The Construction and Management System of Eco-clean Small Watershed in the Subtropical Zone

This study aimed to investigate the construction and management system of eco-clean Nver-Zhai small watershed to solve the existing eco-environment problems. The study area was di- vided into three protection zones which include ecological restoration of conservation area, ecolog- ical control area and wetland protection area. These three protection zones were treated in several selected protection ways and monitored at the Ecological Station of Cili County to assess the eco- logical benefit of these treatments. Finally, based on the results, the construction and management system of Nver-Zhai were built. 1 INSTRUCTION As be the smallest unit of water collection, a small watershed is the radical departure for water source protection. Only when small watersheds are well managed and protected, can the ecological system be protected, also the quality of water into reservoirs and rivers be basically guaranteed (1). Establishing small eco-clean watershed, which unit was set based on a valley and follows the laws of ecology and nature without affecting the landscape, is a way to construct and manage the water resource comprehensively.Via this method,the rational use and optimization of resources in a valley can be realized, the harmony between human beings and nature can be kept and the sustainable de- velopment of economic social (2) and circulative eco-system can be built. Since 2003, the research on small eco-clean watersheds has began all over China and got some progress in Beijing city and Shandong province and other places(3-11). However, few researches has been carried out in south part of China. This paper reported the establishing process of Nver-Zhai eco-clean small watersheds based on the topographic feature of Nver-Zhai watershed and integration of mountain, water, forest, cropland and road. This process was monitored at the Ecology Localization Research and Experi- ment Station of Cili County and the monitoring results were used to analyze the mechanism and comprehensive effect of the process of restoration and reconstruction of vegetation in subtropical forest ecosystem. The study area, Nver-Zhai small watershed, is located in the hinderland of Wuling Mountain in the middle of Yangtze River (111° 14'27.68"E、29 ° 24'04.61"N) and is approximately 7km away from the northwest of Cili County. It is the second grade tributary of Lishui River and approximate- ly in a north-south direction. The altitude of the outlet is 210m. The highest peak is 917.4m and the length of the main gully is about 1.2km. The total area of the small watershed is 3.15km 2 with the population of 277. This area is a typical subtropical humid zone with adequate rainfall. The average annual rainfall is about 1400mm and the rainfall from April to August takes up more than 60% of the annual rainfall. The altitude of the watershed ranges from 210.0m to 917.4m. The parent rocks are consisted of shale and sandstone and the soil is mainly rea soil, mountain yellow soil and yel- low-brown soil. The terrain of small watershed is complicated. The density of gully is about 2.6km/km 2 and the vertical gradient of the main gully is about 28.4‰. In the watershed there exist paddy field 4.13 hm 2 ,vegetable field 1.54 hm 2 ,dry land 5.07 hm 2 , woodland 202.32hm 2 ,water area 38.80hm 2 , house site 4.62hm 2 , road 24.52hm 2 ,the land use status quo to see in Figure.1.