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Showing papers on "Nonpoint source pollution published in 2010"


Journal ArticleDOI
Chengfeng Le1, Yong Zha1, Yunmei Li1, Deyong Sun1, Heng Lü1, Bin Yin1 
TL;DR: It is revealed that water eutrophication in most lakes was initiated in the 1980s when the national economy underwent rapid development and the problem is still serious, with frequent occurrence of damaging algal blooms, which have disrupted the normal supply of drinking water in shore cities.
Abstract: Lake water eutrophication has become one of the most important factors impeding sustainable economic development in China. Knowledge of the current status of lake water eutrophicatoin and determination of its mechanism are prerequisites to devising a sound solution to the problem. Based on reviewing the literature, this paper elaborates on the evolutional process and current state of shallow inland lake water eutrophication in China. The mechanism of lake water eutrophication is explored from nutrient sources. In light of the identified mechanism strategies are proposed to control and tackle lake water eutrophication. This review reveals that water eutrophication in most lakes was initiated in the 1980s when the national economy underwent rapid development. At present, the problem of water eutrophication is still serious, with frequent occurrence of damaging algal blooms, which have disrupted the normal supply of drinking water in shore cities. Each destructive bloom caused a direct economic loss valued at billions of yuan. Nonpoint pollution sources, namely, waste discharge from agricultural fields and nutrients released from floor deposits, are identified as the two major sources of nitrogen and phosphorus. Therefore, all control and rehabilitation measures of lake water eutrophication should target these nutrient sources. Biological measures are recommended to rehabilitate eutrophied lake waters and restore the lake ecosystem in order to bring the problem under control.

512 citations


Journal ArticleDOI
TL;DR: The role of vegetation in protecting streams from nonpoint source pollutants and in improving the quality of degraded stream water has been extensively studied as mentioned in this paper, with a focus on the role of riparian vegetation.
Abstract: We review the research literature and summarize the major processes by which riparian vegetation influences chemical water quality in streams, as well as how these processes vary among vegetation types, and discuss how these processes respond to removal and restoration of riparian vegetation and thereby determine the timing and level of response in stream water quality. Our emphasis is on the role that riparian vegetation plays in protecting streams from nonpoint source pollutants and in improving the quality of degraded stream water. Riparian vegetation influences stream water chemistry through diverse processes including direct chemi- cal uptake and indirect influences such as by supply of organic matter to soils and channels, modification of water movement, and stabilization of soil. Some processes are more strongly expressed under certain site condi- tions, such as denitrification where groundwater is shallow, and by certain kinds of vegetation, such as channel stabilization by large wood and nutrient uptake by faster-growing species. Whether stream chemistry can be managed effectively through deliberate selection and management of vegetation type, however, remains uncer- tain because few studies have been conducted on broad suites of processes that may include compensating or reinforcing interactions. Scant research has focused directly on the response of stream water chemistry to the loss of riparian vegetation or its restoration. Our analysis suggests that the level and time frame of a response to restoration depends strongly on the degree and time frame of vegetation loss. Legacy effects of past vegetation can continue to influence water quality for many years or decades and control the potential level and timing of water quality improvement after vegetation is restored. Through the collective action of many processes, vegeta- tion exerts substantial influence over the well-documented effect that riparian zones have on stream water qual- ity. However, the degree to which stream water quality can be managed through the management of riparian vegetation remains to be clarified. An understanding of the underlying processes is important for effectively using vegetation condition as an indicator of water quality protection and for accurately gauging prospects for water quality improvement through restoration of permanent vegetation. (KEY TERMS: assessment; biogeochemistry; buffers; legacy effects; nonpoint source pollution; resilience; resto- ration; rivers ⁄streams; soils; watershed management.)

