Studies Of Ecological Water Type And Traditional Control Measures Of Soil Erosion Based On The Relation Between Runoff And Sediment In The Water Source Area Of Beijing And Tianjin

The traditional guiding ideology and treatment on soil erosion control pay attention to ecological and economic benefits of the harnessing area, which will reduce the sediment yield. However, the reduction of sediment could lead to the decrease of water, which will aggravate the water contradiction between upstream and downstream in the water source areas of Beijing and Tianjin. Environmental effects of traditional slope and channel measures on water and sediment were studied by investigation and ecological water-carrying treatment was studied by location experiment in Dongbei watershed locating in Pingquan County, Chengde City. The problems about building ecological water-carrying watershed should be improve from slope of forest and grass measures, slope engineering measures and channel engineering measures. The main results were summarized as follows:(1) The traditional slope of forest and grass measures pay attention to economic benefits, building lots of commercial forest, economic forest and firewood forest which increase water consumption of living being and reduce runoff. Especially when the grass cover degree is effective, bringing slope engineering measures into force may reduce runoff and induce soil erosion. Results showed that natural meadow has best runoff-increase and soil-reduce. For moderate and mild degraded grassland under the management of closing hills, the vegetation coverage could improve by2.84%and1.97%in shady slope and sunny slope per year. Large areas of moderate and mild degraded grassland under the management of closing hills could not only reduce sediment yield, recover vegetation,but also increase runoff, if give up economic benefits of the harnessing area under the backround of eco-compensate and eco-security.(2) The traditional slope engineering measures were design by average runoff of many years, traditional fish-scale pits measures had significant effects on sediment trapping and reduction of water yield. Building eco-water transfer watershed, some traditional measures like fish-scale pits should be limited in areas where occurred serious soil erosion, and their preparation standard should be degraded. It suggests that the size of fish-scale pits could be designed by sediment and the rate of grass recovering. Small fish-scale pits may be destroy by downpour, suggesting that the outside of fish-scale pits can be reinforced by bamboo which could not only reduce sediment, but also increase runoff. Some Hippophae rhamnoides and native shrub grass should be plant in the small fish-scale pits, but not the tree species of water consumption.(3) The traditional channel engineering measures have problems of less sedimentation. Masonry check dam usually form small reservoir causing large of runoff evaporation. Dry masonry check dam often destroy under overproof rainstorm. The traditional channel engineering measures have two defects, one the one hand, low-use water resource, on the other hand, increase manage cost. Building eco-water transfer watershed, the dam should be developed on rational location and improve construction quality, designing according to the condition of manages and erosion. A small watershed can have several types of dam, adjusting measures to conditions and combine in-sand quantity and water transfer. Building wood for fence check dam, dry masonry check dam, masonry check dam successively from gully head to gully toe, which ensure reducing sediment and increasing water yield.