11-03-2014, 10:36 AM
Quantity of water supply
Quantity of water to be supplied depends on population its characteristics, climatic conditions , the type of sewerage system.
It depends on policy regarding metered water supply , fire fighting requirements, number and type of industries, area under public gardens and efficiency of management.
Higher status more water supply required. Cooler climate less use of water and vice versa. Industries depending on their type require water.
Water requirements in case of fire are very high and large quantity of water has to be rushed to a spot. Thus the distribution main lines and location of reservoirs is important.
The type of sanitation technology demands different water requirement. Dry latrines need least conventional sewerage system needs the most.
Water supply is designed for 30 yrs. Population forecast is also considered.
Percapita rate of water supply population upto 10,000: 70 to 100 lts. , 10 to 50,000 : 100 to 125 lts. Above 50,000 : 125 to 200 lts.
Rate of water supply: consumption of water is seasonal, daily and hourly variation. Seasonal demand may vary by 1.3 times av annual demand. Maximum monthly demand may vary by 1.5 times, The hourly demand may vary by 2.5 times the average. The reservoir and the distribution system has to be designed for this.
Peak factor: the peak demand in India.
Population upto 50,000: 3 times av rate of water supply
50- 200 thousand 2.5 times
2 lakhs and above 2 times av rate.
Pressure: 7 meters for single storeyed,12 mts. For 2 storeys, 17 mts. For 3 storyed and 22 mts. For 4 storied houses.
Water meters reduce consumption. Intermittant water supply increases the water consumption. Phasing can be done for each 5 years. Efficient system saves water wastages.
Balancing the required quantity of water with sources of water supply.
Ground water level changes with season and drawl of water. Ground water is in movement and the direction and speed can be identified with dyes and test wells.
The ground water has dissolved impurities like carbonates, silicates, chlorides of magnesium and calcium.
Yield of water: Water is drawn from and the level of water drops after some time the water level becomes stationery. Then the well is allowed to fill up and the time it takes to refill to that level is say t1 and the time pump was operated is t2 then Y yield = Q/ t1 +t2
Surface water supply is preferred over ground water. The yield of surface water can be calculated by study of catchment av annaul rainfall and the coefficient of run off.
Tha annual rainfall measurement is taken at various places and 35 years reading is taken to take average.
The percentage of run off depends on the following factors.
Greater rainfall, greater is percentage of run off
Depending on dry or wet season the runoff changes
Porous soil means greater absorption.
More vegetation and trees there is less runoff.
Steeper slope more runoff
Rate of runoff more if rain fall rate is high.
The amount of water in the reservoir may be calculated as W= R xAxP ( where W is amount of water, R is the annual rainfall in bad year, A is catchment area and P is likely percentage of runoff for that year.)
The demand of water is compared with the supply available in bad year. The water stored in a reservoir is calculated by v= h/6( A1 +A2+A3) where H is contour interval, A1is areas of water spread at lower level )
Quantity of water to be supplied depends on population its characteristics, climatic conditions , the type of sewerage system.
It depends on policy regarding metered water supply , fire fighting requirements, number and type of industries, area under public gardens and efficiency of management.
Higher status more water supply required. Cooler climate less use of water and vice versa. Industries depending on their type require water.
Water requirements in case of fire are very high and large quantity of water has to be rushed to a spot. Thus the distribution main lines and location of reservoirs is important.
The type of sanitation technology demands different water requirement. Dry latrines need least conventional sewerage system needs the most.
Water supply is designed for 30 yrs. Population forecast is also considered.
Percapita rate of water supply population upto 10,000: 70 to 100 lts. , 10 to 50,000 : 100 to 125 lts. Above 50,000 : 125 to 200 lts.
Rate of water supply: consumption of water is seasonal, daily and hourly variation. Seasonal demand may vary by 1.3 times av annual demand. Maximum monthly demand may vary by 1.5 times, The hourly demand may vary by 2.5 times the average. The reservoir and the distribution system has to be designed for this.
Peak factor: the peak demand in India.
Population upto 50,000: 3 times av rate of water supply
50- 200 thousand 2.5 times
2 lakhs and above 2 times av rate.
Pressure: 7 meters for single storeyed,12 mts. For 2 storeys, 17 mts. For 3 storyed and 22 mts. For 4 storied houses.
Water meters reduce consumption. Intermittant water supply increases the water consumption. Phasing can be done for each 5 years. Efficient system saves water wastages.
Balancing the required quantity of water with sources of water supply.
Ground water level changes with season and drawl of water. Ground water is in movement and the direction and speed can be identified with dyes and test wells.
The ground water has dissolved impurities like carbonates, silicates, chlorides of magnesium and calcium.
Yield of water: Water is drawn from and the level of water drops after some time the water level becomes stationery. Then the well is allowed to fill up and the time it takes to refill to that level is say t1 and the time pump was operated is t2 then Y yield = Q/ t1 +t2
Surface water supply is preferred over ground water. The yield of surface water can be calculated by study of catchment av annaul rainfall and the coefficient of run off.
Tha annual rainfall measurement is taken at various places and 35 years reading is taken to take average.
The percentage of run off depends on the following factors.
Greater rainfall, greater is percentage of run off
Depending on dry or wet season the runoff changes
Porous soil means greater absorption.
More vegetation and trees there is less runoff.
Steeper slope more runoff
Rate of runoff more if rain fall rate is high.
The amount of water in the reservoir may be calculated as W= R xAxP ( where W is amount of water, R is the annual rainfall in bad year, A is catchment area and P is likely percentage of runoff for that year.)
The demand of water is compared with the supply available in bad year. The water stored in a reservoir is calculated by v= h/6( A1 +A2+A3) where H is contour interval, A1is areas of water spread at lower level )