445 citations


Journal ArticleDOI
TL;DR: In this article, the authors performed a meta-analysis to quantify the relationship between pollutant removal efficacy and buffer width, buffer slope, soil type, and vegetation type, concluding that a 30m buffer under favorable slope conditions (approximately 10%) removes more than 85% of all the studied pollutants.
Abstract: Vegetated buffers are a well-studied and widely used agricultural management practice for reducing nonpoint-source pollution. A wealth of literature provides experimental data on their mitigation efficacy. This paper aggregated many of these results and performed a meta-analysis to quantify the relationships between pollutant removal efficacy and buffer width, buffer slope, soil type, and vegetation type. Theoretical models for removal efficacy (Y) vs. buffer width (w) were derived and tested against data from the surveyed literature using statistical analyses. A model of the form Y = K x (1-e(-bxw)), (0 10%). Buffers composed of trees have higher N and P removal efficacy than buffers composed of grasses or mixtures of grasses and trees. Soil drainage type did not show a significant effect on pollutant removal efficacy. Based on our analysis, a 30-m buffer under favorable slope conditions (approximately 10%) removes more than 85% of all the studied pollutants. These models predicting optimal buffer width/slope can be instrumental in the design, implementation, and modeling of vegetated buffers for treating agricultural runoff.

230 citations


Journal ArticleDOI
TL;DR: Wang et al. as mentioned in this paper summarized and presented an overview of the current state of water pollution in China, as well as recent progress and the potential future development in water pollution control technology.
Abstract: This paper summarizes and presents an overview of the current state of water pollution, as well as recent progress and the potential future development of water pollution control technology, in China. Although China has made significant strides in water environmental protection over the past decades, analysis reveals that water pollution in the nation is still not sufficiently controlled, with a number of surface waters currently suffering varying degrees of pollution. High nitrogen and phosphorous concentrations in many great lakes have caused eutrophication problems, and the frequency of blue algal bloom has increased. Likewise, river pollution has not been effectively controlled. Nitrogen, phosphorous, organic compounds, and heavy metals are ubiquitous in China's rivers, with up to 80% of urban rivers contaminated to varying degrees—a situation that continues to deteriorate. Next, eutrophication has occurred in many large reservoirs, with numerous toxic substances negatively affecting water quality. Fi...

203 citations


Journal ArticleDOI
Xiaowen Ding1, Zhenyao Shen1, Qian Hong1, Zhifeng Yang1, Xing Wu1, Ruimin Liu1 
TL;DR: In this paper, the authors improved the export coefficient model by introducing the precipitation impact factor, α, and terrain impact factor β, which were defined to characterize the nonuniformities of precipitation and terrain, respectively.

155 citations


Journal ArticleDOI
TL;DR: In this article, a sub-hourly rainfall-runoff model was developed and tested in the Soil and Water Assessment Tool (SWAT) for watersheds with urbanization.
Abstract: Increasing urbanization changes runoff patterns to be flashy and instan- taneous with decreased base flow. A model with the ability to simulate sub-daily rainfall-runoff processes and continuous simulation capability is required to real- istically capture the long-term flow and water quality trends in watersheds that are experiencing urbanization. Soil and Water Assessment Tool (SWAT) has been widely used in hydrologic and nonpoint sources modeling. However, its subdaily modeling capability is limited to hourly flow simulation. This paper presents the development and testing of a sub-hourly rainfall-runoff model in SWAT. SWAT algorithms for infiltration, surface runoff, flow routing, impoundments, and lagging of surface runoff have been modified to allow flow simulations with a sub-hourly

142 citations


Journal ArticleDOI
TL;DR: In this article, the authors evaluated the long-term impact of point and diffuse source pollution on nitrate load in a lowland catchment using the eco-hydrological model SWAT (Soil and Water Assessment Tool) and to determine the contribution of Point and diffuse sources to Nitrate Load in the entire catchment.

