During July, 1996 monthly inflow to Tarbela Reservoir was 20 billion cubic meters and outflow was 18.70 billion cubic meters. Find the rate of change of storage and change in storage during the period

Problem 12. (7.76 Chin) During a critical 24-month period the average monthly inflows to a reservoir and the average water demand are given in Table 7.10. Use these data to estimate the minimum required storage volume of the reservoir to overcome that critical period. TABLE 7.10 Average inflow Average demand (m³/s) Average inflow Average demand Average Average inflow (m³/s) demand (m³/s) Month* (m³/s) (m³/s) (m³/s) Month Month 1000 1100 1200 1300 1350 1270 1120 1230 1320 1250 1240 1550 1600 850 1300 17 1400 1400 1400 1130 10 1200 18 11 12 13 19 20 21 1310 1370 1100 1000 1170 1210 1000 1400 1400 940 1000 1300 1260 1400 14 820 1100 22 1200 1400 1400 880 1040 1200 1300 15 23 1100 930 16 1290 24 1080 1000

A catchment is idealized as a 25 km × 25 km square. It has five rain gauges, one at each corner and one at the centre, as shown in the figure. G₂ G₁ O G5 GA G3 During a month the precipitation at these gauges is measured as G₁ = 300 mm. G₂ = 285 mm, G₂ = 272 mm, G₂ = 290 mm and G5 = 288 mm. The average precipitation (in mm up to one decimal place) over the catchment during this month by using the Thiessen polygon method is

A drainage basin has a area of 7322 km2. The average annual precipitation for this area is 909 mm. The average surface water flow at the outlet of the catchment is 21.4 x 108 m3/year and the average groundwater flow out of the basin is 94.6 mm/year. Assume trailing zeros are significant if present. Determine the annual average evaporation in mm/year. (give your answer to one decimal place)