In Sri Lanka, people have been practicing irrigated rice cultivation using small tanks, which are found mostly as clusters known as tank cascade systems.
There are 1,162 such cascade systems functioning at present in the dry and intermediate zones of Sri Lanka. They traditionally utilize water resource in an integrated manner. The rice is cultivated below these tanks with the influence of groundwater raised due to these water bodies. They cultivate according to rainy seasons taking maximum benefit of rainfalls. Tank water has been released during the major rainy season only when the crop is not supported from groundwater and rainfalls during dry spells.
This practice could save major portion of the tank water for subsequent minor season, where rainfall is too small. some tanks built up in the upper area of the cascade system can release water to lower tanks in any emergency, when the crop is affected with water scarcity during the minor season. This system is operational even at present, however silting of the tanks due to soil erosion has led to reduce its potential.
Dr. P.B. Dharmasena,
Former National Consultant of FAO (Agriculture and Water Management)