DROUGHT MONITORING AND ASSESSMENT USING METEOROLOGICAL, HYDROLOGICAL, AND REMOTE SENSING INDICES, CASE STUDY: WADI KHEMIS BASIN (NW ALGERIAN)

Abstract

Drought poses significant challenges to water resources, agriculture, ecosystems, and livelihoods in semi-arid regions. Understanding and assessing meteorological, hydrological, and agricultural drought dynamics is crucial for developing effective adaptive strategies and enhancing resilience. This study conducts an integrated assessment of drought patterns in the Wadi Khemis Basin, a semi-arid region in northwest Algeria, from 1982 to 2011, utilizing a combination of meteorological, hydrological, and remote sensing indices. Specifically, the Standardized Precipitation Index (SPI), Reconnaissance Drought Index (RDI), Streamflow Drought Index (SDI), and Normalized Difference Vegetation Index (NDVI) were employed to characterize short- and long-term meteorological, hydrological, and agricultural droughts, respectively. Hydrometeorological stations across the basin with data from 1982 to 2011 were selected for the analysis. DrinC software (Drought Indices Calculator) was used to calculate the SPI, RDI, and SDI values, while Google Earth Engine (GEE) was used to calculate NDVI values. Statistical analyses, including the Mann-Kendall and Sen's slope tests, were conducted to assess trends, and Pearson correlation analysis was performed to investigate the relationships among the three drought types. The analysis identified multi-year meteorological drought episodes in 1983 1984, 1988-1989, and 1998-2000 based on the 12-month SPI and RDI, accompanied by statistically significant upward trends across the short- and long-term timescales. Severe hydrological droughts occurred in 1997-1998, 2005-2007, and 2007-2008 based on the 12 month SDI, with significant downward trends across all timescales. Agricultural droughts were manifested in 1983, 1992, 1998, 1999, and 2002-2008 according to annual NDVI values, with no significant trend detected. Moderate SPI/SDI and RDI/SDI correlations across timescales demonstrate the lagged propagation of meteorological drought impacts through the hydrological system, likely because of the mountainous terrain, spatial variation of the slope, complexity of the hydrographic network, consolidated lithology, permeable soils, semi-arid climate, and karst hydrogeology of the Wadi Khemis Basin. Conversely, poor SPI/NDVI and RDI/NDVI correlations highlight the intricate connection between meteorological and agricultural droughts, influenced by factors such as widespread groundwater exploitation for irrigation, which enhances vegetation resilience to meteorological drought, and the cold winter semi-arid climate, which constrains vegetation growth more than precipitation deficits. This study's findings have significant implications for water resource planning and drought mitigation strategies, contributing to enhanced climate resilience and mitigated drought impacts in the region