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The plan area of a reservoir is 1 km². The water level in the reservoir is observed to decline by 20 cm in a certain period. During this perod the reservoir receives a surface inflow of 10 hectare-meters, and 20 hectare-meters are abstracted from the reservoir for irrigation and power. The pan evaporation and rainfall recorded during the same period at a near by meteorological station are 12 cm and 3 cm respectively. The calibrated pan factor is 0.7. The seepage has from the reservoir during this period in hectare-meters is
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- 0.0
- 1.0
- 2.4
- 4.6
Correct Option: D
Area = 1 km² = 100 ha
Change in storage = inflow – outflow
⇒ ds = I – Q
I = Surface inflow + rainfall
= 100 + .03 × 100
= 13 ha.m
Q = Irrigation and power + evaporation + seepage loss. = 20 + C p. Ep. A + Seepage loss
= 20 + 0.7 × .12 × 100 + Seepage loss = 28.4 + Seepage loss
ds = – 0.20 × 100 = – 20 (decline, ∴ –ve sign)
∴ – 20 = 13 – (28.4 + Seepage loss)
⇒ Seepage loss = 4.6 ha–m
