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## Conceptual models >## Sloping aquifer |

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.

a b

Typical sloping aquifer system: a - non-leaking, b - leaking. Position of the pumping and observation wells see in the figure above.

Pumping regimes:

One well pumped at a constant rate

Pumping

Recovery

One or several wells pumped at a variable rate

Pumping

References

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.