139 citations


Journal ArticleDOI
TL;DR: In this article, a suite of BMPs in a pasture-dominated watershed in their effectiveness at controlling nutrient losses was evaluated using the Soil and Water Assessment Tool (SWAT) model.
Abstract: The nonpoint source pollution problem can be controlled by implementing vari- ous best management practices (BMPs) in the watershed. However, before such practices are adopted, their effectiveness at various spatial and temporal scales must be evaluated. The objective of this research was to evaluate a suite of BMPs in a pasture-dominated watershed in their effectiveness at controlling nutrient losses. A total of 171 different BMP combinations incorporating grazing and pasture management, riparian and buffer zones, and poultry litter applications were evaluated for their effectiveness using the Soil and Water Assessment Tool (SWAT) model. The SWAT model was parameterized using detailed farm and watershed-scale data. The stochasticity in weather was captured by generating 250 various possible weather realizations for a 25-year period, using measured historical climate data for the watershed. Model results indicated that losses of both total nitrogen, mineral phosphorus, and total phos- phorus increased with an increase in litter application rates. For the same application rates, greatest losses were predicted for fall application timings compared to spring and summer applications. Overgrazing resulted in greater nutrient losses compared to baseline conditions for all application rates, timings, and litter characteristics, indicating that overgrazing of pasture areas must be avoided if any improvement in the water quality is to be expected. Variability in weather conditions significantly affected BMP performance; under certain weather condi- tions, an increase in pollutant losses can be greater than reductions due to BMPs implemented in the watershed. Buffer strips and grazing management were two most important BMPs affecting the losses of total nitrogen and total phosphorus from the pasture areas.

133 citations


Journal ArticleDOI
TL;DR: In this article, the authors used the soil and water assessment tool (SWAT) to analyze and visualize the fate of NPS nitrogen and phosphorus loads in diverse formats from different land cover types in different years.

119 citations


Journal ArticleDOI
TL;DR: The study demonstrates that the level of concentration of nonpoint source pollutants in surface water within an urban watershed heavily depends on the spatiotemporal variations in areas that contribute towards runoff compared to the spatial extent of change in major land use/land cover.
Abstract: Urban land use and land cover change significantly affect spatial and temporal patterns of runoff, which in turn impacts surface water quality. With the exponential growth in urban areas over the past three decades, changes in land use and land cover to cater for the growth of cities has been a conspicuous spectacle in urban spaces. The main goal of this study was to assess the impacts of land cover change on runoff and surface water quality using a partial area hydrology framework. The study employed ArcHydro GIS extension and a modified version of Long-Term Hydrologic and Nonpoint Source Pollution model (L-THIA-NPS) in estimating runoff and nonpoint source pollutant concentration around Lake Calumet between 1992 and 2001. Data employed include National Land Cover Data set, rainfall data, digital elevation model (DEM), Soil Survey Geographic (SSURGO) data, and The United States Environmental Protection Agency’s STORET (storage and retrieval) water quality data. The model was able to predict surface water quality reasonably well over the study period. Sensitivity analysis facilitated a manual calibration of the model. Model validation was executed by comparing simulated results following calibration and observed water quality data for the study area. The study demonstrates that the level of concentration of nonpoint source pollutants in surface water within an urban watershed heavily depends on the spatiotemporal variations in areas that contribute towards runoff compared to the spatial extent of change in major land use/land cover.

118 citations


Book ChapterDOI
TL;DR: In this article, the ability of constructed and restored wetlands to mitigate a variety of water-quality contaminants common to most agricultural landscapes has been evaluated, including sediment, nitrate, microbial pathogens, particulate phosphorus, hydrophobic pesticides, and selected trace elements.
Abstract: Nonpoint source pollution (NPSP) from agricultural runoff threatens drinking water quality, aquatic habitats, and a variety of other beneficial uses of water resources. Agricultural runoff often contains a suite of water-quality contaminants, such as nutrients, pesticides, pathogens, sediment, salts, trace metals, and substances, contributing to biological oxygen demand. Increasingly, growers who discharge agricultural runoff must comply with water-quality regulations and implement management practices to reduce NPSP. Constructed and restored wetlands are one of many best management practices that growers can employ to address this problem. This review focuses on the ability of constructed and restored wetlands to mitigate a variety of water-quality contaminants common to most agricultural landscapes. We found that constructed and restored wetlands remove or retain many water-quality contaminants in agricultural runoff if carefully designed and managed. Contaminant removal efficiency generally exceeded 50% for sediment, nitrate, microbial pathogens, particulate phosphorus, hydrophobic pesticides, and selected trace elements when wetlands were placed in the correct settings. There are some potentially adverse effects of constructed and restored wetlands that must be considered, including accumulation of mercury and selenium, increased salinity, mosquito habitat, and greenhouse gas emissions. Proper wetland management and design features are discussed in order to reduce these adverse effects, while optimizing contaminant removal.

