Multi‐Index Assessment of Hydrometeorological Droughts in the Tekeze River Basin, Northwestern Ethiopia

Abstract

Drought is a recurring natural hazard impacting agriculture, water resources, and various socioeconomic sectors. This study evaluated the performances of multiple meteorological and hydrological drought index estimation methods in the Tekeze River basin, northwestern Ethiopia. Monthly rainfall and temperature data from 15 meteorological stations with varying record lengths (28–59 years) and streamflow data from nine functional stations (1991–2018) were used to compute hydrometeorological drought indices. Standardized precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI), reconnaissance drought index (RDI), rainfall anomaly index (RAI), decile index (DI), and streamflow drought index (SDI) were calculated using DrinC software, R programming, and empirical formulas at 1, 3, 6, and 12‐month timescales. Results from the analysis revealed a basin‐wide prevalence of mild drought, with SPI indicating severity and negative values over longer timescales. The RDI analyses showed lower drought severity but also decreased its frequency over longer timescales. The DI calculation using basin station averages indicated 48.4%, 10.7%, and 8.0% incidence rates for severe, moderate, and mild droughts, respectively. RAI had generally lower positive and negative values compared to SPI. SPEI‐1 analysis classified almost all stations as experiencing mild drought. Conversely, SDI6 analysis at a 6‐month timescale revealed diverse impacts, with the Tekeze River basin experiencing sustained severe drought (SDI6 < −2.0) for three consecutive years (2004–2006). Spearman’s rank correlation coefficients of the indices were positive, with RAI showing particularly strong and statistically significant positive correlations with other indices. This study provides valuable insights for policymakers, researchers, and water resource managers in the Tekeze River basin, aiding in the development of effective drought mitigation and preparedness strategies.