Improved yield from aquifers of limited saturated thickness using inverted wells

Inverted wells, in which the solid casing extends over the full depth of the permeable aquifer, but with slotted screens projecting upwards alongside the solid casing, can provide high yields in moderately transmissive aquifers for which all permeable strata are within about 30 m of the non-pumping water level. The use of inverted wells has been pioneered in the Rajshahi Barind in northwest Bangladesh. Conceptual and computational models of inverted wells are developed. By examining a step-pumping test using a numerical model, the important flow processes are identified and quantified. The sustainability of the substantial groundwater abstraction in the Rajshahi Barind is examined by considering the recharge processes which depend on losses from flooded rice fields, the hydraulic conductivity of the overlying Barind Clay and the seasonal recovery of observation well water levels.