST OF ABBREVIATIONS
ATC: Arusha Technical College

FAO: Food Agricultural organizations

GOZ: Government of Zanzibar

ZIDP: Zanzibar Irrigation Development Program

ZIMP: Zanzibar Irrigation Master Plan

CWR: Crop Water Requirements

ETo: Reference Evapotranspiration

ETc/ ETcrop: Crop Evapotranspiration

Kc: Crop Coefficient

MAFC: Ministry of Agriculture food security and cooperative

DID: Department of Irrigation and Drainage

CWC: Central Water Commission

IR: Irrigation Requirements

MIC: Main Irrigation Canal

SIC: Secondary Irrigation Canal

TIC: Tertiary Irrigation Canal

SC: Secondary Canal

PIC: Primary Irrigation Canal

PDC: Primary Drainage Canal

Ha: Hectare

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 CHAPTER ONE

1.0 INTRODUCTION

1.1 GENERAL OVERVIEW

Irrigation canals network are designed and managed to receive water from a source and to
distribute it among farms in order to meet their water needs. Various design decisions must be
made in order to rehabilitate or develop irrigation canal network, including those related to
specification of the characteristics of hydraulic structures used to convey, regulate, or divert
water. An irrigation system comprises all the physical and organizational facilities and services
required to convey water for the irrigation of crops from a source of supply to the farmers' fields.
Systems may vary in size, scope and design from one merely aiming at spreading the flood water
of a river over adjacent areas, or conveying small flows from a surface or ground water source
over limited distances and areas to large networks ramifying over the land like the branches of a
tree (FAO, 1982).

Before designing a canal network, a topographical survey of the area should be done and a
topographical map of the area drawn. On this map the layout of the canal system is planned so
that water delivery will be as efficient as possible (FAO. 1992). The layout of irrigation schemes
is indicated mainly by topography, types of crop grown, soil type and the irrigation method. In
surface irrigation, the topography of the land is the critical factor for the selection of canal
alignment, and shape of the farm unit.

1.2 BACKGROUND INFORMATION

Agriculture in Zanzibar is therefore weak and suffers from low and unstable production. The
arable lands of Zanzibar are estimated at 130,000 ha, of which 5,100 ha has been previously
identified as potential area for irrigation. In order to improve such unstable and low production,
the government of Zanzibar (GOZ) is establish the department of irrigation to propose an
irrigated agriculture development and prepared the Zanzibar Irrigation Development Program in
August 1997 (ZIDP), following the successful launch of the National Irrigation Development
Plan for the Mainland. The ZIDP concluded that the highest priority should be given to surface
fed gravity smallholder irrigation schemes in Pemba. In Unguja, this method could be used for
schemes with high value crops and a few areas where rice is irrigated under gravity.

1
 The ZIMP has identified 57 schemes with a total area of 8,521 ha as potential for
irrigation development in Zanzibar. Unguja has 18 schemes of with an area about
6,629ha, while Pemba has 39 schemes with an area of 1,892ha. Cheju irrigation schema is one
among of 18 irrigation scheme of Unguja which has potential area of 1200ha.

1.3 PROBLEM STATEMENT

The total potential area of Cheju irrigation scheme is 1200ha, but only about 90ha has so far
been developed for irrigated agriculture by using tubular wells, this make the agricultural
activities at Cheju irrigation scheme rely highly on rains and this makes production vulnerable to
adverse rainfall patterns. Concurrently, rainfall is not promising due to climate change and this
result to prolonged dry spell, hence crop yield decreases. Thus, this situation obligates the need
of designing a canal network to locate main canal, secondary canals and tertiary canal at the
remained area of the scheme by using ground water as a water source of that scheme.

1.4 PROJECT OBJECTIVES

1.4.1 Main objectives

The main objective of the project is to design lined irrigation canals network at Cheju irrigation
scheme.

1.4.2 Specific objectives

i. To conduct a topographical survey along the proposed irrigation scheme area.

ii. To perform soil laboratory tests in order determine soil characteristics of the area.
iii. To determine irrigation water need for rice crops.
iv. To draw topographical map.
v. To draw canal profiles and farm layout.
vi. To design main and secondary canal.

1.5 SCOPE OF THE PROJECT

2
 The scope of this project has limited on drawing topographical map of the scheme, designing
farm layout and design of main and secondary irrigation canals on 72ha of an area.

1.6 SIGNIFICANCE OF THE PROJECT

Upon completion of conveyance system design, there will be availability of water at farm levels
there by contributing in the improvement of food production to farmers, as they can grow several
crops more than once.

CHAPTER TWO

2.0 LITERATURE REVIEW

3
2.1 INTRODUCTION

Irrigation is defined as the process of artificially supplying water to soil for growing crops. It is a
science of planning and designing an efficient, low-cost, economic irrigation system tailored to
fit natural conditions. It is the engineering of controlling harnessing the various natural sources
of water, by the construction of dams and reservoirs, canals and head works and finally
distributing the water to the agricultural fields (Punmia and Pande, 1992).

According to Theo Meijer, irrigation is the provision of measures that enables users to
adequately supply their crops with water, which is collected elsewhere. Thus the water is
collected elsewhere and transported to the plants. The elsewhere can be groundwater that is
pumped through pipes to the surface and sprinkled on the plants. An activity that can be applied
by the farmers themselves. Irrigation water can also be collected from a stream, river other open
water source sources and transported to fields through canals. Water residues are discharged in a
drain that transports the water away from the field.

Most irrigation schemes are provided with a complementary irrigation canals network to convey
and distribute water into the fields evenly, and field drainage network to remove excess water
from the fields. The canal network of irrigation schemes is dictated mainly by topography, types
of crop grown and the irrigation Method employed. In surface irrigation, the topography of the
land is the critical factor for the selection of canal alignment, and shape of the farm unit. The
design and operation of farm irrigation system is influenced by the quantity and timing of water
delivery to the farm. Delivery schedules are either demand, rotational, or continuous flow.
Delivery systems operating under rotation schedules deliver water for a fixed duration of time
according to a prearranged schedule (James, 1988).

2.2 CROP WATER REQUIREMENTS

4
 Crop water requirements are determined by the climatic evaporative potential, plant
characteristics, and all of the factors that influence growth and development of the crop. For
purposes of irrigation planning, design, and management, computations are usually made to
determine reference evapotranspiration (ETo), which is multiplied by a crop coefficient (K c) to
determine the evapotranspiration of a particular crop at a given growth stage. Irrigation
requirements tend to be significantly greater than crop water requirements because of the need to
allow for imperfect application uniformities and efficiencies, and for maintaining a favorable salt
balance in the crop root zone. Crop water requirements include transpiration of water by the
plants and evaporation from the soil and from the plants. These combined amounts result in
evapotranspiration (ET), the major component of which is usually transpiration of water by the
plants (Hargreaves, et al. 1985).

2.3 METHODS OF ESTIMATING CROP WATER REQUIREMENT

2.3.1 Direct Methods

Evapotranspiration can be measured directly by means of lysimeters. Lysimeters are tanks or

containers of soil in which plants are grown under conditions similar to the surrounding soil and
vegetation. Changing water content in the lysimeter is measured by weighing, by comparing
applied water with the amount of drainage, or by other suitable methods. The ET of various
grasses grown in lysimeters has been used to develop and/or calibrate numerous equations for
estimating ETo. However, due to the wide variations in the ET of grasses and in the management
and design of lysimeters, there has been considerable variation in the calibration of equations for
computing ETo. The emphasis on the use of lysimeters has shifted more toward the
determination of crop coefficients than reference crop evapotranspiration because equations
(most notably, the PenmanMonteith equation) have been shown to predict reference ET with
excellent accuracy for most agricultural locations around the world (Hargreaves, et al. 1985)

Crop ET can also be determined by intensive soil water studies where the soil is fairly uniform
and the depth to groundwater will not influence soil water within the root zone. Soil water is
determined by field moisture sampling before and after each irrigation with some measurements
between irrigations to determine water depletion in the root zone (Hargreaves, et al. 1985).

2.3.2 Indirect Methods

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2.3.2.1 Pan Evaporation Method

A Class A evaporation pan set in a large irrigated pasture or other irrigated area provides an index
that has been widely used for estimating crop ET. The principal source of energy for evaporation
is solar radiation. If the pan reflects five percent of radiation back to the atmosphere and an
extensive irrigated grass area reflects 25 to 30%, then it seems logical to assume a ratio of ET of
grass to pan evaporation (Ep) of 0.75 to 0.80. The California Department of Water Resources
(1986) gives ET/Ep ratios for irrigated pastures and turf grasses ranging from 0.70 for the coldest
weeks to 0.78 for the warmest months.

The equation used is: ETo=pan evoparation pan coefficient

K pan E pan

2.3.2.2 Blaney-Criddle Method

If no measured data on pan evaporation are available locally, a theoretical method (such as
Blaney-Criddle method) to calculate the reference crop evapotranspiration ETo has to be used.
There are a large number of theoretical methods to determine the ETo. Many of them have been
determined and tested locally. If such local formulae are available they should be used. If such
local formulae are not available one of the general theoretical methods has to be used. The
Blaney-Criddle method is simple, using measured data on temperature only. But, however, this
method is not very accurate, it provides a rough estimate or "order of magnitude" only.
Especially under "extreme" climatic conditions the Blaney-Criddle method is inaccurate, in
windy, dry, sunny areas, the ETo is underestimated (up to some 60 percent), while in calm,
humid, clouded areas, the ETo is overestimated up to some 40 percent(Allen et al., 1986)
The equation used is;
ETo=p (0.46 T mean+ 8).

Where:
ETo = Reference crop evapotranspiration (mm/day) as an average for a period of 1 month.
T mean = mean daily temperature (C) and

p = mean daily percentage of annual daytime hours.

6
 From which ETcrop=Kc ETo .

2.3.2.3 Penman-Monteith method

Penman-Monteith method as modified by Allen et al (1986) is the most accurate method used to
compute ETo arid and humid locations. Because of its accuracy, the Penman-Monteith method is
recommended when air temperature, relative humidity, wind speed, and solar radiation data are
available or can be reliably estimated. The method is accurate because it considers all
climatically data required in crop water requirement and it is integrated in most of computer
software for computing crop water requirement (Neitsch et al., 2005.).
Allen et al. (1989) express the Penman Monteith equation as:-
890 U 2 ( e ae d )
0 . 408 ( R nG ) +
T +273 ...2.4.2
ETo=
+ ( 1+0339 U 2 )

2.4 REFERENCE EVAPOTRANSPIRATION

Reference ET is calculated based on a calibrated equation for a selected reference crop using
lysimeter measurements. The equation form may be empirically developed, involving only a few
external environment variables, or it may be derived from the principles of physics, heat transfer,
and other scientific fields of study. Some of the more complex reference ET equations include
many variables and can be very precise. However, in practice the complexity of a reference ET
equation must be justified by the availability of climatological and other data if an equation is
very complete from atheoretical standpoint it may be preferred over an empirically derived
equation, but only if there is sufficient data to support its application. In general, reference ET
equations can usually be categorized as temperaturebased methods, radiationbased methods,
and combination methods (Hargreaves, et al. 1985).

Hargreaves, et al. (1985) and Hargreaves and Samani (1985) propose the use of an equation for
estimating ETo from air temperature and latitude. It is classified as a temperaturebased method,
and several previous versions were proposed and subsequently improved upon before the current
equation form was developed. The equation is:

7
 ETo=0 .0023 R A ( T +17 . 8 ) T R .2.4.1

In which ETo and RA are in the same units of equivalent water evaporation (often in mm), R A is
extraterrestrial solar radiation. T is the mean air temperature in oC or the average of mean
maximum and mean minimum daily temperatures, and TR is the average daily temperature range
for the period considered (mean daily maximum minus mean daily minimum). The value of TR
is influenced by solar radiation, local advective energy, and the frontal temperature differences
associated with storms and abrupt weather changes. Therefore, Eq. 2.4.1 will not be accurate for
the days of major weather changes but usually provides very satisfactory results when T and TR
are averaged over periods of five or more days. Thus, Eq. 2.4.1 is often applied to the calculation
of weekly ETo.

Where ETo is in units of mm/day for a grass reference crop; is the slope of the saturation vapor
pressure function (kPa/C); is a psychrometric constant (kPa/C); Rn is net solar radiation

U2
(MJ/m2/day); is the wind speed (m/s) at 2.0 m height; T is the mean daily air temperature

(C); eaed represents the vapor pressure deficit of air (kPa); and G is the soil heat flux density
(MJ/m2/day).

2.5 IRRIGATION REQUIREMENTS

The irrigation water need is defined as the crop water need minus the effective rainfall. It is
usually expressed in mm/day. An irrigation water need per day, however, does not mean that has
to be supplied by irrigation every day. In theory, water could be given daily .But, as this would
be time consuming and laborious. It is possible to supply water required for 3days for instance at
a time. Rice can grow well under flooded conditions. Rice consumes more water than any other
irrigated crop and it requires up to 23 times more water compared to other crops .Rice requires
700 and 1500 mm of water per growing season (Bhuiyan, 1992).

