S Masoudiashtiani - PhD Candidate, Civil and Environmental Engineering Department, Utah State University, USA.,
R. C. Peralta - Professor, Civil and Environmental Engineering Department, Utah State University, USA.,
M. E. Banihabib - Associate Professor and Head, Department of Irrigation and Drainage Engineering, College of Aburaihan, University of Tehran, Iran.,

Groundwater is often a relatively reliable, clean, and safe source of water supply. However, in some locations, including sites in arid and semiarid regions, the aquifer saturated thickness maybe insufficient for vertical tube wells to extract desired water rates. Radial Collector (RC) wells are advantageous for obtaining sustained groundwater yield from thin aquifers located near hydraulically connected surface water. An RC well abstracts groundwater with less drawdownat the well casing than usually occurs at a traditional vertical well extracting the same pumping rate. An RC well consists of a central caisson from which multiple horizontal lateral lines extend horizontally. Available steady-state analytical solutions differ in assumptions, situationalsuitability, and accuracy. Applying numerical simulation models (finite difference, finite element, and analytic element), to compute RC head response to pumping also involvessimplifying assumptions that impact accuracy. The empirical equation of Patel et al. seems most accurate of all empirical and analytical equations. Assume an RC well located 100-350 m from a river, in a shallow unconfined aquifer having 8-15 m saturated thickness of unconsolidatedsand and gravel of hydraulic conductivity equal to or exceeding 500 m/d. Assume the RC well has a 3-m caisson radius, 24 symmetrically placed laterals, lateral lengths of 35-100 meters, and total steady pumping not exceeding 250 liters per second. The Patel Equation computes caisson head about 4 % higher than heads computed by a numerical analytic element (AEM) model. For the same range of situations, the McWhorter and Sunada (M&S) Equation computes heads less than 2.6 % greater than the Patel Equation. Having a total error of less than seven percent is good news of well designers experienced in using the Thiem Equation. The M&S Equation is based upon the Thiem Equation, and comparably easy to use.

Radial Collector well, unconsolidated and unconfined aquifer, Ranney well