Impact of climate change and anthropogenic activities on stream flow and sediment discharge in the Wei River basin, China

Abstract

Abstract. Reduced stream flow and increased sediment discharge are a major concern in the Yellow River basin of China, which supplies water for agriculture, industry and the growing populations located along the river. Similar concerns exist in the Wei River basin, which is the largest tributary of the Yellow River basin and comprises the highly eroded Loess Plateau. Better understanding of the drivers of stream flow and sediment discharge dynamics in the Wei River basin is needed for development of effective management strategies for the region and entire Yellow River basin. In this regard we analysed long-term trends for water and sediment discharge during the flood season in the Wei River basin, China. Stream flow and sediment discharge data for 1932 to 2008 from existing hydrological stations located in two subcatchments and at two points in the Wei River were analysed. Precipitation and air temperature data were analysed from corresponding meteorological stations. We identified change-points or transition years for the trends by the Pettitt method and, using double mass curves, we diagnosed whether they were caused by precipitation changes, human intervention, or both. We found significant decreasing trends for stream flow and sediment discharge during the flood season in both subcatchments and in the Wei River itself. Change-point analyses further revealed that transition years existed and that rapid decline in stream flow began in 1968 (P < 0.01), and that sediment discharge began in 1981 (P < 0.01) in the main river. In the two subcatchments, the transition years were 1985 (P < 0.01) and 1994 (P < 0.05) for water discharge, and 1978 and 1979 for sediment discharge (P < 0.05), respectively. The impact of precipitation or human activity on the reduction amount after the transition years was estimated by double mass curves of precipitation vs. stream flow (sediment). For reductions in stream flow and sediment discharge, the contribution rate of human activity was found to be 82.80 and 95.56 %, respectively, and was significantly stronger than the contribution rate of precipitation. This evidence clearly suggests that, in the absence of significant decreases in precipitation, strategies for managing the region need to focus on human activities to control erosion without restricting stream flow.

Variations in the Runoff-Sediment Relationship of the Weihe River Basin Based on the Copula Function

“…During the last 50 years, the runoff in Weihe River has dramatically decreased; principally in the late 1990s when the average was only 3.60 billion m³ compared to 6.20 billion m³ in the 1950s [22,23]. The mean annual sediment contribution of the Weihe River to the Yellow River is 390 billion kg, and in the flood season occurring between June-September it reaches approximately 90% of the mean annual sediment yield [4]. The average sediment yield in the 2000's was reduced to 160 billion kg, principally due to human activity and climate change, compared to 680 billion kg in the 1950's [24].…”

“…The data reveal a 300% decline in runoff and sediment yield from soil and water conservation programs from the 1970's to the 1990's relative to the 1960's. Water projects, such as reservoirs and dams, disturb the runoff by increasing the evaporation, the drinking water supply and the agricultural irrigation while Prior research has been conducted to explain the causes of decreasing runoff and sediment yield in the WRB [4,22,32]. These studies concluded that climate change, especially the variations in precipitation and anthropogenic activity, were the main culprits.…”

“…Moreover, the RSR inflection points at the Linjiacun and Zhangjiashan stations are not significant at the 5% significance level. Most hydrological studies of the WRB suggested a variable contribution from human activity to runoff and sediment yield leading to changes in RSR [4,32]. These studies indicated: (a) a reduced runoff producing a much lower capacity of sediment transport and an increase in the probability of sediment deposition; and (b) check dams, water reservoirs and the conversion of cropland to grassland leading to larger trapping of sediment than runoff.…”

“…However, there was a strong decrease in runoff and sediment yield from 1996 to 2014, which is more pronounced from 1996 to 2002. Prior research has been conducted to explain the causes of decreasing runoff and sediment yield in the WRB [4,22,32]. These studies concluded that climate change, especially the variations in precipitation and anthropogenic activity, were the main culprits.…”

“…In recent years, considerable research has been conducted on variations in runoff and sediment deposition throughout the globe [4,5]. For instance, Dunjó et al (2004) [6] investigated the effect of land use and land cover on the variations of runoff and sediment yield at a micro level.…”