Journal ArticleDOI
TL;DR: Spatial regression method in conjunction with kriging not only makes better stream NO(3)NO(2)-N concentration predictions than the OLS method, but also gives estimates of the uncertainty of the predictions, which provides useful information for optimizing the design of stream monitoring network.

Journal ArticleDOI
TL;DR: The study suggested that adjusting the structure of land use and controlling fertilizer use are helpful methods to control the NPS pollution in the Daning River Watershed.

Journal ArticleDOI
TL;DR: This study evaluated the reduction effect of non-point source pollution by applying best management practices (BMPs) to a 1.21 km2 small agricultural watershed using a SWAT (Soil and Water Assessment Tool) model.
Abstract: This study evaluated the reduction effect of non-point source pollution by applying best management practices (BMPs) to a 1.21 km2 small agricultural watershed using a SWAT (Soil and Water Assessment Tool) model. Two meter QuickBird land use data were prepared for the watershed. The SWAT was calibrated and validated using daily streamflow and monthly water quality (total phosphorus (TP), total nitrogen (TN), and suspended solids (SS)) records from 1999 to 2000 and from 2001 to 2002. The average Nash and Sutcliffe model efficiency was 0.63 for the streamflow and the coefficients of determination were 0.88, 0.72, and 0.68 for SS, TN, and TP, respectively. Four BMP scenarios viz. the application of vegetation filter strip and riparian buffer system, the regulation of Universal Soil Loss Equation P factor, and the fertilizing control amount for crops were applied and analyzed.

Journal ArticleDOI
TL;DR: A survey system of radon/methane/nitrate/salinity to find sites of submarine groundwater discharge (SGD) and groundwater nitrate input and has proven effective in revealing areas of SGD and non-point source pollution.

Journal ArticleDOI
TL;DR: In this article, a large-scale monitoring of the key stormwater pollutants found in urban discharges during both wet and dry weather from seven urban catchments in South Eastern Australia is presented.
Abstract: Quantifying the quality of urban storm water is an important prerequisite to the effective management of urban runoff, which is recognized as the major nonpoint source of pollution in urban areas. Although data on urban storm-water quality are widely available, they are often based on relatively limited data sets, usually containing few samples per event and/or few events per catchment. This paper reports on a large scale monitoring of the key storm-water pollutants found in urban discharges during both wet and dry weather from seven urban catchments in South Eastern Australia. The catchments are all separately sewered (with wholly piped systems) with varying sizes and land uses. Using the same monitoring technique, between 16 and 52 pollutographs were captured at each site for total suspended solid (TSS), total phosphorus, and total nitrogen (TN), while event mean concentrations (EMCs) of heavy metals and major ions, as well as species of N and P, were recorded at a subset of sites. It was found that EMCs of TSS were around 50% less than have been typically reported in earlier literature. During wet weather, nutrients were similar to previously reported, as were most metals concentrations. However, zinc concentrations were significantly higher than previously reported. EMCs of TSS were higher during storm flows than in baseflow, while TN concentrations were consistently higher during baseflow. EMCs of all pollutants monitored were poor with simple hydrological parameters (e.g., event rainfall depth); however, event pollution loads correlated very well with the rainfall intensity to a power, summed over the event duration. It was not possible to distinguish an impact of land use on pollutant concentrations. The first-flush effect was found not to be significant at all sites except the smallest catchment with the simplest drainage layout (the roof of a large building). All these findings have significant implication for treatment strategies with the significantly lower than previously observed TSS requiring consideration in future modeling and treatment design.

Journal ArticleDOI
TL;DR: In this paper, the authors applied a hydro-economic model to an aquifer, El Salobral-Los Llanos aquifer (Mancha Oriental, Spain), where nitrate concentrations higher than those allowed by the EU Water Framework Directive and Groundwater Directive are locally found due to the intense fertilizer use in irrigated crops.

Journal ArticleDOI
TL;DR: In this article, non point source (NPS) pollution may degrade water quality and is of concern to water quality managers and environmental risk regulators whose responsibility it is to monitor the status of water bo...
Abstract: Non point source (NPS) pollution may degrade water quality and is of concern to water quality managers and environmental risk regulators whose responsibility it is to monitor the status of water bo...

