Abstract:
The droughts are recurring natural phenomenon, governed by regional climatic parameters. The mean annual precipitation and mean annual potential evapotranspiration are the readily available climatic parameters. The ratio of mean annual precipitation (Pa) to global terrestrial mean annual precipitation (Pg), and ratio of mean annual potential evapotranspiration (Ep) to mean annual precipitation (Pa) have been used to define the climatic regions. This is an attempt to develop relationship between average drought frequency and evapotranspiration/precipitation ratio in arid, semiarid and sub-humid climatic regions in India. The average drought frequency (i e., yr-1) is found to decrease gradually from dry to wet regions. The return period varies from two to three years in the arid regions (12> Ep/Pa 5), three to five years in semi-arid regions (5>Ep/Pa 2), and five to eight years in sub-humid regions (2>Ep/Pa 3/4). Also, another relationship describing the average frequency of occurrence in terms of the ratio of mean annual deficit to mean annual precipitation, (Ep-Pa)/Pa is developed. The results have been compared with the documented drought experiences elsewhere. These relationships may contribute as a reliable tool for the prediction of regional drought frequency and a base for further critical analysis of drought and for planning of drought management strategies for a given region.
