Introduction

to Hydrology
Lecture content

1) Definition and scope of Hydrology

2) Examples of water resources and engineering problems to which Hydrology provides
answers
3) Methodological approach to hydrological sciences

4) Water balance and the hydrological cycle

5) Hydrological processes overview
6) Hydrological data and space and time scales

Goal: to understand the philosophy of representing the functioning of

hydrological/natural systems through an engineering (quantitative)
description
Hydrology – Introduction - Autumn Semester 2017 1
Definition and scope

Hydrology – Introduction - Autumn Semester 2017 2

Hydrology - Definition
“Hydrology, which treats all phases of the earth's water, is a subject of great
importance for people and their environment. Practical applications of hydrology
are found in such tasks as the design and operation of hydraulic structures, water
supply, wastewater treatment and disposal, irrigation, drainage, hydropower
generation, flood control, navigation, erosion and sediment control, salinity
control, pollution abatement, recreational use of water, and fish and wildlife
protection. The role of applied hydrology is to help analyze the problems
involved in these tasks and to provide guidance for the planning and
management of water resources”.
[Chow et al. 1998]

WATER USE vs WATER CONSERVATION

ê
SUSTAINABLE WATER RESOURCES MANAGEMENT

Hydrology – Introduction - Autumn Semester 2017 3

Elements of
Hydrology and
other
geosciences

Hydrology as
science behind
water resources
problems
Hydrology – Introduction - Autumn Semester 2017 4
Examples of water engineering problems

Hydrology – Introduction - Autumn Semester 2017 5

 Examples of water resources engineering problems to which
Hydrology can provide answers

Control of excess of water Conservation (quantity) Conser-

vation
(quality)
Studies and Flood storm Storm Bridges, Sewerage Water supply Irrigation Hydropower Navigation Pollution
facilities mitigation drainage culverts control
required
How much - - - - x x x x x
water is
needed?
How much
water can be
expected?
Min. flow - - - x x x x x x

Annual yield - - - x x x x x x

Flood peaks x x x - x x x x

Flood volume x x - - - - - - x

Groundwater - x - x x x - - x

Hydrology – Introduction - Autumn Semester 2017 6

Hydrology for Water Resources Management How much water is needed?
How much water can be expected?

digital.lib.uiowa.edu/gpc
Hydrology – Introduction - Autumn Semester 2017 7
 How much water is needed?
How much water can be expected?

Hydrology – Introduction - Autumn Semester 2017 8

image provided by electrical-engineering-portal.com

Hydrology – Introduction - Autumn Semester 2017 9

 Saltina, Brig – flood (1993)

Debris flow Brig, Jean-Pierre Jordan 1993

Debris flow Brig, Roberto Loat BAFU 1993

Hydrology – Introduction - Autumn Semester 2017 10
W. Gujer, Siedlungswasserwirtschaft, 2002

Frankfort Municipal Utilities

Hydrology – Introduction - Autumn Semester 2017 11

 [http://water.usgs.gov/outreach/Posters/water_quality/images/WaterQuality_BW.jpg]

Hydrology – Introduction - Autumn Semester 2017 12

 140 NATURAL (1929-1953)
POST-DAM (1954-1974)
120 RECENT (1982-2003)

100

Qm (mil m3)
80

60

40

20

MAY

JUN
MAR

AUG

NOV
JAN

JUL

DEC
APR

OCT
SEP
FEB
Q347 - Restwassermenge

Bundesamt für Umwelt BAFU

Hydrology – Introduction - Autumn Semester 2017 13

 How much water is needed?
How much water can be expected?

Hydrology – Introduction - Autumn Semester 2017 14

 Hailey King, NASA

[http://oceanexplorer.noaa.gov/edu/learning/7_water_cycle/activities/groundwater.html#activity]

Hydrology – Introduction - Autumn Semester 2017 15

Flood irrigation Trickle irrigation
http://photogallery.nrcs.usda.gov/Index.asp Wordpress.com

Furrow irrigation
USDA Natural Resources Conservation Service

Hydrology – Introduction - Autumn Semester 2017 16

 How much water is needed?
How much water can be expected?

Hydrology – Introduction - Autumn Semester 2017 17

 http://www.britannica.com/technology/water-supply-system/Water-treatment

Hydrology – Introduction - Autumn Semester 2017 18

Hydrology – Introduction - Autumn Semester 2017 19
 Auengebiet Gérine im Kanton Freiburg (Foto J.Cl. Bersier, Freiburg)

Fischabstieg am WKW Elz; Quelle: Archiv Wasserkraft Volk AG

Hydrology – Introduction - Autumn Semester 2017 20

 http://www.power-technology.com

Hydrology – Introduction - Autumn Semester 2017 21

 How much water is needed?
How much water can be expected?

