Last Minutes

Question 1

Jacob approximation of W(u)
When can it be applied?

Answer 1

W(u) = ln(0.56/u)
Can be applied when t is long enough that u is less than 0.05.

Question 2

Image well approximation for fixed head boundary
What is different about the no-flow boundary equation

Answer 2

s = Q/2πT ⋅ ln(r_image/r_real)
where
s = total drawdown
r(image) = distance of location where s is being measured from image well
r(real) = distance where s is being measured from real well
Q is pumping rate out of real well and into image well
For NO FLOW, the radius terms in the ln() term are multiplied, not divided

Question 3

Steady state distance drawdown equation for confined aquifer, fully penetrating well

Answer 3

s1-s2 = Q/2πT ⋅ ln(r2/r1)
where
s1 > s2
s1, s2 are drawdowns at r1 and r2 away from a pumping well pumping at rate Q

Question 4

Steady state radius of influence (Rsub0) for confined aquifer, fully penetrating well

Answer 4

Set one of the drawdowns equal to 0 and calculate what the corresponding r for that condition

Question 5

Steady state distance drawdown equation for unconfined aquifer, fully penetrating pumping well, multiple obs wells
using corrected drawdown

Answer 5

H1^2-H2^2 = Q/πK ⋅ ln(r2/r1)
to convert to drawdown, need to use corrected drawdown s*
s1-s2 = Q/2πKH0 ⋅ ln(r2/r1)
where
s* = s-(s^2/2H0)
s1 > s2
H1 (s1), H2 (s2) are heights above confining layer (drawdowns) at r1 and r2 away from a pumping well pumping at rate Q
H0 = is the saturated thickness prior to any pumping (at R0)

Question 6

Image well equation for fixed head boundary, unconfined aquifer

Answer 6

H = sqrt(H0^2 - Q/πK ⋅ ln(rimage/rreal)