Effect of Land Use and Rainfall Factors on Soil and Water Loss in Purple Soil Region

This study was carried out in Hemingguan small watershed and its 3 experiment plots in which the observation time were divided into 2 periods(from 1983 to 1986 and from 1989 to 2000) in hilly region of the central Sichuan,and the characteristics of soil and water loss of different land uses,the response of runoff and soil erosion on rainfall factors and benefits of comprehensive control measures in small watershed were analyzed.The results show as follows: In first period,runoff depth in different rainfall intensities in turn was wastelandgrasslandslopeland,but erosion modulus in order slopeland wastelandgrassland.In second period,runoff depth successively was terrace landgrasslandforestry,and erosion modulus terrace landgrasslandforestry.The correlation degree among runoff on slopeland,soil erosion,low covered grassland and precipitation was much high,which showed that soil erosion was mainly influenced by rainfall factors.The correlation coefficient among precipitation erosion in forestry,high covered grassland and terrace land was much low,it may be that vegetative cover and soil characteristic play an important role on retarding runoff and erosion processes,which showed land use or vegetative cover had obvious effect on soil and water loss.Owing to the action of comprehensive control measures of soil and water conservation,long-tern average runoff amount from 1990 to 2004 had reduced by 30.67%,average sediment transportation by 91.29% and average sediment content by 76.05% than those parameters from 1985 to 1989 respectively.