This report by ICRISAT deals with a survey of thirty-two tanks and farm data from Andhra Pradesh and Maharashtra states to assess the economic performance of irrigation tanks in semi arid tropics of India. It uses district-wise data on climatic and institutional variables to analyze the factors affecting tank-irrigation density. Results indicate that the spatial distribution of irrigation tanks is determined primarily by physical factors—hard rock substratum, post-monsoon rains, low moisture-holding capacity of soils and by population density.

Tank irrigation, formerly a source of relative stability, has become a source of instability for agricultural production in many parts of India. Important factors for the decline in tank irrigation are: environmental degradation such as deforestation, soil erosion, siltation, tankbed cultivation, and lack of administrative setup to provide timely repair and maintenance of tanks, and to ensure proper water control and tank management.

Simulation results show that with improved water control and by keeping sluices closed on rainy days, a 20 per cent larger command area can be irrigated. As per the study, there is potential for economically beneficial tank irrigation and there are tanks which generate internal rates of return of 23 per cent. High water-use efficiency and command-area utilization are the major factors associated with high rates of return from tank irrigation. Since tank irrigation has potentially high economic payoffs, means to rehabilitate irrigation tanks should be found.

In order to increase water-use efficiency, tank-water controllers should be reintroduced at the village level, and authorized to operate the water sluices for better water control. A Tank Irrigation Authority is proposed for better water control and management. Another concept proposed is Composite Watershed Management (CWM) on alfisols involving a system of runoff and erosion controlling land management for enhanced groundwater recharge and sustained well irrigation. 

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