CE$7$E$05-1$

Q$6($a$)$ A $25cm$ diameter well fully penetrates a confined aquifer that is $18m$ thick. Following a period of pumping at a rate of $19$ litres $se{c}^{-1},$ the drawdown in wells at $8m(r_1)$ and $16m(r_2)$ were found to be $8\mathrm{.}5m$ and $4\mathrm{.}3m$ respectively. Determine the Transmissivity $(m^2{d}^{-1})$ and the hydraulic conductivity of the aquifer $(m{d}^{-1})?$

$[6]$

$($b$)$ Explain the following terms: unconfined aquifer, aquitard, hydraulic conductivity, transmissivity, effective porosity.

$[6]$

$($c$)$ Figure Q$6$ below shows a section through a confined aquifer taken at right angles to the coast.

Figure Q$6$

The distance of the toe of the saltwater wedge from the coast is $600m.$ Considering the discharge of freshwater per unit width towards the sea $(Q_0^{\text{'}})$ is $2\mathrm{.}5m^2{d}^{-1}$ and the thickness of the medium sand aquifer is $200m$ with the upper confining layer being $18m$ below sea level.

$($i$)$ Calculate the hydraulic conductivity, $K_f,$ for the freshwater section of the aquifer?

$($ii$)$ What effect will decreasing $Q_0^{\text{'}}$ have on inland penetration of seawater?

$[8]$