Showing papers on "Nonpoint source pollution published in 2012"
TL;DR: The main causes for NPS pollution were excessive inputs of nitrogen fertilizer and pesticides, which were partly the result of the inadequate agricultural extension services and the rapid expansion of intensive livestock production with little of waste management.
Abstract: Non-point source (NPS) pollution has been increasingly serious in China since the 1990s. The increases of agricultural NPS pollution in China is evaluated for the period 2000-2008 by surveying the literature on water and soil pollution from fertilizers and pesticides, and assessing the surplus nitrogen balance within provinces. The main causes for NPS pollution were excessive inputs of nitrogen fertilizer and pesticides, which were partly the result of the inadequate agricultural extension services and the rapid expansion of intensive livestock production with little of waste management. The annual application of synthetic nitrogen fertilizers and pesticides in China increased by 50.7 and 119.7%, respectively, during 1991-2008. The mitigation measures to reduce NPS pollution include: correct distortion in fertilizer prices; improve incentives for the recycling of organic manure; provide farmers with better information on the sound use of agro-chemicals; and tighten the regulations and national standards on organic waste disposal and pesticides use.
408 citations
TL;DR: In this paper, the authors provide an overview of the current NPS pollution modelling technology in China and compared several methods used for estimation of the NPS load in China. But they found that most of these methods are derived directly from models developed by several developed countries, especially the USA, and they may not be suitable to the actual situation of China.
205 citations
TL;DR: A wholesale implementation of the "polluter pays" approach to agriculture is likely infeasible, but elements of the polluter-pays approach could be incorporated into agricultural water quality policy.
Abstract: Agricultural nonpoint source water pollution has long been recognized as an important contributor to U.S. water quality problems and the subject of an array of local, state, and federal initiatives to reduce the problem. A "pay-the-polluter" approach to getting farmers to adopt best management practices has not succeeded in improving water quality in many impaired watersheds. With the prospects of reduced funding for the types of financial and technical assistance programs that have been the mainstay of agricultural water quality policy, alternative approaches need to be considered. Some changes to the way current conservation programs are implemented could increase their efficiency, but there are limits to how effective a purely voluntary approach can be. An alternative paradigm is the "polluter pays" approach, which has been successfully employed to reduce point source pollution. A wholesale implementation of the polluter-pays approach to agriculture is likely infeasible, but elements of the polluter-pays approach could be incorporated into agricultural water quality policy.
158 citations
TL;DR: In this paper, the impact of climate change on hydrological behavior considering future land-use types and rural residential area and their propagation to NPS pollution loads was assessed and developed.
139 citations
TL;DR: In this paper, the authors evaluated seven constructed surface flow-through wetlands having contrasting design and water management for their effects on the fate of chemical (salts, nutrients, and dissolved organic carbon), physical (suspended solids), and biological contaminants.
139 citations
TL;DR: The proportion of agricultural land use in the entire watershed was best in explaining lake water quality, both relative to estimated nutrient surplus at agricultural field level and near-lake land use, which somewhat contrasts typical strategies of management policies that mainly target agricultural nutrient applications and implementation of near-water buffer zones.
Abstract: Mitigating nutrient losses from anthropogenic nonpoint sources is today of particular importance for improving the water quality of numerous freshwater lakes worldwide. Several empirical relationships between land use and in-lake water quality variables have been developed, but they are often weak, which can in part be attributed to lack of detailed information about land use activities or point sources. We examined a comprehensive data set comprising land use data, point-source information, and in-lake water quality for 414 Danish lakes. By excluding point-source-influenced lakes (n = 210), the strength in relationship (R2) between in-lake total nitrogen (TN) and total phosphorus (TP) concentrations and the proportion of agricultural land use in the watershed increased markedly, from 10–12% to 39–42% for deep lakes and from 10–12% to 21–23% for shallow lakes, with the highest increase for TN. Relationships between TP and agricultural land use were even stronger for lakes with rivers in their watershed (5...
