Quantification of recharge from the rainwater harvesting structures—a case study in hard rock area of Odisha (India)

Rainwater harvesting structures have been proved as one of the best options to conserve runoff in hard rock areas in India. Volume of rainwater conserved in a structure depends on the design dimension of the structures, soil type, climate, and land topography. These structures also act as groundwater recharge means if constructed at an appropriate location. Direct quantification of amount of water recharged from the structures in field condition is not feasible, but there are few indirect methods to quantify important water budget parameters. In this paper, water balance approach was used to estimate all inflow to the structure and outflow from the rainwater harvesting structures located in Bargharianala microwatershed in Nayagarh district of Odisha (India). Rainfall and runoff to the structures were inflow components, and evaporation, seepage/percolation losses, and extraction for irrigation from the structures were the outflow components. Monthly water level change was measured from the water harvesting structures and the changes in water level were used to determine the effect of recharge/subsurface flow. Seepage and percolation rate was estimated based on the piezometric observations. Result showed that annually recharge from structure with 0.38 ha m capacity was only 0.03 m during initial construction of the structure which further increased to 0.25 m after subsequent years. For 0.5 to 0.75 ha m structure, the recharge amount varied from 0.318 to 0.18 m with average of 0.25 m. In case of structure of 0.2 ha m capacity, with a recharge well within the structure, recharge was increased up to 0.86 m. The impact of these structures was observed up to 300 m areal extents covering the area of influence of 15 ha command area in hard rock areas of Odisha. The water table depth in dug wells located within the command area raises up to 1 m during pre-monsoon season.