For most crops, the reference evapotranspiration at mid-season can be taken as a reasonable
estimate of the peak water requirement. It is reasonable to assume that 70 per cent of average
rainfall is available to the crop; the net irrigation requirement (In mm/d) can be estimated as:

8
 I n=ETo(0 . 70 P) .2.4.3

Where: In (mm/d) is the net irrigation requirement, ETo (mm/d) is the reference

evapotranspiration and P (mm/d) is the average rainfall.

Additional water has to be supplied to take account of field application losses which, with
surface irrigation, are typically about 40 per cent, giving an application efficiency of 0.60. The
field irrigation requirement (If) can be estimated as:
In ET ( 0. 70 P )
I f= = O .2.4.4
0 . 60 0 . 60

The field irrigation requirement represents the rate (in mm/d) at which water must be delivered
to the field to prevent the crop suffering a shortage of water.

2.6 IRRIGATION CANALS

A conveyance subsystem for irrigation includes open channels through earth or rock formation,
flumes constructed in partially excavated sections or above ground, pipe lines installed either
below or above the ground surface, and tunnels drilled through high topographic obstructions.
Irrigation conduits of a typical gravity project are usually open channels through earth or rock
formations. These are called canals.

A canal is defined as an artificial channel constructed on the ground to carry water from a river
or another canal or a reservoir to the fields. Usually, canals have a trapezoidal cross section. An
irrigation canal carries water from its source to agricultural fields. The slope of an irrigation
canal is generally less than the ground slope in the head reaches of the canal and, hence, vertical
falls have often to be constructed.

2.6.1 Main canal

The main canal takes its supplies directly from the river through the head regulator and acts as a
feeder canal supplying water to branch canals and major distributaries. Usually, direct irrigation
is not carried out from the main canal.

2.6.2 Field canals for small irrigation schemes

9
 Field canals (tertiary canals and sometimes secondary canals) usually run at an average gradient
of 1:500 (0.0020 or 0.2%) to 1:300 (0.0033 or 0.33%). When the existing land slope exceeds the
proposed canal gradient, drop structures can be used in order to avoid the canal being suspended
too much above the ground level, which would require too much fill.

2.6.3 Secondary canals

A Secondary canal consists of several tertiary units, and normally receives water from a division
structure on the main canal. Boundaries of secondary units are generally distinct topographic
features such as drainage channels. Secondary canals are often located on a ridge, irrigating areas
on both sides of the canal, as far as the bordering.

2.6.4 Tertiary canals

The farmers receive their water from the tertiary canal in which there grouped in it. The upper
limit of the length of the tertiary canal is about 1500 to 2000 meters. The area of a tertiary unit is
normally 50 to 100 ha, but occasionally up to 150 ha, and is subdivided into quaternary units of
8 - 15 ha each. The tertiary units should be designed prior the design of the other infrastructure of
the scheme. First a suitable size of the units should be determined and subsequently the tertiary
units are arranged in the project area. Only when the tertiary units are determined the other
infrastructure can be mapped out (John V.R, 2004).

2.6.5 Design command area

Gross command area is the total area which can be economically irrigated from an irrigation
system without considering the limitation on the quantity of available water. It includes the area
which is, otherwise, uncultivable. For example, ponds and residential areas are uncultivable areas
of gross command area.

10
 The required canal discharge depends on the field area to be irrigated ('command area'), and the
water losses from the canal. For a design command area A (m 2), the design discharge required Q
(l/s) for irrigation hours (H) every day, is given by the field-irrigation requirement multiplied by
the area, divided by the time (in seconds) (Stern, 1979.).

If A
Q= +canal losses
H 60 60

2.7 PLANNING OF AN IRRIGATION CANAL SYSTEM

Planning of an irrigation canal project includes the determination of canal alignment, and the
water demand. The first step in the planning of an irrigation canal project is to carry out a
preliminary survey to establish the feasibility or otherwise of a proposal. Once the feasibility of
the proposal has been established, a detailed survey of the area is carried out and, thereafter, the
alignment of the canal is fixed. The water demand of the canal is, then, worked out. To determine
the feasibility of a proposal of extending canal irrigation to a new area, information on all such
factors which influence irrigation development is collected during the preliminary (or
reconnaissance) survey. During this survey all these factors are observed or enquired from the
local people (Asawa. 2008).
The information on the following features of the area, are to be collected:

i. Type of soil,
ii. Topography of the area,
iii. Crops of the area,
iv. Rainfall in the area,
v. Water table elevations in the area,
vi. Existing irrigation facilities, and
vii. General outlook of the cultivators with respect to cultivation and irrigation.

2.7.1 Alignment of irrigation canals.

11
 Desirable locations for irrigation canals on any gravity project, their cross-sectional designs and
construction costs are governed mainly by topographic and geologic conditions along different
routes of the cultivable lands. Main canals must convey water to the higher elevations of the
cultivable area. Branch canals and distributaries convey water to different parts of the irrigable
areas. On projects where land slopes are relatively flat and uniform, it is advantageous to align
channels on the watershed of the areas to be irrigated. Aligning a canal (main, branch as well as
distributary) on the watershed ensures gravity irrigation on both sides of the canal. Besides, the
drainage flows away from the watershed and, hence, no drainage can cross a canal aligned on the
watershed. Thus, a canal aligned on the watershed saves the cost of construction of cross-
drainage structures (Asawa. 2008).

2.7.2 Curves in canals

Because of economic and other considerations, the canal alignment does not remain straight all
through the length of the canal, and curves or bends have to be provided. The curves cause
disturbed flow conditions resulting in eddies or cross currents which increase the losses. In a
curved channel portion, the water surface is not level in the transverse direction.

There is a slight drop in the water surface at the inner edge of the curve and a slight rise at the
outer edge of the curve. This results in slight increase in the velocity at the inner edge and slight
decrease in the velocity at the outer edge. As a result of this, the low-velocity fluid particles near
the bed move to the inner bank and the high-velocity fluid particles near the surface gradually
cross to the outer bank. The changes in the velocity on account of cross currents depend on the
approach flow condition and the characteristics of the curve. When separate curves follow in
close succession, either in the same direction or in the reversed direction, the velocity changes
become still more complicated (Asawa. 2008).

Therefore, wherever possible, curves in channels excavated through loose soil should be
avoided. If it is unavoidable, the curves should have a long radius of curvature. The permissible
minimum radius of curvature for a channel curve depends on the type of channel, dimensions of
cross-section, velocities during full-capacity operations, earth formation along channel alignment
and dangers of erosion along the paths of curved channel. In general, the permissible minimum
radius of curvature is shorter for flumes or lined canals than earth canals, shorter for small cross-

12
 sections than for large cross-sections, shorter for low velocities than for high velocities, and
shorter for tight soils than for loose soils (Asawa. 2008).

Table 2.1. Values of minimum radii of channel curves for different channel capacities
Channel capacity (m3/s) Minimum radius of curvature (metres)
Less than 0.3 100
0.3 to 3.0 150
0.3 to 15 300
15.0 to 30 600
30.0 to 85.0 900
More than 85 1500
Source: (Asawa .2008)

2.7.3 Duty of water

For proper planning of a canal system, the designer has to first decide the duty of water in the
locality under consideration. Duty is defined as the area irrigated by a unit discharge of water
flowing continuously for the duration of the base period of a crop. The base period of a crop is
the time duration between the first watering at the time of sowing and the last watering before
harvesting the crop. Obviously, the base period of a crop is smaller than the crop period. Duty is
measured in hectares/m3/s. The duty of a canal depends on the crop, type of soil, irrigation and
cultivation methods, climatic factors, and the channel condition (Asawa. 2008).

Well irrigation has higher duty than canal irrigation due to the fact that water is used
economically according to the needs. Open wells do not supply a fixed discharge and, hence, the
average area irrigated from an open well is termed its duty. Between the head of the main canal
and the outlet in the distributary, there are losses due to evaporation and percolation. As such,
duty is different at different points of the canal system.

2.7.4 Irrigation-canal losses

When water comes in contact with an earthen surface, whether artificial or natural, the surface
absorbs water. This absorbed water percolates deep into the ground and is the main cause of the
loss of water carried by canal. In addition, some canals water is also lost due to evaporation. The
loss due to evaporation is about 10% of the quantity lost due to seepage. The seepage loss varies

13
 with the types of the materials through which the canal runs. Obviously, the loss is greater in
coarse sand and gravel, less in loam, and still less in clay soil. If the canal carries silt-laden water,
the pose of the soil are sealed in course of time and the canal seepage reduces with time (Asawa.
2008).

In almost all cases, the seepage loss constitutes an important factor which must be accounted for
in determining the water requirements of a canal. For the purpose of estimating the water
requirements of canal, the total loss due to evaporation and seepage, also known as conveyance
loss, is expressed as m3/s per million square meters of either wetted perimeter or the exposed
water surface area. Conveyance loss can be calculated using the values given in Table 2.2. The
total loss (due to seepage and evaporation) per million square meters of water surface varies
from 2.5m3/s for ordinary clay loam to 5.0m3/s for sandy loam (Asawa. 2008).

Table 2.2 Conveyance losses in canals

Loss in m3/s per million square metres of
Material
wetted perimeter (or water surface)
Impervious clay loam 0.88 to 1.24
Medium clay loam underlaid with hard pan at
1.24 to 1.76
depth of not over 0.60 to 0.90 m below bed
Ordinary clay loam, silty soil or lava ash loam 1.76 to 2.65
Gravelly or sandy clay loam, cemented gravel,
2.65 to 3.53
sand and clay
Sandy loam 3.53 to 5.29
Loose sand 5.29 to 6.17
Gravel sand 7.06 to 8.82
Porous gravel soil 8.82 to 10.58
Gravels 10.58 to 21.17
Source: (Asawa. 2008).

2.8 DESIGN OF LINED CANAL

2.8.1 General Descriptions

Canal lining is considered for the reasons of prevention of seepage losses, prevention of scour
and erosion, prevention of damage by livestock or people, to allow for increase curvature,
reduction of land acquisition and many others. Lining of canals is an important feature of
irrigation projects as it minimizes generally the loss of water due to seepage. The water thus
saved can be usefully employed for the extension and improvement of irrigation facilities.

14
 2.9 HYDRAULIC DESIGN

The design of a channel involves the selection of channel alignment, shapes, size, and bottom
slope and whether the channel should be lined to reduce seepage and/or to prevent, the erosion of
channel sides and bottom. Since a lined channel offers less resistance to flow than an unlined
channel. Procedures are not presently available for selecting optimum channel parameters
directly. Typically, the design of a channel is done by trial and error. Channel parameters are
selected and an analysis is done to verify that the operational requirements are met with these
parameters. A number of alternatives are considered, and their costs are compared. Then, the
most economical alternative that gives satisfactory performance is selected.

The design of canal generally assumes that steady and uniform flow exists in the canal. In
addition to that assumption and also depending on the design concept, sediment content in the
irrigation water and the soil characteristics of the field are taken into account. The hydraulic
design of unlined canal and earthen lining canal can be carried out using various methods. The
most common methods are Chezys Formula and Manning Equation.

2.9.1 Chezys Equation

According to M.H Ali, the earliest formula for open channel design was proposed by Chezy
(in 1775). The Chezys equation is expressed as

V =C RS

Where: V = Velocity of flow (m/s)

R = Hydraulic radius of the flowing section (m)

S = Slope of water surface (take as equal to the slope of channel (m/m))

C = Chezys constant, which varies with surface roughness and flow rates

Later on, difference scientists and engineers worked on this formula. After conducting a series of
experiment, Kutter, Basin and Manning proposed a method for determining C in Chezys
formula. But due to simplicity, Mannings formula is widely used.

2.9.2 Manning formula

15
The Manning formula is widely used for canal design. However its flow factor n depends on
several factors, including the canal slope, depth of flow and bed slope. These factors are more
dominant in rough and shallow canals with low water levels, common in smallholders irrigation
schemes (John V.R., 2004). The canal dimensions and longitudinal slope, whether for irrigation
or drainage, can be calculated through trial and error with the Manning formula. This formula is
derived from the continuity equation and the equation for unsteady flow. These equations have
been simplified by assuming steady uniform flow in the canal (this assumes long canals with
constant cross-section and slope) (Andreas &Karen, 2002).

The Continuity equation is expressed as

Q= A V .2.9.1

Where: Q = Discharge (m3/sec) A = Wetted cross-sectional area (m2) V = Water velocity (m/sec)

1
1 6
Manning suggested C= n R in Chezys formula. Manning equation expressed as

2 1
1
V = R 3 S2 ..2.9.2
n

2 1
2 1
AR3S2
Q= or Q=k m A R 3 S 2 2.9.3
n

Where:
Q = Discharge (m3/sec)
1
km km=
and n = Manning roughness coefficient: n

A = Wetted cross-sectional area (m2)

P = Wetted perimeter (m)
A
R=
R = Hydraulic radius (m) P

S = Canal gradient or longitudinal slope of the canal

16
 Table 2.3: Manning roughness coefficient values
Surface Km n
lined irrigation canals
Well finished 70 0.014
Average finished 65 0.015
Poor finish 60 0.017
60 0.017
Soil cement
Bricks 55 0.018
Correction for curved reaches -5 +0.001
Correction for small depth (y<0.5 m) -5 +0.001
Earth Irrigation Canals:
Straight minor weed growth Q>10 m3/s 40-50 0.02-0.025
Straight short grass, Q<10 m3/s 36 0.028
Straight short grass Q<0.2 m3/s 24 0.042
Correction for curved reaches -5 +0.001

Drains, Earth
Bush & weed clearance 2 or 3 times per year 24 0.0417
Less well maintained 10-20 0.1-0.05
Source: T.K.E. Meijer: Design of Smallholders Irrigation Systems, 1993, WAU

Madan Das and Mimi Das (2009), suggest that for a given discharge Q, Manning n and bed slope
S, wetted perimeter P is minimum when A is minimum. For minimum P and A, cost of
excavation and lining used to prevent seepage and erosion will be minimum. Thus in the design
of canal considering P to be minimum is termed as method of economic section.

