Spatial Variations in Terrestrial Water Storage with Variable Forces across the Yellow River Basin

Abstract

Terrestrial water storage (TWS) variations are a result of the interconnected impact of various variables including climate, hydrology, ecology, and anthropogenic activities. Previous studies have indicated that climate factors (e.g., precipitation and potential evapotranspiration), vegetation restoration, and water withdrawals (irrigational and industrial water use) are the major determinants of TWS depletion across the Yellow River Basin (YRB). However, few studies have provided explicit information about the main forcing variables that determine spatiotemporal variations in TWS and the synergies among these factors. This study explored the explicit understanding of hydro-climatic and socio-ecological determinants and the key interacting processes that affected the TWS variations across the Yellow River Basin in northern China. The multivariate adaptive regression splines model was employed to establish the relationship function of the long-term trends for the dependent (TWS) and independent (explanatory) variables consisting of normalized difference vegetation index (NDVI), hydro-climate, and human water withdrawal. The long-term trends estimated from the MARS model reproduced the ones calculated by Gravity Recovery and Climate Experiment gravity satellites, with a determination coefficient (R2) of 0.83 and a mean absolute error (MAE) of 1.2 mm. The results showed that precipitation, minimum temperature, runoff, base flow, water withdrawal for electricity, and NDVI were the main drivers of the spatiotemporal variations in the TWS, of which minimum temperature and runoff played a considerable role in TWS variations through the interplay with other variables. The critical values of the trend for interactive variables, which could alter the acting direction of the synergy on the TWS, were also estimated. In view of the connotation of interactive variables, we suggested that spatiotemporal variations in TWS resulted from the coupling of the hydrological energy system, hydrological ecosystem, and hydrological system in the YRB, of which the hydrological system plays the most significant role, followed by the hydrological ecosystem.

Spatial and Temporal Characteristics of NDVI in the Weihe River Basin and Its Correlation with Terrestrial Water Storage

“…Some studies [59,60] show that the water consumption function of vegetation in arid and semi-arid areas exceeds the water storage function. Zhou et al [61] show that the water consumption function of vegetation in the Loess Plateau is dominant. This is consistent with the result that the change in water reserves is negatively correlated with NDVI in a large area.…”

Analysis and partitioning of terrestrial water storage in the Yellow River source region

“…However, there was a notable decreasing trend of −2.76 mm/yr from 2004 to 2015. Zhou et al (2021) demonstrated a declining trend in TWS across the Yellow River Basin in northern China, with rates ranging from −3.8 mm/yr to −6.6 mm/yr, as determined by the analysis of GRACE satellite data. Additionally, the study highlighted the significant influence of minimum temperature and runoff on the variations in TWS (Zhou et al, 2021).…”

“…Zhou et al (2021) demonstrated a declining trend in TWS across the Yellow River Basin in northern China, with rates ranging from −3.8 mm/yr to −6.6 mm/yr, as determined by the analysis of GRACE satellite data. Additionally, the study highlighted the significant influence of minimum temperature and runoff on the variations in TWS (Zhou et al, 2021). Bahrami et al (2020) indicated the significant role of SWE in TWS variation, using multisource remote sensing and the Water‐Global Assessment and Prognosis Global Hydrology Model (WGHM) in Canada from 2002 to 2011.…”