Abstract
Soil erosion has been recognized as one of the major threats to our environment and water quality worldwide, especially in China. To mitigate nonpoint source water quality problems caused by soil erosion, best management practices (BMPs) and/or conservation programs have been adopted. Watershed models, such as the Annualized Agricultural Non-Point Source Pollutant Loading model (AnnAGNPS), have been developed to aid in the evaluation of watershed response to watershed management practices. The model has been applied worldwide and proven to be a very effective tool in identifying the critical areas which had serious erosion, and in aiding in decision-making processes for adopting BMPs and/or conservation programs so that cost/benefit can be maximized and non-point source pollution control can be achieved in the most efficient way. The main goal of this study was to assess the characteristics of soil erosion, sediment and sediment delivery of a watershed so that effective conservation measures can be implemented. To achieve the overall objective of this study, all necessary data for the 4,184 km2 Daning River watershed in the Three-Gorge region of the Yangtze River of China were assembled. The model was calibrated using observed monthly runoff from 1998 to 1999 (Nash-Sutcliffe coefficient of efficiency of 0.94 and R2 of 0.94) and validated using the observed monthly runoff from 2003 to 2005 (Nash-Sutcliffe coefficient of efficiency of 0.93 and R2 of 0.93). Additionally, the model was validated using annual average sediment of 2000–2002 (relative error of −0.34) and 2003–2004 (relative error of 0.18) at Wuxi station. Post validation simulation showed that approximately 48% of the watershed was under the soil loss tolerance released by the Ministry of Water Resources of China (500 t·km−2·y−1). However, 8% of the watershed had soil erosion of exceeding 5,000 t·km−2·y−1. Sloping areas and low coverage areas are the main source of soil loss in the watershed.
Highlights
Soil erosion has increased throughout the 20th century [1], and has become an extremely serious environmental problem worldwide
Characteristics of soil erosion and sediment yield within Daning River watershed for the current condition simulation are given in Tables 2–4 and Figures 3 and 4
The Annualized Agricultural Nonpoint Source Pollution (AnnAGNPS) model is an advanced technological watershed evaluation tool that has been developed through a partnership between the U.S Department of Agriculture (USDA)—Agriculture Research Service (ARS) and the USDA—Natural Resources Conservation Service (NRCS) to aid in the evaluation of watershed responses to agricultural management practices [3,5,12,29]
Summary
Soil erosion has increased throughout the 20th century [1], and has become an extremely serious environmental problem worldwide. It has been recognized as a threat to the productivity of the farms and the quality of surface waters in the Three-Gorge area of the Yangtze River of China. The accurate quantification of soil erosion and sediment in the watersheds of the region is urgently needed and essential for efficiently planning land use, enhancing agricultural production and productivity, reducing reservoir sedimentation and improving stream water quality. Several watershed-scale hydrological and water quality models, such as AnnAGNPS (Annualized AGricultural Non-Point Source) [3] and SWAT
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