Question $3(20$ marks$)$

Figure below shows a concrete dam and reservoir on a silty sand. The crest of the dam is $150$ m

long $-$ that is$,$ length of the dam perpendicular to the picture. The reservoir has a top surface area

of approximately $10$ ha $.$ The saturated hydraulic conductivity of the silty sand is $8\mathrm{.}0{10}^{-3}c\frac{m}{s}.$

a$)$ determine the quantity of seepage under the dam using flow net analysis; and

b$)$ calculate the rate of drop in the reservoir water level due to seepage $($if you could not

answer part a$,$ assume a seepage rate of $1\frac{m^3}{?}$ day$).$

Figure $2$