Question

Hydrology question: A watershed of 21000 sq. km. received total precipitation of 21 in. in 2000. The annual stream flow was recorded as 5000 cfs. Estimate the average daily ET for the watershed. You can have as many assumptions possible but need to elaborate.

Answer 1

Answer:

combined evapotranspiration is 12.63 in/yr

for avg daily 0.035 in/day

Explanation:

areas = 21000 sq. km

precipitation in year 2000 = 21 in/yr.

stream flow (Q) = 5000 ft³/s

runoff =  $\frac{Q}{A}$

runoff= $\dfrac{5000\ ft^3/s}{21000\ km^2}\times (\dfrac{1 km^2}{(3280.84 ft)^2} ) \times \dfrac{86400s}{days} \times \dfrac{365}{years} \times \dfrac{12 in}{ft}$

runoff= 8.37 in/yr

total precipitation = 21 in/yr

hence

Evapotranspiration for watershed

ET= P - R

ET = 21 - 8.37 = 12.63 in/yr

so the combined evapotranspiration is 12.63 in/yr

for avg daily ET= 12.63/365 in/day

                         = 0.035 in/day