基于SWAT模型的布尔哈通河流域面源污染的变化研究

【目的】揭示土地利用变化下面源污染时空变化特征,探究流域景观格局与面源污染的关系。【方法】以布尔哈通河流域为研究对象,利用SWAT分布式水文模型模拟1986-2016年4期土地利用变化下面源污染分布特征,运用Fragstats4.2软件计算了1986年和2016年布尔哈通河各子流域的景观格局指数,最后使用CANOCO5.0软件分析子流域面源污染和景观指数之间的关系。【结果】①构建的SWAT模型模拟的径流量和总磷量在校准期和验证期的决定系数R²和纳什效率系数NSE都达到0.6以上,模型能很好地模拟流域水文水质状况,1986-2016年,SWAT模拟的总磷年负荷分别为74.04、73.78、82.50 t和128.31 t。②面源污染与景观格局存在密切关系,景观组成格局方面,林地面积与总磷负荷负相关,农田和建设用地面积与总磷负荷正相关;景观空间格局方面,林地斑块破碎化程度与总磷负荷正相关,而农田斑块的破碎化程度与总磷负荷负相关。流域斑块之间的越高流通性和聚集性,对养分流失改善有积极作用,而流域内景观异质性的增加和形状的复杂化,则会导致污染负荷输出风险的增加。【结论】流域面源污染负荷急剧增加,面源污染防治的关键控制区域在坡度较高的北部区域和农田及城镇集中的东部区域,该区域规划土地利用和优化景观格局时,应优先考虑防止林地斑块破碎化程度的提高和控制城镇面源污染源。

Using SWAP to Study the Changes in Nonpoint Source Pollution in Burhatong River Basin

【Background】Nonpoint source pollution can cause eutrophication and biodiversity loss in rivers and lakes.In China,nonpoint source pollution from agriculture has become an environmental concern and understanding its composition and spatial distribution in watershed is essential to improving its management and mitigating its detrimental impact.【Objective】The purpose of this paper is to study the impact of land usage on spatiotemporal change in nonpoint source pollution,and elucidate its relationship with watershed landscape.【Method】We took the Burhatong river basin as an example and used the distributed hydrological model SWAT to simulate dynamics of nonpoint source pollution induced by four land use changes from 1986 to 2016.The Fragstats 4.2 software was used to calculate the landscape pattern index of the sub-basins,and its relationship with nonpoint source pollution was analyzed using the CANOCO5.0 software.【Result】①The determination coefficient and the Nash efficiency coefficient of the runoff and total phosphorus amount simulated by the SWAT in calibration and verification were all higher than 0.6.The model can thus be used to simulate water quality in the watershed.For the four land usage changes from1986 to 2016,the total annual phosphorus load simulated by the model was 74.04,73.78,82.50 and 128.31 tons,respectively.②There is a close relationship between nonpoint source pollution and landscape pattern.In terms of landscape composition pattern,the total phosphorus load was negatively correlated to forest land,while positively correlated to farmland and construction land.In terms of landscape spatial pattern,the total phosphorus was positively correlated to fragmentation of forest land,while negatively correlated to fragmentation of farmland.Increasing materials flow between patches and enhancing patch aggregation can reduce nutrient loss,while increasing landscape heterogeneity and complexity increases pollution risk.【Conclusion】Nonpoint source pollution in the watershed of Burhatong basin has increased steadily,especially in the slopped areas in the north and agricultural and urban areas in the east.Reducing forest land fragmentation and controlling urban nonpoint source pollution can help mitigate its detrimental impact.