Water Quality

Water quality testers can be used for onsite measurement for limited parameters. other parameters need to be properly calculated at a PheD-approved water quality testing laboratory. records of water quality test results needs to

Water availability/supply (A) Water demand (B)

a1. Surface water retained in the watershed/area

B1. Domestic water demand a2. groundwater recharge B2. irrigation water demand

B3. industrial and/or other water demand Total water supply = cubic metres

(cu m)/per annum

Total water demand = cu m/per annum

The water budget, calculated on the above basis, should serve as an indication and in practice

3.2.8 Water Budget (Activity Code C-8)

A water budget is a tool for understanding and accounting for the movement and uses of water on, through and below the earth’s surface.

The budget should take into account the following questions:

a Where is the water? Where are the hydrologic elements located in the watershed? a How does the water move between these hydrologic elements? What are the pathways

through which water travels?

a Where are water users located and how much water are they using? a What are the trends? Are water levels declining, increasing or constant? Water budget (WB) = Total water available (A) – Total water demand (B)

The water budget estimates provide a useful understanding of the demand for drinking water in the GP/block compared to total water demand. The results of the water budget estimate will not make a difference in the water supply situation unless they are properly understood and followed up by the required changes in water use practices.

may vary by at least 10-15 per cent due to the uncertainties of land use and rainfall.

T o o l k i T f o r T h e P r e P a r aT i o n o f a D r i n k i n g WaT e r S e c u r i T y P l a n T o o l k i T f o r T h e P r e P a r aT i o n o f a D r i n k i n g WaT e r S e c u r i T y P l a n

The water availability in the project area should be assessed based on the ground and surface water available.

a. groundwater

To calculate groundwater recharge, generally the percentage of rainfall for the watershed (village) area and about 10 per cent of the rainfall for the agricultural area is considered to be groundwater 3.2.8.1 Assessment of Water Availability The primary source of water is rainfall.

The estimation of total rainfall received over the entire area is based on the total area and total rainwater received over that area. The amount of rainwater will be stored on the surface in ponds, lakes and reservoirs and some of it as groundwater.

1. area of village ... hectare ... square kilometre (sq km) 2. rainfall received from June to September

(monsoon)

millimetre (mm) ... metre (m)

3. Projected rainfall from october to May (non-monsoon)

... mm ... m 4. Total rainfall from June until May the following year ... mm ... m 5. Total rainwater received over the area 1 x S. no. 4 ... cu m

recharge. Both the village’s and agricultural areas must be computed to arrive at the total annual groundwater recharge, estimated according to: a) recharge due to rainfall

b) recharge due to seepage from canals c) recharge due to irrigation

d) recharge due to seepage from tanks

Total area available for recharge ... ha ... sq m

infiltration factor • Sandy area: 20-25% rainfall

• Area with higher clay content: 10-20% rainfall • Weathered and fractured areas: 10-15% rainfall • Un-weathered: 5-10% rainfall

• Vesicular and jointed basalt: 10-15% rainfall • Weathered basalt: 4-10% rainfall

• Limestone, sandstone, quartzite, shale areas: 3-10% rainfall

a) recharge due to rainfall

b) groundwater recharge due to seepage from canal. a certain portion (10 per cent) of canal water will seep into the groundwater and can be accounted for as shown below:

d) groundwater recharge due to seepage from tanks

c) groundwater recharge due to irrigation. artificial irrigation from canal/bore well water will recharge groundwater. it is generally considered to be 40 per cent of the total water delivered by the canal irrigation system and 35 per cent of the total water delivered for a bore well-based irrigation system.

i) length of the canal in the area ... m ii) Wetted area of canal ... sq m iii) annual water available in canal i x ii = ... cu m

iv) Seepage available as recharge from canal 0.1 x (iii) above = ... cu m

number of irrigation tanks

Water spread area of irrigation tanks ... sq km Seepage as recharge from irrigation

tanks: 0.45 m/year

... sq km x 0.45 = ...

Water delivered by canal for irrigation ... cu m return flow from canal irrigation: 40% 0.4 x ... cu m = ...

Water delivered from bore well for irrigation ... cu m return flow from groundwater-based irrigation 0.35 x ...cu m = ...

Total groundwater recharge

a) recharge due to rainfall ... cu m b) recharge due to seepage from canal ... cu m c) recharge due to irrigation ... cu m d) recharge due to seepage from tanks ... cu m Total groundwater recharge ... cu m

T o o l k i T f o r T h e P r e P a r aT i o n o f a D r i n k i n g WaT e r S e c u r i T y P l a n T o o l k i T f o r T h e P r e P a r aT i o n o f a D r i n k i n g WaT e r S e c u r i T y P l a n

Water that is stored in tanks, ponds and other water-harvesting structures such as check dams or farm ponds, etc., is considered to be available surface water. These values may nevertheless vary depending upon rainfall, its distribution and different land uses.

b. Surface Water

number of tanks/ponds ... tanks Total storage capacity of surface water of each tank ... cu m

Total water available/supply = groundwater recharge + Storage of surface water

... cu m cu m

... cu m 3.2.8.2 Assessment of Water Demand

The water demand assessment for the project area is estimated under the following headings:

a) irrigation water demand b) Water requirement by animals c) Water requirement by households d) Water demand by industries e) ecological water demand

a. irrigation water demand

irrigation water demand needs to be calculated separately for the kharif, rabi and summer seasons. Water-intensive crops such as paddy and sugarcane require 1.0 hectare metre (ha m) or 10,000 cu m while other crops such as maize, jowar, sunflower, groundnuts, etc., require less than 0.5 ha m (5,000 cu m). Where the land is irrigated, the total area under different crops in each season has to be computed in order to quantify the irrigation water requirement for the whole year.