Study of Non-Point Pollution in the Ashe River Basin Based on SWAT Model with Different Land Use

Abstract

The Ashe River Basin (ARB), long known as the “Golden Waterway” in Manchu, has become one of China’s most polluted rivers. The basin area of the Ashe River is 3545 km2 and the total length of the river is 257 km. There have not been specific studies on land use change and non-point pollution in the ARB region. This paper uses the ARB watershed as the study area, simulates the watershed using the SWAT (Soil and Water Assessment Tool) model, and analyzes the hydrological processes and the temporal and spatial changes of total nitrogen and total phosphorus in the watershed with hydrology and water quality as the objectives under different periods of land use to reduce pollution in the watershed and protect the environment. The results show that the simulation of runoff, and even theR2 and NS(both the coefficient of determination and the Nash–Sutcliffe efficiency coefficient are simulated by SWAT-CUP, which is generally used to validate the simulation results of the hydrological model, where the closer the result is to 1, the better the effect) of total nitrogen and total phosphorus in the watershed, are also all above 0.75 and have good applicability during regular and validation periods. Since 2000, the simulated monthly average total nitrogen and total phosphorus levels have progressively grown. The most polluted areas are concentrated in the middle and lower reaches of the watershed near the main streams owing to the rise in load per unit area caused by the collection of pollutants from the upper watershed to the watershed outlet, and even an increase in fertilizer application due to the larger area of cultivated land.

The impacts of anthropogenic activity and climate change on the formation of harmful algal blooms (HABs) and its ecological consequence

“…In recent years, the community structure of river phytoplankton has been influenced not only by the natural habitats of rivers but also by human activities and the upstream and downstream relationships of rivers (Zhao et al, 2020a). Human activities have gradually changed the types of land use in river basins, mainly through changes in nutrient enrichment, hydrological regimes, riparian habitat quality, and other ecological processes, resulting in a series of adverse effects on river ecosystems (Chen et al, 2022). With the escalation in anthropogenic stress, the loss of natural land, and the increase in pollutants discharged into rivers, the number of pollution-sensitive phytoplankton species in rivers decreased, and pollution-resistant species became the dominant group (Moghadam, 1975;Montoya-Moreno and Aguirre-Ramírez, 2013).…”

Ecological health evaluation of rivers based on phytoplankton biological integrity index and water quality index on the impact of anthropogenic pollution: A case of Ashi River Basin

“…In recent years, the community structure of river phytoplankton has been influenced not only by the natural habitats of rivers but also by human activities and the upstream and downstream relationships of rivers (Zhao et al, 2020a). Human activities have gradually changed the types of land use in river basins, mainly through changes in nutrient enrichment, hydrological regimes, riparian habitat quality, and other ecological processes, resulting in a series of adverse effects on river ecosystems (Chen et al, 2022). With the escalation in anthropogenic stress, the loss of natural land, and the increase in pollutants discharged into rivers, the number of pollution-sensitive phytoplankton species in rivers decreased, and pollution-resistant species became the dominant group (Moghadam, 1975;Montoya-Moreno and Aguirre-Ramírez, 2013).…”

“…In recent years, water pollution in the basin has become an increasingly serious concern in light of the steady expansion of the regional economy and grain production. During the wet season, a large quantity of pesticides and fertilizer residues enters the Ashi river combined with surface runoff from the extensive farmland in the middle reaches of the Ashi River Basin (ASRB) (Chen et al, 2022). The region downstream of the ASRB is densely populated, with land use dominated by cities and towns that are severely impacted by anthropogenic activities.…”

Spatial Pattern Evolution and Influencing Factors on Agricultural Non-Point Source Pollution in Small Town Areas under the Background of Rapid Industrialization

“…Physical models are constructed based on the intrinsic mechanisms of ANSP formation, simulating the process of pollutant generation and transport; then, ANSP loads are calculated through mathematical models. Physical models mainly include ANSWERS [19], SWRRB [20], SWAT [4], HSPF [21], and other models, which are mostly applicable to watershed-scale studies [22]. The empirical model is based on the data of each pollution unit and establishes the relationship between pollution units and ANSP emissions through multivariate linear correlation analysis; it then calculates the ANSP load of different units.…”