Drought assessment and monitoring in Jordan using the standardized precipitation index

Drought is one of the most unforgiving natural disasters that could leave severe environmental, economic, and societal impacts. Jordan has witnessed several droughts recently along with recurring summer heat waves, which could be a consequence of global warming, and due to the fact that freshwater resources in Jordan are scarce, it is vital to utilize proper modeling and forecasting techniques that will improve the country's preparedness for possible future droughts. In this study, the annual precipitation data for Amman-Zarqa Basin over the 1980-2016 record were analyzed to identify the occurrence of major droughts in 21 rain stations. Three dimensionless indices which depend solely on precipitation were applied: standardized precipitation index (SPI), standardized precipitation ratio (SPR), and percentage departure from normal (PDN). A comparison was also made among these indices and it was concluded that the SPR and PDN predicted higher numbers of moderate and severe droughts on the expense of extreme droughts compared to the SPI. It was also found that the 1998-1999 year was the driest year in the studied record in which 15 out of 21 stations witnessed extreme droughts. SPI trends were analyzed using the Mann-Kendall test, and it was found that most of the stations experienced negative trends implying increasing droughts over recent years; however, the trends were statistically insignificant for most stations.