Impacts of soil and water conservation measures on annual runoff in the upper Chaohe River Basin in northern China based on hydrological analysis method

Based on precipitation data and hydrological data of the upper Chaohe River Basin, the relations of rainfall and runoff, soil and water conservation and runoff during 1961-2005 were analyzed. The impacts of soil and water conservation measures on annual runoff were assessed by different hydrological analysis methods. Results show that average annual runoff-reducing effects of soil and water conservation measures calculated by different methods were not same. During the compared period of 1981 to 2005, the average annual runoff-reducing effects were 23.79%, 30.67%, 30.79% and 31.69% respectively calculated by empirical formula method, runoff coefficient method, double accumulative curve method and time series contrasting method accordingly. The results also show that the average annual runoff-reducing effects of soil and water conservation measures of different periods calculated by different methods had the same variation tendency. The average annual runoff-reducing effect was the largest during 2001-2005, followed during 1981-1990, and the smallest during 1991-2000. The runoff-reducing effects of soil and water conservation measures were more prominent in the low water period.