Question $4(20$ marks$)$

A reservoir having a water spread of $30,000m^2$ and water storage of $1$ million

cubic metre receives the Sun's radiation at average rate of $0\mathrm{.}03$ Langley$/$sec and

$6\%$ of this radiation is re$-$radiated back into atmosphere. The average

temperature rise of the water on that day was observed to be $2C.$ Make

necessary assumptions and estimate the average rate of evaporation in $m\frac{m}{h}r.$

Assume that $1$ Langley equals $1\mathrm{.}1ca\frac{l}{c}{m}^2$; Latent heat of evaporation is $525ca\frac{l}{g}$;

Specific heat of the water is $1\mathrm{.}02ca\frac{l}{g}\frac{?}{?}C$