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Environmental Modeling Community of Practice
Water levels in nested well clusters (wells located closely together) indicate upward or downward flow in aquifers or flow between adjacent geologic units. Flow is governed by Darcy's Law:
where q is the Darcy flux (volume of water per unit area per unit time) and K is the hydraulic conductivity. The change of head (roughly water level) divided by the distance determines the gradient and direction of flow.
Different assumptions about the distances are used in the calculator and are illustrated below.
The vertical gradient calculator determines vertical gradients between adjacent wells. (They are assumed to be located very close together; for wells far apart use one of the horizontal gradient calculators.) It illustrates the effects of screen length on gradient calculations. These differences come about because the gradients are theoretically determined from piezometers that are only open at the bottom and thus have an effective screen length of zero. In practice, wells with screens of various lengths are used to calculate the gradients and the screen lengths may have an influence on the calculated gradients. For reference, the gradients are also calculated assuming that the screen lengths are zero, as if the wells were true piezometers. More information ...
Definition of inputs for each well (piezometer):
Assumptions concerning screen lengths:
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