Quantitative Analysis on the Influence of Long-term Soil and water conservation Measures Harnessing on Runoff and Sediment Yield of Watershed

Abstract

Abstract Contempoary research on the soil and water conservation benefit mainly focus on the benefit calculation after a certain harnessing stage. However, little was known about how the harnessing messures affect the runoff and sediment during the harnessing process.This paper takes Lianshui watershed as the research object to analyze 32 years’ monitoring data of the outlet station in this watershed by virtue of Mann-Kendall Test and calculate quantificationally the contribution of long-term soil and water conservation measures harnessing to the runoff and sediment yield of this watershed in different stages by virtue of mathematical model, thus to identify the influence on long-term long-scale soil and water conservation measures harnessing on runoff and sediment yield variation. The results have showed that: After the 3 soil and water conservation harnessing stages during the period from 1983 to 2002, the sediment yield of Lianshui watershed has significantly decreased, however, the annual runoff hasn’t been changed along with the extension of the harnessing period, with regard to the influence on sediment reduction in the watershed, the contribution rate of water and soil conservation measures was 41.41% compared with the natural factors after 1st harnessing stage (1991-1998), 49.74% after 2nd harnessing stage (1999-2002), and in 3rd harnessing stage (2003-2009) it reached 67.68%, it can be seen that the influence of water and soil conservation measures on watershed sediment yield can gradually increase along with the extension of harnessing period and continuous expansion of harnessing scale and eventually become the dominant factor.