ABSTRACT
In recent years, eutrophication has become an increasingly serious environmental problem in lake systems. Excessive nutrient enrichment is the root cause of eutrophication. Although lakes naturally receive nutrient inputs from their catchments and the atmosphere, many human activities such as sewage inflows, runoff from agricultural fields, and industrial effluents have greatly accelerated the eutrophication process. To assess the relative roles of natural, climate-induced changes versus human-related activities, such as the removal of vegetation, it is important to evaluate the natural trajectory of nutrient transportation over the catchments and its contribution to a lake’s eutrophication. The eutrophication of the lakes in the most developed region in China, the mid-lower reaches of the Yangtze River, has brought great attention from the public, scholars, and government. As there are many types of lakes in the Yangtze River basin, and the causes of eutrophication are different for each type, Honghu Lake basin, which is located at the middle reach of the Yangtze River, was chosen as the study area. Computational simulations with the SWAT (Soil and Water Assessment Tool) model were used to reflect the historical nutrient sedimentation and transportation processes. With the application of the SWAT model, the principle of nutrient transportation in the natural agricultural environment (the environment under which the nutrient sedimentation and transportation processes are only controlled by natural factors, such as topography, climate changes, and natural vegetation cover, etc.) has been discussed in order to provide scientific basis for the mechanism research of lake water eutrophication.
