Ground catchment is a broad term that describes all types of ground surfaces that serve as source of surface runoff used in water harvesting. These can range from open land surfaces whether paved or unpaved, including rocky areas, roads, home compounds, pasture lands, forests and other open areas. The sizes could vary from a few square metres for micro ground catchments to extensive land areas and whole watersheds used for large storages such as dams.
Most ground surfaces are covered by soil, thus, water harvesting is hampered by losses due to infiltration, soil moisture storage, deep percolate losses, evaporation and transpiration by plants. Therefore, the runoff coefficient of ground catchments is low. Furthermore, ground catchments yield runoff that is laden with sediments, dirt, as well as other pollutants. But due to the vastness of available runoff, e.g. in watershed, they offer the best option for large scale water harvesting projects.