122 citations
TL;DR: A broad division emerged at about the 100th meridian, with eastern areas typically under higher stress than western areas, reflecting the generally higher housing, road, and agriculture densities and higher levels of atmospheric deposition in the eastern division.
Abstract: Water quality is a continuing national concern, in part because the containment of pollution from nonpoint (diffuse) sources remains a challenge. We examine the spatial distribution of nonpoint-source threats to water quality. On the basis of comprehensive data sets for a series of watershed stressors, the relative risk of water-quality impairment was estimated for the over 15,000 fifth-level watersheds in the contiguous United States. A broad division emerged at about the 100th meridian, with eastern areas typically under higher stress than western areas, reflecting the generally higher housing, road, and agriculture densities and higher levels of atmospheric deposition in the eastern division. Recent trends in some stressors are encouraging, but the prospect of further substantial population growth indicates continued pressure on water quality, suggesting that renewed focus on controlling nonpoint-source pollution will be needed if the goals of the Clean Water Act are to be attained.
95 citations
TL;DR: In this paper, the authors compare two tradable permit markets in their ability to meet a safety first environmental target at least cost when some polluters have stochastic, correlated, and non-measurable emissions.
Abstract: We compare two tradable permit markets in their ability to meet a safety first environmental target at least cost when some polluters have stochastic, correlated, and non-measurable emissions. In both markets, the point source permit defines the allowable level of the observed (deterministic) point source pollution load. The permit for unobservable and stochastic nonpoint source pollution cannot be defined in this way. One market bases the nonpoint permit on expected nonpoint pollution and uses a trading ratio between the two pollution types to manage stochasticity. This model follows existing point-nonpoint markets for water quality trading. The second model defines the nonpoint permit as a multi-attribute good, where the attributes inform the market about the stochasticity of the underlying pollution load. The multi-attribute permit market is demonstrated to out-perform the trading ratio market. This result is an artifact of polluters directly pricing stochasticity in the former market but not in the latter, where stochasticity is only controllable under highly restrictive conditions.
82 citations
TL;DR: In this paper, six PFAAs with different chain lengths were monitored in stormwater runoff from seven storm events (2009-2011) at various outfall locations corresponding to different watershed land uses.
80 citations
TL;DR: The results found that the East River is mainly characterized by sediment deposition in most of the segments and at most times of a year, and can provide decision support for watershed managers about where the best management practices can be implemented effectively and at low cost.
71 citations
TL;DR: Results indicate that dissolved oxygen, crops and irrigated cropland, fertilizer application, seasonally high water table, and soil properties that affect infiltration and denitrification are among the most important factors in predicting elevated nitrate concentrations.
Abstract: Recently recharged water (defined here as <60 years old) is generally the most vulnerable part of a groundwater resource to nonpoint-source nitrate contamination. Understanding at the appropriate scale the interactions of natural and anthropogenic controlling factors that influence nitrate occurrence in recently recharged groundwater is critical to support best management and policy decisions that are often made at the aquifer to subaquifer scale. New logistic regression models were developed using data from the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) program and National Water Information System for 17 principal aquifers of the U.S. to identify important source, transport, and attenuation factors that control nonpoint source nitrate concentrations greater than relative background levels in recently recharged groundwater and were used to predict the probability of detecting elevated nitrate in areas beyond the sampling network. Results indicate that dissolved oxygen, crops and irrigated cropland, fertilizer application, seasonally high water table, and soil properties that affect infiltration and denitrification are among the most important factors in predicting elevated nitrate concentrations. Important differences in controlling factors and spatial predictions were identified in the principal aquifer and national-scale models and support the conclusion that similar spatial scales are needed between informed groundwater management and model development.
TL;DR: The Principal Component Analysis showed that the TP and zinc (Zn) in top soil and copper (Cu) and Cr in subsurface can work as indicators for NPS phosphorus loss, which is promising for water safety in agricultural area.
