Ground Catchment

Open reservoirs can be used to capture rainwater runoff for agriculture or domestic use and for recharging an aquifer. Oftentimes these natural reservoirs are the cheapest option for water storage. However, modifications can be made to increase volumes or gain access to the water. Small dams can be built or linings (to prevent infiltration) can be added. Diversions can also be created to send water to crops or nearby villages. For additional expense, underground tanks can be built in a runoff basin, which can be made with an increased depth to width ratio (more deep than wide), which means less evaporation losses overall.

Climate change considerations
Less rainfall and longer dry periods mean reduced soil moisture for crops. Groundwater recharge may be reduced if infiltration decreases. Many near-coast aquifers will be at risk from salt water intrusion as a result of sea level rise. Ponds, tanks, and reservoirs may not fill enough to support agriculture, or may be damaged by extreme floods. Larger more intense floods could also cause catastrophic, large dam failures. Open water reservoirs could create breeding grounds for mosquitoes, which can lead to increased malaria and water-borne diseases. Therefore, smaller reservoirs help reduce risk and expense.



Natural rock catchment and Open water reservoir	Natural or artificial ground catchment and Lined sub-surface tanks	Natural ground catchment and Open water reservoir

Ground catchment and storage links

Small Reservoirs Project. Small Reservoirs Project: Planning and evaluating ensembles of small, multipurpose reservoirs for the improvement of smallholder livelihoods and food security.