Dug-wells, dug-cum-bore wells, and tubewells

Abstract

For optimum potential, dug wells should have a large diameter, adequate water column, high permeability and low hydraulic gradient. In non-arid regions their depth is limited to 60 m, and in Maharashtra and Madhya Pradesh in India, the dug-wells are generally limited to 20 m. A water column of about 5 m in the lean part of the year should be adequate. There is good reason to put a bore in an existing well (dug-cum-bore wells) when: (1) the formation tapped in the open well is fine-grained or poor in productivity, and there is a good chance of encountering a coarse-grained or productive formation below a depth of 15 m; (2) the formation tapped in the open well is limited in depth but underlain by an effective confining bed followed in depth by a good confined aquifer; or (3) the potential productive water table zone is tapped fully in the existing due well by improvement in respect to increased depth, diameter and water column. A tubewell taps a potential confined aquifer below a confining layer and therefore effectiveness of the tubewell will depend upon the effectiveness of the confining bed. (Robinett-Arizona).