Question

During the month of March, the average river inflow to a reservoir is 3 m’/s while the dam bottom outlet releases 10 m²/s. Total rainfall for the month is measured as 20 mm uniformly distributed. The average seepage from the reservoir is estimated 0.5 m3/s. The surface areas of the lake are measured from aerial photos as 11.7 and 10.3 km2 and also the staff gauge readings of water surface are recorded as 107.2 m and 105.2 m in the beginning and at the end of the month respectively. The reservoir volume at the start of the month was 98000 ML. Calculate average daily evaporation from the lake surface in mm/day.

Answer 1

aven 9 1ъери - 3 m/s Pout flow = 10 mil) See Q seepage = 0.5 ml see Rainfall - 20 mm (monthly) Average Area of lake = 11,7410.3 A Are = 11 km2 1. Maren = 31 Days Deplection Due to Discharge = (10+0.5-3)*486400x3) X106 = 1.82618 m = 1826.18 mm Met Oepletion = 1826 18-20 = 1806:18 mm Evaporation = fall in level - Depletion ou to discharge.

Fall in level = 107.2 - 105.2 = am = 2000 mm Evaporation = 2000 -1806.18 193.818 mm lona th = 193.818 -31 A C219 mm I Day