Long‐term streamflow trends in the middle reaches of the Yellow River Basin: detecting drivers of change

Abstract

Abstract:The catchments in the Loess Plateau, in China's middle reaches of the Yellow River Basin, experienced unprecedented land use changes in the last 50 years as a result of large-scale soil conservation measure to control soil erosion. The climate of the region also exhibited some levels of change with decreased precipitation and increased temperature. This study combined the time-trend analysis method with a sensitivity-based approach and found that annual streamflow in the Loess Plateau decreased significantly since the 1950s and surface runoff trends appear to dominate the streamflow trends in most of the catchments. Annual baseflow exhibited mostly downward trends, but significant upward trends were also observed in 3 out of 38 gauging stations. Mean annual streamflow during 1979À2010 decreased by up to 65% across the catchments compared with the period of 1957À1978, indicating significant changes in the hydrological regime of the Loess Plateau. It is estimated that 70% of the streamflow reduction can be attributed to land use change, while the remaining 30% is associated with climate variability. Land use change because of the soil conservation measures and reduction in precipitation are the key drivers for the observed streamflow trends. These findings are consistent with results of previous studies for the region and appear to be reasonable given the accelerated level of the soil conservation measures implemented since the late 1970s. Changes in sea surface temperature in the Pacific Ocean, as indicated by variations in El Niño-Southern Oscillation and phase shifts of the Pacific Decadal Oscillation, appear to have also affected the annual streamflow trends. The framework described in this study shows promising results for quantifying the effects of land use change and climate variability on mean annual streamflow of catchments within the Loess Plateau.

Groundwater storage trends in the Loess Plateau of China estimated from streamflow records

“…There are 10 catchments where groundwater storage exhibited upward trends ranging from 0.0011 to 0.0119 mm per year with an average value of 0.0047 mm per year (Table 1). These groundwater trends are consistent with the annual baseflow trends obtained by Gao et al (2015), but opposite to their annual streamflow trends. The baseflow trends of Gao et al (2015) provide an independent measure of the groundwater storage trends as baseflow is a result of groundwater discharge and the good agreement between the two estimates suggests that the method used in our study is appropriate for estimating groundwater storage trends.…”

“…These groundwater trends are consistent with the annual baseflow trends obtained by Gao et al (2015), but opposite to their annual streamflow trends. The baseflow trends of Gao et al (2015) provide an independent measure of the groundwater storage trends as baseflow is a result of groundwater discharge and the good agreement between the two estimates suggests that the method used in our study is appropriate for estimating groundwater storage trends. It should also be noted that the magnitudes of the upward trends in groundwater storage are similar to those of the Souris-Red-Rainy and the Missouri regions reported by Brutsaert (2010).…”

“…The downward trends in groundwater storage are similar to those of the South Atlantic-Gulf region in the US (Brutsaert, 2010), of the Kherlen River basin in Mongolia (Brutsaert and Sugita, 2008), and of the Australian catchments reported by Zhang et al (2014) over a similar period. The reductions in groundwater storage in the catchments of the Loess Plateau are consistent with the annual streamflow and baseflow trends of Gao et al (2015). There are 10 catchments where groundwater storage exhibited upward trends ranging from 0.0011 to 0.0119 mm per year with an average value of 0.0047 mm per year (Table 1).…”

Determining the hydrological responses to climate variability and land use/cover change in the Loess Plateau with the Budyko framework

“…In the Wuding River basin, the elasticity and decomposition methods consistently demonstrated that human activities and climate change contributed 65% and 35%, respectively, to streamflow reduction during 1961-2009 (Liang et al, 2015). With the time-trend analysis method and sensitivity-based approach, Gao et al (2015) found that on average 70% of the streamflow reduction in the Loess Plateau between the 1950s and 2010 resulted from land use changes.…”

“…The streamflow within the Loess Plateau has exhibited an obvious downward trend over the past six decades (Zhang et al, 2008;Zhao et al, 2014;Gao et al, 2015;Zhang et al, 2016). Many studies have investigated the effects of land use/cover change and climate variability on streamflow in the Loess Plateau to support future water resource and local ecosystem management efforts.…”