A reductionist physical approach to unsaturated aquifer recharge from a circular spreading basin

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Abstract
In this paper the process of aquifer recharge from a circular area through the unsaturated zone is investigated. The same basic methodology described previously by the authors for the case of a long strip recharging area (Morel‐Seytoux et al., 1988) is applied. An approximate solution to the three‐dimensional problem is obtained by matching two unidimensional flows, a vertical and a radial one. The mathematical formulation is obtained first for the case of a constant infiltration rate and then for a time‐dependent rate through the unsaturated zone. The formulation leads to an integrodifferential equation whose solution is obtained numerically using the “discrete kernel” approach (Morel‐Seytoux et al., 1973; Morel‐Seytoux and Daly, 1975). In both cases, concrete examples illustrate the influence of the parameters on the discharge into the saturated zone and on the water table level. Also, a criterion to evaluate the efficiency of the recharge is provided for practical purposes. This criterion allows comparison between different recharge designs.