Nonuniform thickness and sloping aquifers
Assumptions for aquifers with non-uniform thickness:
✓aquicludes underlie and overlie the aquifer;
✓water level not lower than the aquifer top;
✓both pumping and observation wells are of full penetration;
✓aquifer thickness changes along the x-axis;
✓aquifer thickness exponentially decreases along the x-axis;
✓aquifer is infinite;
✓drawdown is calculated at any distance from the pumping well in the direction of decreasing thickness; in the direction of increasing thickness there is a limitation for the distance such as: ratio of thickness decrease to corresponding horizontal distance must be less than 0.2 (aquifer slope ratio less than 0.2).
Typical wedge-shaped aquifer.
Assumptions for sloping aquifer:
✓aquifer is unconfined, isotropic, sloping, underlain by either aquiclude or aquitard, leaking during the pumping test;
✓initial water saturated thickness of the aquifer is not variable in space;
✓aquiclude and water shed slopes are equal;
✓existing solutions presume the aquiclude slope ratio less than 0.2;
✓drawdown in the pumping well must not exceed one half in the aquifer initial water saturated thickness;
✓for leaking aquifer the aquitard storage is neglected;
✓aquifer is infinite.
Typical sloping aquifer system: a - non-leaking, b - leaking. Position of the pumping and observation wells see in the figure above.
One or several wells pumped at a variable rate
Hantush M.S. Flow of ground water in sands of nonuniform thickness. Part 3. Flow to wells // Journal of Geophysical Research. 1962. Vol. 67, N 4. P. 1527–1534.
Hantush M.S. Hydraulics of gravity wells in sloping sands // Journal of the Hydraulics Division. Proceedings of the American Society of Civil Engineers. 1962. Vol. 88, N HY4. P. 1–15.
Hantush M.S. Hydraulics of wells // Advances in Hydroscience / Edited by Ven Te Chow. New York; London: Academic Press, 1964. Vol. 1. P. 281–432.