We have investigated stream-aquifer interaction with a single pumping well in an aquifer bounded by two parallel nearby streams. This study presents steady-state semi-analytical solutions to calculate the fraction of water withdrawal from two streams. Potential theory is used to describe the capture zone between two streams when low-permeability streambeds are not present. Steady-state flow equations in the aquifer and two streambeds are solved following rigorous mass balance requirements if low-permeability streambeds are present. When the low-permeability streambeds are not present and the regional flow exists between two streams, this study finds that the maximal capture size without extracting water from the down-gradient stream decreases with the normalized well location in an approximately linear fashion. Furthermore, the normalized flux from the up-gradient stream decreases with the normalized well location faster than the linear fashion. When the low-permeability streambeds exist and the regional flow is neglected, the normalized flux across either streambed varies with the normalized well location in a linear function. Furthermore, the magnitude of the slope of that function is nearly unity when the hydraulic conductance ratio of the two streambeds is one and is less than unity when the hydraulic conductance ratio of the two streambeds is either greater or smaller than one. When the normalized well location with equal fluxes from two streams versus the hydraulic conductance ratio of the two streambeds are plotted semi-logarithmically, we observed a segmented curve including a steep segment at the beginning, followed by a flat segment, and a final steep segment. 2007 Elsevier B.V. All rights reserved.
