A well adjacent to a river will take a portion of its supply from the river A theoretical formula is developed which permits the draft on the river to be computed in terms of the distance of the well from the river, the properties of the aquifer, and time. The formula applies where the river can be considered to flow in a straight course which extends for a considerable distance both upstream and downstream from the well location.

In addition to the notation used by the authors, the following is also used: b = the thickness of the artesian aquifer, ft b′ = the thickness of the confining bed through which vertical leakage takes place in proportion to the drawdown, ft K′ = permeability of the confining bed, ft/sec T = transmissibility of the aquifer which is equal to Kb in confined flow systems, and equals KD in unconfined flow systems, ft/sec S = storage coefficient which, in artesian aquifers, is the volume of water that a unit decline of head releases from storage in a vertical prism of the aquifer of unit cross‐section; its ultimate value in water table aquifers is the specific yield of the aquifer, which is designated by V in the authors' paper, demensionless B = leakage factor, which equals ft [Hantush and Jacob, 1954] erf (Z) = the error function or the probability integral = dv erfc (Z) = the complementary error function = 1 − erf (Z)

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