Study On Soil Erosion Sensitivity And Its Dynamic Monitoring In Watershed

Soil erosion is one of the ecological environment problems in the earth. With society, economic development and environment change, soil erosion becomes more and more serious, but the need of water and soil resources is increasing. As the study on soil erosion prediction before was not fit for the modern requirements of sustainable development of resource and environment, the research on soil erosion sensitivity becomes important. Watershed is a hydrology unit as well as an ecosystem, and any unreasonable development in watershed will affect the balance of resource supply and demand. By using the study on evaluation of soil erosion in region for reference, research was carried out in a watershed surrounding the Shanzai Reservoir of Fuzhou City, and an index system of watershed soil erosion sensitivity was developed in the research. The whole watershed soil erosion sensitivity was assessed based on RS, GPS and GIS technique. In order to make the prevention of soil erosion and monitoring management in watershed more efficient, the dynamic monitoring of soil erosion was developed. The thesis analyzed how rainfalls and land use influence soil erosion, and predicted soil loss basing on the describtion of the relationship between soil erosion and soil erosion sensitivity. The results showed that: (1) According the assessment results, with an annual average rainfall of 1266mm, the study watershed is a low soil erosion sensitivity watershed, and the changes of moderate sensitivity area as well as low sensitivity area corresponds to the changes of the rainfall. (2) Area with low vegetation coverage is always an erosion sensitive area. The main land use types of high sensitive area are barren land, burned area, beach land and fallowed nonirrigated farmland. (3) Corresponding to the same rainfall erosivity, the sensitivity grade sequence can be described as burned area, barren land and beach land > forest type 1 > forest type 2 > paddy field and nonirrigated farmland > grassland and forest type 3>residences. (4) As the rainfall below 217mm, the insensitivity area in the watershed is about 90%, and the low sensitivity area is more than 90% when the rainfall between 1193mm and 2868mm. (5) Each land use in the watershed has its sensitivity corresponding to different rainfall. The sensitive area of all land use type except burned area, barren land and beach land has an increasing trend when the rainfall above 423mm. The moderate sensitive area of burned area of barren land and beach land increased when the rainfall above 635mm. When it achieves 1193mm, there is no insensitive area in the watershed. (6) The study watershed was in the category of low degree erosion. The area of soil erosion is small. A mighty serious eroded area (sediment yield is higher than 8000t/km2) contributed most of sediments in the watershed. The soil loss in the year of 1986, 2000, 2002 and 2003 is 107198.85ton, 373396.71ton, 215864.45ton and 76403.39ton. The soil erosion amount of the watershed is 630.95t/km2 .The high sensitive area always has the large soil loss and soil erosion amount. The study could support the practice work of soil erosion prevention and monitoring management as well as the land use in watershed. The development of the index system could benefit and enrich the theory of watershed planning and management.