Watershed prioritization of Ukai dam catchment in Gujarat using remote sensing and GIS – A research report by National Institute of Hydrology

In the present study, watershed prioritization of the catchment immediately upstream of the Ukai reservoir has been carried out using remote sensing technique. The Watershed Response Model (WRM) has been used for this purpose. This model utilizes the Normalized Difference Vegetation Index (NDVI) and the Soil Brightness Index (SBI), the two important parameters responsible for soil erosion.

These two parameters have been determined using remote sensing data in the study. The ERDAS Imagine system has been used for carrying out digital image analysis. The other two parameters, i.e., morphological and topographical have also been considered and ILWIS system has been used for estimation.

The immediately contributing catchment, upstream of the Ukai reservoir has been divided into sixteen watersheds and different vegetation, soil, topography and morphology related parameters have been estimated for all the watersheds separately. The integrated effect of all the parameters has been evaluated for recommending the priority rating of the watersheds for conservation planning.

Investigation of basins for conservation planning is quite cumbersome and expensive. Therefore, it requires a selective approach to identify smaller hydrological units, which would be suitable for more efficient and targeted resource management programs. The identification of these critical sub-basins, which need soil and water conservation measures on preferential basis, is particularly important in the areas that are close to the reservoir. A criterion, which can be used to determine priority for conservation planning, may be soil erosion or sediment yield of a basin.

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