Meteorological drought assessment using SPI and RDI indices in the Ourika Basin, Morocco

Abstract

The Ourika basin is located on the northern edge of the Marrakech High Atlas, within a semi-arid to sub-humid climate. Its fragile natural environment is exposed to extreme and harsh climatic conditions, such as droughts and floods. The aim of our study is to evaluate and monitor meteorological and hydrological droughts in the Ourika basin during the experimental period from 1980 to 2019. The severity and duration of droughts are estimated using two drought indices: The Standardized Precipitation Index (SPI) and the Reconnaissance Drought Index (RDI). These indices were computed and analyzed using Drinc software. 8 meteorological drought sequences have been identified: 3 episodes were classified as severe droughts (1998-1999, 2004-2005, and 2016-2017), and 5 episodes were classified as moderate droughts, recorded during the years 1980-1981, 1982-1983, 1990-1991, 1994-1995, and 2006-2007. Analysis of hydro-rainfall data over the experimental study period (40 years) reveals disruptions accompanied by a decrease in rainfall and runoff. This indicates that the Ourika basin has generally experienced periods of moderate and severe meteorological and hydrological droughts, with a noticeable trend towards increasing drought conditions.