Understanding the role of catchment and climate characteristics in the propagation of meteorological to hydrological drought

Abstract

Hydrological and meteorological droughts are complex hazards that cover a wide spatiotemporal spectrum and can affect the economic, environmental, and social sectors. However, it is challenging to characterize hydrometeorological drought and its propagation from precipitation deficits to soil moisture, discharge, and groundwater deficits and to ascertain to what extent catchment characteristics may affect drought features. This research explores the link between hydrometeorological drought characteristics and catchment characteristics. It investigates their propagation from meteorological to hydrological drought conditions in nine selected catchments from the Awash basin in Ethiopia using standardized indices of precipitation (SPI), soil moisture deficits (SPEI), streamflow (SRI), and base flow (SBI). The study results indicate that the propagation of meteorological to agricultural and hydrological droughts increases with increasing aggregation time scale and has a proportionally higher probability of propagation for moderate, severe, and extreme droughts. Across all catchments, the average lag time between hydrological and meteorological drought magnitude occurrence is 4–6 months, with lag times likely to increase by 7–8 months at a higher aggregation time scale. Meteorological drought has a 0.5 higher probability of occurrence than hydrological drought in a given period. In contrast, it has a lower (0.3) probability of the surface deficit becoming a groundwater deficit. At a 3-month cumulative time scale, the probability of propagating meteorological drought using the SPI to hydrological drought using the SRI is higher than that of propagating hydrological drought using the SBI. Therefore, the results suggest that while the propagation of meteorological droughts (SPI and SPEI) to hydrological droughts (SRI and SBI) slightly increases with aggregation time, the time taken for precipitation to become apparent in hydrological variables increases. The results confirmed that the probability of meteorological drought leading to hydrological drought progression is critical and needs to be considered in water resource management and planning.