2.9.3 Most Efficient Hydraulic Section

Theoretically speaking, the most efficient hydraulic section yields the most economical channel.
However, it must be kept in mind that the above formulation is oversimplified. For example, it
did not take into consideration the possibility of scour and erosion which may impose restrictions
on the maximum flow velocity. The conveyance or carrying capacity of a given channel section
increase directly with the hydraulic radius (R). This means it increases with decreases in the
wetted perimeter (P). The best hydraulic section is one that has the least wetted perimeter for the
same area (A). The channels in this work will be designed for the best hydraulic efficiency
practicable. The best hydraulic section may not necessarily be the most practicable. Hence the
most economical slope for a channel must simulate the following conditions.

17
 i. Maximum discharge for a given cross sectional area
ii. Minimum excavation and lining i.e. least expenditure for the design amount of discharge
iii. Least wetted perimeter or its equivalent so that there is minimum resistance of flow and
consequently there is optimum discharge.

The Table below gives the geometric attributes of three best hydraulic sections.

Table 2.4: Best Hydraulic Sections

Wetted Hydraulic Top Hydraulic

Cross sectional Shape Area
Perimeter Radius Width Depth
A P R W D
1 4 3
Trapezoid half of a Hexagon 3 y2 2 3 y y 3 y y
2 3 4
1
2 y2 4y y 2y y
Rectangle half of a Square 2
1 1
Triangle half of a Square y2 2 2 y 2 y 2y y
4 2

Source: Mays, 2005

Where y is the depth of the channel, R is the hydraulic depth, S is the slope of channel and n is
mannings coefficient for the channel lining.
For a concrete lined channel n = 0.015. For a rectangular channel, designing for the best
hydraulic section we have: B = 2d; P = 4d; and A = 2d2. Where B, d, P, A are the bottom width,
depth, wetted perimeter and Area of channel respectively.

18
 T
zy B zy

y 1V
zH

B
Figure 1 Trapezoidal section

For the trapezoidal channel, the half of top width is equal to the length of one slanting side,
which is the condition for economic section.

( B+22 zy )= y 1+ z 2

Also the trapezoidal channel section is economical when hydraulic radius R is half of the depth (

y
R=
2 ). Also where a trapezoid channel is used the best hydraulic section will have side slope

3
of 3 horizontal to 1 vertical. For trapezoidal channel, designing for the best hydraulic

2y
B= , P=2 3 y A= 3 y 2 .
section, 3 and

2.9.4 Design discharge of a canal

The capacity of a canal at any given point is the amount of water which will pass that point under
normal condition. In preparation plans for construction or enlargement it is necessary to know
the agricultural area which the canal is to serve and the duty of water for which provision must
be made during the period of greatest irrigation requirement (Frederick & Daniel 1913).

19
 Irrigation canals should be able to transport peak flows. The design capacity depends on the
rotation schedule. Under continuous flow arrangements the design capacity equals the
requirements of the total area under demand. The design capacity of on-demand or rotation
systems depends on the duration that it carries water. A canal that only carries water for 50% or
25% of the time requires respectively double and four times higher capacities. If farmers can take
water without prior notice, the canals need very large capacities. It is recommended to increase
the flexibility of the scheme to react to water needs and increase the design capacity of the canals
with 10% to 40%, at respectively the intake to the end of the secondary canals (John V.R, 2004).

According to (MAFC,1999), it is advisable to design the tertiary canals for continuous flow for
economic reasons, and to design the quaternary canals on a rotation basis, since most farmers do
not irrigate more than 8 - 10 hrs a day.

In this case the tertiary canals should be designed for continuous flow and the capacity of the
field distribution system will be increased to Q x 24/t, when Q is the design capacity for
continuous flow and (t) is the irrigation period in hours.

In the absence of accurate data, the distribution system is usually designed for 1 litre/s/ha
continuous flow and proportionally increased with the irrigation by rotation.
The design capacity of a tertiary canal between two Quaternary division box is given by:

Q=( A 1+ A 2+ An)q

Where: Q1 = tertiary canal upstream for continuous flow q =Irrigation model l/s/Ha and
A =Quaternary area irrigated.

2.9.5 Maximum Permissible Velocities

According to R.K Sharma and T.K Sharma (2002), the Permissible Velocity is defined as the
highest velocity at which water may be carried safely in a channel. Maximum permissible
Velocity is specified so that the discharge is passed within the smallest section without causing
erosion. Maximum Permissible Velocities recommended for various types of soil are shown in
Table 2.5.

20
 Table 2.5: Maximum Permissible Velocities
Soil type velocities (m/s) CBIP Practice velocities (m/s)
Ordinary soil 0.6 1.0 0.6 0.9
Very light loose sand to average sand 3 0.6 0.3 0.6
Sandy loam, black cotton and similar 0.5 1.0 0.6 0.8
Murum, hard 0.75 1.25 0.9 1.0
Gravel 1.25 1.25
Rock 1.25 2.0 1.5
Source: R.K Sharma and T.K Sharma (2002).

2.9.6 Minimum Velocity

Minimum velocity is taken as a fraction of maximum permissible velocity, say 0.8Vmax.The

minimum non- silting and non- weed velocity is considered as 0.3 to 0.5 m/sec. objection to the
slack velocity are (i) It tends to encourage weed growth, (ii) It increases transmission losses
through the canal, and (iii) It results in increased cross section area and hence uneconomical
section (R.K Sharma &T.K Sharma, 2002).

2.9.7 Canal Cross-Section

The selection of a cross section for canal is one involving economy of construction and
maintenance as well as security against failures which prove disastrous to an irrigation system. It
requires the consideration of the theory of flow of water in channel and the exercise of
engineering judgment. From the standpoint of theory alone it would appear the section which
will carry the necessary amount of water, conserve grade so as to cover the greatest possible area
and require the least amount of excavation in its construction, is the one which should be
selected. For a canal of given slope and fixed area of cross section, the greatest velocity will be
attained by selection the section with maximum hydraulic radius (Frederick & Daniel 1913).

2.9.8 Longitudinal canal sections

21
 Andreas and Karen (2002) suggest that, the best way to present canal design data for
construction is to draw a longitudinal profile of the canal route and to tabulate the data needed
for construction. The longitudinal profile shows the chainage or distance along the canal at the
horizontal or x-axis and the elevations of the natural ground, the ground after leveling and the
canal bed at the vertical or y-axis. The data are tabulated under the graph, showing the elevation
of ground and canal bed in figures at each given distance. Water depths could also be shown. The
chainage starts from a reference point, which is usually the beginning of the canal. Where
possible the survey results of the topographic survey are used. If these are not sufficient a
detailed survey of the proposed alignments should be made.

2.9.9 Side Slope

To limit excavation and expropriation cost, canal side slopes are designed as steep as possible.
Soil material, depth of the canal and occurrence of seepage will determine the maximum
steepness for a stable side slope. Side slopes can be steeper for lined canals compared to unlined
canals. For small canals (where h<0.40 m) side slopes of lined canal can be vertical. For larger
canals the side slope values in Table 2.6 are recommended. Particularly for the larger canals
stability of the lined side slope has to be checked against sliding and overturning. Water pressure
from behind the lining is an important factor in this balance (DID MANUAL 2009).

The side slope depends on the material which is used for constructing the canal, and canals
constructed with heavy clay can have steeper side slopes than those built with sandier material.
Lined canals which are constructed from bricks or concrete can even have vertical side slopes
(FAO. 1992).

Table 2.6 Side Slopes for Lined Canal

Canal depth Canal depth Canal depth
Types of Soil
h less than 0.4 m 0.40 m< h < 0.75 m 0.75 m <h <1.5m
Sandy soil, cohesive sandy soil Vertical 1:1 1:1
Loose sandy soil Vertical 1:1 1:1.25
Sandy loam, porous clay Vertical 1:1 1:1.5
Soft peat Vertical 1:1.25 1:1.5
Source: DID MANUAL 2009

2.9.10 Bank Width

22
 Canal banks hold water within the water section of a channel. The width of the banks may vary
according to the importance and capacity of the canal. In case of distributaries, service road
should be provided on one bank for inspection and maintenance purpose. However, in case of
main and branch canals service road should be provided on both the banks. Bank widths at all
elevations must provide stability against water pressure at the sides of the channel section. They
should also keep percolating water below ground level outside the banks and prevent piping of
bank materials (Asawa G.L, 2008). For considerations of operation, maintenance and inspection,
minimum bank width along the canals required are as given in Table 2.7.

Table 2.7 Minimum Embankment Width for Lined Canal

Discharge Q
Hierarchy Without farm road (m) With Farm Road (m)
(m3/s)
Main canal Q > 15.0 3.50 6.00
5.0 - 15.0 1.50 6.00
1.5 - 5.0 1.50 6.00
Secondary canal
0.5 - 1.50 1.50 6.00
Tertiary canal 0.15 - 0.50 1.50 6.00
Quaternary canal < 0.15 1.50 5.00
Source: DID MANUAL 2009.
2.9.11 Bed Width and Depth ratio
The bed width and water depth will depend on the required cross sectional area of the flow. The
ratio of the bed width and water depth in earth canal can be controlled by the following formula.
(a)For channel up to 15 cumecs

Y= 0.5 B ,

Where: y= depth of water in the channel and B =Base width of channel

(b) For channel greater than 15cumecs
Table 2.8. Assumed values of water depth for canal
Discharge Q (cumecs) Depth (m)
15 1.7
30 1.8
75 2.3
150 2.6
300 3.0
Source :( S.K Garg 1999)

23
2.9.12 Canal shape

Canals with the same cross-sectional area, longitudinal slope and roughness, but with different
shapes, will carry different discharges because of different wetted perimeters and hydraulic
radius. The most efficient geometry is when the wetted perimeter is minimal for a given
discharge.

Under these circumstances, the cross sectional area for a given discharge will also be minimal.
The optimum canal shape, hydraulically, also tends to be the cheapest to construct as the amount
of surface lining material required will be minimized (FAO-Andreas et al, 2002).

2.9.13 Berms
A berm is a narrow horizontal strip of land between the inner toe of the bank and the top edge of
cutting. Berms between water section and inner bank slopes are required along the channels
where bank materials are susceptible to sloughing. Berms slope towards water section to
facilitate drainage.

2.9.14 Freeboard
Freeboard is the vertical distance from the water surface at full supply level to the top of bank.
Freeboard provides the margin of safety against overtopping of the banks due to sudden rise in
the water surface of a channel on account of improper operation of gates at the head regulator,
accidents in operation, wave action, landslides, and inflow during heavy rainfall.

Design of channels should specify adequate freeboards to prevent overtopping of the banks
during sudden rises in water surface. Adequate freeboard would depend on dimensions of the
flow section, flow condition, bank material, method of construction of bank, and resulting
damage due to failure of bank (Asawa 2008).
The freeboard can be calculated using the following equation
F = C h
Where: C = 0.8 for discharges of up to 0.5 m 3/sec up to 1.35 for discharges in excess of
80 m3/sec and h = Water depth (m)

For lined canals, F ranges from 0.40 m for discharges less than 0.5m 3/s up to 1.20m for
discharges of 50m3/s or more. For very small lined canals, with discharges of less than 0.5 m 3/s,

24
 the freeboard depths could be reduced to between 0.05-0.30 m. The Central Water Commission
of India (CWC) has recommended the value of freeboard as given in Table 2.9.

Table 2.9: Freeboard of irrigation channels as suggested by CWC

Discharge (m3/s) up to 0.7 0.7 to 1.4 1.4 to 8.5 over 8.5
Freeboard (m) 0.46 0.61 0.76 0.92
Source: Asawa G.L, 2008

Alternatively, Table 2.10 may be used for the estimation of freeboard.

Table 2.10: Freeboard in irrigation channels

Bed width (m) Discharge (m3/s) Freeboard(m)

Less than 1.0 0.30
1 to 1.5 0.35
Greater than 1.5 Less than 3.0 0.45
-do 3 to 30 0.60
-do 30 to 60 0.75
-do Greater than 60 0.90
Source: Asawa G.L, 2008

2.9.15 Canal Curvature

The minimum radius for earth canals constructed in less erosive soils should not be less than 5 to
8 times the water width in the canal. The following range is suggested: canals conveying 5 to 15
m3/s, 6 times the water width: 15 to 50m 3/s, 7 times the water width: over 50 ml/s, 8 times the
water width. If the canal is concrete lined or if a flume is used, a minimum radius of curvature of
3 times the water width should be used to avoid bend losses. If the canal is lined with brick,
masonry, rip-rap, stone pitching or other hard material resistant to erosion it should also have a
minimum radius of 3 times the water width (Labye Y. et al, 1988).

