Question

A well is pumped at Q = 300 m3 /hr in a confined aquifer. The aquifer transmissivity is 25 m2 /hr and the storage coefficient is 2.5x10-4 . Calculate the drawdown at a distance 200 m from the well after pumping for (1) 50 hr, (2) 200 hr.

Answer 1

Answer:

(a). The draw-down at a distance 200 m from the well after pumping for 50 hr is 5.383 m.

(b). The draw-down at a distance 200 m from the well after pumping for 50 hr is 6.707 m.

Explanation:

Given that,

Energy $Q=300\ m^3/hr$

Transmissivity $T = 25\ m^2/hr$

Storage coefficient $S=2.5\times10^{-4}$

Distance r= 200 m

We need to calculate the draw-down at a distance 200 m from the well after pumping for 50 hr

Using formula of draw-down

$s= \dfrac{Q}{4\pi T}(-0.5772-ln\dfrac{r^2S}{4tT})$

Put the value into the formula

$s=\dfrac{300}{4\pi\times25}(-0.5772-ln\dfrac{(200)^2\times2.5\times10^{-4}}{4\times25\times50})$

$s=5.383\ m$

We need to calculate the draw-down at a distance 200 m from the well after pumping for 200 hr

Using formula of draw-down

$s= \dfrac{Q}{4\pi T}(-0.5772-ln\dfrac{r^2S}{4tT})$

Put the value into the formula

$s=\dfrac{300}{4\pi\times25}(-0.5772-ln\dfrac{(200)^2\times2.5\times10^{-4}}{4\times25\times200})$

$s=6.707\ m$

Hence, (a). The draw-down at a distance 200 m from the well after pumping for 50 hr is 5.383 m.

(b). The draw-down at a distance 200 m from the well after pumping for 200 hr is 6.707 m.