Page 316 - Industrial Wastewater Treatment, Recycling and Reuse

290 Industrial Wastewater Treatment, Recycling, and Reuse

7.2.5 Water Balance for India
The water balance for India is estimated on the basis of average annual precip-
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itationofIndiawhichisaround4000 km .Theprecipitationcontributesnearly
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2150 km to ground water and 1150 km to surface runoff. The available
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total water resources have been estimated to 1953 km . Out of 1953 km ,
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Ganga-Brahmaputra-Maghna basin shares 1202 km and the remaining basins
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share 751 km . (Hydrology and Water Resources System for India, 2007).
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The utilisable part of the water resources is estimated to 1122 km from
the total annual water availability in India. An additional demand of 123–
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169 km is projected to be required by 2050 anticipating the increased usage
in irrigation, domestic and industrial sectors. The per capita availability of
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water was seen to decrease from 3000 m in 1951 to 1100 m in 1998. It
is predicted that the per capita water availability will further shrink to
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687 m by 2050. The per capita water availability is presented in Table 7.2.
7.2.5.1 Atmospheric Water Balance
Under Indian condition, the equation for atmospheric water balance is
obtained by equating inflow to the sum of outflow and change in storage
and is given below:
V I + E T + V AI ¼ P + V 0 + V AE
where V I is inflow of water vapor that reaches to the Indian atmosphere from
land and sea routes; E T , total quantity of evapotranspiration; V AI , initial
water vapor content of atmosphere; P, total precipitation; V 0 , outgoing
water vapor content; and V AE , the water vapor content present at the
end of period under consideration.
A schematic of the atmospheric water balance is shown in Table 7.3
(Source: Hydrology and Water Resources System for India). It is inferred
from Table 7.3 that the inflow of water vapour should be large enough
to maintain the balance between natural vapourisation and precipitation.

7.2.5.2 Hydrologic Water Balance
The hydrologic water balance of India can be deduced from average annual
conditions and the pertinent equation is given below:

Table 7.2 Per capita availability of water (http://www.nih.ernet.in/rbis/india_
information/Water%C2%A0Budget.htm)
Year 1951 1991 2010 2025 2050

Population (Million) 361 846.3 1157 1333 1581
Average water resources 3008 1283 938 814 687
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(m /capita/year)
Source: Hydrology and Water Resources System for India.