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Water Demand Estimates
The major water demand in a river basin is for irrigation. To 
estimate the irrigation water demand it is necessary to decide 
on the area which is proposed to be irrigated in the year. This 
area may be less than the total nominal command area. Further, 
the initial water demand arising from the proposed irrigated 
area may need to be reduced in the light of the available water 
forecast. The reduced area and water demand can be assumed 
to be proportional, that is, assuming with reduced water supply 
there will be no increase in water use efficiency. A reduced crop 
area should be decided in close discussion with the irrigation 
farming community.
The water demand can be estimated from the irrigated area 
using a crop water demand per unit of area. The crop water 
demand can get from a model such as CROPWAT. The total 
irrigation water demand is obtaining by adding the transmission 
loss of water diverted from the river to the estimate water to 
be delivered to the command area. These irrigation demand 
estimates should be divided into annual and permanent crop 
estimates.
Water demand for town can be obtained from the town 
water supply department, normally this is calculated from the 
population and a water service level of a number of liters per 
capita per day. The water demand for industry should also be 
obtained from the provincial governments.
The high security water demand is the sum of the permanent 
crop estimate (including transmission loss), town water and 
industrial water demand estimates.

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«Молодой учёный» . № 28 (370) . Июль 2021 г.
География
Water Balance Estimates
Water shares for each group of water users (which could 
be divided geographically into river reaches as well as into the 
different classes of water use) are determined by allocating water 
from the estimated available supply in order of priority.
Water balance should be determined in March — April 
which is the time when farmers are making decisions on planting 
annual crops. The area of land that farmers prepare and plant 
should be informed by the annual water forecast. Farmers may 
gamble on preparing and planting more area than is forecast to 
be supplied with water, taking a risk that rain will fall and either 
the crop water demand will be partially met from rain or that 
additional water will become available.
Information on water available should be updated and fresh 
advice given to farmers each month after the initial forecast until 
the peak annual flow for the year is recorded.