CHAPTER 1 WATER SOURCES
1.1Surface Water Surface waters are nonuniformly distributed over the Earths surface. Types of surface water are: River Pond Lake Reservoir 1.1.1 Quality of Surface Water CLASS I (VERY GOOD) WATER QUALITY INDEX > 92.70 DETAILS Natural condition Water supply no treatment required Aqua-culture supports sensitive river species Water supply basic treatment required Aqua-culture supports most river species Recreation used for recreational purposed Water supply extensive treatment required Aqua-culture supports hardened river species Source of drinking for animals Irrigation only (plantation)
II (GOOD)
76.50 92.70
III (AVERAGE) IV (POLLUTED) V (VERY POLLUTED)
51.90 76.50
31.00 51.90
< 31.0
None of the above
Table 1.0: Water Quality Index (WQI) and Classes
WQI = (0.22*SIDO) + (0.19*SIBOD) + (0.16*SICOD) + (0.15*SIAN) + (0.16*SISS) + (0.12*SIPH) Subindex for DO (in % saturation):
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SIDO = 0 SIDO = 100 SIDO = -0.395 + 0.030x2 0.00020x3 Subindex for BOD: SIBOD = 100.4 4.23x SIBOD = 108 * exp (-0.055x) 0.1x Subindex for COD: SICOD = -1.33x + 99.1 SICOD = 103 * exp (-0.0157x) 0.04x Subindex for AN: SIAN = 100.5 105x SIAN = 94 * exp (-0.573x) 5 * |x-2| SIAN = 0 Subindex for SS: SISS = 97.5 * exp (-0.00676x) + 0.05x SISS = 71 * exp (0.0061x) 0.015x SISS = 0 Subindex for pH: SIpH = 17.2 17.2x + 5.02x2 SIpH= -242 + 95.5x 6.67x2 SIpH = -181 + 82.4x 6.05x2 SIpH = 536 77.0x + 2.76x2
for x <= 8 or x >= 92 for 8 < x < 92
for x <= 5 for x > 5 for x <= 20 for x >= 20
for x <= 0.3 for 0.3 < x < 4 for x >= 4
for x <= 100 for 100 < x < 1000 for x >= 1000
for x < 5.5 for 5.5 <= x < 7 for 7 <= x < 8.75 for x >=8.75
1.1.2 Sources of Surface Water Surface water supplies may be categorized as continuous unregulated rivers, rivers or streams containing impoundments, or natural lakes. The volumes of these freshwater sources depend on: Geographic Landscape temporal variations (climate) the impact of human activities. Total Global Water 97.5% Salt Water 68.9% Glaciers and permanent snow cover Freshwater AZI / JKA / PSIS / 2011 29.9% Fresh groundwater 2.5% Total Global Freshwater 0.9% other including soil moisture, swamp water and permafrost 0.3% Freshwater lakes and river storage. Only this portion is renewable
1.2Sub-surface Water Sub-surface water is nonuniformly distributed over under the Earths surface. Types of surface water are: Ground water Shallow well Deep well 1.2.1 Quality of sub-surface water Sub-surface water quality comprises the physical, chemical, and biological qualities of sub-surface water. Temperature, turbidity, color, taste, and odor make up the list of physical water quality parameters. Sub-surface water quality is influenced by the quality of it source. Changes in source waters or degraded quality of source supplies may seriously impair the quality of the sub-surface water. The quality of sub-surface water is the resultant of all the processes and reactions that act on the water from the moment it condensed in the atmosphere to the time it is discharged by a well or spring and varies from place to place and with the depth of the water table. Sub-surface waters have unique features, which render them suitable for public water supply. They have excellent natural quality and can be consumed directly without treatment. Sub-surface water is particularly important as it accounts for about 88% safe drinking water in rural areas, where population is widely dispersed and the infrastructure needed for treatment and transportation of surface water does not exist. 1.2.2 Sources of Pollution in Sub-Surface Water Sub-surface water, by its very location, has a large measure of protection from contaminants that are found in surface waters. However, once sub-surface water becomes contaminated, its location and low rate of replacement with fresh water makes it difficult to return it to a pristine state. Two major sources of contaminants are of concern: uncontrolled releases of biological and chemical contaminants and saltwater intrusion from over pumping of wells. Uncontrolled Releases - Discharge from improperly operated or located septic systems - Leaking underground storage tanks - Improper disposal of hazardous or other chemical wastes - Spills from pipelines or transportation accidents - Recharge of groundwater with contaminated surface water
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- Leaking landfills - Leaking retention ponds or lagoons Saltwater Intrusion - Freshwater aquifers near oceans or above saline aquifers may become contaminated with saltwater when water is pumped from wells
1.3
Water Catchment Areas Catchment areas are natural drainage area for precipitation, collection area for water supplies, river system or an area where all the surface runoff concentrated at a point of outlet. The area is defined by the notional line or watershed on surrounding high land. Typically a catchment area is a valley or series of valley containing a river system. Catchment area also called watershed or water basin. Examples of a catchment area are forested areas, urban catchment, rural catchment, parking lots, park, and recreation area, golf course and so on.
1.3.1 Dams
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Dam is a barrier that built across a river or stream to hold back the water and form a reservoir. It was an oldest technology that shows the existence of civilized societies. The purposes of built a dam are: Water Supply Flood Control Power Production Navigation Recreation and Aesthetics There are several types of dam: Gravity Dam - Weight of dam resist opposing forces - Usually concrete or masonry - The advantage is simple design - The disadvantage is large amounts of materials and construction Arch Dam - Strength of materials transfers forces to foundation/bedrock - Advantage is economic because use less of materials - Disadvantage is requires steep terrain between it (v-shaped valleys) Multiple Arch Dam - Continuous structure - Often a type of buttress dam - Advantage is less material required - Disadvantages are difficulty to construct and failure of key parts could lead to loss of entire dam Buttress Dam - Buttresses support dam - Advantages are less material required and strong rock foundation not required - Disadvantages are height limitation and construction difficulty Earth or Rock fill Dam - Made from earth or rock - Simple design - Can be small or large - Variety of construction techniques
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