In general, the minimum radius of curvature is usually taken as three times the water surface
width for concrete-lined canals, and three to seven times the surface water width and for erodible
canals (MAFC. 1999).

2.10 WATER CONTROL AND DIVERSION STRUCTURES

Water control and diversion structures are necessary to gives easy and effective control of
irrigation water on the farm. Good control will reduce the labour required to irrigation and check

25
 erosion and water loss. The structures include drops, check gates, portable check dam, diversion
boxes, turnout boxes, siphons and pipe turnouts.

2.10.1 Turnouts

When water is to be taken from a lateral channel into field distribution channel or from a channel
into a field, a turnout is used. Kraatz and Mahajan (1982) define an outlet or farm turnout as a
structure at the head of a watercourse, farm irrigation canals, or a farm or field lateral, which
connects it with a supply canal. They are needed to provide a quick and easy means of taking
water from the head ditch to field ditches or border dikes.

Turnouts may be portable or built in. They are sometime equipped with gates to control the flow
of water. The most common turnouts are box turnouts, spiles and siphon tubes (Michael A.M.,
2008).

2.10.2 Division boxes

A division box or a division structure is a structure put along a canal at a point where two or
more canals meet. It is used to divide and control the flow from one canal to several other canals
or fields. The structure consists of two or more controllable openings provided with metal or
wooden slide gates or stop planks. The flow from one canal is divided between two or more
canals or fields by partially or completely opening or closing the appropriate gates.

The division box is constructed at the junction point where an irrigation sub lateral branches into
two or three farm ditches. The division box is not used to divide water carried in by the sub
lateral between farm ditches. It used to turn the whole flow of water alternatively into one of the
ditches according to preset irrigation schedule (Kraatz & Mahajan 2008)

2.10.3 Check gates.

Checks are placed in an irrigation channel to form and adjustable dam to control the elevation of
the water surface upstream. To apply water from channels to a field it is often necessary to raise
the water level. The water level in the channel should be at least about 8 to 12cm above the
ground surface in order that siphon tubes or pipe turnout may be used efficiently. Checks gates

26
 placed at intervals along the channel keep a satisfactory water level for applying water to the
field (Michael A.M., 2008).

2.10.4 Drop Structures

A drop (or fall) structure is a regulating structure which lowers the water level along its course.
The slope of a canal is usually milder than the terrain slope as a result of which the canal in a
cutting at its headworks will soon outstrip the ground surface. In order to avoid excessive
infilling the bed level of the downstream canal is lowered, the two reaches being connected by a
suitable drop structure (Novak et al, 2007).
The drop is located so that the fillings and cuttings of the canal are equalized as much as
possible. Wherever possible, the drop structure may also be combined with a regulator or a
bridge. The location of an offtake from the canal also influences the fall site, with offtakes
located upstream of the fall structure (Novak et al, 2007).
Drops are usually provided with a low crest wall and are subdivided into the following types:
(i) The vertical drop,
(ii) The inclined drop and
(iii) The piped drop.

27
 CHAPTER THREE

3.0 METHODOLOGY

The project is a problem solving by designing irrigation canals network at Cheju irrigation
scheme. In order to come up with proper design, various approaches have been used. This project
report had considered all the possible economical and easy methods used in design of irrigation
structures adopted in Tanzania. To be familiar with the methodology which were used in this
project, one have to understand a number of processes to be done in order to accomplish the
whole design work of irrigation canals network.

3.1 Description of the Study Area

3.1.1 Location

Cheju Scheme is located at Cheju village within south eastern part of Zanzibar main Island
(Unguja Island), about 30 km, south east of Zanzibar town. The Scheme has a total potential area
of 1200ha only about 90ha has so far been developed for Irrigated agriculture by using four
tubular wells as a source of water.

3.1.2 Climate

3.1.2.1 Rainfall

The mean annual rainfall of the project area site is 1554.64mm. Although the rains are distributed
throughout the year, there are two prominent rainy seasons. The main rainy season or Masika
extends from the end of March to May and is responsible for about half of the total rainfall. The
short rains or Vuli fall in the months of October to December. Little more than half of
remaining rainfall is received during this season.

28
3.1.2.2 Evaporation

The minimum evaporation is in September (100mm/month) and maximum evaporation is in

November (190 mm/month). From May to September the evaporation lies between 100 and 130
mm/month. The overall average evaporation is 137mm/month. The Rainfall exceeds potential
evaporation during the months of April, May and November.

3.1.2.3 Temperature

The mean monthly maximum temperature ranges from 28.5 during the coldest month (July)
to 32.0oC during the hottest month (February) and the mean monthly minimum temperature
range from 19.1oC during the month of September to 23.4oC during the hottest month of April.

3.1.2.4 Wind
There are two dominant prevailing winds. South monsoon winds prevail during the months of
June to December while North monsoon winds prevail during the months of January to May.
Wind speed is lowest in March (144.3 km/day). From April it starts increase and attains the
highest value during the months of June to September (197.1 km/day).

3.1.2.5 Relative humidity

The relative humidity is high. Early morning (0600 hours) value range from 89% to 96% with
mean of 91%.The relative humidity decreases during the afternoon (1500 hours) from 56% to
73% with a mean of 62%.

3.1.2.6 Soils

According to the geological map of Zanzibar, the soil of Cheju, and Zanzibar in general, have
been divided into three main groups .these are: sandy, calcareous red soils, and clay soils
(Therma, 1981). But in general the soil type of Cheju scheme heavy clay soil.

29
 Figure 2: Map of Cheju village showing location of Cheju irrigation scheme

A number of reference books, manuals, journals and design reports will be consulted so as the
skills gained can be used during designing of the project as literature review provide a theoretical
background to the study area concerned and experiencing different approach used by others to
tackle the same problem.

3.2 Site Visits

Data were collected involve primary (include soil data, topographical survey data wells discharge
data), and secondary data (include Water sources, population, Climatic data, Crop and Cropping
pattern). Field visit will be done as to prepare an inventory of land use, topography, water source,
agricultural activity including soils i.e. texture, structure,to asses and observe existing situation
of project area in consultation with different stakeholders.Some of the Secondary data will be
collected from local authorities and survey office while primary data will be collected at site.

30
3.3 Consultation

Through consultation, gathering information and data collection concerning the study area
becomes possible. Moreover, Experts and technical people are the key sources of information on
technical issues and knowledge.

3.4 Design
During data analysis and computations, the design process was involving manual work through
the use of empirical formula and design soft ware. Different design softwares to be used are.

i. Microsoft excel sheet

This was used to filter and arrange the topographical data of study area (Cheju scheme) in order
to be imported in AutoCAD civil3D program to draw topographical map.

ii. Hydraulic computation sheet

This was used to balance the preliminary canal profile data in order to get designed canal
parameters like velocity (v), height(y), breadth(b), slope(S) etc.

iii. Cropwat 8.0 and Climwat 2.0

To determine crop water requirements (CWR or ETcrop) ,Cropwat 8.0 in combination with
Climwat 2.0 were used for analysis of meteorological data i.e determining parameters such as
reference evapotranspiration (ETo), determination of effective rainfall from the monthly average
total rainfall for different years of the collected data, determination of net irrigation requirements
and determination of irrigation scheduling.

iv. AutoCAD Civil 3D

AutoCAD Civil 3D was used to prepare a contour map which provided a clear picture on the
topography of the project area. This software is capable of providing the direction of flow of
water, watersheds, and existing ground profiles from a drawn contour map.

31
 CHAPTER FOUR

4.0 DATA COLLECTION AND ANALYSIS

4.1 Data collection

Frequent site visits were carried out so as to ascertain information observed from the studies, as
well as to collect farmers ideas and interests that could be incorporated in the design according
to the nature of their environment. Data collection involved: Topographical field survey data,
Water sources, Soil data and Meteorological data.

4.1.1 Topographical Survey data

A plan for scope and methods of topographical survey was established by stages. The control
point and temporary benchmark are installed in/nearby the project area in order to correctly mark
the location of various facilities such as irrigation canals, drainage canals, and roads

In this project, topographical survey was conducted by team of surveyors and technicians from
engineering section of department of irrigation Zanzibar in collaboration with other experts from
Korea Rural Community Corporation. A total of about 259 survey points were used to draw the
topographical map of study area. The lists of topographical data are attached on appendix 1

4.1.2 Water sources

The scheme is planned to be provided with irrigation water by using tubular wells. In order to
meet crop water requirement for 75ha of project area at Cheju irrigation scheme, there are 2
tubular wells which used to irrigate this area. Each tubular is expected cover the 38ha, reference
being made on yield of the existing boreholes in Cheju (average of 35 l/s) and crop water
requirement.

4.1.3 Meteorological data

In this project, meteorological data were collected to the meteorological station which is closer to
the project site. The detailed information about climatic condition of 10 years was collected
through metrological data from Zanzibar Meteorological Station. The collected meteorological
parameters include maximum and minimum temperatures, humidity, rainfall, and average
minutes of daily sunshine as they appear in the tables below.

32
 Table 4.1: Average meteorological data from 2004 to 2013
RELATIVE TOTAL
MAX.TEMP MIN.TEMP WIND RUN SUN SHINE
MONTH HUMIDITY RAIN FALL
(C) (C) (Km/Day) (Av. Mins)
(%) (mm)
JANUARY 32.69 24.55 77.8 81.43 493 8.61
FEBRUARY 32.84 24.4 77.3 50.33 424 8.54
MARCH 32.37 24.62 81.6 213.8 333 7.67
APRIL 30.65 24.59 84.7 360.11 379 6.22
MAY 29.87 23.9 82.5 198.79 426 6.99
JUNE 29.32 22.95 78.9 60.12 466 8.11
JULY 29.25 22.21 76 13.46 504 8.08
AUGUST 29.58 21.24 76.1 32.03 471 8.3
SEPTEMBER 30.67 21.32 76.7 41.45 478 8.62
OCTOBER 31.24 22.35 79 93.57 437 9.02
NOVEMBER 31 23.29 84.2 233.8 333 8.18
DECEMBER 31.73 24.18 82.1 175.75 377 8.65
Source: Tanzania Meteorological agency, Zanzibar office
4.1.4 Soil data

Soil survey was conducted in the project area by taking soil sample in a several point in a study
area by using augering method. The soil samples are taken in a depth of 0 to 30cm and 30 to
60cm in a several auger holes in a project area. The purpose of taking these soil samples was for
identifying different soil types whose characteristics serve as basis for the design decision
particularly on the type and method of irrigation system to be employed.

Photo 3.1: Salum taking soil samples at Cheju Photo 3.2: collected soil samples at Cheju from
different depth

33
4.1.5 Laboratory Soil Test

Soil samples which collected at the project area were tested at ATC Soil and Bitumen Laboratory
(photo 3.3 3.4). The soil parameters were tested includes: grain size distribution (wet sieve
analysis), permeability with specific gravity of soil and Atterberg limits i.e Liquid limit, Plastic
limit. Soil laboratory tests were done to measure the engineering properties of the soils where the
canals are to be constructed. The results of these tests are attached on appendices 3a- 3g

Photo 3.3: Sieve analysis test at ATC laboratory Photo 3.4: Atterberg analysis test at ATC laboratory

4.2 DATA ANALYSIS

4.2.1 Crop water requirement analysis

Estimating the crop water requirements (CWR) and irrigation requirements (IR) for a proposed
cropping pattern is an essential part of the planning and design of capacity of canals. To estimate
the crop water requirements and irrigation requirements of project area, there are some
essentially data needed. The data obtained from meteorological station, soil data, coverage area
of the project and the type of crop grown at project area (rice) were used to analyze the crop
water requirement and irrigation requirements of rice crop by using the CROPWAT version 8
program. The analyses of irrigation requirement of rice for actual project area are shown in a
figure below.

34
 Figure 3: The analysis of irrigation requirement of rice for actual project area.

As stated before (at 4.1.2 water source) that the project area is planned to be provided with

irrigation water by using two tubular wells and cover the area of 72h, but each tubular well

has capacity (discharge ) of 35l/sec which cover the area of 3 6 h .

From the above analysis the maximum irrigation requirement for rice crop is 0.69/ s/ha at

month of March which was used to design the canal discharge for the project area for each

month. For 36h the discharge of canal will be 225 l / sec ( 0.69 l/s /h 3 6 h ). But because

the tubular well has discharge of 35 l/sec , which is greater than 25/sec, than for safely

designing of irrigation canal network at 36haof an area, the discharge of 35 l/sec should be

used in order to meet crop water requirement.

35
 Figure 4: Summary crop water analysis of rice crop for actual project area.

4.2.2 Soil data analysis

After conducting soil laboratory test the obtained results are summarized in a table below

Table 4.2 Summary of soil laboratory test results

S/N DISCRIPTION SAMPLE 1 SAMPLE2
01 Depth of sample taken 030 cm 30 cm60 cm

02 Proportion of material passing 0.425m sieve 97.31% 87.15%

03 Liquid limit 46.25% 71%
04 Plastic limit 19.92% 28%
05 Plastic index 26.33% 42%
06 Linear shrinkage 14.29% 15%
07 Specific gravity of soil 2.527 2.612
08 Permeability of soil 0.00000271053 0.00000866964

By using the values of proportion of material passing 0.425m sieve, liquid limit and plastic
index, according to AASHTO method of classification, the soils (sample 1 and 2) are classified
as clayey soils which fall on A-7, A-7-5a, and A-7-6.

