Analysis of drought in upper Moulouya Basin (Morocco): A combination of drought indices, classic and innovative trend tests

Abstract

This study aimed to examine the temporal and spatial variation of drought in the upper Moulouya Basin, Morocco's arid and semi-arid region. For this purpose, the Standardized Precipitation Index (SPI) was calculated at various time scales (3, 6, 12, and 24 months) using precipitation data collected from eight stations between 1977 and 2019. The data trends were analysed by classical modified Mann-Kendall (MMK) and Innovative Trend Analysis (ITA). Severe drought events were identified in the 1980s, and 1998-2000, while exceptionally wet years were recorded in periods 1996-1997 and 2008-2012. SPI trend analyses revealed a holistic increase on almost all timescales and at all stations. The increase was found to be higher in more extended time scales. Except for a few stations, SPI values in dry, normal, and wet classes of ITA method increased in the second half (1998-2019) compared to the first half (1978-1997). The ITA method detected different trends for different classes at two stations compared to the MMK method. This situation revealed the importance of analysing the trends of different methods in drought studies. These results are essential for water resources management and adaptation to climate change in arid and semi-arid zones.