12. Trends and Pattern of Rainfall over Semiarid Sahibi Basin in Rajasthan, India

Study of the spatial and temporal trends of rainfall is very important for water resources planning and management. Therefore, this study has been attempted to examine the spatial and temporal trends and pattern of rainfall over the semiarid Sahibi Basin in Rajasthan State of India for a period of 57 years (1961–2017). Rainfall data for nine stations located over the basin have been obtained from the Department of Water Resources, Rajasthan. Statistical methods such as Mann–Kendall test, Sen’s slope estimator, and linear regression were employed to detect the rainfall trends. Percent change for rainfall, and years of excess and deficient rainfall, have also been identified. The findings have shown high interannual variability in mean annual rainfall with an average of 633.95 mm (SD = 204.93, CV = 32.33). However, no significant rising or declining trend has been observed in the mean annual rainfall over the basin during the 57-year period, whereas Kotkasim and Tapukara stations have shown significant increasing and decreasing trends, respectively. Further, pre-monsoon season rainfall has shown a significant increasing trend. Spatial analysis has shown an increase in rainfall amount from northeastern and western parts to the southeast. The observed spatial and temporal differences in the amount of rainfall are high. These results may be valuable for efficient and sustainable planning and management of water resources for agricultural purposes in the basin.