TL;DR: In this paper, a quantitative model of Puget Sound is presented to help improve our understanding of the annual biogeochem- ical cycles in this system using the unstructured grid Finite- Volume Coastal Ocean Model framework and the Integrated Compartment Model (CE-QUAL-ICM) water quality kinet- ics.
Abstract: Nutrient pollution from rivers, nonpoint source runoff, and nearly 100 wastewater discharges is a potential threat to the ecological health of Puget Sound with evidence of hypoxia in some basins. However, the relative contribu- tions of loads entering Puget Sound from natural and an- thropogenic sources, and the effects of exchange flow from the Pacific Ocean are not well understood. Development of a quantitative model of Puget Sound is thus presented to help improve our understanding of the annual biogeochem- ical cycles in this system using the unstructured grid Finite- Volume Coastal Ocean Model framework and the Integrated Compartment Model (CE-QUAL-ICM) water quality kinet- ics. Results based on 2006 data show that phytoplankton growth and die-off, succession between two species of al- gae, nutrient dynamics, and dissolved oxygen in Puget Sound are strongly tied to seasonal variation of temperature, solar radiation, and the annual exchange and flushing in- duced by upwelled Pacific Ocean waters. Concentrations in the mixed outflow surface layer occupying approximately 5-20 m of the upper water column show strong effects of eutrophication from natural and anthropogenic sources, spring and summer algae blooms, accompanied by depleted nutrients but high dissolved oxygen levels. The bottom layer reflects dissolved oxygen and nutrient concentrations of upwelled Pacific Ocean water modulated by mixing with biologically active surface outflow in the Strait of Juan de Fuca prior to entering Puget Sound over the Admiralty Inlet. The effect of reflux mixing at the Admiralty Inlet sill result- ing in lower nutrient and higher dissolved oxygen levels in bottom waters of Puget Sound than the incoming upwelled Pacific Ocean water is reproduced. By late winter, with the reduction in algal activity, water column constituents of interest, were renewed and the system appeared to reset with cooler temperature, higher nutrient, and higher dissolved oxygen waters from the Pacific Ocean.
TL;DR: Results indicate that by coupling remote sensing data and parameter retrieval techniques to "Dualistic Structure" models, estimations of NPS loads on the catchment scale can be improved by spatial pixel-based modeling.
TL;DR: The distribution pattern of DDTs, hexachlorocyclohexane, and other OCPs in the present study shows heterogenic nature of nonpoint source of pollution.
Abstract: The levels of 17 organochlorine pesticides residues (OCPs) in surface water and sediments from Tamiraparani river basin, South India were investigated to evaluate their potential pollution and risk impacts. A total of 96 surface water and sediment samples at 12 sampling stations were collected along the river in four seasons during 2008-2009. The ΣOCP concentrations in surface water and sediments were in the range of 0.1 to 79.9 ng l(-1) and 0.12 to 3,938.7 ng g(-1) dry weight (dw), respectively. Among the OCPs, the levels of dichlorodiphenyltrichloroethanes (DDTs), aldrin, dieldrin, cis-chlordane, trans-chlordane, and mirex were dominant in the sediments. The dominant OCPs in water samples are heptachlor, o,p'-DDE, dieldrin, o,p'-DDD, and mirex, which show different source of contamination pattern among sampling seasons. The distribution pattern of DDTs, hexachlorocyclohexane, and other OCPs in the present study shows heterogenic nature of nonpoint source of pollution. Notable contamination of water and sediment sample that was observed in upstream (S2) 58 ng l(-1) and downstream (S11) 1,693 ng g(-1) dw explains agricultural and municipal outfalls, whereas frequent damming effect reduces the concentration level in the midstream. The overall spatial-temporal distribution pattern of ΣOCP residues are illustrated by GIS package.
TL;DR: The ADAPT model as mentioned in this paper is a daily time step, field-scale water table management model that was developed as an extension of the GLEAMS model to predict subsurface drainage and nitrate-N losses from an agricultural system.
