Simulation of spatial and temporal distribution on dissolved non-point source nitrogen and phosphorus load in Jialing River Watershed, China

Abstract

Jialing River, which covers a basin area of 160,000 km 2 and a length of 1,280 km, is the largest tributary of the catchment area in Three Gorges Reservoir Area, China. In recent years, water quality in the reservoir area section of Jialing River has been degraded due to land use and the rural residential area induced by non-point source pollution. Therefore, the semi-distributed land-use runoff process (SLURP) hydrological model has been introduced and used to simulate the integrated hydrological cycle of the Jialing River Watershed (JRW). A coupling watershed model between the SLURP hydrological model and dissolved non-point source pollution model has been proposed in an attempt to evaluate the potential dissolved non-point source pollution load; it enhances the simulation precision of runoff and pollution load which are both based on the same division of land use types in the watershed. The proposed model has been applied in JRW to simulate the temporal and spatial distribution of the dissolved total nitrogen (DTN) and dissolved total phosphorus (DTP) pollution load for the period 1990-2007. It is shown that both the temporal and spatial distribution of DTN and DTP load are positively correlated to annual rainfall height. Land use is the key factor controlling the distribution of DTN and DTP load. The source compositions of DTN and DTP are different, where average DTN pollution load in descending order is land use 67.2%, livestock and poultry breeding 30.5%, and rural settlements 2.2%; and for DTP, livestock and poultry breeding is 50%, land use 48.8%, and rural settlements 1.2%. The contribution rates of DTN and DTP load in each sub-basin indicate the sensitivity of the results to the temporal and spatial distribution of different pollution sources. These data were of great significance for the prediction and estimation of the future changing trends of dissolved non-point source pollution load carried by rainfall runoff in the JRW and for studies of their transport and influence in the Three Gorges Reservoir.

Development of regional pollution export coefficients based on artificial rainfall experiments and its application in North China

“…Contrary to previously reported results suggesting a uniform export coefficient over whole regions (Wu et al 2012;Worrall et al 2015), the export coefficients for the same land use in this study varied between different areas. The export coefficient values were related to the spatial variety of land use, average rainfall-runoff coefficient and precipitation.…”

“…Other studies have used non-engineering practices, such as national policy and technical guidelines, to control NPS pollution (Tian et al 2010). In all of these studies, NPS models were used to simulate NPS load and distribution (Wu et al 2012;Choi et al 2013). Accurate simulations play a key role controlling pollution, and a reasonable preliminary estimation can eliminate potential waste and effectively save resources (Dowd et al 2008).…”

Impacts of climate and land-use changes on the migration of non-point source nitrogen and phosphorus during rainfall-runoff in the Jialing River Watershed, China

“…In general, nitrogen and phosphorus are the main limiting factors to eutrophication for water bodies (Ma et al, 2008), Jialing River Watershed is the largest catchment of the Three Gorges Reservoir area, agricultural sloping land in the watershed accounts for a large proportion. The excessive nitrogen and phosphorus loading from fertilizers, rural dwellers, and distributed livestock farms in the agricultural watershed has become the principal source of NPS pollution (Yan et al, 1999;Wu et al, 2010aWu et al, , 2012, and it can be discharged into receiving water with rainfall-runoff, which can induce eutrophication in the receiving water and loss of biodiversity in the aquatic ecosystem. Therefore, to carry out forecasting NPS nitrogen and phosphorus pollution load of the Jialing River Watershed is of great significance for the protection of the water environment safety in the Three Gorges Reservoir and the whole Yangtze River, and for the promotion of the sustainable development of ecological environment in the reservoir area.…”

“…The choice of SLURP hydrological model instead of the SCS method to simulate runoff is mainly based on four aspects: Firstly, The model can be used to investigate issues such as the effects of land use change or climate change on water resources (Kite 1993). Secondly, SLURP hydrological model has physical mechanism, which simulates physical processes of runoff formation, and it is more suitable for large-and mediumsized mountain watersheds (Jing and Chen, 2011), it has previously obtained good simulation results in mountain basins in Canada, America and China (Haberlandt et al 2001;Zhang et al 2005;Krysanova et al 2007;Wu et al, 2010aWu et al, , 2012; more importantly, SLURP hydrological model and the improved export coefficient method both take land-use types as the basic research unit, they can be easily coupled with each other to simulate non-point source nitrogen and phosphorus pollution load from surface runoff to interflow which are also based on the same division of land-use types; In addition, the model can also be used to predict and analyze the corresponding runoff and non-point source pollution load of the watershed under circumstances of the existing future climate and land use changes; Therefore, the integrated NPS pollution forecasting model composed of nitrogen and phosphorus load model and the SLURP hydrological model was developed to effectively simulate the impacts of climate change and human activities on runoff and pollution load.…”

Effects of a commercial, suspended eastern oyster nursery upon nutrient and sediment chemistry in a temperate, coastal embayment

“…phytoplankton, nutrients, zooplankton); (2) oysters are only put into the system when the water temperature will support growth and are removed once they reach 25 mm; therefore, the load to the system changes weekly; and (3) this embayment is affected by many other seasonal human activities (boating, fishing, dredging). However, because the FLUPSY takes water from the embayment (input) and has a known discharge pipe, we can use the fixed-station, estuarine-transect approach commonly used in estuaries to determine anthropogenic point and non-point sources in a watershed (Cutter & San Diego-McGlone 1990, Maie et al 2006, Wu et al 2012. This approach involves a 2-step process: (1) quantification of the inputs (nutrients, total suspended material [TSM], chlorophyll [chl] a) from the freshwater endmember (salt marsh), saltwater endmember (Great Peconic Bay), sediments within the embayment, and the FLUPSY; and (2) sampling a fixed-station, estuarine transect during different time periods throughout the season when the FLUPSY is utilized.…”