Submitted to: Hydrological Sciences Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2009
Publication Date: 4/1/2010
Citation: Gao, P., Zhang, X.J., Zhang, X., Wang, F., Li, R., Mu, X. 2010. Trend and change-point analyses of streamflow and sediment discharge in the Yellow River during 1950 to 2005. Hydrological Sciences Journal. 55(2):275-285. Interpretive Summary: The Loess Plateau of China is one of the most severely eroded regions in the world, and the Yellow River running through the plateau has the highest sediment load in the world. Great effort has been taken in the Loess Plateau to control soil erosion and to reduce sediment in the Yellow River in the past 50 years. The objectives of this work are to analyze changes in sediment discharge and streamflow in the Yellow River in the past 50 years and to investigate whether those changes are caused by soil and water conservation effort. Streamflow and sediment yield at four hydrological stations in the Yellow River mainstream were analyzed. Results showed that streamflow and sediment yield decreased significantly since 1950s and the decreasing trends were very likely caused by human activities such as implementing soil and water conservation measures, constructing dams and reservoirs, building water diversion irrigation systems, converting cropland to grasslands, and changing land uses in the Loess Plateau. Overall results indicate that the implemented conservation measures were effective in reducing soil erosion and surface water runoff in the basin. This conclusion would play an important role in developing future strategic conservation plans for the region.
Technical Abstract: The Yellow River being the second largest river in China is famous for its highest sediment content in the world. Since late 1950s, a great number of soil and water conservation measures have been implemented in the Yellow River basin to control soil erosion. Our hypothesis is that those measures and changes might have brought about significant changes in streamflow and sediment discharge in the Yellow River mainstream. Our objectives are to statistically analyze annual precipitation, streamflow, and sediment discharge from 1950 to 2005 for any trend and transition year when a change in trend mean occurs, and to further relate those change trends and change points to human activities aimed at controlling soil and water loss and restoring eco-environments in the Yellow River basin during the past 50 years. Trend analysis showed that strong decreasing trends in annual streamflow and sediment discharge existed since late 1950s at three stations located at upper, middle, and lower reaches of the Yellow River mainstream (P=0.01). Change point analysis further revealed that more rapid decrease began in 1985 for both streamflow and sediment discharge at the three stations (P=0.05), except for sediment discharge at the middle reaches station where it began in 1979. Double mass curves of precipitation vs. streamflow and precipitation vs. sediment for the periods before and after the transition years showed remarkable decreases in regression slopes between the two periods. Frequency distributions of streamflow and sediment discharge after the transition years were shifted to much smaller values compared with those before, indicating reduction in annual streamflow and sediment discharge. In light of that, there was no decreasing trend in precipitations in the Yellow River basin in the past 50 years, the decreasing trends in streamflow and sediment discharge were very likely caused by human activities. Enhanced human activities after 1970s such as implementing soil and water conservation measures, constructing dams and reservoirs, building water diversion irrigation systems, converting cropland to grasslands, and changing land uses were most likely responsible for the faster decreases in streamflow and sediment discharge after the transition years in the basin.