Abstract: This article presents an overview of the Agricultural Drainage and Pesticide Transport (ADAPT) model and a case study to illustrate the calibration and validation steps for predicting subsurface drainage and nitrate-N losses from an agricultural system. The ADAPT model is a daily time step, field-scale water table management model that was developed as an extension of the GLEAMS model. The GLEAMS algorithms were augmented with algorithms for subsurface drainage, subsurface irrigation, deep seepage, and related water quality processes. Recently, a frost depth algorithm was incorporated to enhance the model’s capability to predict flow during spring and fall months. In addition to the normal GLEAMS output, ADAPT gives estimates of pesticides and nutrients in drainage. The model has four components: hydrology, erosion, nutrient transport, and pesticide transport. Predictions of surface runoff and subsurface drainage by ADAPT are very sensitive to hydrology input parameters, such as NRCS curve number, hydraulic conductivity, depth of the impeding layer, and hydraulic conductivity of the impeding layer. In the erosion component, slope, hydraulic length, and crop management are the most sensitive factors. Nutrients generally follow the trends in surface runoff and subsurface drainage. In addition, nitrogen and phosphorus concentrations in soil horizons are sensitive to nutrient losses. Recently, the ADAPT model was further calibrated and validated in southern Minnesota to evaluate impacts of subsurface drain spacing and depth, rate and timing of nitrogen application, and precipitation changes on water quality. ADAPT is written in FORTRAN, and the source code is available to interested model users. Considering the limited technical support and text editor-based input files, development of a user-friendly interface to create input files would greatly enhance ADAPT’s acceptability by users involved in modeling agricultural systems equipped with subsurface drains.
TL;DR: The results show that soil organic matters (SOM) seem to be the main carrier of PAHs, and it is not feasible to build a simple and universal relationship between enrichment ratio and sediment discharge following the traditional enrichment theory.
TL;DR: In this article, the authors investigated the effect of aquifer heterogeneity, well design variability, and spatio-temporal nitrate source variability on nitrate in domestic and large production wells of a semiarid, irrigated agricultural region.
Abstract: [1] Understanding the long-term effect of nonpoint source (NPS) pollution on groundwater of agricultural regions is an increasing challenge of global importance. A novel groundwater modeling framework is developed to assess and evaluate the dynamic, spatio-temporally distributed linkages between nonpoint sources above a groundwater basin and groundwater discharges to wells, streams, or other compliance discharge surfaces (CDSs) within a groundwater basin. The modeling framework allows for efficient evaluation of NPS pollution scenarios and of their short- and long-term effects on pollutant exceedance probabilities in CDSs. Using the model, we investigate the effect of aquifer heterogeneity, well design variability, and spatio-temporal nitrate source variability on nitrate in domestic and large production wells of a semiarid, irrigated agricultural region. Results show that the timing of nitrate breakthrough in wells is significantly controlled by aquifer recharge and pumping rates in NPS areas and by the effective porosity of the aquifer system. Results further show that mixing within a domestic or large production well is a dominant source of dispersive behavior in pollutant breakthrough. In production wells with shorter screens, macrodispersivity due to aquifer heterogeneity accelerates the earliest breakthrough. Variability in well construction and spatio-temporal variability of nitrate sources most strongly control the temporal dynamics of the nitrate exceedance probability and the variability of nitrate between wells, regardless of the degree of aquifer heterogeneity. Hence, characterization of the heterogeneity of external sources and sinks is critical to understand variability and uncertainty about nonpoint source pollution in groundwater discharge locations across basins.
TL;DR: Overall results, using the b diversity measures UniFrac, coupled with PCoA, showed that bacterial contamination of the low-flowing river was not significantly different between agricultural activities and urban runoff.
TL;DR: This article reviews how this approach differs from traditional conservation efforts, the specific practices of drainage management and the current state of knowledge on the ecology of drainage ditches, and a bottom-up approach is utilized.
