Hydrologic response of a watershed to land use changes: a remote sensing and GIS approach

In the arid and semi-arid tropics, low annual rainfall together with high intensity rains has resulted in excess runoff, soil erosion and low moisture intake leading to poor crop yields. Therefore, adoption of soil and water conservation measures is necessary for the optimal utilization of natural resources and to increase the productivity of land on a sustainable basis. Remote sensing and GIS techniques can be used for generating development plans for the watershed area in consonance with the production potential and limitation of terrain resources, and can also be used for assessing the impact of these measures before actual implementation in the field. This paper describes a case study for the Jasdan taluka (district) of Rajkot in Gujarat, India. The aims are to prioritize watersheds on the basis of runoff generated, expressed as yield, due to existing land use conditions; to suggest soil and water conservation measures; and to evaluate the hydrologic response of these measures on runoff. The Soil Conservation Service Curve Number (CN) method was used for computing the runoff; subsequently runoff yield in percentage was calculated for prioritizing the watersheds. Satellite and other collateral data were used to identify the problems and potential in the watersheds and recommend measures for soil and water conservation. The impact of these measures was assessed by computing runoff under alternative land use and management practices. It was found that the runoff yield decreased by 42.88% of the pre-conservation value for the watershed.