A watershed is an area of land that collects and discharges rainwater to a common outlet, such as a river, stream, or lake. To answer this question, the following information should be used: Mean annual streamflow from a 600 mi² watershed = 315 ft³/s Mean annual precipitation in the watershed = 37 inches.
Mean annual runoff expressed as a depth per unit area in inches Runoff is the portion of precipitation that is discharged from the surface of the ground to the rivers. The following formula will be used to calculate the mean annual runoff expressed as a depth per unit area in inches :Average annual runoff = Average annual precipitation.
Average annual actual evapotranspiration Average annual precipitation is given as 37 inches. The only unknown value is the average annual actual evapotranspiration. We will calculate this value and use it to calculate the mean annual runoff.
b. Annual average evapotranspiration Average annual evapotranspiration is defined as the sum of annual evaporation from the soil surface and transpiration from plants' surface, and vegetation, temperature, wind, and relative humidity.