Numerical approaches for approximating technical effectivessness of artificial recharge structures

This report describes various numerical approaches to quantify technical effectiveness of low-technology artificial recharge structures as seen commonly in rural environment and communities in semi-arid developing countries. The described methodologies enable benefits of artificial recharge facilities, i.e. their ability to replenish the aquifer, to be approximated. Technical effectiveness of recharge facilities is thereby evaluated on three scales: On a recharge basin scale, the rate of infiltration in relation to evaporation is established for different hydrogeological scenarios. This determines if the structure is fit for the purpose and can be investigated by measurements of water level declines in reservoirs during periods of no inflow and outflow except for recharge and evaporation loss. In a second step, the area of benefit, i.e. the zone of impact of the artificial recharge structure is studied, which is dependant on time scale and hydrogeological conditions at the site. This establishes the likely beneficiaries of the scheme. Thirdly, the hydraulic capacity, which is the accumulated infiltration over a long period that includes dry periods, is put into context with naturally occurring recharge in the area and the overall water demand in the local community surrounding the structure. This determines the overall significance of the scheme for the local rural community. The work described was carried out as part of the DFID-funded project on “Augmentation of Groundwater by Artificial Recharge” (AGRAR).