4.2.3 Topographical map

The AutoCAD Civil 3D computer program was used to prepare topographical map of project
area by using the topographical survey data of project area. The topographical map of the area
was produced to a 1:1,000 scale with contour interval of 0.5m for the entire area. The map as a
result of survey data has been used in design of farm lay out and longitudinal profile. The detail
information about the farm layout has been presented in appendix 07

36
4.2.3.1 Land Consolidation

The purposes of the land consolidation are as following; a) improvement of irrigation, drainage
and soil, b) alignment of farm road, c) collectivization of farmland, d) preparation of farming
mechanization, e) improvement of productivity and work efficiency, f) improvement of water
resource management.

4.2.3.1.1 Farmland

The dimensions of primary farmland, secondary farmland and tertiary farmland will be 150m x
300m (4.5ha), 100m x 150m (1.5ha) and 100m x 50m (0.5ha) respectively. The scale of the
primary farmland section looks inefficient, but it can be overcome through the managerial
methodology of water supply into the farmland.

4.2.3.1.2 Irrigation Canal

Irrigation canal was designed as follows; (a) primary irrigation canal (PIC) main irrigation canal
(MIC) which provides water into the secondary irrigation canal (SIC), (b) SIC which provides
water into the Tertiary irrigation canal (TIC) and (c) Tertiary irrigation canal (TIC) which
provides water into the farmlands.

Primary irrigation canal (PIC) will be arrayed along the primary farmland section which can be
given the irrigation water by gravity, while The secondary irrigation canal (SIC) will be provided
with water by the PIC and supply this water to secondary farmland section. The slope for both
PIC and SIC is the 1/2,000 and drop structure will be placed accordingly to regulate flow
velocity and dissipate hydraulic energy. Both PIC and SIC will be trapezoidal shaped concrete
lined canals. The detail information about the profile of main and secondary canal has been
presented in hydraulic sheet in appendix 8 and 9 respectively

4.2.4 Canals Hydraulic Design and consideration:

Mannings equation of flow was used to calculate dimensions of the canals. Through the use of
hydraulic sheet calculation Mannings coefficient value has been taken into account with respect
to the type of lining material for small irrigation canals.

37
During hydraulic design in a spread sheet, the dimensions of canal for both the PIC and SIC
were probably set as a guide in accordance to irrigation manual as fellows; (a) bed width 0.25m,
(b) cross-sectional slope of canal 1:1, freeboard of 0.15m and manning roughness coefficient of
0.03 for small irrigation canal were used. So by using the following Mannings equation under
condition of most economic section of trapezoidal canal.

( B+22 zy )= y 1+ z 2

B+ 2 zy =2 y 1+ z 2

0.25+2 1 y=2 y 1+12

0.25+2 y=2 y 2

2 y 22 y=0.25

2 y ( 21 ) =0.25

2 y=0.60

y=0.3 m

Then the depth of canal water level will be 0.3m, and total height of canal will be 0.45m. Both
PIC and SIC dimensions of this scheme look smaller than others because it is planned to provide
water resource from the tubular well by farmland section. The detail information about the
designed parameter has been presented in hydraulic sheet in appendix 04 and 5

4.2.5 Water Control Structures

Water control and diversion structures are necessary to gives easy and effective control of
irrigation water on the farm. Good control will reduce the labour required to irrigation and check
erosion and water loss. The structures which are going to be installed in this scheme include
drops, diversion boxes, and turnout boxes. These structures have been selected from a list of

38
 standard drawing that is recommended to be used for irrigation development to control flow
of water in the canal and to divert water from a main canal to secondary canal and from
secondary canal to the tertiary canals.

CHAPTER FIVE

5.1 CONCLUSION AND RECOMMENDATION

5.2 CONCLUSION

The objective of this project was to design main and secondary lined irrigation canal network by
using ground water as a source of irrigation water. at Cheju Scheme which is located at Cheju
village within south eastern part of Zanzibar main Island (Unguja Island), about 30 km, south
east of Zanzibar town. The total project area is 72ha which is planned to be provided with

irrigation water by using 2 tubular wells capacity of 35 l/s to meet crop water requirement for

72ha of project area. And each tubular is expected cover the 32ha, reference being made on yield

of the existing boreholes in Cheju (average of 35 l/s ) and crop water requirement.

The proposed canals network comprises of two main canals with length of 610m and 570m
and eight secondary canals of different lengths. SC1=299m, SC2=292m, SC3=323,
SC4=282m, SC5=360m, SC6=272, SC7=343m and SC8=275m and they are located at a distance
of 150m apart. The dimensions of designed main canals and secondary canal s were looked
smaller because it planned to be irrigated by using tubular wells and according to this design, the
discharge of 35l/s for each tubular well ( 2 tubular wells) will be enough to irrigate the area of
72ha.

5.3 RECOMMENDATION
Because Cheju irrigation scheme is planned to be irrigated by using tubular wells, the farm
operation management should strictly follow the proposed water distribution schedule. The
proper proposed irrigation application in this scheme is to irrigate by shift and not for whole
scheme this is die to small discharge of boreholes.

The effort in this project has been directed to the designing of irrigation canals network only
at Cheju scheme, but in order to get effective irrigation scheme, adequate drainage systems in

39
 this scheme should be designed as a future project in this scheme. The recommendations
have been put forward in a designing of drainage canals which used to drain water from the
field and to direct that water to the supplementary water sources and the drainage water
collected within supplementary water sources will be recycled back to the scheme.
Supplementary water sources should be placed adjacent to the scheme. So that all primary
drainage canals (PDC) will be directed towards this supplementary water sources and the
drainage water collected within supplementary water sources will be recycled back to the
scheme. These supplementary sources will be devised with detention method if the
geological condition cannot allow storing water. In order to re-utilize the water from the
Supplementary water sources, it is necessary to install the pump station or pump machine.

Proper maintenance of the system after construction of irrigation infrastructure is very

essential to enable the farmers to realize benefit out of the infrastructures to be invested
throughout the designed life span of the system. Farmer shall have a time- table for
removing the sediment from the canal or whenever necessary during irrigation period as will
be planned by technical personnel.

40
REFERENCES:

Allen, R.G., M.E. Jensen, J.L. Wright and R.D. Burman. 1989. Operational Estimates of
Reference Evapotranspiration. Agronomy Journal, 81(4):650662.

Asawa, G.L. (2008). Irrigation and Water Resources Engineering..New Delhi: New Age
International(P) Limited.

Andress P. Savva, Karen Frenken, FAO 2002. Planning, Development, Monitoring and
evaluation of irrigated agriculture with farmers participation; Volume II, Harare Zimbabwe.

Bhuiyan, S. I. 1992. Water Management in Relation to Crop Production: Case study on rice.
Outlook Agric. 21(4):293299.

California Department of Water Resources, 1986, Crop Water Use in California. Sacramento.

Department of Irrigation and Drainage manual (DID MANUAL), 2009 Irrigation and
Agricultural Drainage. Malaysia

Dr B.C. Panmia and Dr Pande B.B Lal, 1992. Irrigation and Water Power Engineering. New
Delhi India

FAO 1992, Irrigation Water Management. Training Manual no 7. Canals.

Fredrick H.N and Daniel W.M., 1913. Principle of irrigation engineering New York and London

Garg S.K. (1999).Irrigation Engineering and Hydraulic Structures.14th ed. Khanna Publishers,
Delhi India

Hargreaves, G.H. and Samani, Z.A., 1985. Reference Crop Evapotranspiration from
Temperature, Applied Engineering in Agriculture, Trans. ASCE 1(2):9699.

41
Hargreaves, G.L., Hargreaves, G.H., and Riley, J.P., 1985, Irrigation Water Requirements for
Senegal River Basin. J. of Irrigation and Drainage Engineering, ASCE 111(3) 265275.

Irrigation Design Manual Volume 1, (1999), Ministry of Agriculture food security and
cooperatives, Dar es salaam, Tanzania.

James, L.G. 1988.Principles of Farm Irrigation System Design. Washington State University,

John V.R., 2004. Smallholder Irrigation Schemes-Technical design manual

John S. Scott, 1991: Dictionary of Civil Engineering. The Penguin

Kraatz D.B and Mahajan I.K small hydraulic structure- FAO, 1982. irrigation and drainage
paper 26

Madan M.D and Mimi D. S., 2009 Irrigation and Water Power Engineering. New Delhi, India.

Mays, L.W. (2005), Water Resources Engineering, John Wiley & Sons Inc., U.S.A.

Michael, A. M. 2008. Irrigation Theory and Practice; 2nd edition: Vicas Publishing House PVT
LTD.

M.H. Ali. 2011. Practices of Irrigation and On Farm Water Management. Volume 2. New York

Neitsch, S.L., J.G. Arnold, J.R. Kliniry, J.R. Wolliams. 2005. Soil and Water Assessment, Tool
Theoretical Document.

P. Novak, A.I.B. Moffat, C. Nalluri and R. Narayanan., 2007. Hydraulic Structures 4th Edition.
New York and London

Sharma R.K. and Sharma T.K., 2002. Irrigation Engineering (Including Hydrology) S.Chand and
Co Ltd. New Delhi

Stern, P., 1979, Small-Scale Irrigation, IT Publications, London

Therma, B.P.,(1981) Detail soil survey of Bumbi-Sudi,Cheju, Chechele, Machigini and Kisima
Mchanga Rice irrigation Project areas - Zanzibar and Soil study of some rice growing valleys of
Pemba In: Development of rice cultivation and Extension in Vegetable Production Zanzibar.

42
T.K.E. Meijer 1993. Design of Smallholders Irrigation Systems, Wageningen Agricultural
University

Y. Labye, M.A. Olson, A. Galand and N. Tsiourtis FAO 1988, Design and Optimization of
Irrigation Distribution Network. Irrigation and drainage Paper 44 FAO, Rome

APPENDICES
Appendix 1: Topographical survey data of project area at Cheju Irrigation Scheme
P N E Z D
1 9314996.89 540853.761 22.943 HT
2 9314805.887 541746.013 20.236 TREE
3 9314885.959 541365.473 20.231 TREE
4 9314917.99 541832.751 21.314 AY42
5 9314905.343 541852.001 21.119 AY43
6 9315037.034 541246.936 20.928 SH
7 9314909.639 541844.668 21.24 SH
8 9314909.595 541844.744 21.235 SH
9 9314952.744 541870.005 20.936 SH
10 9314866.469 541819.442 20.937 SH
11 9314892.511 541780.418 21.064 SH
12 9314976.136 541835.252 21.064 SH
13 9314934.328 541807.827 21.365 SH
14 9314887.498 541879.242 20.87 SH
15 9314845.674 541851.842 20.57 SH
16 9314929.312 541906.645 20.567 SH
17 9314887.494 541879.238 20.568 SH
18 9314893.716 541852.496 21.848 TREE
19 9314862.373 541917.533 20.723 SH
20 9314904.227 541944.963 20.323 SH
21 9314820.561 541890.16 20.323 SH
22 9314798.873 541923.524 20.266 SH
23 9314882.541 541978.233 20.267 SH
24 9314840.732 541950.898 20.666 SH
25 9314819.922 541982.849 19.866 SH
26 9314861.788 542010.182 19.566 SH
27 9314778.048 541955.522 19.468 SH
28 9314750.361 541997.701 19.744 SH
29 9314834.04 542052.454 20.445 SH
30 9314792.148 542025.161 20.146 SH
31 9314769.149 542060.345 19.393 SH

43
32 9314825.178 542123.762 17.013 SH
33 9314810.999 542087.699 18.993 SH
34 9314727.3 542032.977 18.993 SH
35 9315052.102 541628.456 20.708 SH
36 9315061.835 541671.241 20.421 SH
37 9315052.102 541628.456 20.708 SH
38 9315061.835 541671.241 20.421 SH
39 9315039.637 541708.349 20.629 SH
40 9315014.25 541620.63 20.981 SH
41 9315021.232 541626.269 21.187 SH
42 9315028.94 541663.76 20.579 SH
43 9315011.152 541639.098 21.013 SH
44 9315006.315 541647.139 20.969 SH
45 9315008.51 541694.865 20.904 SH
46 9314838.497 541825.164 20.176 SH
47 9314887.498 541879.242 20.87 SH
48 9314712.58 542146.28 20.504 3L
49 9315579.803 541021.968 20.588 SH
50 9315481.146 541005.633 19.588 SH
51 9315530.482 541013.761 20.188 SH
52 9315523.468 541056.211 20.064 SH
53 9315474.133 541048.083 19.563 SH
54 9315572.791 541064.409 19.363 SH
55 9315562.767 541125.094 19.251 SH
56 9315464.102 541108.806 19.45 SH
57 9315513.438 541116.943 19.95 SH
58 9315507.097 541155.449 19.923 SH
59 9315457.76 541147.338 19.226 SH
60 9315556.425 541163.616 19.426 SH
61 9315547.241 541219.235 19.391 SH
62 9315448.577 541202.947 20.293 SH
63 9315497.905 541211.13 19.893 SH
64 9315491.325 541251.102 19.865 SH
65 9315441.978 541242.952 20.364 SH
66 9315540.636 541259.23 19.863 SH
67 9315538.166 541274.028 19.799 SH
68 9315532.926 541306.157 19.326 SH
69 9315434.262 541289.875 20.326 SH
70 9315483.598 541298.002 19.825 SH
71 9315477.149 541337.259 20.189 SH
72 9315427.817 541329.112 20.791 SH
73 9315526.485 541345.377 19.591 SH
74 9315468.996 541386.035 20.54 SH

