1. School of Geography, South China Normal University, Guangzhou 510631, China 2. Department of Earth and Environmental Sciences, Michigan State University, East Lansing, MI 48823, USA 3. Guangzhou Institute of Geography,Guangzhou 510070,China
Non-point source pollution is one of the most severe problems impacting water environments. Identifying potential risk areas and risk paths contributing to non-point source pollution is the soution to this problem. This study introduces the minimum cumulative resistance model of landscape ecology, which is based on land use and soil mapping at a scale of 1∶100000 and DEM data with a resolution of 30 m. The model takes high pollution-loaded cultivated land and construction land as the main sources and uses the Topographic Wetness Index and Runoff Curve Numbers, which can describe the underlying resistance surface runoff yield characteristics, to visually identify and analyze the risk areas and risk paths of the Wuhua River Basin. The results show that underlying surface runoff production results in low-yield flow areas that are mainly concentrated in the southwest of the basin, while high-yield flow areas herringbone throughout the study area. The minimum cumulative resistance model can effectively identify the risk areas and risk paths in this basin. The high-risk areas of non-point source pollution are mainly distributed in Jionglong, Tianxin, Longmu, Tiechang, Dengyun, Tongqu, Heshi, Zishi, Qiling, Huacheng, Zhuanshui, Tanxia and Shuizai, which are located along both sides of the river. The spatial distributions of the risk paths of cultivated land and construction land are significantly different. The effects of cultivated land on water quality of the river are greater than those of construction land on it, and the nutrients and sediments from cultivated land are more likely to run into the receiving water via surface runoff. Vegetation buffer zones should be set up on both sides of the river adjacent to cultivated land when we deal with non-point source pollution that originates from cultivated land, and the harnessment of non-point source pollution originating from construction land should be monitored around major source areas. This study provides a novel method for the identification of source areas and risk paths of non-point source pollution and a theoretical basis to formulate future management strategies.
. 五华河流域非点源污染风险区和风险路径识别[J]. 地理学报,
2018, 73(9): 1765-1777.
WAN Luwen et al
. Identifying risk areas and risk paths of non-point source pollution in Wuhua River Basin[J]. Acta Geographica Sinica,
2018, 73(9): 1765-1777.
<p>地表水的非点源污染在点源污染不断得到控制的前提下已经成为水环境污染的首要问题.非点源污染影响因子的复杂性及不确定性一直是流域非点源污染研究的重点和难点.本文利用SWAT(Soil and Water Assessment Tool)模型，以辽河子流域汎河流域为例，模拟了2003—2012年的非点源污染状况,对其空间分布状况进行了分析,并应用增强回归树的方法定量分析各种影响因子(坡度、土地利用类型、高程和土壤类型)对该流域非点源污染的贡献率.结果表明: 在汎河流域,非点源污染呈现较高的空间异质性,其中总氮的空间分布差异较大,总磷的空间分布差异较小.坡度因子与载体泥沙、总氮和总磷均呈极显著正相关关系(<em>P</em><0.01),对泥沙和总磷有显著影响,其贡献率分别为46.5%、38.2%;土地利用因子对载体泥沙、总磷的负荷量有重要影响,其贡献率分别达到27.2%、35.3%;高程较低、坡度较缓的耕地地区易产生较高的总磷负荷量;褐色土壤最易流失总磷,而草甸土易流失总磷,且易受泥沙侵蚀.本研究利用增强回归树模型克服了流域非点源污染影响因子的复杂性,可加深对非点源污染产生机制的理解.</p>
Dowd BM, PressD, Huertos ML.Agricultural nonpoint source water pollution policy:The case of California's Central Coast. , 2008, 128(3): 151-161.http://www.sciencedirect.com/science/article/pii/S016788090800176X
Nonpoint sources of pollution, primarily from agricultural sources, are a major cause of water quality impairment. Yet policies to address this issue remain underexplored in the literature. This article first reviews the agricultural nonpoint source (NPS) pollution policy literature and categorizes its major findings. The North American literature, in particular, rarely analyses NPS policies already in force, and pays even less attention to overcoming implementation barriers to reaching desired environmental outcomes. Second, this paper evaluates a newly adopted policy approach that addresses nonpoint sources of nutrient contaminants in the surface waters of one of the United States most agriculturally productive and environmentally pristine areas, California's Central Coast. The article then reveals the political, budgetary and technical barriers faced by farmers, regulators, and other stakeholders. The article concludes by arguing that more analyses of implemented policies designed to address agricultural NPS pollution will better inform both local-level and federal policymakers towards the successful creation and implementation of policies that achieve environmental outcomes.
