A Lake Has An Area Of 15 Km2. Observation Of Hydrological Variables

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Civil UPSC ESE Exam Solution 2021

UPSC ESE Exam Solution 2021 for Civil Engineering UPSC ESE 2021 GS Paper 1 download exam paper from telegram https://telegram.me/civil_experiences

Precipitation = 700 mm/year,

Average inflow Qin = 1.4 m²/s;

Average outflow Qout = 1.6 m/s

Assume that there is no net water exchange between the lake and the groundwater. What is the evaporation during this year?

[A] 480 mm

[B] 280 mm

[C] 380 mm

[D] 180 mm

ANSWER= [B] 280 mm

Precipitation (P) = 700 mm/yr

Avg inflow (Qin) = 1.4 m ³/sec

Avg Outflow (Qout) = 1.6 ³/sec

lake area = 15 km²

Assuming no chance in storage in a year, we have

Inflow – Outflow = 0

Inflow = Outflow

(700 * 10^-3 * 15 * 10⁶) + (1.4 * 365 * 24 * 60 * 60) = (1.6 * 365 * 24 * 60 * 60) + (E * 10^-3 * 15 * 10⁶)

(where E = evaporation in mm/yr)

solving we get

E = 279.52 mm/yr

E = 280 mm/yr

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