Simulation On Agricultural Non-point Sources Pollution And Risk Assessment In Dahuofang Reservoir Catchment Of Liaoning Province

Non-point source pollution is gaining concern increasingly due to the wide range,randomness and difficult control. Particularly, the agricultural non-point source pollution(ANSP) has been studied deeply worldwide. China has paid attention to the ANSP,especially for the pollution prevention in the important reservoirs and water sourceregions and undertaken some correlated researches. Dahuofang Reservoir is a kind ofreservoir for drinking water source and is ranked as one of nine main urban water supplysources. In recent years, pollution problems of the reservoir become increasingly severe.There is an urgent need to do the research on ANSP in the catchment of DahuofangReservoir.According to the regional characteristic, systematic investigations of pollution fromplanting, livestock breeding and domestic live were done, so the basic information ofANSP in the study area was acquired. By constructing spatial database and attributedatabase requested by SWAT simulation, a SWAT model that is suitable for the study areacan be established. With the simulation of ANSP in catchment area, the inflow load intothe reservoir can estimated and the spatial and temporal distribution characteristic can beanalyzed. With the ANSP risk assessment method based on GIS, pollution risk can berated and assessed, which provides support to the control and management of ANSP inthe study area.By field study and material collection, investigation of basic information of ANSPwas undertaken. The basic data includes the area of arable land in catchment area ofDahuofang Reservoir, type of crops, yield of crops, and using condition of fertilizers.With the basic data, we verified that corn and rice are the major crops; the using amountof fertilizers and pesticide is11489.1t and472.2t. With the investigation results of thetype and quantity of livestock and spatial distribution of large-scale breeding farms, totalamount of nitrogen and phosphorous from breeding industry can be calculated as8294.96t and2249.35t. According to the actual geographic conditions, this researchassumed a buffering area1km off the riverside and another buffering area5km around the reservoir. With the statistic data of population within the buffering area, total amount ofnitrogen and phosphorous from domestic pollution can be calculated as2268.35t and198.11t.By simulation of SWAT model total amount of nitrogen, phosphorous and averagesediment load that flows into Dahuofang Reservoir can be calculated as1873.49t,81.97tand8.27×10~4t. In July and August, the most nitrogen, phosphorous and sediment flowsinto the reservoir. With relevant analysis of the runoff and precipitation, a close relevancebetween the amount of nitrogen, phosphorous and sediment and the runoff andprecipitation can be found. So the generation of ANSP and the migration of the pollutantsare substantially influenced by the runoff, precipitation and the generation of sediment.Spatially, Hun River Basin (Qingyuan part) has the greatest contribution rate of the ANSP,followed by Suzi River Basin and She River Basin, The small river basin around thereservoir has the least contribution rate. The slope generation of ANSP from farmingindustry in the catchment of Dahuofang Reservoir is: sediment1.54×105t, TN1248.83t,TP102.88t. The research shows a close relevance among the soil erosion modulus, thedistribution of slope intensity of TN and TP from farming industry and the spatialdistribution of precipitation.With the support of GIS technology, ANSP risk assessment model can be establishedso that the rating distribution chart of the pollution risk extent can be obtained. A-ratingregion is mainly located alongside the main stream, presenting the greatest ANSP risk.B-rating region is mainly located in the tributaries, presenting the lower risk of ANSP.C-rating region has the least risk of ANSP. There is also an urgent need to make countermeasures to deal with the acute non-pint source pollution in large breeding farms and theurban areas as special concerning areas to prevent the acute non-point source pollutioncaused by storms or the leakage of pollutants.With the research of this thesis, a comprehensive command of the source, generation,distribution and inflow of the ANSP in the study area and the dynamite change ofprecipitation can be acquired. The results of the research will provide basic support to theestablishment of the early-warning platform, the conservation of the water quality in thewater source region and ecological security and the formulation of controlling technologies and management policies of the ANSP.