44
 75 9315419.664 541377.88 21.139 SH
76 9315464.717 541413.997 20.46 SH
77 9315415.378 541405.878 20.96 SH
78 9315514.05 541422.123 19.86 SH
79 9315507.674 541460.981 19.941 SH
80 9315408.993 541444.767 20.947 SH
81 9315458.334 541452.877 20.549 SH
82 9315464.755 541414.003 20.512 C2L1
83 9315452.87 541487.036 20.857 C2L2
84 9315453.009 541486.025 20.711 SH
85 9315403.673 541477.892 21.299 SH
86 9315502.348 541494.117 19.999 SH
87 9315452.374 541488.799 20.922 C2L3
88 9315452.365 541488.797 20.922 SH
89 9315464.756 541413.997 20.488 SH
90 9315441.744 541553.149 20.983 SH
91 9315491.075 541561.3 20.583 SH
92 9315392.406 541545.005 20.383 SH
93 9315385.926 541584.242 20.162 SH
94 9315484.586 541600.556 20.261 SH
95 9315435.257 541592.396 20.76 SH
96 9315427.771 541637.524 20.37 SH
97 9315477.096 541645.715 19.97 SH
98 9315378.434 541629.405 20.87 SH
99 9315418.867 541691.634 19.549 SH
100 9315369.531 541683.494 19.149 SH
101 9315468.194 541699.79 18.849 SH
102 9315462.64 541733.989 18.303 SH
103 9315363.97 541717.728 19.402 SH
104 9315413.318 541725.808 19.004 SH
105 9315428.133 541637.253 20.431 C2L4
106 9315423.457 541745.884 20.004 C2L5
107 9315423.457 541745.879 20.006 SH
108 9315427.578 541637.087 20.434 CL26
109 9315427.678 541637.134 20.402 SH
110 9315427.579 541637.051 20.402 SH
111 9315405.464 541835.537 17.812 C2L7
112 9315405.473 541835.478 17.812 SH
113 9315423.458 541745.879 19.962 SH
114 9315414.541 541777.221 19.548 SH
115 9315473.811 541786.487 18.545 SH
116 9315429.345 541779.572 19.344 SH
117 9315365.882 541764.663 20.027 SH

45
118 9315405.066 541837.613 17.687 SH
119 9315442.853 541846.395 18.69 SH
120 9315398.156 541871.589 15.744 SH
121 9315436.022 541876.962 17.486 SH
122 9315346.37 541847.692 17.25 SH
123 9315384.323 541839.407 18.344 SH
124 9315387.777 541870.24 17.698 SH
125 9315333.204 541847.868 17.815 SH
126 9315374.462 541884.492 17.932 SH
127 9315355.427 541888.411 17.698 SH
128 9315300.474 541849.715 18.793 SH
129 9315339.895 541897.607 17.719 SH
130 9315239.249 541853.291 18.27 SH
131 9315296.709 541907.579 18.157 SH
132 9315247.365 541897.208 18.821 SH
133 9315246.281 541930.325 17.995 SH
134 9315263.76 541957.773 17.058 SH
135 9315245.205 541949.597 17.302 SH
136 9315284.477 541955.244 17.88 SH
137 9315331.62 541950.26 17.111 SH
138 9315348.775 541960.405 18.905 SH
139 9315367.282 541949.344 18.589 SH
140 9315377.814 541973.427 19.734 SH
141 9315328.796 541963.563 18.535 SH
142 9315335.472 541930.311 19.705 SH
143 9315384.496 541940.148 19.908 SH
144 9315377.851 541973.382 19.723 SH
145 9315361.656 541967.657 19.239 SH
146 9315409.126 541983.365 18.24 SH
147 9315384.419 542052.212 19.53 SH
148 9315289.773 542019.966 18.332 SH
149 9315242.433 542003.757 17.731 SH
150 9315337.098 542036.046 17.733 SH
151 9315337.096 542036.044 18.934 SH
152 9315326.282 542074.837 18.339 SH
153 9315231.35 542043.431 18.939 SH
154 9315278.81 542059.162 18.536 SH
155 9315373.751 542090.567 18.938 SH
156 9315316.585 542104.051 19.362 SH
157 9315363.982 542119.758 18.762 SH
158 9315387.635 541003.778 21.437 SH
159 9315477.824 541032.926 20.274 SH
160 9315443.251 541021.065 20.937 SH

46
161 9315449.059 541030.899 20.452 TREE
162 9315418.671 541058.515 20.72 SH
163 9315447.834 541065.127 20.332 SH
164 9315399.744 541053.685 20.693 SH
165 9315430.551 541100.802 20.133 SH
166 9315398.71 541089.356 20.418 SH
167 9315403.052 541101.299 20.491 SH
168 9315426.223 541130.546 20.263 SH
169 9315419.062 541149.884 20.46 SH
170 9315377.132 541122.639 20.164 SH
171 9315355.952 541154.993 20.365 SH
172 9315386.628 541084.932 20.473 TREE
173 9315356.037 541155.036 20.367 SH
174 9315333.05 541190.554 20.641 SH
175 9315318.234 541148.414 20.51 SH
176 9315365.344 541201.953 20.043 SH
177 9315314.287 541219.24 20.344 SH
178 9315277.524 541198.154 20.533 SH
179 9315288.077 541272.508 20.3 AY11
180 9315266.231 541301.118 20.707 AY12
181 9315267.502 541301.015 20.712 TREE
182 9315301.258 541220.777 21.302 TREE
183 9315375.208 541155.639 20.291 MBUYUTREE
184 9315303.813 541147.908 20.839 SH
185 9315243.731 541196.024 20.716 SH
186 9315229.734 541162.693 20.43 SH
187 9315293.944 541079.76 21.315 SH
188 9315086.535 541033.576 21.588 SH
189 9315153.08 541159.769 21.647 SH
190 9315163.85 541210.336 20.854 TREE
191 9315127.394 541073.582 20.8 SH
192 9315113.628 541205.873 20.153 SH
193 9315150.584 541199.82 20.896 SH
194 9315092.927 541236.981 20.236 SH
195 9315132.718 541236.174 21.1 SH
196 9315236.486 541218.653 21.154 SH
197 9315122.463 541107.191 21.081 SH
198 9315106.629 541258.481 21.317 SH
199 9315090.945 541149.398 21.274 SH
200 9315083.618 541297.993 21.162 SH
201 9315054.982 541470.176 21.301 SH
202 9315071.077 541263.913 21.105 SH
203 9315093.517 541356.712 20.332 SH

47
204 9315112.311 541338.015 21.204 SH
205 9315063.79 541292.814 20.952 SH
206 9315073.618 541352.762 21.098 SH
207 9315017.509 541280.417 19.963 TREE
208 9315293.125 541252.064 20.18 SH
209 9315251.631 541242.547 20.041 SH
210 9315334.486 541228.682 20.178 SH
211 9315319.487 541260.693 20.07 SH
212 9315235.257 541277.614 20.09 SH
213 9315095.341 541467.207 20.103 SH
214 9315270.596 541287.027 20.092 SH
215 9315311.711 541289.982 19.926 SH
216 9315249.715 541319.325 20.107 SH
217 9315209.408 541316.591 20.284 SH
218 9315198.086 541344.697 20.006 SH
219 9315297.783 541339.275 20.048 SH
220 9315227.622 541353.613 20.196 SH
221 9315284.189 541375.424 20.542 TREE
222 9315279.847 541374.39 19.969 SH
223 9315206.95 541385.726 20.151 SH
224 9315169.831 541387.903 20.086 SH
225 9315251.79 541405.283 19.999 SH
226 9315148.598 541413.002 20.127 SH
227 9315185.994 541418.19 20.117 SH
228 9315228.125 541438.983 20.031 SH
229 9315165.069 541450.696 20.089 SH
230 9315205.211 541446.718 20.548 TREE
231 9315204.606 541464.011 20.384 SH
232 9315124.108 541447.815 20.121 SH
233 9315134.216 541498.82 20.074 SH
234 9315180.05 541491.484 19.994 SH
235 9315142.128 541486.219 20.045 SH
236 9315162.034 541530.603 20.058 SH
237 9315110.529 541500.523 20.234 TREE
238 9315120.427 541520.134 20.234 SH
239 9315080.852 541514.654 20.457 SH
240 9315132.302 541556.449 21.02 TREE
241 9315131.248 541568.475 20.266 SH
242 9315065.114 541540.437 20.479 SH
243 9315097.235 541556.322 20.238 SH
244 9315070.248 541606.664 20.418 SH
245 9315105.979 541603.678 20.371 SH
246 9315073.159 541593.778 20.351 SH

48
 247 9315070.458 541598.268 20.935 TREE
248 9315085.876 541647.638 20.575 SH
249 9315052.102 541628.456 20.708 SH
250 9315061.835 541671.241 20.421 SH
251 9315004.144 541620.642 21.201 SH
252 9315028.94 541663.76 20.579 SH
253 9315014.25 541620.63 20.981 SH
254 9315021.232 541626.269 21.187 SH
255 9315011.152 541639.098 21.013 SH
256 9315006.315 541647.139 20.969 SH
257 9315008.51 541694.865 20.904 SH
258 9315039.637 541708.349 20.629 SH
259 9314976.706 541689.789 21.048 SH

Appendix 2a Mean Recorded Rainfall (mm) (2004~2013)

Annual
Year Jan Feb Mar Apr May Jun July Aug Sep Oct Nov Dec
rainfall

49
 2004 165 257.6 204.9 549.2 31.6 53 22.8 22.3 20.8 177.3 238.6 190.7 1933.8
2005 63.6 5.4 216.6 633.1 339.1 33.2 37 48.5 8 4.1 133.1 92.4 1614.1
184.
2006 28.1 243.3 343.2 185 195.5 32.5 29.8 60.4 96.2 259.1 362.6 2020.3
6
2007 41 25.2 387.6 271.5 527.4 31.6 11.7 47.9 38.9 113.1 213.7 527.4 2237
2008 74.8 8.2 124.5 584 115.7 64.6 12.3 51.2 13.2 90.2 242.6 63.6 1444.9
106.
2009 126.9 154.1 201.7 111.8 95.4 9.3 24.2 2.1 61.8 194.9 140.2 1228.6
2
2010 46.6 21.1 223.3 252.7 193.8 48.1 0.3 20 43.4 86.6 169.1 102.4 1207.4
147.
2011 48.8 1.7 51.9 463.4 262.8 38.3 0.7 30.2 218 393.2 92.1 1748.5
4
2012 22.3 29 150.5 178.4 121 15.2 2.3 28.5 68.1 8.6 269.4 137 1030.3
2013 61.4 0.1 381.3 123.9 99.7 26.3 5.7 17.7 12.2 79.8 224.3 49.1 1081.5
81.4 198.7 41.4
Average 3
50.33 213.8 360.11
9
60.12 13.46 32.03
5
93.57 233.8 175.75 1554.64

Source: Tanzania Meteorological agency, Zanzibar office

Appendix 2b Mean Relative Humidity (%) (2004~2013)

Section Year Jan Feb Mar Apr May Jun July Aug Sep Oct Nov Dec
2004 79 83 81 83 75 73 73 73 75 78 83 81
2005 69 67 73 76 73 63 59 57 65 74 83 78
2006 77 78 85 86 86 83 81 81 79 82 88 85
Mean 2007 78 77 83 87 86 81 79 81 78 80 83 82
Relative 2008 80 79 82 89 86 82 80 81 81 81 85 81
Humidity
at 3 p.m 2009 77 83 84 85 80 84 80 80 78 79 83 84
2010 80 80 82 88 85 86 77 76 77 78 83 81
2011 78 76 79 86 86 84 76 77 79 81 87 85
2012 77 76 82 83 86 81 78 78 78 79 84 83
2013 83 74 85 84 82 72 77 77 77 78 83 81
Average 77.8 77.3 81.6 84.7 82.5 78.9 76 76.1 76.7 79 84.2 82.1
Source: Tanzania Meteorological agency, Zanzibar office

Appendix 2cMean Maximum and Minimum Temperature (C) (2004~2013)

