Flow from Infiltration Basins to Drains and Wells

Storm-runoff, which usually contains appreciable amounts of suspended load, can be introduced into the aquifer as artificial replenishment only through infiltration basins. Where an impervious layer under these basins prevents the infiltrating water from reaching the main underlying aquifer, a drainage system laid above the impervious layer, or drainage wells, will intercept the infiltrating water and convey it to recharge wells which penetrate this layer. The sand between the basins and the drains acts as a filter so that the water is almost free of suspended load on reaching the recharge wells. The hydraulics of the water flow from the infiltration basins to the drains is studied for too possible basin geometries: Basins in the form of long ditches with drains placed midway between them, and large basins with drainage wells within their boundaries. In both cases, the basin-bottom is covered by a semipervious layer formed by the suspended load in the water. Accurate or approximate analytical solutions are presented for the various flow patterns that may occur. These establish the relationship between rate of infiltration, geometry of basins and drains and aquifer characteristics.