Abstract: Large tracts of lowlands have been drained to expand extensive agriculture into areas that were historically categorized as wasteland This expansion in agriculture necessarily coincided with changes in ecosystem structure, biodiversity, and nutrient cycling These changes have impacted not only the landscapes in which they occurred, but also larger water bodies receiving runoff from drained land New approaches must append current efforts toward land conservation and restoration, as the continuing impacts to receiving waters is an issue of major environmental concern One of these approaches is agricultural drainage management This article reviews how this approach differs from traditional conservation efforts, the specific practices of drainage management and the current state of knowledge on the ecology of drainage ditches A bottom-up approach is utilized, examining the effects of stochastic hydrology and anthropogenic disturbance on primary production and diversity of primary producers, with special regard given to how management can affect establishment of macrophytes and how macrophytes in agricultural landscapes alter their environment in ways that can serve to mitigate non-point source pollution and promote biodiversity in receiving waters
TL;DR: Using a typical agricultural county in the Hai River basin of the North China Plan, methodology is developed to estimate potential load and delivered load for crops, animal production, rural living and from atmospheric N input to estimate the relative roles of different rural forms of pollution.
09 Mar 2012
TL;DR: In the United States, 82% of irrigation resources are used for irrigation purposes as discussed by the authors, which is more likely to occur at the regional level than show in national or global statistics, since the unpredictability of climate change on changing sea temperature and levels, annual snowpack, drought and flood events, as well as changes in water quality, and general ecosystem vulnerabilities.
Abstract: Worldwide, irrigation uses about 69% of available freshwater resources (Fry, 2005). In the United States, 82% of freshwater resources are used for irrigation purposes. Major concerns on future planetary freshwater resources are the effects of climate change on changing sea temperature and levels, annual snowpack, drought and flood events, as well as changes in water quality, and general ecosystem vulnerabilities (US Global Change Research Program, 2011). Changes in the extreme climatic events are more likely to occur at the regional level than show in national or global statistics. The unpredictability of climatic events is of key concern to farmers in all countries, since the availability and cost of irrigation water is likely to be compounded by increased regulations and competition. Over the past 50 years, the urban demand for freshwater in the United States has also been increasing (Hutson et al. 2004), while the quality of both surface and groundwater has been decreasing due to pollution from both point and nonpoint sources (Secchi et al. 2007). Nitrogen, phosphorus and many other inorganic and organic pollutants such as pesticides and herbicides are being found at increasing concentrations in groundwater under agricultural areas (Guimera, 1998). As demands on water and the cost of purification increase, the cost of freshwater resources will increase and the availability will likely decrease for agriculture. Population growth in the 20th century increased by a factor of three while water withdrawals increased by a factor of seven during the same time, with little hope of these rates slowing in the near future (Agarwal et al. 2000).
TL;DR: This study evaluates 171 management practice combinations that incorporate nutrient management, vegetated filter strips (VFS) and grazing management for their performances in improving water quality in a pasture-dominated watershed with dynamic land use changes during 1992–2007 by using the Soil and Water Assessment Tool (SWAT).
Abstract: Implementing a suite of best management practices (BMPs) can reduce non-point source (NPS) pollutants from various land use activities. Watershed models are generally used to evaluate the effectiveness of BMP performance in improving water quality as the basis for watershed management recommendations. This study evaluates 171 management practice combinations that incorporate nutrient management, vegetated filter strips (VFS) and grazing management for their performances in improving water quality in a pasture-dominated watershed with dynamic land use changes during 1992–2007 by using the Soil and Water Assessment Tool (SWAT). These selected BMPs were further examined with future climate conditions (2010–2069) downscaled from three general circulation models (GCMs) for understanding how climate change may impact BMP performance. Simulation results indicate that total nitrogen (TN) and total phosphorus (TP) losses increase with increasing litter application rates. Alum-treated litter applications resulted in greater TN losses, and fewer TP losses than the losses from untreated poultry litter applications. For the same litter application rates, sediment and TP losses are greater for summer applications than fall and spring applications, while TN losses are greater for fall applications. Overgrazing management resulted in the greatest sediment and phosphorus losses, and VFS is the most influential management practice in reducing pollutant losses. Simulations also indicate that climate change impacts TSS losses the most, resulting in a larger magnitude of TSS losses. However, the performance of selected BMPs in reducing TN and TP losses was more stable in future climate change conditions than in the BMP performance in the historical climate condition. We recommend that selection of BMPs to reduce TSS losses should be a priority concern when multiple uses of BMPs that benefit nutrient reductions are considered in a watershed. Therefore, the BMP combination of spring litter application, optimum grazing management and filter strip with a VFS ratio of 42 could be a promising alternative for use in mitigating future climate change.
