The Influence Of Small Watershed Comprehensive Control On The Contamination Of Surface Runoff

Along with the point-contamination be controlled and managed effectively little by little, the influence on the water quality of none point-pollution appear obviously. The researches from many countries and zones indicate that none point-contamination is the principal causation witch induces water quality deteriorated. As soil loss is the serious form of Contamination of rainfall Runoff, the key of reduce none point-contamination is to reduce soil loss. Soil loss control unit is the small watershed in our countries and abroad, so reducing Contamination of rainfall runoff certainly associate with Small Watershed Comprehensive Control.In the research, the experiment fields are of runoff area in Yubei section, Chongqing and Gezigou reservoir small watershed. In rainy phases sampling timely. In Gezigou reservoir small watershed, we divide it into some sub-areas and sampling timely according to land-use ways and grade. The watershed includes economic forest zone, soil and water conservation forest zone, cropland and tenement. Compared with the index of TN, TP, Pb, Cd. COD and heavy metal content in surface runoff in Zhuchangxi small watershed witch does not been controled ,so to analysis the law of Contamination and the characteristic of spacial and timely distribution and the effect on the contamination in runoff in the different control measures. The result follows:(1)The effect of planting pattern on the runoff contamination :Adopt TN, TP, Pb, Cd , COD , sedimentation and heavy metal content in surface runoff to evaluate the comprehensive effect. The order is : terrace of 15°+ economic fruit tree seedling>terrace of 25° + economic fruit tree seedling > poi +corn (intercrop and along with the slope ) > cowpea + poi (25% intercrop ) + poi (75%) (along with the slope) > cowpea (50%) + poi ( 50%) (intercrop and along with the slope) > economic fruit tree seedling (along with the slope) .(2)The special distribution characteristic of runoff contaminate: the Gezigou reservoir small watershed is divided into 7 sections based on the land-use ways and the planting canopy percent and the origin of runoff around the watershed. In a whole, the first and the second sections are controled effectively ,the 5~th and 6~th are mostly worst. The content of Cd in the 4~th and the content of Pb in 5~th and 6~th are the highest. The contamination degree in the second section is the least in which the lower slope is filtrated trough buffer zone, but the most contamination degree appealed in 4~th in which the lower slope planted newly orange. There are remarkably correlation between TN, TP, Pb, Cd , COD and sedimentation in surface runoff; there are also remarkably correlation between the...