Journal ArticleDOI
TL;DR: Results indicated that tea can not be replaced by other crops because comparatively tea resulted in a higher sediment yield, and conversion of cropland into forestland program (CCFP) was found to be the best scenario as the sediment yield export is less than 5 tons/ha and nutrient loss is within the permissible limit.
Abstract: Non-point source water pollution generated by agricultural production is considered a major environmental issue in the Three Gorges Reservoir Area (TGRA) of China. The Annualised Agricultural Non-Point Source Pollution (AnnAGNPS) model was selected to assess the impact of the application of various management treats, including seven crops, five fertilizer levels and three-group management practice scenarios, on water quality from Heigou River Watershed in TGRA. The scenario subsets include conservation tillage practice (CTP), conservation reserve program (CRP) and conversion of cropland into forestland program (CCFP). Results indicated that tea can not be replaced by other crops because comparatively tea resulted in a higher sediment yield. CTP with no-tillage was more effective to reduce sediment yield, but could increased nutrient loss. CRP reduced sediment yield significantly, but slightly benefited on nutrient loss. CCFP reduced not only sediment yield but also the nutrient loss significantly. The conversion of cropland with a slope greater than 10 degrees into forestland was found to be the best scenario as the sediment yield export is less than 5 tons/ha and nutrient loss is within the permissible limit.

Journal ArticleDOI
TL;DR: In this paper, agricultural non-point source offsets may not be a feasible or particularly cost effective compliance option for regulated point sources in water quality trading in the United States, and they are compared against urban nonpoint source and nutrient assimilation offsets.
Abstract: [1] Many advocates of water quality trading in the United States frequently assume that agricultural nonpoint sources will be the primary trading partner for regulated point sources. Virginia requires regulated point sources to offset new nutrient discharges. Nutrient offsets generated by agricultural nonpoint source reductions are compared against urban nonpoint source and nutrient assimilation offsets. Evidence suggests that agricultural nonpoint source offsets may not be a technically feasible or particularly cost effective compliance option for regulated point sources.

Journal ArticleDOI
TL;DR: In this article, the authors compare and assess two models to calculate diffuse nitrogen and phosphorus emissions in a selected watershed, namely, the GIS-based empirical model and the physically-based AnnAGNPS model, for comparative purposes.
Abstract: The aim of this study was to compare and assess two models to calculate diffuse nitrogen and phosphorus emissions in a selected watershed. The GIS-based empirical model and the physically-based AnnAGNPS model were evaluated for comparative purposes. The methodologies were applied for the Jiulong River watershed, covering 14,700 km 2 , located in southeast China, with intensive agricultural activities. The calculated loadings by AnnAGNPS model was checked by the measured values at the watershed outlet, whereas the calculated nitrogen and phosphorus emission by GIS-based empirical model spatially provided the potential values in terms of sub-watersheds, districts/counties, and land use type. Both models gave similar levels of diffuse total nitrogen emissions, which also fit well with previous estimates made in the Jiulong River watershed. Comparatively, the GIS-based empirical model gave sound results of source apportionment of non-point source pollution (NPS) from the available input data and critical source areas identification of diffuse nitrogen and phosphorus pollution. The AnnAGNPS model predicted reasonable nitrogen loading at the watershed outlet and simulated well for NPS management alternatives under changing land use conditions. The study indicated that the GIS-based empirical model has its advantage in extensive studies as a decisions support tool for preliminary design since it is easily applied to large watersheds with fewer data requirements, while AnnAGNPS has its advantage in detailed emission assessment and scenario development.

Journal ArticleDOI
TL;DR: It is concluded that runoff carrying N and P nutrients from chemical fertilizer inputs in agricultural areas is the major contributor to NPSP in the Taihu lake basin and decrease in excessive use of N andP fertilizers and their synergism with organic manures is recommended that would significantly reduce nutrient pollution in the lake ecosystem.

