Question

In a given year, a catchment with an area of 200 km2 received 1300 mm of rainfall. The average evaporative energy flux due to evapotranspiration was 45 Watts/m2. Assuming negligible change in soil and groundwater storage, and also negligible interception. Estimate the average rate for that year, for the river draining the catchment (in both mm/year and m3/s)

Answer 1

Solution is attatched in the image posted below:

Hope it helps.

Average evaporative energy flux means energy available per unit area per unit time to evaporate water.

Average signifies that condition of throughout the day and night both are considered.

With the help of relations we can calculate the evapotranspiration rate per second which is then used to calculate yearly evapotranspiration.

Rainfall- evapotranspiration will give river drainage value in mm/year.

To find value in m3/s volume is calculated by multiplying area with depth of water remains after evapotranspiration.

As all other losses are considered negligible.