Hydrology Journal

Determination of crop water requirements (CWR) for cropping areas in a watershed is necessary for appropriate utilization of the runoff. The essential prerequisites for determining the CWR are crop-land suitability analysis/evaluation and derivation of cropping areas. In the present study physical qualities which affect the soil-site characteristics were considered in the analysis for crop land suitability. Land suitability of crops was carried out by using the Fuzzy membership and multi-criteria analysis in a Geographic Information System (GIS) environment. Highest suitability crop map was derived on the basis of pixel-wise largest membership value. Cropping areas were computed by the overlay of highest suitability crop map and landuse map of the watershed in a raster GIS environment. CWR for the cropping areas were derived by the Modified Penman Method. Weekly CWR for crops were determined after the estimation of crop coefficient (K_C) and reference crop Evapotranspiration (ET_o) values. CWR is basically a function of loss of moisture through Evapotranspiration (ET) and depends mainly on the prevailing weather conditions and varies according to the crop growth stages. CWR for the cropping areas were derived on the basis of these criteria. CWR, thus obtained, may serve as a guideline for optimal utilization of available water. The details of the methodology involved are illustrated for the Kalyanakere watershed of Karnataka state, India.