Irrigation tank

An irrigation tank or tank is an artificial reservoir of any size. In countries like Sri Lanka and India they are part of historic methods of harvesting and preserving rainwater, critical in regions without perennial water resources. A tank is often an earthen bund (embankment or levee) constructed across a long slope to collect and store surface water from the above catchment and by taking advantage of local topography. The water would be used primarily for agriculture and drinking water, but also for bathing and rituals. The word tank is the English language substitute for several vernacular terms.

Tank irrigation, or reservoir irrigation, utilizes tanks and connected sluices and channels to direct water to the crops. This surface irrigation method can be used to grow crops like rice. Tank irrigation in Thailand is a newer method of irrigation as compared to peninsular India. Similar small-scale reservoir based irrigation methods using earthen bunds are used in countries like Ghana.

A tank cascade is a system of irrigation tanks in single or multiple chains where water from a higher tank flows into lower tanks. Examples of tank cascades include Sri Lanka's tank cascade system, the Indian city of Bangalore's cascading lakes in the Varthur lake series, and the Indian city of Madurai's Vandiyur tank cascade system.