50
 Temperature Year Jan Feb Mar Apr May Jun July Aug Sep Oct Nov Dec
2004 32.6 31.1 31.9 30.1 30.5 29.3 29 29.6 30.3 30.6 30.6 31.3
Mean Max. 2005 32.7 32.4 32.7 30.9 29.4 29.3 28.9 28.7 30.3 31.5 30.8 32.2
Temperature 2006 32.8 33.4 31.5 30.5 29.4 28.3 28.6 29.1 30 30.5 30.1 31.1
2007 32.6 33.8 32.6 30.7 29 29.2 29.3 29.5 31 31 30.8 29.5
2008 32.4 32.3 32.5 29.1 29.6 28.5 28.8 29.2 30.4 31.7 31.1 32.2
2009 33.2 32 32.2 31.1 30.3 29.8 29.1 30.1 31.3 31.7 32.1 32
2010 32 32.3 33.3 31 30.6 29.9 29.9 30 30.4 31.6 31.1 32.1
2011 33.1 33.9 33.2 31.1 30.2 29.8 29.8 29.9 31.6 31.1 30.6 32.4
2012 33 33.2 32.1 30.9 29.7 29.5 29.7 30.1 30.7 31.5 31.7 32.2
2013 32.5 34 31.7 31.1 30 29.6 29.4 29.6 30.7 31.2 31.1 32.3
Average 32.69 32.84 32.37 30.65 29.87 29.32 29.25 29.58 30.67 31.24 31 31.73
2004 24.8 23.9 24.4 24.2 24.3 23 21.7 20.2 20.7 22.6 23.5 23.9
2005 24.1 24.3 24.9 25 24 22.7 22.3 20.2 20.5 21.4 22.6 24
Mean Min. 2006 24.4 24.4 24.7 24.6 23.5 22.8 21.8 21 21.9 22.5 23.8 24.2
Temperature 2007 25.1 24.7 24.7 24 24 22.8 22.2 21.7 21.6 22 22.5 24
2008 24.4 23.9 24.5 24 23.3 22.1 22 21.5 20.8 22.4 23.3 24
2009 24.2 24.3 23.9 24.6 24.1 22.9 22.1 21.2 20.9 22.5 23.4 24.1
2010 24.1 24.4 25.1 24.9 24.6 23.9 22.5 22 21.4 21.8 23.1 23.8
2011 24.3 24.6 24.4 24.6 23.9 23.2 22.7 21.8 22.5 22.8 23.5 24.5
2012 25 24.2 24.3 24.7 23 22.9 22.4 21.6 21.3 22.7 23.6 24.5
2013 25.1 25.3 25.3 25.3 24.3 23.2 22.4 21.2 21.6 22.8 23.6 24.8
Average 24.55 24.4 24.62 24.59 23.9 22.95 22.21 21.24 21.32 22.35 23.29 24.18
Source: Tanzania Meteorological agency, Zanzibar office
Appendix 2d Monthly Evaporation(mm) (2004~2013)
Year JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
2004 148.6 123.5 138.4 129 139.1 138.5 133 141.2 139.3 144.5 123.4 131.6
2005 165.6 144.4 126.9 124.7 107 111.7 125 113.5 139 159.1 111.7 158.9
2006 151.6 136.1 119.8 104.2 104.5 104.5 116 121.8 142.4 140.2 98.6 115.4
2007 187.5 170.7 132.4 105.5 106.2 128.1 151.7 141.9 176.9 163.2 131.4 144.7
2008 160.3 163.2 157 87.2 124.7 129.1 132.3 141.7 141.7 159.6 114.6 97.2
2009 199.4 128.5 132.6 133.3 123.9 131.4 153.8 172.7 190.6 189.8 154.3 115
2010 165.6 171.6 150.8 111.4 115.1 127.1 169.8 167.5 156.9 167.1 113.1 163.1
2011 188.3 180.2 162.9 107 118 134.3 171.2 179.2 184 158.6 120.2 157.1
2012 214.8 199 137.3 128.2 116.5 150.2 175.8 174 173.6 181.1 124 139.5
2013 164.8 158.9 147 121.9 134.2 151.3 152.7 147.3 167.6 167.9 109.5 157.6
Average 174.65 157.61 140.51 115.24 118.92 130.62 148.13 150.08 161.2 163.11 120.08 138.01
Source: Tanzania Meteorological agency, Zanzibar office

Appendix 2e Monthly averages of Wind direction and speed (2004~2013)

JANUARY FEBRUARY MARCH APRIL
Year
09 00 am 03 00 pm 09 00 am 03 00 pm 09 00 am 03 00 pm 09 00 am 03 00 pm

51
 Sp
Dir Spd Dir Spd Dir Spd Dir Spd Dir Dir Spd Dir Spd Dir Spd
d
20
2004 50 10 090 14 010 06 060 08 360 06 100 09 06 150 09
0
19
350 12 030 15 360 10 020 15 190 08 180 10 06 130 12
2005 0
18
360 08 050 10 360 06 040 10 330 06 150 07 06 150 10
2006 0
21
330 10 030 15 340 10 020 15 350 06 150 10 08 150 12
2007 0
21
330 09 360 11 340 08 020 10 180 05 120 10 06 150 09
2008 0
21
360 09 020 10 360 05 060 09 350 04 030 09 07 130 10
2009 0
21
360 10 20 12 360 09 030 09 350 06 210 10 07 120 10
2010 0
21
360 08 030 10 360 07 330 10 180 06 130 07 06 150 09
2011 0
21
360 13 030 14 360 11 030 11 360 07 270 07 09 180 11
2012 0
21
030 09 030 12 360 09 060 12 220 06 160 10 07 160 10
2013 0
20
Average 289 9.8 69 12.3 321 8.1 67 10.9 287 6 150 8.9 4 6.8 147 10.2
MAY JUNE JULY AUGUST
Year 09 00 am 03 00 pm 09 00 am 03 00 pm 09 00 am 03 00 pm 09 00 am 03 00 pm
Sp
Dir Spd Dir Spd Dir Spd Dir Spd Dir Spd Dir Spd Dir Dir Spd
d
2004 210 7 130 11 200 9 150 15 190 9 120 15 210 6 120 12
2005 210 10 150 12 210 10 150 15 210 8 120 15 180 8 120 12
2006 180 7 150 11 180 9 150 11 210 6 120 13 210 5 130 12
2007 180 8 150 15 210 8 150 12 180 10 120 13 220 8 120 14
2008 180 6 150 10 210 5 140 8 210 8 130 12 180 8 120 14
2009 210 7 150 11 210 7 120 13 180 8 140 15 180 7 130 15
2010 210 8 140 11 200 8 140 13 200 8 130 15 210 10 120 15
2011 210 7 150 11 180 7 120 12 180 9 120 14 210 8 130 15
2012 210 7 180 12 210 8 150 14 240 8 120 16 210 7 120 14
2013 210 8 170 12 210 9 150 16 210 8 120 16 210 7 150 14
Average 201 7.5 152 11.6 202 8 142 12.9 201 8.2 124 14.4 202 7.4 126 13.7
SEPTEMBER OCTOBER NOVEMBER DECEMBER
Year 09 00 am 03 00 pm 09 00 am 03 00 pm 09 00 am 03 00 pm 09 00 am 03 00 pm
Sp
Dir Spd Dir Spd Dir Spd Dir Spd Dir Spd Dir Spd Dir Dir Spd
d
35
2004
190 6 120 13 180 7 150 10 140 7 130 9 0 8 30 9
36
2005
210 8 120 14 140 10 120 15 60 5 250 10 0 12 50 12
35
2006
210 9 130 15 180 8 160 12 210 6 90 7 0 7 30 8
33
2007
180 8 120 14 210 8 120 12 30 6 160 8 0 9 30 10
2008 180 7 90 12 160 7 150 10 30 6 150 8 36 8 30 10

52
 0
2009 180 7 130 14 130 8 130 13 30 6 120 7 80 6 120 7
36
2010
180 8 120 14 210 7 120 10 90 6 90 7 0 7 60 9
2011 180 9 150 14 150 8 150 11 90 10 150 11 30 8 60 9
2012 240 7 120 13 150 8 150 12 90 6 130 8 10 6 90 7
35
2013
150 8 140 14 160 8 140 12 30 7 120 9 0 8 60 9
25
Average
190 7.7 124 13.7 167 7.9 139 11.7 80 6.5 139 8.4 8 7.9 56 9
Source: Tanzania Meteorological agency, Zanzibar office NOTE
a. All times quoted are local times
b. Wind direction in degrees from True North and speeds quoted in knots (kt)
c. 1 knot = 1.86 kilometer per hour

Appendix 2f Mean monthly sunshine hours (hrs)

Au
Section Year Jan Feb Mar Apr May Jun July Sep Oct Nov Dec
g
2004 8.6 9.1 7.3 6.2 7.4 8.4 8.9 8.2 8.6 9.6 8.4 8.1
2005 9.5 7.9 7.9 7.1 6.7 8.4 7.6 7.8 8.4 8.6 8.2 9.1
2006 8.5 8.7 8.1 5.4 7.3 7.3 8.6 8.4 9.1 8.5 8.3 8.7
Mean
2007 9.2 9.2 7.6 6.8 6.1 8 8.2 7.6 8.9 9.5 8.6 8.5
monthly
2008 7.3 7.3 8.3 4.5 7.8 7.9 7 7.8 8.2 8.8 7.9 9.2
sunshine
2009 9.4 7.4 7.3 6.8 7.2 7.7 7.4 8.3 9.4 8.6 8.5 8.3
hours
2010 7.9 9.5 7.5 6.8 7.5 8.1 8.6 8.4 8.5 9.6 8.7 8.6
(hrs)
2011 9.3 8.6 7.9 6.3 6.7 8 8.2 8.5 8.1 8.2 6.9 8.1
2012 8.3 9.1 7.5 5.9 6.4 8.9 9 9.2 8.6 9.5 8.5 9.2
2013 8.1 8.6 7.3 6.4 6.8 8.4 7.3 8.8 8.4 9.3 7.8 8.7
6.2
Average
8.61 8.54 7.67 2 6.99 8.11 8.08 8.3 8.62 9.02 8.18 8.65
Source: Tanzania Meteorological agency, Zanzibar office

53
Appendix 3a Particle size determination wet sieving (Sample 1)
TECHNICAL COLLEGE ARUSHA
SOILS & BITUMEN LABORATORY
SIEVE ANALYSIS OF SOIL

Project : DESIGN OF IRRIGATION CANALS NETWORK

Description of Soil. CLAY SOIL SAMPLE 1
Location: CHEJU IRRIGATION SCHEME
Test Performed By:B120021 Date Of test: 11/04/2015
Sample Size (ASTM D 1140-54)
Norminal diameter of Approximate minimum
largest particle weight of Sample (gm)
No10 Sieve (2mm) 200
No4Sieve(4.75mm) 500
inch Sieve(9mm) 1000.07
Sieve Particle size Cummulative mass Cummulative %
No (mm) retained (gms) % Retained Passsing
5 125
4.24 106
3" 90
3" 75
2" 63
2" 50
1" 37.5
1" 31.5
1" 25
" 19 0.00 0.00 100.00
" 12.5 0.00 0.00 100.00
3/8" 9.5 0.00 0.00 100.00
" 6.3 2.57 0.26 99.74
4 4.75 4.37 0.44 99.56
6 3.35 7.31 0.73 99.27
8 2.36 10.60 1.06 98.94
10 2.00 12.33 1.23 98.77
16 1.180 17.01 1.70 98.30
20 0.85 18.87 1.89 98.11

54
 30 0.600 21.25 2.12 97.88
40 0.425 26.93 2.69 97.31
50 0.300 35.31 3.53 96.47
70 0.212 48.36 4.83 95.17
100 0.150 88.42 8.84 91.16
200 0.075 187.36 18.73 81.27
GM
GC

TECHNICAL COLLEGE ARUSHA

SOILS & BITUMEN LABORATORY
SIEVE ANALYSIS OF SOIL

Project : DESIGN OF IRRIGATION CANALS NETWORK

Description of Soil. CLAY SOIL SAMPLE 1
Location: CHEJU IRRIGATION SCHEME
Test Performed By:B120021 Date Of test: 11/04/2015

55
 Particle Size Distribution Curve

100

90

80

70

60

50
%Passing (F%Finer)

40

30

20

10

0
0.0 0.1 1.0 10.0 100.0

Particle Size (mm)

56
Appendix 3bParticle size determination wet sieving (sample 2)
TECHNICAL COLLEGE ARUSHA
SOILS & BITUMEN LABORATORY
SIEVE ANALYSIS OF SOIL

Project : DESIGN OF IRRIGATION CANALS NETWORK

Description of Soil. CLAY SOIL SAMPLE 2 (Depth: 30cm - 60cm)
Location: CHEJU IRRIGATION SCHEME
Test Performed By:B120021 Date Of test: 11/04/2015
Sample Size (ASTM D 1140-54)
Norminal diameter of largest particle Approximate minimum weight of Sample (gm)
No10 Sieve (2mm) 200
No4 Sieve (4.75mm) 500
inch Sieve (19mm) 1000.05
Sieve Cummulative mass Cummulative %
No Particle size (mm) retained (gms) Retained % Passsing
5 125
4.24 106
3" 90
3" 75
2" 63
2" 50
1" 37.5
1" 31.5
1" 25
" 19 0.00 0.00 100.00
" 12.5 0.00 0.00 100.00
3/8" 9.5 7.34 0.73 99.27
" 6.3 18.03 1.80 98.20
4 4.75 34.06 3.41 96.59
6 3.35 59.17 5.92 94.08
8 2.36 85.97 8.60 91.40
10 2.00 94.66 9.47 90.53
16 1.180 111.76 11.18 88.82
20 0.85 117.47 11.75 88.25

57
 30 0.600 121.86 12.19 87.81
40 0.425 128.48 12.85 87.15
50 0.300 134.80 13.48 86.52
70 0.212 142.37 14.24 85.76
100 0.150 160.47 16.05 83.95
200 0.075 197.94 19.79 80.21
GM
GC

