(a) Average rainfall during the month of January is found to be R mm. A Class A pan evaporation recorded an average of [7 + (R/100)] mm/day near an irrigation reservoir. The average January inflow into the reservoir is (100 + R) m3/s and the average irrigation demand during the month is 170 m3/s. The water level drops by (10 times R) mm in that month and the average surface area of the reservoir is 21,000 ha. Estimate the seepage through the banks and the dam during this month. Assume the pan coefficient of 0.7 for the month of January.
(b) Calculate the evaporation in mm/day from the free water surface using Penman's method.
The following data were measured on that day:
Net Radiation = (100 + R) W/m2
Air Temperature = 200C
Humidity = R %
Wind run = 20 km/day measured at 2 m above the surface The wind function f(u) can be calculated as 73 + 0.44 u, when u is in km/day
Vapour pressures is in kPa and γ can be taken as 0.065 kPa/0C