HuangNing, WangHongying, LinTao, et al.Regulation framework of watershed landscape pattern for non-point source pollution control based on 'source-sink' theory: A case study in the watershed of Maluan Bay, Xiamen City, China. , 2016, 27(10): 3325-3334.
White MJ, Storm DE, Busteed PR, et al.Evaluating nonpoint source critical source area contributions at the watershed scale. , 2009, 38(4): 1654-1663.https://www.agronomy.org/publications/jeq/abstracts/38/4/1654
Areas with disproportionately high pollutant losses (i.e., critical source areas [CSAs]) have been widely recognized as priority areas for the control of nonpoint-source pollution. The identification and evaluation of CSAs at the watershed scale allows state and federal programs to implement soil and water conservation measures where they are needed most. Despite many potential advantages, many state and federal conservation programs do not actively target CSAs. There is a lack of research identifying the total CSA pollutant contribution at the watershed scale, and there is no quantitative assessment of program effectiveness if CSAs are actively targeted. The purpose of this research was to identify and quantify sediment and total phosphorus loads originating from CSAs at the watershed scale using the Soil and Water Assessment Tool. This research is a synthesis of CSA targeting studies performed in six Oklahoma priority watersheds from 2001 to 2007 to aid the Oklahoma Conservation Commission in the prioritized placement of subsidized conservation measures. Within these six watersheds, 5% of the land area yielded 50% of sediment and 34% of the phosphorus load. In watersheds dominated by agriculture, the worst 5% of agricultural land contributed, on average, 22% of the total agricultural pollutant load. Pollutant loads from these agricultural CSAs were more than four times greater than the average load from agricultural areas within the watershed. Conservation practices implemented in these areas can be more effective because they have the opportunity to treat more pollutant. The evaluation of CSAs and prioritized implementation of conservation measures at the watershed scale has the potential to significantly improve the effectiveness of state and federally sponsored water quality programs.
SivertunÅ, PrangeL.Non-point source critical area analysis in the Gisselö Watershed using GIS. , 2003, 18(10): 887-898.http://www.sciencedirect.com/science/article/pii/S1364815203001075
In the southeast in Norrk02ping, Sweden, is a small fjord-like bay called Sl01tbaken. The water quality in Sl01tbaken—with its narrow outlet to the Baltic Sea—depends highly on the water quality of the streams that flow in it. While point pollution sources can be identified easily in general, the non-point sources are harder to find. The most important sources for non-point pollution are agricultural areas, and the pollutants are mostly nutrients like phosphorus, which come from the fertilisation of the fields. One important catchment area for Sl01tbaken is the 57.7 km Gissel02 river basin (part of the topographic map 8GNO), which contains large agricultural areas.The transport of water pollutants is based on the same hydrological processes as erosion and sediment transport. The implementation of such a model in a GIS allows the analysis of a large area with a high resolution. When choosing the model, special attention was paid to the possibility of using a verified model that is easy to implement in a commercial GIS without the need of too much expert knowledge. This may allow its widespread use in many administrative applications that need non-point source information. A feasibility test for an enhanced GIS USLE model was done in the Gissel02 drainage basin before it was implemented for all river basins in the whole administrative area of Norrk02pings kommun.It is possible to use the suggested simplified USLE model to estimate the load of both pollutants and sediments, and it is able to show the areas that are critical for the water quality at the outlet of the water basin. The model has been evaluated in three studies [Int. J. Geogr. Inf. Syst. 2 (4) (1988) 365; A GIS to target critical areas for non point source management, in: