Streamflow regimes of the Yanhe River under climate and land use change, Loess Plateau, China

Soil and water conservation measures including terracing, afforestation, construction of sediment-trapping dams, and the Grain for Green Program' have been extensively implemented in the Yanhe River watershed, of the Loess Plateau, China, over the last six decades, and have resulted in large-scale land use and land cover changes. This study examined the trends and shifts in streamflow regime over the period of 1953-2010 and relates them to changes in land use and soil and water conservation and to the climatic factors of precipitation and air temperature. The non-parametric Mann-Kendall test and the Pettitt test were used to identify trends and shifts in streamflow and base flow. A method based on precipitation and potential evaporation was used to evaluate the impacts of climate variability and changes in non-climate factors changes on annual streamflow. A significant decrease (p=0.01) in annual streamflow was observed related to a significant change point in 1996, mostly because of significant decreases in streamflow (p=0.01) in the July to September periods in subsequent years. The annual base flow showed no significant trend from 1953 to 2010 and no change point year, mostly because there were no significant seasonal trends, except for significant decreases (p=0.05) in the July to September periods. There was no significant trend for precipitation over the studied time period, and no change point was detected. The air temperature showed a significant increasing trend (p<0.01), and 1986 (p<0.01) was the change point year. The climate variability, as measured by precipitation and temperature, and non-climate factors including land use changes and soil and water conservation were estimated to have contributed almost equally to the reduction in annual streamflow. Soil and water conservation practices, including biological measures (e.g. revegetation, planting trees and grass) and engineering measures (such as fish-scale pits, horizontal trenches, and sediment-trapping dams) play an important role in reduction of the conversion of rainfall to run-off. Copyright (c) 2014 John Wiley & Sons, Ltd.