Hydrologic and cost benefit analysis at local scale of streambed recharge structures in Rajasthan (India) and their value for securing irrigation water supplies

Dashora, Y.; Dillon, P.; Maheshwari, B.; Soni, P.; Mittal, H. K.; Dashora, R.; Singh, P. K.; Purohit, R. C.; Katara, P.

Hydrologic and cost benefit analysis at local scale of streambed recharge structures in Rajasthan (India) and their value for securing irrigation water supplies | Analyse hydrologique et coût bénéfices à l’échelle locale des structures de recharge par le lit d’un cours d’eau au Rajasthan (Inde) et de leur valeur pour sécuriser les approvisionnements en eau d’irrigation Análisis hidrológico y de costo-beneficio a escala local de las estructuras de recarga en cauces en Rajasthan (India) y su valor para asegurar el suministro de agua de riego 拉贾斯坦邦(印度)小尺度河床补给结构的水文和成本效益分析及其安全灌溉供水的意义 Análises hidrológicas e de custo benefício na escala de estruturas locais de recarga de leito fluvial no Rajastão (Índia) e seu valor em assegurar a oferta de água para irrigação

2019

A hydrological study of four streambed recharge structures, locally called check dams, in a monsoonal area of hard-rock terrain in Rajasthan, India, was conducted over 3 years to evaluate their contribution to agricultural production. Their catchment area totalled 3,003 ha, and mean annual recharge from the 4 impoundments was 779,000 m³ or 26 mm. The calculated components of the annual water balance of these check dams are presented, together with a sensitivity analysis on unmeasured parameters and documentation of capital and maintenance costs of check dams. The maximum recharge was found to occur in the wettest year for the two structures on first-order streams; however, for the two structures on second-order streams, the maximum recharge occurred in the average rainfall year because, at these sites, groundwater levels rose so that the stream became hydraulically connected to the aquifer for a period in the wettest year causing mean dry weather infiltration rates to diminish. The study also evaluated the effect of manual desilting and mechanical desilting on mean dry-weather-infiltration rate. For the check dam that was manually desilted, the recharge increased by 84% over that of the preceding year, whereas for the mechanically desilted check dam it reduced by 18%, and the two control check dams increased by 13%. A present value analysis for net benefits of additional crop production attributable to recharge from check dams indicated that, after accounting for average annual maintenance costs 2.9% of capital costs, the benefit:cost ratio of the four check dams averaged 4.1. Hence this study shows that these check dams are economically attractive at the local level for securing irrigation water supplies.

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