TL;DR: In this paper, the authors evaluated whether nitrogen (N) saturated upland forests can degrade downstream water quality in the Tatara River Basin, northern Kyushu, western Japan.
Abstract: This study evaluated whether nitrogen (N) saturated upland forests can degrade downstream water quality in the Tatara River Basin, northern Kyushu, western Japan. Our hypothesis is that elevated atmospheric N deposition degrades downstream water quality in a watershed containing N-saturated forests because a considerable amount of atmospherically deposited N passes into the streams without being retained. Synoptic stream water samplings were conducted at 23 sites across a wide range of land-use categories in the basin over 1 year. A long-term temporal analysis of downstream water quality over the last 30 years (1977–2007) was conducted and compared with long-term trends in related factors such as urban/agricultural activity, sewage wastewater treatment, atmospheric N deposition, and forest condition. The results showed that atmospherically deposited N to N-saturated forests can be a large enough non-point source of N leaving the watershed to impact downstream water quality. This was highlighted by the reduction in pollutant exports derived from urban/agricultural activities, an increase in atmospheric N deposition, and the maturation of coniferous plantation forests in the past 30 years. These have led to reductions in total phosphorus and organic nitrogen concentrations in downstream water, whereas downstream nitrate (NO3
−) concentrations increased over the last 30 years. The consequent increase in the downstream N:P ratio indicated P limitation. Reducing the NO3
− exports from N-saturated upland forests is suggested as a strategy to improve regional downstream NO3
− pollution, but involves intercontinental-scale action in reducing atmospheric N emissions.
TL;DR: Evaluating the effects of human activities such as land uses and reservoir operation on the hydrological and NPS pollution processes in a highly agricultural area using the Soil and Water Assessment Tool (SWAT) reveals that SWAT can consistently simulate the daily streamflow, and monthly/annual sediment and nutrient loads in the basin.
Abstract: Nonpoint source (NPS) pollution is tightly linked to land use activities that determine the sources and magnitudes of pollutant loadings to stream water. The pollutant loads may also be alleviated within reservoirs because of the physical interception resulting from changed hydrological regimes and other biochemical processes. It is important but challenging to assess the NPS pollution processes with human effects due to the measurement limitations. The objective of this study is to evaluate the effects of human activities such as land uses and reservoir operation on the hydrological and NPS pollution processes in a highly agricultural area—the Iowa River Basin—using the Soil and Water Assessment Tool (SWAT). The evaluation of model performance at multiple sites reveals that SWAT can consistently simulate the daily streamflow, and monthly/annual sediment and nutrient loads (nitrate nitrogen and mineral phosphorus) in the basin. We also used the calibrated model to estimate the trap efficiencies of sediment (∼78%) and nutrients (∼30%) in the Coralville Reservoir within the basin. These non-negligible effects emphasize the significance of incorporating the sediment and nutrient removal mechanisms into watershed system studies. The spatial quantification of the critical NPS pollution loads can help identify hot-spot areas that are likely locations for the best management practices.
TL;DR: In this article, 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 NPS 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.
Abstract: Jialing River, which covers a basin area of 160,000 km2 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.
