Evaluation of satellite products for drought characterization and impact assessment on water resources in the Tensift Basin (Morocco)

Effective drought characterization and monitoring are urgent challenges especially in arid and semi-arid regions. The Tensift basin is in the center-west of Morocco and is exposed to recurrent droughts. The effects of climate change, which has already led to several economic, agricultural, hydrological and social losses over the past decades, exacerbate the situation. The objective of this study is to characterize the drought in the Tensift basin and to assess its impact on water resources by using the potential of satellite products. For this purpose, satellite products and reanalysis data were selected for the evaluation of observed data in the study area. These datasets were used due to the availability of long-term data, near real-time data series, relatively high spatial and temporal resolutions and open access data. In particular, precipitation and temperature retrieved by ERA5-Land (https://cds.climate.copernicus.eu) and CHIRPS (https://www.chc.ucsb.edu/data) datasets, as well as the corresponding data observed by in-situ stations, were used and statistically analyzed and evaluated by common metrics (R, R², BIAS, RMSE, and the Nash and Sutcliffe Efficiency) to compare their performance and accuracy. The obtained results showed that most meteorological stations agree with satellite and reanalysis products, with some slight errors. Based on these results, several drought indices during the period 1982-2021 have been calculated at several spatio-temporal scales to determine the impacts of drought on water supply. The results show that the Tensift Basin suffered from multiple droughts over the past 40 years. The years 2000 and 2015, 2017, 2019, 2020, 2021 were common drought periods by either the Standardized Precipitation Index (SPI) and the Standardized Precipitation and Evapotranspiration Index (SPEI); however, the Vegetation Condition Index (VCI), which was provided by NOAA-AVHRR data (https://www.star.nesdis.noaa.gov), indicate more dry years than the other indices. The drought indices provide a powerful tool to monitor drought and its impacts on water resources. These tools could potentially allow decision makers to better manage water resources as to minimize drought impacts. Furthermore, the considered drought indices could be used separately or in combination within a drought early-warning system in the study area for drought monitoring and forecasting.

Keywords: Drought, Water supply, Satellite products, Tensift basin, Remote sensing, Reanalysis data