TECHNICAL COLLEGE ARUSHA

SOILS & BITUMEN LABORATORY
SIEVE ANALYSIS OF SOIL

Project : DESIGN OF IRRIGATION CANALS NETWORK

Description of Soil. CLAY SOIL SAMPLE 2 (Depth: 30cm - 60cm)
Location: CHEJU IRRIGATION SCHEME
Test Performed By:B120021 Date Of test: 11/04/2015

58
 Particle Size Distribution Curve

100

90

80

70

60

50
%Passing (F%Finer)

40

30

20

10

0
0.0 0.1 1.0 10.0 100.0

Particle Size (mm)

59
Appendix 3b Atterberg limits determination (Sample 1)
TECHNICAL COLLEGE ARUSHA
SOILS & BITUMEN LABORATORY
ATTERBERG LIMITS DETERMINATION
(CASSAGRANDE METHOD - ASTM D.420 / AASHTO T. 86 )

Project : DESIGN OF IRRIGATION CANALS NETWORK

Description of Soil: CLAY SOIL SAMPLE 1
Location: CHEJU IRRIGATION SCHEME
Test Performed By:B120021 Date Of test: 11/04/2015

TEST METHOD: ASTM D.420 / AASHTO T. 86 / CML 2000 1.3 & 1.4
Determination of Liquid limit & Plastic limit
Type of test LIQUID LIMIT PLASTIC LIMIT
Test No 1 2 3 4 1 2 Averag
Number of Blows 33 26 22 19
Moisture Can No 1 B1 44B 55 4 18
Mass of can +Wet soil 26.19 25.90 26.37 24.37 16.55 17.56
Mass of can + dry soil 21.40 21.12 21.42 20.05 15.57 16.42
Mass of can (gms) 10.82 10.77 10.81 10.83 10.69 10.65
Mass of Water (gms) 4.79 4.78 4.95 4.32 0.98 1.14
Mass of dry soil (gms) 10.58 10.35 10.61 9.22 4.88 5.77
water content(%) 45.27 46.18 46.65 46.85 20.08 19.76 19.92

60
 DETERMINATIO N O F LIQ UID

24

22

20

18
Water Content (%)

16

14

12
1 10 100

Number of Blows

T
E
DO
A
IN
M
R
D
U
Q
L
F
T
IM
(S
A
C E
D
N
R
G
)
O
H
T
M

n
o
rc
te
a
W
)
(%

ro
e
b
m
u
N
s
lw
fB

Sample Preparation
(a) As received V
(b) Air Dried C
(c) Washed on
0.425mm
0
(iii) Oven dried C
(iv) Unknown

Proportion of material passing

0.425m sieve % 97.31

Liquid (%): 46.25

Plastic Limit(%): 19.92
Plasticity index (%): 26.33
Linear Shrinkage (%): 14.29

Determination of Linear Shrinkage & Shrinkage Product

61
 Initail Length of
length of Oven dry Change % Passing
specimen Specimen in length % Linear 0.425mm
Mould No (mm) (mm) (mm) shrinkage Sieve Shrinkage product
1 140 120 20 14.29 97.31 1390.1
Appendix 3c Atterberg limits determination (Sample 2)
TECHNICAL COLLEGE ARUSHA
SOILS & BITUMEN LABORATORY
ATTERBERG LIMITS DETERMINATION
(CASSAGRANDE METHOD - ASTM D.420 / AASHTO T. 86 )

Project : DESIGN OF IRRIGATION CANALS NETWORK

Description of Soil. CLAY SOIL SAMPLE 2
Location: CHEJU IRRIGATION SCHEME
Test Performed By:B120021 Date Of test: 11/04/2015

TEST METHOD: ASTM D.420 / AASHTO T. 86 / CML 2000 1.3 & 1.4
Determination of Liquid limit & Plastic limit
Type of test LIQUID LIMIT PLASTIC LIMIT
Test No 1 2 3 4 1 2 Averag
Number of Blows 33 28 24 18
Moisture Can No K Y2 Y3 544 13 60
Mass of can +Wet soil 19.55 18.48 19.17 25.31 14.17 13.97
Mass of can + dry soil 15.96 15.29 15.64 19.19 13.42 13.23
Mass of can (gms) 10.74 10.73 10.72 10.78 10.70 10.63
Mass of Water (gms) 3.59 3.19 3.53 6.12 0.75 0.74
Mass of dry soil (gms) 5.22 4.56 4.92 8.41 2.72 2.60
water content(%) 68.77 69.96 71.75 72.77 27.57 28.46 28.02

DETERMINATIO N O F LIQ UID

24

22

20

18
Water Content (%)

16

14

12
1 10 100

Number of Blows

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Sample Preparation
(a) As received V
(b) Air Dried C
(c) Washed on
0.425mm
0
(iii) Oven dried C
(iv) Unknown

Proportion of material passing

0.425m sieve % 87.15

Liquid (%): 71.00

Plastic Limit (%): 28.02
Plasticity index (%): 42.98
Linear Shrinkage (%): 15.00

Determination of Linear Shrinkage & Shrinkage Product

Length of
Initail length Oven dry Change % Passing
of specimen Specimen in length % Linear 0.425mm
Mould No (mm) (mm) (mm) shrinkage Sieve Shrinkage product
5 140 119 21 15.00 87.15 1307.3

Appendix 3d Specicific Gravity Test (Sample 1)

ARUSHA TECHNICAL COLLEGE
SOILS & BITUMEN LABORATORY
SPECICIFIC GRAVITY TEST

Project : DESIGN OF IRRIGATION CANALS NETWORK

Description of Soil: CLAY SOIL Sample 1
Location: CHEJU IRRIGATION SCHEME
Test Performed By:B120021 Date Of test: 11/04/2015

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Test No 1 2 3
Pycnometer No 5 10 12
Volume of Pycnometer at 25C 50 50 50
Mass of empty Pycnometer (gm) 29.02 26.70 26.30
Method of air removal Vaccum pump
Mass of Pycnometer + water (gm) 79.03 76.73 76.37
Temperature C 22 22 22
Mass of Pycnometer + water + soil (gm) 85.07 82.73 82.45
Evaporating dish No 21 21 21
Mass of evaporating dish (gm) 10.62 10.62 10.62
Mass of evaporating dish + dry soil (gm) 20.62 20.62 20.62
Mass of oven dry soil (gm) 10.00 10.00 10.00
Mass of water equal to the volume of soil solids(gm) 3.960 4.000 3.920
Temperature correction factor 1.0007 1.0007 1.0007
Specific gravity of Soil solids 2.527 2.502 2.553

Temperature correction factor = Density of water at a particular temperature/Density of water at 25C

Specific gravity of Soil solids is = 2.527

Appendix 3e Specicific Gravity Test (Sample 2)

ARUSHA TECHNICAL COLLEGE

SOILS & BITUMEN LABORATORY
SPECICIFIC GRAVITY TEST

Project : DESIGN OF IRRIGATION CANALS NETWORK

Description of Soil: CLAY SOIL Sample 2
Location: CHEJU IRRIGATION SCHEME
Test Performed By:B120021 Date Of test: 11/04/2015

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Test No 1 2 3
Pycnometer No 7 85 46
Volume of Pycnometer at 25C 25 25 25
Mass of empty Pycnometer (gm) 19.73 20.09 19.64
Method of air removal Vaccum pump
Mass of Pycnometer + water (gm) 44.68 44.89 44.44
Temperature C 22 22 22
Mass of Pycnometer + water + soil (gm) 47.94 47.79 47.50
Evaporating dish No 22 22 22
Mass of evaporating dish (gm) 10.62 10.62 10.62
Mass of evaporating dish + dry soil (gm) 15.62 15.62 15.62
Mass of oven dry soil (gm) 5.00 5.00 5.00
Mass of water wqual to the volume of soil solids(gm) 1.740 2.100 1.940
Temperature correction factor 1.0007 1.0007 1.0007
Specific gravity of Soil solids 2.876 2.383 2.579

Temperature correction factor = Density of water at a particular temperature/Density of water at 25C

Specific gravity of Soil solids is = 2.612

Appendix 3f Permeability Test (Sample 1)

TECHNICAL COLLEGE ARUSHA
SOILS & BITUMEN LABORATORY
PERMEABILITY TEST
(FALLING HEAD PERMEAMETER)
Project : DESIGN OF IRRIGATION CANALS NETWORK
Description of Soil: Sample 1
Location: CHEJU IRRIGATION SCHEME
Test Performed By:B120021 Date Of test: 13/04/2015

Basic Data
A: Diameter of Stand Pipe (mm) 9.00

65
B: Cross Section area of Stand Pipe (mm2) 63.6700
C: Diameter of Permeameter Cell (mm) 70.1000
D: Cross section area of Permeameter (mm2) 3859.4500
E: Length of Sample (mm) 45.1000
F: Volume of Permeameter Cell (cc) 174.0600
G: Average test temperature (C) 22
H: Specific gravity of Soil Solids 2.572
Determination of Moisture Content at the end of the test
I. Test No 1
J. Moisture Can No C-2
K. Mass of can +Wet soil 181.94
L. Mass of can + dry soil 156.06
M. Mass of can (gms) 54.06
N. Mass of Water (gms) 25.88
O. Mass of dry soil (gms) 102.00
P. Water content (%) 25.37
Determination of Density of the test soil sample
Q: Test No 1
R: Mass of Cell +Wet soil + Filter paper (gm) 490.72
S: Mass of Cell (gm) 168.73
T: Mass of filter paper (gm) 0.8
U: Mass of wet soil (gms) 321.19
V: Bulk density (gm/cc) 1.845
W: Dry density of soil (gm/cm) 1.472
Porosity and Void ratio of the soil sample
X: Void ratio of the soil Sample = (H-W)/W 0.747
Y: Porosity of Soil Sample = X/(1+X) 0.428
Coefficient of Permeability
1: Test No 1 Date
2: Initial Head of water in stand pipe(cm) h1 35.5 13/4/2015
3: Final Head of water in stand pipe(cm) h2 34.4 14/04/2015
4: Starting time 17:25 13/4/2015
5: Finishing time 17:25 14/04/2015
6: Test duration t (sec) 86400 -
7: Coefficient of permeability =[(B*E)/(D*t)]*ln[h1/h2](mm/sec) 0.00000271053
Coefficient of permeability (mm/sec) 0.00000271053
Appendix 3g Permeability Test (Sample 2)
SOILS & BITUMEN LABORATORY
PERMEABILITY TEST
(FALLING HEAD PERMEAMETER)

Project : DESIGN OF IRRIGATION CANALS NETWORK

Description of Soil: CLAY SOIL Sample 2
Location: CHEJU IRRIGATION SCHEME
Test Performed By:B120021 Date Of test: 14/04/2015
Basic Data
A: Diameter of Stand Pipe (mm) 9.00
B: Cross Section area of Stand Pipe (mm2) 63.6700
C: Diameter of Permeameter Cell (mm) 70.1000

66
D: Cross section area of Permeameater (mm2) 3859.4500
E: Length of Sample (mm) 45.1000
F: Volume of Permeameter Cell (cc) 174.0600
G: Average test temperature (C) 22
H: Specific gravity of Soil Solids 2.612
Determination of Moisture Content at the end of the test
I. Test No 1
J. Moisture Can No C-2
K. Mass of can +Wet soil 256.67
L. Mass of can + dry soil 218.28
M. Mass of can (gms) 54.06
N. Mass of Water (gms) 38.39
O. Mass of dry soil (gms) 164.22
P. Water content(%) 23.38
Determination of Density of the test soil sample
Q: Test No 1
R: Mass of Cell +Wet soil + Filter paper (gm) 494.94
S: Mass of Cell (gm) 168.73
T: Mass of filter paper (gm) 0.82
U: Mass of wet soil (gms) 325.39
V: Bulk density (gm/cc) 1.869
W: Dry density of soil (gm/cm) 1.515
Porosity and Void ratio of the soil sample
X: Void ratio of the soil Sample = (H-W)/W 0.724
Y: Porosity of Soil Sample = X/(1+X) 0.420
Coefficient of Permeability
1: Test No 1 Date
2: Initial Head of water in stand pipe(cm) h1 35.5 14/4/2015
3: Final Head of water in stand pipe(cm) h2 32.1 15/04/2015
4: Starting time 18:50 14/4/2015
5: Finishing time 18:50 15/04/2015
6: Test duration (sec) 86400 -
7: Coefficient of permeability = [(B*E)/(D*t)]*ln[h1/h2](mm/sec) 0.00000866964

Coefficient of permeability (mm/sec) 0.00000866964

APPENDIX 04 HYDRAULIC COPUTATION SHEET OF MAIN IRRIGATION CANAL
APPENDIX 05 HYDRAULIC COPUTATION SHEET OF MAIN IRRIGATION CANAL
APPENDIX 06 TOPOGRAPHIC MAP OF PROJECT AREA AT CHEJU SCHEME
APPENDIX 07 FARM LAYOUT OF PROJECT AREA AT CHEJU SCHEME
APPENDIX 08 MAIN IRRIGATION CANAL PROFILE
APPENDIX 09 SECONDARY IRRIGATION CANAL PROFILE
APPENDIX 10 CROSS SECTION OF IRRIGATION CANAL No 1
APPENDIX 11 CROSS SECTION OF IRRIGATION CANAL No 2

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