Rain water harvesting in rainfed bhatina watershed area in Birbhum district of West Bengal.

In India about 90 million hectare of land depands upon rainfall for cultivation and provide livelihood to the 70% of the population. Rain eater harvesting in that area may use for supplemental irrigation at the critical stages of crop growth like, seed germination (pre-sowing irrigation), at tillering, flowering etc. for sustainable agriculture. Rainwater harvesting is crucial even in high rainfall area, as the rain comes only for two to four months or less in a year and dry spell exist in rest of the year. Water harvesting is not a new method in India, irrigation tank, khadins, beach terraces were constructed to trap rain water in acient India. But, in modern agriculture harvesting of underground water causes arsenic and fluoride problem in underground water and depletion of water table. In this moment, soil and water conservation measure in crucial. Old ponds need desiltation, silt may be used as meanture, old irrigation and village tanks are to be renovated in addition to building new one. (Bali, 1980) From an economic view point, a pond should be located where the largest volume can be obtained with least amount of earth fill. This condition will gererally occur at a site where the vally is narrow, side slopers are relatively steep and slope of vally floor will permit a large deep basin. Pomds with a large area of shallow water should be avoided due to excessive evaporation losses and the growth of noxious aquatic plants. where water must be used for irrigation. ponds should be located as close to the poont of use as is possible (singh et al., 1981). A field study was done on constration of water harcvesting structure in Bhatina watershed which is located between latutude 24 08'25" to 24 10'53" n and lomgitude 87 42'00" E in Eastern plateau and hill Zone (late rite zone of west bengal0. the water harvesting structure was constructed to preserve run-off water for supplying life saving irrigation at critical stage the benifit cost ratio were analysed which is more than 1.5 and so the WHS is taken up in Bhatina watershed araea may be considered feasible as per soil and water conservation works.