Journal ArticleDOI
TL;DR: In this article, the authors evaluate the water quality effects of alternative con- servation practice scenarios using the SWAT (Soil and Water Assessment Tool) model in the Little River Experimental watershed, a representative coastal plain watershed located in southern Georgia.
Abstract: The goal of this study was to evaluate the water quality effects of alternative con- servation practice scenarios using the SWAT (Soil and Water Assessment Tool) model in the Little River Experimental watershed, a representative coastal plain watershed located in southern Georgia. We simulated the water quality effect of two suites of upland conservation practices (CPs)—one targeting erosion and the other targeting nutrients. We also simulated the impact of riparian forest buffers. Finally, we evaluated three different management scenar- ios for implementing the upland CPs: using a random approach, using subwatershed stream order as a prioritization criterion, and using subwatershed nonpoint source pollutant load as a prioritization criterion. The study showed that using subwatershed nonpoint source pollut- ant load as a prioritization criterion resulted in the most rapid water quality improvements. This improvement in water quality was nonlinear, while the other implementation schemes yield linear returns. Full implementation of the suite of CPs targeting erosion resulted in the greatest reductions of sediment (54.7%) and total phosphorus (55.9%) loads from upland crop areas. Full implementation of the suite of CPs targeting nutrient reduction resulted in the greatest total nitrogen load reduction (10.3%). Overall, an intact riparian forest buffer offered the most comprehensive reduction of nonpoint source pollutant loads—20.5% for sediment, 19.5% for total phosphorus, and 7.0% for total nitrogen. Simulation results indicate that at the current time, the single greatest contributor to nonpoint source pollutant reduction in the Little River Experimental watershed may be the current level of riparian forest cover.

Journal ArticleDOI
TL;DR: In this paper, the results of a study suggest that establishment of agroforestry and grass buffers help reduce NPSP pollution from pastured watersheds, and that the loss of sediment and total nitrogen were smaller for the buffered treatments.
Abstract: Conservation practices including agroforestry and grass buffers are believed to reduce nonpoint source pollution (NPSP) from pastured watersheds. Agroforestry, a land management practice that intersperses agricultural crops with trees, has recently received increased attention in the temperate zone due to its environmental and economic benefits. However, studies are limited that have examined buffer effects on the quality of water from grazed pastures. Six treatment areas, two with agroforestry buffers, two with grass buffers, and two control treatments were used to test the hypothesis that agroforestry and grass buffers can be used to effectively reduce NPSP from pastured watersheds. Vegetation in grass buffer and pasture areas includes red clover (Trifolium pretense L.) and lespedeza (Kummerowia stipulacea Maxim.) planted into fescue (Festuca arundinacea Schreb.). Eastern cottonwood trees (Populus deltoides Bortr. ex Marsh.) were planted into fescue in agroforestry buffers. Soils at the site are mostly Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalfs). Treatments were instrumented with two-foot H flumes, water samplers, and flow measuring devices in 2001. Composite water samples were analyzed for sediment and total nitrogen after each runoff event to compare treatment differences. Treatments with agroforestry and grass buffers had significantly lower runoff volumes as compared to the control. The loss of sediment and total nitrogen were smaller for the buffered treatments. The results of this study suggest that establishment of agroforestry and grass buffers help reduce NPSP pollution from pastured watersheds. It is anticipated as trees grow and roots occupy more soil volume, the reduction in N in runoff will increase on the agroforestry watershed.

Journal ArticleDOI
TL;DR: In this article, a pollution offset system for trading non-point source water pollution permits is presented, where the permits are defined as allowable nitrate loading to a groundwater aquifer.
Abstract: Water pollution from non-point sources is a global environmental concern. Economists propose tradable permit systems as a solution, but they are difficult to implement due to the nature of non-point sources. We present a pollution offset system for trading non-point source water pollution permits. Conventional pollution offset systems suffer from thin markets and transaction costs. In this paper, we show how to overcome these problems with a centrally managed common-pool market. We define permits as allowable nitrate loading to a groundwater aquifer. This trading system utilizes estimates of potential nitrate leaching from land uses, a set of transport coefficients generated from a simulation of nitrate transport in groundwater, an online trading system, and a linear program to clear the market. We illustrate the concept using a hypothetical case study.

