Effect of Water Depth in Groundwater Recharge Basins on Infiltration

Sediment or organic clogging layers on the wetted perimeter are the rule rather than the exception for infiltration basins for artificial recharge of groundwater. When the water depth in such basins is increased, the clogging layer is compressed. This causes infiltration rates to increase much less than expected from the water depth increase alone, and rates may actually decrease. Such decreases are especially severe where the decreased turnover rate (increased detention time) of the water in the infiltration basins due to increasing the water depth leads to increased growth of suspended algae. These algae form a filter cake on the basin bottom. Also, because of photosynthesis, these algae increase the pH of the water, which can cause precipitation of calcium carbonate. This precipitate and the algal filter cake both aggravate the clogging problem and cause infiltration rates to decrease even further. Consolidation theory is used to explain the compression of the clogging layer. The conclusions are supported by field and laboratory studies. Careful analysis of the situation and on‐site experimentation are needed to determine the optimum water depth for recharge basins.