Change of NonPoint Pollutant During the Accumulation Process of Slope Runoff in the DryHot Valley in Yuanmou County

The ‘grazing closure’ and ‘grazing closure + antislope contour stairs’ measures integrated with water harvesting engineering were conducted on 3 types of severely degraded meadows to intercept and gather runoff in Yuanmou dryhot valley in order to promote the natural recovery of the grass vegetation. The total nitrogen content (TN), total phosphorous content (TP), and chemical oxygen demand (COD) of the slope runoff in the rainy season and later on in the dry season of 2008 were determined. The results showed that restoration of the natural vegetation could greatly reduce the slope runoff and soil erosion, so as to greatly reduce the output of nonpoint pollutant. The slope runoff collection process included runoff interception and sand sedimentation that could significantly reduce the concentration of the nonpoint pollutants. It was showed by the study that the concentration of TN and TP was deducted by 46.63% and 38.08% respectively in the course while the runoff flowed from the sand setting pound into the impounding basin. The concentration of the nonpoint pollutants in the runoff water storage system could be further reduced, so it was demonstrated that the soil and water erosion control would play an important role in cutting down the nonpoint pollutant output remarkably.