Assessing the Impact of Drought and Upstream Dam Construction on Agriculture in Arid and Semi-Arid Regions: A Case Study of the Middle Draa Valley, Morocco

This study assesses the impact of drought and upstream dam construction on agriculture in arid and semi-arid regions with the Middle Draa Valley (MDV) case study in Morocco. This Valley, nestled in the arid landscapes of Morocco, has a rich tapestry of history, culture, and natural beauty. However, its oases are facing a water shortage crisis due to the effects of climate change and human pressure on water resources for irrigation. We analyzed the Standardized Precipitation Evapotranspiration Index (SPEI) and the Normalized Difference Vegetation Index (NDVI) to monitor vegetation dynamics in this valley. The SPEI shows a declining trend, indicating increasing water scarcity, which has led to the overexploitation of groundwater and significant vegetation degradation. The NDVI remained relatively stable until 2015 but has since declined, signaling ecosystem deterioration. The correlation between SPEI and NDVI in the oases suggests that vegetation depends not only on precipitation and evapotranspiration but also on other factors such as insufficient releases from upstream dams and the use of groundwater for irrigation. This is confirmed by analyses of the correlation between dam releases and NDVI, as well as data on groundwater table levels. This situation poses an urgent warning for decision-makers to consider which water management measures and agricultural practices to adopt. The most practical solution to avoid further degradation of the oases in the short term is to conserve the remaining groundwater resources exclusively for irrigation date palms and to develop strict long-term water policies.