Quantitative Analysis of Terrestrial Water Storage Changes Under the Grain for Green Program in the Yellow River Basin

Abstract

Afforestation‐induced changes in water resources have attracted worldwide attention. However, a clear picture of quantitative attribution of terrestrial water storage (TWS) variation from hydroclimatic and anthropogenic factors is still lacking. In this study, a quantitative analysis of TWS variation was conducted in the Yellow River basin of China under the Grain for Green project with consideration of irrigation. The results showed that the TWS has decreased (increased) more and more quickly (slowly) in the Loess Plateau (headwater region). The TWS increase corresponded to increased runoff and soil moisture in the headwaters, and the TWS depletion corresponded to decreased runoff and groundwater in the Loess Plateau and downstream regions. Regarding the TWS change (TWSC), it exhibited a negative trend across the basin. The increase in evapotranspiration (ET) dominated the basin‐averaged TWSC reduction, while the increase in ET was highly related to the increases in vegetation cover and irrigation water use. For spatial TWSC variations, the value of precipitation minus ET could account for most changes in TWSC, except for those in the headwater region and a region near the internally drained area. The increased vegetation coverage, which can affect multiple hydrological processes, played an important role in these two excluded regions. Importantly, the irrigation‐induced TWSC was considerable and varied with different irrigation water sources (i.e., surface water and groundwater). Overall, the impacts of afforestation and irrigation on TWS are sufficiently important. The research in this study can provide guidance for the water resource management during revegetation efforts.

Understanding Terrestrial Water Storage Declining Trends in the Yellow River Basin

“…This also can be inspected from the differences between GLOBWB and GLOBWB(N) results. High correlation between TWSA and SPEI during 2003–2010 is consistent with the insight that TWS dynamics are closely related to precipitation/ET during the same period reported by Lv et al (), but the correlation has become much weaker since 2010 according to the results in this study. This insight adds a new finding to the related pattern of TWS dynamics to precipitation/ET variations in recent years, but more attention should still be given to the mechanism on how precipitation/ET variability influences TWS variations.…”

“…As was pointed by Jin et al () and Lv et al (), increasing vegetation coverage probably gave rise to ET in the YRB, and significant correlation can be found between areas with vegetation greening and increasing ET during 2003–2010. According to Li et al () and Lu et al (), increasing irrigation is another major reason of increasing ET.…”

“…Ecological restoration for sustainable water development has been given a high priority in recent decades (Cai & Rosegrant, 2004;Wei & Guangqian, 2002). Therefore, water that is saved by agricultural irrigation will probably be shifted to serve ecological and environmental functions, such as wetlands reserve practices (Cui et al, 2005;Wei & Guangqian, 2002;Zhao et al, 2014) As was pointed by Jin et al (2017) and Lv et al (2019), increasing vegetation coverage probably gave rise to ET in the YRB, and significant correlation can be found between areas with vegetation greening and increasing ET during 2003-2010. According to Li et al (2017) and Lu et al (2018), increasing irrigation is another major reason of increasing ET.…”

Streamflow Decline in the Yellow River along with Socioeconomic Development: Past and Future

“…The area of afforestation and grass planting (AGP) for the purpose of water and soil conservation in the YRB increased from 8000 km 2 in 1959 to 12,000 km 2 in 1969, 31,000 km 2 in 1979, 95,000 km 2 in 1989 and 170,000 km 2 (23% of the catchment area) by the 2010s, which effectively improved plant productivity, expanded vegetation cover and increased transpiration, and thereby reduced the streamflow [21,[43][44][45]. However, the processes and underlying mechanisms between revegetation and streamflow decline are complicated, and the area where these processes occurred is very large.…”

“…However, the processes and underlying mechanisms between revegetation and streamflow decline are complicated, and the area where these processes occurred is very large. For these reasons, it is currently difficult to directly quantify the basin-wide AGP impact on streamflow [44]. Because the potential evaporation in the YRB has not shown any increasing trend over the past decades [36], evaporation change is unlikely to be responsible for the streamflow decline at Lijin.…”