n This manuscript was handled by Phillipe Baveye, Editor-in-Chief, with the assistance of Xunhong Chen, Associate Editor

ofte with first-order free surface equation is used to describe the movement of water table. A point-sink solution of commo. The simulate groundwater flow due to pumping in a collector well. Mikels and Klaer (1956) mentioned that a radial collector well can be approximated as one vertical well with a radius of 75–80 % of its lateral length. McWhorter and Sunada (1977) also mentioned that one vertical well with a radius of 61 % of lateral length could approximate a radial collector well. Bischoff (1981) stream in an unconfined aquifer. He indicated that the pumping rate is an important factor to determine the quantity of pumped water from background aquifer. Su et al. (2007) used a numerical model to simulate an unsaturated region occurring between the bottom of a partially-penetrating stream and the water table due to pumping in two radial collector wells beneath the stream. They found that the unsaturated region increases with the ratio of hydraulic conductivity of the aquifer to that of streambed. Kim et al. (2008) carried out sand-tank experiments of a collector well consisting of one caisson and one lateral. Their results showed that the water pumped from the caisson increases if the lateral lengt