During the last few decades, the frequency of drought has significantly increased in Morocco especially for arid and semi-arid regions, leading to a rising of several environmental and economic issues. In this work, we analyse the spatial and temporal relationship between vegetation activity and drought severity at different moments of the year, across an arid area in the western Haouz plain in Morocco. Our approach is based on the use of a set of more than 30 satellite Landsat images acquired for the period from 2008 to 2017, combined with the Standardized Precipitation Index (SPI) at different time scales and Standardized Water-Level Index (SWI). The Mann-Kendall and Sen’s slope methods were used to estimate SPI trends, and the Pearson correlation between NDVI and SPI was calculated to assess the sensitivity of vegetation types to drought. Results demonstrated that SPI experienced an overall downward trend in the Chichaoua-Mejjate basin, except for SPI3 in summer. The vegetation activity is largely controlled by the drought with clear differences between seasons and time scales at which drought is assessed. Positive correlations between the NDVI and SPI are dominant across the entire study area except in June when almost half of correlations is negative. More than 80% of the study domains exhibit a correlation exceeding 0.4 for SPI3 and SPI6 in March. Importantly, this study stresses that the irrigation status of land can introduce some uncertainties on the remote sensing drought monitoring. A weak correlation between the SPI and the SWI was observed at different time scale. The fluctuations of the piezometric levels are strongly affected by the anthropogenic overexploitation of aquifers and proliferation of irrigated plots.

在过去的几十年中，摩洛哥的干旱频率显着增加，特别是在干旱和半干旱地区，导致若干环境和经济问题的加剧。在这项工作中，我们分析了摩洛哥豪乌兹平原西部干旱地区一年中不同时刻植被活动与干旱严重程度之间的时空关系。我们的方法是基于使用一组在2008年至2017年期间获取的30多个卫星Landsat图像，并结合不同时间尺度的标准降水指数（SPI）和标准水位指数（SWI）。使用Mann-Kendall和Sen的坡度方法估算SPI趋势，并计算NDVI和SPI之间的皮尔森相关性以评估植被类型对干旱的敏感性。结果表明，除夏季的SPI3外，Chichaoua-Mejjate盆地的SPI总体呈下降趋势。植被活动主要受干旱控制，在评估干旱的季节和时间尺度之间存在明显差异。在整个研究区域中，NDVI和SPI之间的正相关性占主导地位，除了6月几乎一半的负相关性之外。3月份，超过80％的研究域显示SPI3和SPI6的相关性超过0.4。重要的是，这项研究强调，土地的灌溉状况会给遥感干旱监测带来一些不确定性。在不同的时间尺度上观察到SPI和SWI之间的相关性较弱。