Standardized precipitation index based dry and wet conditions over a dryland ecosystem of northwestern India

Abstract

Droughts are extreme meteorological and hydrological events having severe impacts on the natural environment and socioeconomic conditions of the affected region especially over a dryland ecosystem like Rajasthan state in northwestern India. Therefore, in this paper an attempt has been made to investigate the dry and wet conditions over the state based on standardized precipitation index (SPI). For this study, diurnal rainfall data of 33 stations have been procured and used for the period 1961–2017. The analysis has been carried out at different time scales i.e. early, mid, late, whole rabi season and annually. To examine the trends in rainfall and SPI, Mann-Kendall test has been applied. Spatial plotting of rainfall and SPI has been done by means of inverse distance weighting interpolation technique. The analysis has shown an increasing trend in annual SPI over majority of stations (23 stations), with significant increasing trend at 5 stations (significant at 95% confidence level). Seasonally, incremental drying conditions have been witnessed during mid- and late rabi seasons, which are opposite to early rabi season when about 70% of the stations have witnessed wetting conditions. Almost all the stations have evidenced severely dry years except Banswara, Barmer, Nagaur and Sirohi stations. Overall, the northwestern, southeastern and northeastern parts have suffered from high drought severity, whereas central regions have relatively low severity of droughts. Finally, the results of this study may be beneficial for decision makers in formulating water management policies to mitigate the impact of dryness and wetness.

Keywords

• drought severity
• rainfall
• season
• spatial distribution
• trend analysis
• rajasthan