Proceedings of the International Non Point Source Management Symposium, Austin, TX, November 7, 1989; Vatten 48 (1992) 117]. Then, implemented in a very simple GIS that allowed only rough estimates of terrain models and distances, the model was able to estimate the total suspended solids (TSS) and total phosphorus (TP) loads in the Svart02 river basin of 1539 km in the same region as Gissel02 and the Bornsj02 river basin outside Stockholm. Besides an estimated of 0.91–0.98 (verified by a more than one year measurement from manual and automated sampling stations in the whole river basin), the benefit with the GIS implemented USLE was the possibility to identify the risk areas with high spatial accuracy. During the last decade, both available databases and software have changed the possibilities to identify areas at risk of nutrient leakage. Schein [GIS Methods for Monitoring Sustainable Development by Analysis of Land-use and Land Cover Changes in the Surroundings of Link02ping (Sweden), Institut für Photogrammetrie und Fernerkundung, Technische Universit01t Dresden, Germany] and Schein and Sivertun [Method and models for sustainable development monitoring and analyses in GIS, in: Proceedings of the International Workshop on Geo-Spatial Knowledge Processing for Natural Resource Management, University of Insubria, Varese, Italy, June 28–29, 2001] show that the enhanced land use data available through the European Union agricultural support program can be used together with remote sensing data to fine tune the modified GIS USLE model. The problems with the new 50×50 m digital elevation data now available are also pointed out here. Obvious errors in the data and possibilities to enhance the model by introducing a better terrain model were two important suggestions in these works. In this article, two modifications to the original model are suggested. One is enhancement of the digital terrain model by using height curves from the digital 1:50?000 scale topographic map, and the other is a smooth distance function that better reflects the impact of nutrients on water bodies.Because of its easy implementation on standard low cost systems, the GIS USLE model is suitable for analysing huge areas for critical places. The results can lead to more detailed studies in the risk areas thus identified or to investigations on the effect of land use changes, or can be used simply for taking care in the use of fertilisers and other chemicals in the critical agricultural areas.
Endreny TA, Eric FW.Watershed weighting of export coefficients to map critical phosphorous loading areas. , 2010, 39(1): 165-181.http://onlinelibrary.wiley.com/doi/10.1111/j.1752-1688.2003.tb01569.x/abstract
ABSTRACT: The Export Coefficient model (ECM) is capable of generating reasonable estimates of annual phosphorous loading simply from a watershed's land cover data and export coefficient values (ECVs). In its current form, the ECM assumes that ECVs are homogeneous within each land cover type, yet basic nutrient runoff and hydrological theory suggests that runoff rates have spatial patterns controlled by loading and filtering along the flow paths from the upslope contributing area and downslope dispersal area. Using a geographic information system (GIS) raster, or pixel, modeling format, these contributing area and dispersal area (CADA) controls were derived from the perspective of each individual watershed pixel to weight the otherwise homogeneous ECVs for phosphorous. Although the CADA-ECM predicts export coefficient spatial variation for a single land use type, the lumped basin load is unaffected by weighting. After CADA weighting, a map of the new ECVs addressed the three fundamental criteria for targeting critical pollutant loading areas: (1) the presence of the pollutant, (2) the likelihood for runoff to carry the pollutant offsite, and (3) the likelihood that buffers will trap nutrients prior to their runoff into the receiving water body. These spatially distributed maps of the most important pollutant management areas were used within New York's West Branch Delaware River watershed to demonstrate how the CADA-ECM could be applied in targeting phosphorous critical loading areas.
