Well
Conflict Problem
Background
A
dispute has arisen between two farmers after one of the farmers installed a 500
GPM irrigation well 2000 ft from the small domestic water supply well of the
other farmer (see above). After the irrigation well had been operating
for 3 months it was observed that the water level in the domestic well had
declined over 30 feet. The owner of the domestic well claims that the
decline in water level in his well is due to pumping from the irrigation well
and is trying to restrict that pumping. The owner of the irrigation well
claims that the decline is related to the recent drought; he has been advised
that the "radius of influence" of his well is at most 500 feet.
You
are asked to determine whether it is possible for the water level decline in
the domestic well to be produced by pumping from the irrigation well. It
is known that both wells produce from the same completely confined
aquifer. A prior well pumping test on the irrigation well indicates that
the confined aquifer has a transmissivity of 1350 ft2/day and a
storativity of 10-4.
Problem
1:
Solve the problem analytically.
Problem
2:
Solve the problem numerically and compare the result to your analytical
solution.
Hints:
- Assume
the initial head is zero and spatially-constant. (‘Initial’ refers to the
instant the irrigation well is installed but has not yet started pumping).
- Use
the ‘Distance Display’ capabilities when editing geometric features and/or the
‘Ruler’ tool to properly represent distances between model features.
- Make
sure the ‘no-flow’ side boundaries are sufficiently far away so that they are
outside the area of influence under maximum pumping conditions.
- Use
a large number of grid cells (NX=100) in your model.