The Study On Soil Erosion Properties In Typical Section Of Dry-hot Valley Of Jinsha Basin

Special climate and human activities in dry-hot valley of Jinsha basin caused thesparse vegetation and serious soil erosion, even a series of serious ecological systemdegradation problems. This fact has already caused the attention of people. Selectingdifferent treatment slope and woodland catchment and farmland catchment in dry-hotvalley of Jinsha basin typical section set for the object of study. Using the runoff plot andthin triangular weir methods, surveying the plots and catchments present land use patternsand observing the rainfall, runoff and sediment were in order to analysis the characteristicsof water and soil losses in dry-hot valley of Jinsha basin typical section. The results are asfollows:1. The results of water and soil losses characteristics in runoff plot showed that:（1）The losses of runoff in five different processing slope plots was the followingorder:slope(2#)﹥slope(1#)﹥natural slope﹥level terrace﹥anti-slope terrace.This showedthat afforestation of the anti-slope terrace and level terrace and good vegetation were goodat closuring runoff from running off the erosion. The anti-slope terrace and level terracecan decrease runoff71.18%and49.00%than that on natural slope. The runoff of1#plot’scan reduce18.51%than2#plot.（2）The order in losses of sediment in five different processing slope plots were thesame as losses of runoff. The anti-slope terrace and level terrace and increasing vegetationcovers were remarkable in the factof reducing sediment. The anti-slope terrace and levelterrace can decrease sediment49.93%and31.47%than that on natural slope.1#plot’ssediment was less13.04%than2#plot’s.（3）Single rainstorm or extraordinary rainstorm played a leading role in effect ofrunoff and sediment. Rainfall, runoff and sediment were significantly associated, showingthat the three closely related.2. The results of comparying soil erosion characteristics between woodland andfarmland catchment showed that:（1）If rainfall in the rainy season was more concentrated and influenced by the earlyrainfall, catchments can also have runoff under the less rainfall. Extraordinary rainstormcontributed the value to runoff and sediment of two catchments and was easy to scour thesurface even resulting in serious soil erosion. The woodland catchment’s runoff amountswere less and decrease by9.09%and6.03%than farmland catchment’s in the condition of two rainy seasons. When rainfall was4.8mm to27.6mm, the farmland catchment’s runofftrend was less than the woodland catchment’s and if rainfall was greater than27.6mm, theresults was contrary.（2）Sediment yield of Woodland catchment has been lower than the farmlandcatchment. Sediment productions of woodland catchment were less38.42%and66.59%than farmland catchment in rainy season of2010and2011. The first time of runoff rainfallcontributed greatly to the sediment yield values of catchments.（3）Catchment scale of rainfall, runoff and sediment had close relationship. Thecorrelation coefficient between runoff and sediment yield were greater than that of rainfalland sediment.3. Differences of runoff and sediment on the scale of runoff plot and catchment werecompared. The results showed that:Less rainfall in the dry-hot valley, the runoff and sediment beginning and ending timeof plot were consistent with catchment’s. The period of the runoff, runoff and runoffcoefficient in plots was more than catchment’s. Heavy rain conditions, the differencebetween the two runoff coefficients was smaller. Catchment’s sediment yield was greaterthan the runoff plot value.