Effect Of Soil And Water Conservation On Water Resources And Water Environment

China has been suffering from serious soil erosion for a long time.The Loess Plateau in the northwest of China was one of the areas with the most severe soil erosion in China or even in the world.As early as in 1953,the Jiuyuangou Catchment in The Loess Plateau was listed as the demonstration experiment catchment of soil and water conservation.Meanwhile,soil and water conservation comprehensive management(SWCCM) were launchedcomprehensively.The Jiuyuangou Catchment was listed as national key catchment,the effect of the soil and water conservation comprehensive management which developed further remarkable.During the fifty years,this catchment has become the typical catchment of SWCCM which is mainly based on dam farmland by means of experimental research, experimental extension as well as comprehensive management.The configuration of each soil and water conservation which has the high regulation standard is complete by means of treating while experiment.The soil and water erosion have not appeared at the late stage of SWCCM.However,the quantitative evaluation of the conservation effect is scarce,especially for the effect on non-point pollution.Therefore,this paper analyse and calculate the effect of soil and water conservation on water resources and water environment based on the measured data of the Jiuyuangou Catchment.The main research results of this paper are as follows.(1) Soil and water conservation measures could retain the runoff and sediment effectively.This research calculate the effect of soil and water conservation on water resources by using Hydrological Method which include curve of double cumulate method,different series contrastive method and formula of experience method as well as Soil Conservation Method.The results show that soil and water conservation measures could retain the runoff and sediment effectively.With the gradual perfection of soil and water conservation in the Jiuyuangou Catchment,the retention efficiency of water and soil increases constantly,which exceeded 85%and 95%respectively at the later stage of SWCCM.(2) Soil and water conservation measures could retain the soil nutrients which include Nitrogen,phosphorus,organic matter and so on effectively.Based on the calculation results under Soil Conservation Method,this paper calculate the retention efficiency of each soil nutrient under soil and water conservation by using non-point source pollution model which consider the change of enrichment coefficient and basic level of soil nutrient at different management stage.The results show that the retention efficiency of soil nutrient improved with the constant perfection of soil and water conservation.From 1953-2005,the retention efficiency of nitrogen,phosphorus and organic matter under soil and water conservation has up to 80%or so.(3) The main soil and water conservation in Loess Plateau is check dam farmland.The calculation result in selected year show that the rank of retention ability of runoff,sediment and soil nutrient under various measures is as follows:dam land > terrace farmland > grassland > forestland,except 1977.Check dam farmland make great contributes in soil and water conservation ecological construction in the Jiuyuangou Catchment.(4)The Jiuyuangou Catchment withstand the challenges of rainstorm many times.The analysis results under five representative rainstorm at the different stage show that,soil and water conservation measures which make great contributes in ecological construction could retain the runoff,sediment and soil nutrient effectively in strom flood.