Determining water resources suitability for sheep grazing using GIS (Case study: rangelands of southwest of Sabzevar)

According to the important role of water in livestock growth, and on the other hand, the loss of rangeland forage in the absence of sufficient water for drinking, the necessity of considering the water resources suitability is highly emphasized. Therefore, for optimal use of existing potentials of livestock and rangeland, the quantity, quality and distribution of water resources need to be taken into consideration. Given that several factors are involved in determining the suitability of water resources, this research was aimed to identify the most important factors affecting the suitability of water resources, limiting factors, and the classification of southwestern rangelands of Sabzevar on the basis of water resources suitability for sheep grazing, as the dominant livestock in these rangelands. This research was conducted using FAO (1990) method in GIS. First, DGN maps of the study area were prepared and the boundary of the region was determined. Then, water resources of the region were investigated in terms of quantity and quality (TDS, EC, and Mg+2). Finally, the layers of quantity, quality and equidistant points from water resources (prepared for four slopes of 0-10, 10-30, 30-60, and >60%) were integrated to produce the water resources suitability model. Results showed that the water resources of the study area had no limitation in terms of quantity so that all were classified as S1 suitability class, but in terms of quality, all water resources except one were classified as S2 suitability class. The final model of water resources suitability showed that 62.7, 2.4, and 34.9% of the rangelands in the study area had the suitability class of S2, S3, and N, respectively. Accordingly, slope, inappropriate distribution of water resources and salinity were identified as the most important limiting factors.