Hughes KJ, Magette WL, KurzI.Identifying critical source areas for phosphorus loss in Ireland using field and catchment scale ranking schemes. , 2005, 304(1-4): 430-445.http://linkinghub.elsevier.com/retrieve/pii/S0022169404005104
NiraulaR, KalinL, SrivastavaP, et al.Identifying critical source areas of nonpoint source pollution with SWAT and GWLF. , 2013, 268(23): 123-133.http://linkinghub.elsevier.com/retrieve/pii/S0304380013004006
Identification of critical source areas (CSAs) (areas contributing most of the pollutants in a watershed) is important for cost-effective implementation of best management practices. Identification of such areas is often done through watershed modeling. Various watershed models are available for this purpose, however it is not clear if the choice (and complexity) of a model would lead to differences in locations of CSAs. The objective of this study was to use two models of different complexity for identifying CSAs. The relatively complex Soil and Water Assessment Tool (SWAT) and the simpler Generalized Watershed Loading Function (GWLF) were used to identify CSAs of sediment and nutrients in the Saugahatchee Creek watershed in east central Alabama. Models were calibrated and validated for streamflow, sediment, total nitrogen (TN) and total phosphorus (TP) at a monthly time scale. While both models performed well for streamflow, SWAT performed slightly better than GWLF for sediment, TN and TP. Sub-watersheds dominated by urban land use were among those producing the highest amount of sediment, TN and TP loads, and thus identified as CSAs. Sub-watersheds with some amount of agricultural crops were also identified as CSAs of TP and TN. A few hay/pasture dominated sub-watersheds were identified as CSAs of TN. The identified land use source areas were also supported by field collected water quality data. A combined index was used to identify the sub-watersheds (CSAs) that need to be targeted for overall reduction of sediment, TN and TP. While many CSAs identified by SWAT and GWLF were the same, some CSAs were different. Therefore, this study concludes that model choice will affect the location of some CSAs.
Blazquez-CabreraS, GastónA, BeierP, et al.Influence of separating home range and dispersal movements on characterizing corridors and effective distances. , 2016, 31(10): 2355-2366.http://link.springer.com/10.1007/s10980-016-0407-5
WangJ, ShaoJ, WangD, et al.Identification of the "source" and "sink" patterns influencing non-point source pollution in the Three Gorges Reservoir Area. , 2016, 26(10): 1431-1448.http://link.springer.com/10.1007/s11442-016-1336-6
ChenL, TianH, FuB, et al.Development of a new index for integrating landscape patterns with ecological processes at watershed scale. , 2009, 19(1): 37-45.http://link.springer.com/10.1007/s11769-009-0037-9
Habitat patches situated amidst an otherwise inhospitable landscape are often considered as islands in the sense of the equilibrium theory of insular zoogeography. Their species richness can be affected by isolation from other areas of suitable habitat. However, the isolation of habitat islands is not only dependent on the distance from the source area, as with oceanic islands, but also on the characteristics of the interjacent landscape. To account for the latter, the use of a measure of isolation termed ‘minimal cumulative resistance’ (MCR) is proposed. A simple model is described for calculating MCR from a grid-based map on which estimated dispersal resistances are assigned to landscape types. Application of the model is illustrated with a specific case: the allocation of new forests in the western part of the Netherlands. Although its application is bound by a number of restrictions, it is concluded that the model can be a useful aid in physical planning and nature conservation.
WangJinliang, XieDeti, Shao Jing'an, et al. Identification of source-sink risk pattern of agricultural non-point source pollution in cultivated land in Three Gorge Reservoir Area based on accumulative minimum resistance model. , 2016, 32(16): 206-215.
Thomas IA, JordanP, Mellander PE, et al.Improving the identification of hydrologically sensitive areas using LiDAR DEMs for the delineation and mitigation of critical source areas of diffuse pollution. , 2016, 556(6): 276-290.https://linkinghub.elsevier.com/retrieve/pii/S0048969716303941