ABSTRACT
Drought is one of the major climatic hazards, causing hardship due to water scarcity in semi-arid and arid regions of India. During its extended period, the drinking water problem becomes critical in these areas and people migrate to greener regions for survival. In this study, long-term rainfall records and groundwater table data are investigated for a hydrometeorological description of drought events that have occurred in Rajasthan and Gujarat states in western India. Using the climatic index based on the ratio of mean annual potential evapotranspiration (Ep) to precipitation (Pa) (=Ep/Pa), the semi-arid and arid climatic regions are delineated. Rainfall records of 24 rain gauge stations for the last 68–88 years show that about 35 to 48 percent of drought events persisted for two or more consecutive years, and the onset of monsoon was often delayed. The quantum, distribution, and termination of monsoon rains play a major role in the crop production and availability of utilizable water for domestic and other uses in the subsequent lean period. The drought recurs, on an average, every three to four years in semi-arid regions and two to three years in arid regions; and the probability of occurrence of severe and extreme intensity droughts increase with the Ep/Pa ratio. The longest persistence droughts experienced in these areas were for 5 consecutive years. The occurrence of drought events of two and three consecutive years is relatively more in areas with the Ep/Pa ratio of 4.5–6.0 and 7.0–8.0, respectively. Groundwater is a major source of drinking water and for agriculture in this region.
