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

(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.

Step-by-step explanation:

Given that,

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

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

Storage coefficient
`S=2.5*10^(-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= (Q)/(4\pi T)(-0.5772-ln(r^2S)/(4tT))`

Put the value into the formula

`s=(300)/(4\pi*25)(-0.5772-ln((200)^2*2.5*10^(-4))/(4*25*50))`

`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= (Q)/(4\pi T)(-0.5772-ln(r^2S)/(4tT))`

Put the value into the formula

`s=(300)/(4\pi*25)(-0.5772-ln((200)^2*2.5*10^(-4))/(4*25*200))`

`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.