Hydrology – Introduction - Autumn Semester 2017 22

Flood Wallis, 2000

Unwetter 2000 im Wallis (2), PLANAT 16.10.2000

Unwetter 2000 im Wallis (1), PLANAT 16.10.2000

Unwetter 2000 im Wallis (3), PLANAT 16.10.2000

Hydrology – Introduction - Autumn Semester 2017 23

 Ufererosion in Wolfenschiessen, Kanton NW 27.08.2005

Hydrology – Introduction - Autumn Semester 2017 24

Methodological approach

Hydrology – Introduction - Autumn Semester 2017 25

 The reference geographical unit: the river basin
terms used as synonymous of “river basin”:
• watershed
• catchment

Process understanding river network

(measurement, observation)

ê
Mathematical Modelling
(simulation, prediction)

unsaturated
soil zone
groundwater/aquifer
(saturated)
http://research.ncl.ac.uk/shetran/images/ShetranProcesses.jpg

Hydrology – Introduction - Autumn Semester 2017 26

 Methodological approach
The watershed as hydrologic
system

Physical
Hydrology Engineering
Hydrology

[Chow et al. 1998]

Hydrology – Introduction - Autumn Semester 2017 27

 Physical Hydrology / System Engineering Hydrology / System
= Process understanding, Monitoring, Measuring … = Modelling, Conceptualisation, Reproducing processes…

Catchment/ Catchment characteristics

What is a catchment? Influence of catchment characteristics on the hydrograph
How to describe catchment characteristics? (e.g. Relief, Land use, stream density etc.)
e.g. Hypsometric curve, Drainage density

• Mechanisms
• Distribution in Switzerland
Precipitation Frequency analysis
• Measurement (instruments, errors) DDF / IDF Design hyetograph
• Areal rainfall
• Storm rainfall SCS – method, Alternating block method,
Generating
Triangular hyetograph, Chicago, Huff
Snow hydrology

Potential input
• Measurement techniques
• Characterising variables
• Snowmelt
• Snowmelt
modelling Modelling R-R-Transformation
Reasons for modelling
Time and space scales of R-R-Modelling
Structure of a hydrological model / Model components?

R-R-Modelling
Types of models
Precipitation Modelling methods:
excess Evapotranspiration • Measurement/ Estimation/ Evaporation Lumped; Distributed, Semi-distributed
Calculation
• AET vs. PET Modelling approaches for runoff concentration:
Infiltration - Basin response function (via Nash-cascade, Isochrones method, etc. )
• Measurement Estimation of model parameter (Method of moments, Least square)
• Mechanisms: Dunne, Horton
Interception
• Infiltration models: Soil
Horton, SCS-CN, Phi-Index,
Percentage method moisture
Surface flow
Subsurface flow

Potential input
Groundwater flow
Total runoff
• Measurement
• Influencing factors
• Streamflow regimes
• Hydrologic yearbook / flow duration curve
• Hydrograph analysis / Hydrograph components/
Baseflow separation

Erosion & Sediment transport Flood frequency analysis

• Problems Using runoff data from measurements or
• Influencing factors via synthetic precipitation or runoff data
• Estimation of erosion: U.S.L.E. Deterministic Probabilistic
• Types of sediment transport e.g. Probable
Maximum Flood (PMF)
direct indirect
Extreme value Regionalisation
analysis (Index-Flood)
R-R-Modelling

Hydrology – Introduction - Autumn Semester 2017 28

Water balance

Hydrology – Introduction - Autumn Semester 2017 29

How much water is available on our planet?

Hydrology – Introduction - Autumn Semester 2017 30

Water balance

• The water balance defines the conservation of mass across the different compartments
of the hydrological cycle (atmosphere, water bodies, soil and ground, vegetation,
snowpack and ice, …)
• it is computed with regard to a reference geographical unit / scale
• Earth
• continent
• region
• river basin
• soil column
•…
• The concept of conservation of mass implies the identification of an incoming and an
outgoing flux, and of a storage variation over a given unit of time.

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The hydrological cycle

[Chow et al. 1998]

32
Hydrology – Introduction - Autumn Semester 2017 32
Global annual water balance

estimates and not measurements

[Chow et al. 1998]

Hydrology – Introduction - Autumn Semester 2017 33

Water balance – continental scale
average annual volumes

estimates
and not
measurements

average annual volumes per area

[L'vovich, 1973]
Hydrology – Introduction - Autumn Semester 2017 34
Water availability – continental scale estimates
and not
measurements

Hydrology – Introduction - Autumn Semester 2017 35

Water balance – fluxes

Volumes volumes
and [km3]

average residence time

of water in the different
compartments of the
hydrological cycle fluxes
[km3/yr]

estimates and not measurements

residence time in the atmosphere:

T = V / Q

V = 14⋅103 km3
Q = (416 + 108)⋅103 = 524⋅103 km3/yr
T = 14/524 ⋍ 0.027 yr ⋍ 9.75 days

