34.-Radial collector wells - Some insight into factors controlling yield and capture zone

Abstract

The pumping test data of three Radial Collector (RC) wells located at Rayka and Dodka in the Mahi and at Sabarmati in the Sabarmati riverbeds were analysed using anisotropic models with river infiltration effects. It was shown that ignoring aquifer anisotropy resulted in overestimation of design yield of these RC-wells. It was also found that maintaining some surface flow over the radials results in significantly higher yield and reduction of subsurface capture distance in comparison with the case when no surface water could be maintained. Hence, any strategy to increase RC-well yield, such as construction of Under Ground Check Dams (UGCD) by raising subsurface water level during the lean flow season (as is planned in case of Sabarmati at Ahmedabad) should be re-evaluated. We suggest that the height of the proposed UGCD be increased so as to maintain —50 cm column of ponded water at the Sabarmati RC-well at Ahmedabad. Similar proposal should also be considered for increasing the yield of Rayka and Dodka RC-wells.