Question 3 A 12 inch diameter wellis installed in a confined

Question 3: A 12 inch diameter wellis installed in a confined aquifer with a saturated thickness of 100 feet. The aquifer has a transmissivity of 40,000 gpd/ft. Compute the drawdown at wells that are located 0.5 ft and 400 ft from the pumping well 1 year after pumping at a rate of 600 gpm.

Solution

Solution:-

Given

Q = 600 gpm = 864*10³ gpd

Let Storage coefficient(S) = 0.004

T = 40000 gpd/ft

Time (t) = 1 year = 365 days

Let drawdown = s

Case 1

When r = 0.5 ft

We know that

s = Q/(4?T) *(log(4Tt/(r²S)) - 0.5772)

s = 864*10³/(4?*40000) * (log(4*40000*365/(.5²*0.004)) – 0.5772)

s = 17.5 feet   Answer

Case 2

When r = 400 feet

Draw down(s) = 864*10³/(4?*40000)*(log(4*40000*365/(400²*0.004)) – 0.5772)

Draw down(s) = 7.53 feet     Answer