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[[Image:MasonryTank.jpg|thumb|right|300px|Stone masonry round berked under construction showing wires for roofing materials. Somaliland. Eric Fewster, BushProof / Caritas.]]

These are natural, artificial or modified catchments that have low to relatively high runoff coefficients. Water from these catchments is captured and stored in lined sub-surface reservoirs excavated below ground level. The reservoirs are known by different names (''berkeds'' in Somaliland, ''taankas'' in India, hemispherical sub-surface tanks in Kenya – also included in this category are excavated water cellars such as the ''shuijiao'' in China) and have been lined with many different materials. These tanks normally have a larger depth to surface ratio compared to open ponds and their scale means a roof of some description is a possibility. When the lining is constructed well, there will be no leakage, and water will either evaporate or be abstracted. These tanks are often privately-owned by one or more families, but can be communal.