This method is a mathematical model, in which all the components in the water balance equation are known, and the only component which is considered unknown is the rainfall recharge.

The study was undertaken in the Bhadra River Basin using remote sensing  input.  Norms recommended by the Central  Groundwater Estimation Committee Report (1997) were followed, which states that the groundwater recharge should be estimated based on groundwater level fluctuations.

The study area and the type of data used are described. Thematic maps of the area  using the satellite data and conventional data on 1:50,000 scale were developed. The areal extent of built-up areas, areas under rabi and kharif crops, rock outcrops and surface water-bodies were obtained from the landuse/cover map, while the areas with slopes greater than 20%, were realised from the slope map.

The authors calculated the recharge values from monsoon rainfall, non-monsoon rainfall, hilly areas, surface water bodies, ground water irrigation etc. Other factors such as present state of groundwater development, future state of groundwater development were also taken into consideration in preparing the assessment.

The monsoon rainfall recharge was calculated, which is 4342.20 ha m and the total annual recharge is 17673.21 ha m. From the results obtained, the authors conclude that the present stage of groundwater development for the entire Bhadra river basin is 32% and stage of development after five years is 42%, which is less than that recommended by Central Groundwater Estimation Committee.

This paper was presented at the National Seminar on Water and Culture organised by Kannada University and Sahayoga in 2007.

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