Investigating the drought propagation dynamics between meteorological and groundwater drought in the Yellow River Basin, China

Abstract

Understanding the mechanisms and propagation relationships between meteorological and groundwater droughts is crucial for producing early warnings of future hydrological droughts and groundwater management. However, scant research exists for mechanism of this unseen groundwater drought propagation. The drought characteristics and seasonal effects of meteorological drought and groundwater drought in the Yellow River Basin (YRB) were delved, based on the Standardized Precipitation Evapotranspiration Index (SPEI) and Groundwater Drought Index (GDI). Considering the problem of traditional drought propagation methods is not comprehensive, the modified drought propagation method was proposed, from both linear and nonlinear perspectives concerning their relationship. The findings indicate varying degrees of declining trends in meteorological and groundwater drought (slope = -0.0004/m, P < 0.01; slope = -0.0089/m, P < 0.01) in the YRB. The spatial distribution of worsening drought conditions is primarily concentrated in the central northern part of the YRB. However, groundwater drought has a larger affected area and a stronger declining trend. In terms of drought characteristics, meteorological and groundwater droughts have distinct seasonal patterns, but other characteristics show notable spatial heterogeneity. Meteorological droughts tend to occur early, have a high frequency, low intensity, and short duration. On the other hand, groundwater droughts exhibit opposite characteristics, occurring late, having a low frequency, high intensity, and long duration. The propagation time from meteorological drought to groundwater drought, calculated using linear and nonlinear methods, showed consistent seasonal effects, with the longest propagation time in winter and the shortest in summer. However, there are differences between the linear and nonlinear methods, with the linear method showing longer propagation times (12 months) compared to the shorter times in the nonlinear method (6 months). As for the characteristics of drought propagation, the modified drought propagation characteristic method proposed in this study demonstrates higher sensitivity and propagation rates compared to traditional single linear or nonlinear methods in the YRB. It compensates for the underestimation of traditional methods, providing better compensation and reducing uncertainty in the southern part of the YRB.