Journal ArticleDOI
Dingjiang Chen1, Jun Lu1, Hailong Wang2, Yena Shen1, Mark O. Kimberley2 
TL;DR: High riverine nutrient retention capacity during summer due to hydrophyte growth and coverage on the river bed is favorable to the avoidance of algal bloom in both river systems and coastal water in southeast China.
Abstract: Background, aim, and scope Riverine retention decreases loads of nitrogen (N) and phosphorus (P) in running water. It is an important process in nutrient cycling in watersheds. However, temporal riverine nutrient retention capacity varies due to changes in hydrological, ecological, and nutrient inputs into the watershed. Quantitative information of seasonal riverine N and P retention is critical for developing strategies to combat diffuse source pollution and eutrophication in riverine and coastal systems. This study examined seasonal variation of riverine total N (TN) and total P (TP) retention in the ChangLe River, an agricultural drainage river in east China.

Journal ArticleDOI
TL;DR: In this article, a module to simulate bacteria fate and transport in watersheds was first tested in SWAT 2000 and fully integrated into the SWAT2005 code, which has been used to model bacteria in the U.S. and France.
Abstract: A module to simulate bacteria fate and transport in watersheds was first tested in SWAT 2000 and fully integrated into the SWAT2005 code. Since then, few investigators have utilized SWAT to model bacteria fate and transport in spite of bacteria being a major cause of streams impairment in the U.S. In this article, bacteria equations are briefly presented. Modeling applications, which range from 16 to 3,870 km2, from Missouri, Kansas, and Georgia in the U.S. and from Brittany in France, are reviewed, highlighting the modeling successes and the challenges. In all cases, land use included agricultural and forested land with a mix of point and nonpoint sources. Nonpoint sources included indirect (manure deposited on land) and direct contributions from cattle or wildlife to the streams. In some cases, urban and residential contributions were included. Strategies to represent the different sources, calibration methods, and goodness of fit were compared. Changes to the model's code that were necessary to handle contributions from urban areas were reviewed. Overall, SWAT reasonably simulated the range and frequencies of bacteria concentrations. In all cases, direct bacteria inputs into streams appeared to have a major impact on the model results. This review also indicates that the model processes that simulate the release and transport of bacteria in surface runoff may need to be revisited. This improvement could enable SWAT to be more reliable for predicting bacteria concentrations and evaluating the impact of different management scenarios on bacteria contributions to surface water resources.

Journal ArticleDOI
TL;DR: The AnnAGNPS model, a large-scale watershed model designed to predict sediment and nutrient loads, was used to evaluate non-point source pollution in a typical agricultural watershed and found a poor correlation was observed when comparing the model's predicted nitrogen, phosphorus, and sediment with the observed counterparts.

Journal ArticleDOI
TL;DR: In this article, a comprehensive modeling approach has been developed for use in formulating a watershed management plan to improve the water quality of Cedar Creek reservoir, one of five large water supply reservoirs in north central Texas operated by Tarrant Regional Water District.
Abstract: A comprehensive modeling approach has been developed for use in formulating a watershed management plan to improve the water quality of Cedar Creek reservoir, one of five large water supply reservoirs in north central Texas operated by Tarrant Regional Water District. Eutrophication, or specifically the increase in concentrations of chlorophyll-a (chl'a') over the last 18 years, is a major concern for the water managers. To develop a watershed management plan, the watershed model SWAT was linked with the lake eutrophication model WASP. Several intensive field campaigns and surveys were conducted to collect extensive water quality and land management data for model setup and calibration. In addition to the streamflow, the SWAT model was well calibrated for sediment (including channel erosion) and nutrients. Further, a simple modification to the SWAT in-stream routine allowed simulation of the nutrient load due to channel erosion. The in-stream water quality parameters for SWAT were based on an independent QUAL-2E model calibration. The calibrated SWAT model showed that more than 85% of the total N and total P loading to the lake are from watershed nonpoint sources. Although cropland occupies only 6% of the watershed area, it contributed more than 43% of the sediment, 23% of total N, and 42% of total P loading from the watershed. The channel erosion contributed about 35% of the total sediment load. The watershed model identified subbasins that contribute considerable amounts of sediment and nutrients. Based on these loads, the calibrated WASP model showed that the watershed nonpoint-source nutrient load (total N and total P) should be reduced by at least 35% to see a significant reduction in chl'a' concentrations when compared to the WASP calibration levels.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the land use-soil interactive effects on water and sediment yields for the 117,845-ha drainage area upstream of the U.S. Geological Survey flow gauging station 08101000 in the Cowhouse Creek watershed located in north central Texas.