Hydrology – Introduction - Autumn Semester 2017 36

Water balance – country scale

the water balance is

computed for the
hydrologic year
(in CH starting in
October)

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Water balance – river basin scale
P = R + E + ΔS

[Hydrologie Skript]

Hydrology – Introduction - Autumn Semester 2017 38

Water balance of the Nile river (process variability in space and time)

http://www.youtube.com/watch?v=xqjXTebE5I0

http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4044
Hydrology – Introduction - Autumn Semester 2017 39
Water balance – urban scale

water

wastewater

food
waste

!
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The hydrological cycle at the event scale

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Flowchart representation of the hydrological cycle

[Chow et al. 1998]

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Characteristic temporal and spatial scales
and
hydrological data

Hydrology – Introduction - Autumn Semester 2017 51

Space and time scales of hydrological processes

typically:

space: 1 m “point scale” (1D)

1 m2 (2D)
ê
106 m (1D)
106 km2 “watershed” (2D)

time: 1 s “instantaneous”
ê
1 year

Hydrology – Introduction - Autumn Semester 2017 52

Technical space and time scales of hydrological processes

[s]
1 3.6 103 ≈8.6 104 ≈2.6 106 ≈3.2 107

instantaneous hourly daily monthly / annual multi annual

seasonal
1 point Ÿ Ÿ Ÿ Ÿ Ÿ Ÿ
hillslope Ÿ Ÿ (Ÿ) (Ÿ) (Ÿ)
[m]

watershed Ÿ Ÿ Ÿ Ÿ Ÿ
regional Ÿ Ÿ Ÿ Ÿ Ÿ
>106 global Ÿ Ÿ Ÿ Ÿ Ÿ

Ÿ used, consistent with typical process scales

(Ÿ) generally not used, inconsistent with typical process scales

Hydrology – Introduction - Autumn Semester 2017 53

Temporal and spatial nature of hydrological data

point / local

continuous = sequence of instantaneous data

hillslope

discrete =
a) aggregated from continuous to larger
temporal scales (e.g. from 1h to 1 day, watershed
from 1h to 1 month, etc.)
b) measured at discrete times

Hydrology – Introduction - Autumn Semester 2017 54

Use of hydrological data in water engineering problems

• average values are used in

planning problems and
preliminary analyses
• extreme values are used to
design water engineering
infrastructures against complexity of the analysis
extreme events (e.g. floods,
low flows, droughts, …) uncertainty
• continuous data (time series)
are used in management and required data
and optimization of water
resources infrastructures
PLANNING DESIGN MANAGEMENT

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Water engineering problems and hydrologic variables

Water engineering problem Typical reference hydrologic variable

Design of flood protection measures Peak flow discharge
Flood volume and duration
Design of storm drainage Extreme values of rainfall depth
Peak flow discharge
Design of a reservoir Annual water yield
Seasonal/monthly water yield
Design of an irrigation system Evapotranspiration
Soil water content
Landslide risk analysis Extreme values of rainfall depth and
intensity
River bed erosion River discharge
Surface erosion Overland flow
Water allocation to multiple users Discharge time series
(hydropower, irrigation, water supply, …)
… …
Hydrology – Introduction - Autumn Semester 2017 56
Uncertainties
HYDROLOGICAL MODEL CONCEPTUALIZATION
ê

meteorological forcing simulated hydrological variables

(precipitation, temperature, • watershed representation (topography, (streamflow, soil water content,
radiation, wind, etc.) land cover, soil, …) evapotranspiration, …)
• mathematical model of basin hydrological
processes (infiltration, runoff formation,
evapotranspiration, etc.)

typical uncertainties typical uncertainties

output is uncertain
• due to lack of data • due to poor knowledge
of the physical system ê
• due to climate variability
• due to spatial design values are
• uncertainties due to heterogeneities and
spatial variability of uncertain
anisotropies
meteorological forcing ê
• model approximations
• uncertainties due to
probabilistic analysis
measurement errors • model parameters
Hydrology – Introduction - Autumn Semester 2017 57
From physical processes to hydrological models

Models can be
• empirical: description of hydrological processes based
on cause-effect relationships experimentally
derived or inferred from data analysis

• conceptual: description of hydrological processes based

on the conceptualisation of the physical
mechanisms

• physically based: description of hydrological processes based on

the representation of the physical mechanisms
by means of physics laws

Hydrology – Introduction - Autumn Semester 2017 58

Keywords
• water balance • precipitation • river basin /
watershed /
• time scales • interception
catchment
• spatial scales • evaporation
• river network
• volumes • evapotranspiration
• fluxes • infiltration
• storage • percolation
• hydrological cycle • unsaturated zone
• systems analysis • saturated zone
• hydrological data • water table
• continuous • groundwater
• discrete • runoff
• event • overland flow
• hydrological process • interflow
• hydrological model • baseflow
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