Question

The average surface area of a reservoir in the month of June is 20 $k{m}^2$. In the same month the avg. rate of inflow is 10 $m^3/s$; out flow rate is 15 $m^3/s$, monthly rainfall is 10 cm, monthly seepage loss is 1.8 cm and storage change is 16 million $m^3$.
The evaporation (cm) in that month is:

• A. 46.8
• B. 136
• C. 13.6
• D. 23.4

Answer 1

The correct option is D 23.4

Change in storage

$\Delta s$ = inflow - outflow

$\Delta s=x+y-z-\alpha -\beta$

$-16\times {10}^6{m}^3=(10\times 86400\times 30)m^3+(20\times {10}^6\times 0.1)m^3-(15\times 86400\times 30)m^3-(1.8\times 10{}^{-2}\times 20\times {10}^6)m^3-E$

$E=\frac{4.68\times {10}^6{m}^3}{20\times {10}^6{m}^2}=0.234m$

= 23.4 cm