Runoff Cost Of Sediment Control Of Soil And Water Conservation Practices With Hydrological Methods In Beiluo River Basin

Beiluo River, one sub-branch of Wei River, is selected as research area to analyze runoff and sediment change and the impact of soil and water conservation practices on them with the observed data of hydrology stations. The runoff cost of sediment control of soil and water conservation practices in Beiluo River basin and other typical basins in northern China are analyzed. The main findings are as follows:The annual variation characteristics of hydrological elements are also analyzed, the results show the means value ,variation, extremes ratio of precipitation, runoff and sediment are 511.4 mm, 0.19 and 2.49, 659.156×104 m3, 0.45 and 6.79, 7610.5×104 t, 0.76 and 90.7, respectively. Analyzing the annual change and trends of precipitation, runoff and sediment by using moving average method, Mann-Kendall and Spearman method, the author obtains that the precipitation, runoff and sediment have been significantly in attenuation trend. By analyzing accumulating curves of runoff and sediment deduced by unit precipitation distance away from averages, I find that the change could be divided into 6 stages: low water but average sediment period (from 1950 to 1962), abundance water and sediment period (from 1963 to 1969), low water but average sediment period (from 1970 to 1982), abundance water but low sediment period (from 1983 to 1991), abundance water and sediment period (from 1992 to 1994), and low water and sediment period (from 1995 to 2006). The characteristics of precipitation, runoff and sediment in each decades are analyzed, the results are: precipitation and runoff have decreasing trends, the change of sediment is a hump-type.The monthly changes of runoff and sediment are analyzed by uneven coefficient methods. The results are: (1) the curve of monthly average runoff and sediment has a peak; (2) the uneven coefficient of the runoff and sediment appeared to vary in a wavy manner during the decades, which in the 1990s are the biggest, but the smallest uneven coefficient of the runoff is in the 1960s and of the sediment is in the 1980s; and (3) the concentrating scheduled time of the runoff is August and of the sediment is July or August; The maximal centralized degree of runoff is 70's and 90's of last century, and the centralized degree of sediment is about 90%.Calculating the effect of human activity on runoff and sediment by using"empirical formula method", the result shows that: (1) from 1970 to 2006, the average reduction of annual runoff induced by anthropoid activities is 23589×104m3 and the effect of reducing runoff is 28.3%; the average annual sediment reduction is 2573.2×104t and the effect of reducing sediment is 28.2%; (2) influenced by precipitation and anthropoid activities, the average annual runoff reduction is 27140×104m3 and the average annual sediment reduction is 3285.2×104t, we can conclude that anthropoid activities cast an importantly effect on the runoff and sediment.The characteristics of runoff cost of control sediment of soil and water conservation in Beiluo River are presented. Based on the result of"empirical formula method", from 1970 to 2006, the mean of runoff cost of sediment control of soil and water conservation practices in Beiluo River is 11.76m3/t. The relationship between runoff cost of sediment control of measures and the influencing factors are analyzed. The results show that: (1) there are significant negative correlations between the runoff cost of sediment control of measures and precipitation; (2) with the natural runoff and sediment is increasing, the runoff cost of sediment control of measures is decreasing; and (3) in this basin, forestry and grass have less influence on runoff than terrace and dam, while control the same sediment.The runoff cost of sediment control of the different measures, integrated measures on Beiluo River, and different scale basins in the northern area of China are at last discussed. The results show that: (1) the runoff cost of sediment control of individual measures is dissimilar in different basin; (2) the regional differences of the runoff cost of sediment control of integrated measures in different scale basins also are obvious. If the soil and water conservation measures with smaller RRS are selected, it can save more runoff when reducing the same amount of sediment that perhaps improves the water resources condition in arid and semi-arid area.