Water Resources and Environmental Hydraulics · Surface Water Resources · 1 mark · Numerical answer
A Class-A pan starts a week at 250 mm water depth and ends at 240 mm, with 10 mm rainfall during the week. Pan coefficient is .8. Find lake evaporation in integer mm.
The pan balance is ending depth=starting depth+rainfall−evaporation. Thus pan evaporation is 250+10−240=20 mm. Lake evaporation is $K_pE_{pan}=.8(20)=\mathbf{16}$ mm. Simply using the10 mm level fall would miss the rainfall input.
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