TL;DR: In this article, a representative small watershed in the central part of the TGR area was selected to monitor the loss of nitrogen (N) and phosphorous (P) continuously along with the runoff from 2007 through 2009 to understand the exact sources and loadings.
Abstract: Non-point-source pollution has become a major threat to the water quality of the Three Gorges Reservoir (TGR); however, nutrient loadings from terrestrial sources are unclear due to a lack of in situ monitoring. A representative small watershed in the central part of the TGR area was selected to monitor the loss of nitrogen (N) and phosphorous (P) continuously along with the runoff from 2007 through 2009 to understand the exact sources and loadings. Results show that the non-point-source nitrogen and phosphorus comes mainly from the storm runoff from residential areas, citrus orchards and sloping croplands, which contributes up to 76% of the loadings in this watershed. Thus, a crucial measure for controlling non-point-source pollution is to intercept storm runoff from the three sources. Paddy fields provide a sink for non-point-source N and P by intercepting the runoff and sediment along with their different forms of nitrogen and phosphorus. The N and P removal efficiency by paddy fields from residential areas is within the range of 56% to 98%. Paddy fields are an important land-use option for reducing the non-point-source loading of N and P in the TGR area.
TL;DR: In this paper, a land score system for prioritizing habitat restoration sites using the cost-benefit analysis framework was developed, with the objective of decreasing nutrient pollution in the Tarawera Watershed in the Bay of Plenty.
TL;DR: Wang et al. as discussed by the authors integrated blind number theory, dynamic factors, and pollution load model, parameter uncertainty and model dynamics could be better understood in the new and comprehensive pollution loa...
Abstract: The presence of nonpoint source (NPS) pollution due to agricultural activities at the Three Gorges Reservoir Area in China has been of concern to the public in recent years. Due to the extent of the polluted area and seasonal dispersion mode, sediments have greatly impacted the water quality in the area. Generation and formation of adsorbed NPS pollution involves great uncertainty, which makes monitoring and controlling pollution very difficult. Rainfall erosivity factors, which are calculated by surface rainfall data from watershed hydrological simulation, and sediment delivery ratios were both selected and determined as the dynamic factors, whereas blind number theory was introduced and used to describe and deal with the factors' uncertainty of the Revised Universal Soil Loss Equation (RUSLE). Through the integration among blind number theory, dynamic factors, and pollution load model, parameter uncertainty and model dynamics could be better understood in the new and comprehensive pollution loa...
TL;DR: In this paper, a case study in the middle part of the Three Gorges Reservoir Region (TGRR) was conducted to evaluate the non-point source (NPS) pollution.
Abstract: Non-point source (NPS) pollution has been increasingly recognized as a major contributor to the declining quality of aquatic environment in recent years. Because of the data shortage, the non-point source loads estimation in the large-scale watershed is always difficult in most developing countries. In this study, small-scale watershed extended method (SWEM) was introduced with a case study in the middle part of Three Gorges Reservoir Region (TGRR). Small-scale watershed extended method is the method which uses physical-based models in some small typical catchments of the targeted large watershed, and then the parameters obtained from those small catchments are extended to the surrounding area until the non-point source pollution loads in the entire watershed or region are obtained. The selected small catchments should have sufficient data. Here, the middle part of the Three Gorges Reservoir Region, about 12,500 km2, was chosen as the targeted region for the case study. In this region, considering the data availability, Xiaojiang River was screened as a typical watershed and was simulated with Soil and Water Assessment Tool model through accurate parameter calibration and validation. And then the parameter group obtained in Xiaojiang River Watershed was extended to the entire study area to quantify the total non-point source pollution loads. After which, the spatio-temporal characteristics of the non-point source pollution in the middle part of the Three Gorges Reservoir Region were analyzed, as well as the pollution from each tributary and different under layer surface conditions. The small-scale watershed extended method provides a practical approach for non-point source pollution loads estimation in the large-scale watershed or region.