A4,000-km^2 watershed receives 102cm of precipitation in one
year. the avg. flow of the river draining the watershed is 34.2
m^3/s. infiltration is est. to be 5.5 x 10^(-7) cm/s
andevapotranspiration is est. to be 40 cm/y. determine the change
instorage in the watershed over one year. the ratio of runoff
toprecipitation (both in cm) is termed the runoff
coefficient. compute the runoff coefficient for this
watershed.

1) The change in storage of the catchment is 707676800 cubic meters.

2) The runoff coefficient of the catchment is 0.83.

Explanation:

The water budget equation of the catchment can be written as

where

'P' is volume of  precipitation in the catchment =

Is the water inflow

ET is loss of water due to evapo-transpiration

is the change in storage of the catchment

is the outflow from the catchment

I is losses due to infiltration

Applying the values in the above equation and using the values on yearly basis (Time scale is taken as 1 year) we get

Part b)

The runoff coefficient  C is determined as

where symbols have the usual meaning as explained earlier

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