Showing papers on "Nonpoint source pollution published in 2002"

Sources of nutrient pollution to coastal waters in the United States: Implications for achieving coastal water quality goals

Abstract: Some 60% of coastal rivers and bays in the U.S. have been moderately to severely degraded by nutrient pollution. Both nitrogen (N) and phosphorus (P) contribute to the problem, although for most coastal systems N additions cause more damage. Globally, human activity has increased the flux of N and P from land to the oceans by 2-fold and 3-fold, respectively. For N, much of this increase has occurred over the past 40 years, with the increase varying by region. Human activity has increased the flux of N in the Mississippi River basin by 4-fold, in the rivers of the northeastern U.S. by 8-fold, and in the rivers draining to the North Sea by more than 10-fold. The sources of nutrients to the coast vary. For some estuaries, sewage treatment plants are the largest single input; for most systems nonpoint sources of nutrients are now of relatively greater importance, both because of improved point source treatment and control (particularly for P) and because of increases in the total magnitude of nonpoint sources (particularly for N) over the past three decades. For P, agricultural activities dominate nonpoint source fluxes. Agriculture is also the major source of N in many systems, including the flux of N down the Mississippi River, which has contributed to the large hypoxic zone in the Gulf of Mexico. For both P and N, agriculture contributes to nonpoint source pollution both through losses at the field scale, as soils erode away and fertilizer is leached to surface and ground waters, and from losses from animal feedlot operations. In the U.S. N from animal wastes that leaks directly to surface waters or is volatilized to the atmosphere as ammonia may be the single largest source of N that moves from agricultural operations into coastal waters. In some regions, including the northeastern U.S., atmospheric deposition of oxidized N from fossil-fuel combustion is the major flux from nonpoint sources. This atmospheric component of the N flux into estuaries has often been underestimated, particularly with respect to deposition onto the terrestrial landscape with subsequent export downstream. Because the relative importance of these nutrient sources varies among regions and sites, so too must appropriate and effective mitigation strategies. The regional nature and variability of nutrient sources require that nutrient management efforts address large geographic areas.

The Economics of Nonpoint Pollution Control

Abstract: A timely literature on the design of economic incentives for nonpoint pollution control has been emerging. We describe the nonpoint pollution control problem, some of the peculiar challenges it poses for policy design, and the policy-related contributions of the theoretical and empirical literature on the economics of nonpoint pollution.

Integration of GIS with USLE in Assessment of Soil Erosion

Abstract: A Geographic Information System (GIS) has been integrated with the USLE (Universal Soil Loss Equation) model in identification of rainfall-based erosion and the transport of nonpoint source pollution loads to the Gediz River, which discharges into the Aegean Sea along the western coast of Turkey. The purpose of the study is to identify the gross erosion, sediment loads, and organic N loads within a small region of the Gediz River basin. Similar studies are available in literature, ranging from those that use a simple model such as USLE to others of a more sophisticated nature. The study presented here reflects the difficulties in applying the methodology when the required data on soil properties, land use and vegetation are deficient in both quantity and quality, as the case is with most developing countries.

Assessment of concentrated flow through riparian buffers

Abstract: Concentrated flow of surface runoff from agricultural fields may limit the capability of riparian buffers to remove pollutants. This study was conducted on four farms in southeastern Nebraska to develop a method for assessing the extent of concentrated flow in riparian buffers and for evaluating the impact that it has on sediment-trapping efficiency. Field methods consisted of mapping field runoff areas and their pathways to and through riparian buffers to streams. Mathematical relationships were developed from a model (VFSMOD) that estimates sediment-trapping efficiency from the ratio of buffer area to field runoff area. Among the farms surveyed, riparian buffers averaged 9 to 35 m wide, and gross buffer area ranged from 1.5 to 7.2 ha, but the effective buffer area that actually contacts runoff water was only 0.2 to 1.3 ha. Patterns of topography and microrelief in fields and riparian zones prevented uniform distribution of field runoff across entire buffer areas. Using the mathematical relationships, it is estimated that riparian buffers at each of the four farms could potentially remove 99%, 67%, 59%, and 41% of sediment from field runoff if the runoff is uniformly distributed over the entire gross buffer area. However, because of non-uniform distribution, it is estimated that only 43%, 15%, 23%, and 34%, respectively, would actually be removed. The results indicate that concentrated flow through riparian buffers can be substantial and may greatly limit filtering effectiveness in this region.

Soil erosion prediction and sediment yield estimation: the Taiwan experience

Abstract: Estimating watershed erosion using geographic information systems coupled with the universal soil loss equation (USLE) or agricultural non-point source pollution model (AGNPS) has become a recent trend. However, errors in over-estimation often occur due to the misapplication of parameters in the equation and/or model. Because of poor slope length calculation definitions for entire watersheds, the slope length factor is the parameter most commonly misused in watershed soil loss estimation. This paper develops a WinGrid system that can be used to calculate the slope length factor from each cell for reasonable watershed soil loss and sediment yield estimation.

Watershed optimization of best management practices using AnnAGNPS and a genetic algorithm

Abstract: [1] An optimization algorithm linked with a nonpoint source (NPS) pollution model can be used to optimize NPS pollution control strategies on a field-by-field basis in a watershed by maximizing NPS pollution reduction and net monetary return. In this paper a methodology is described which integrated a genetic algorithm (GA) (an optimization algorithm) with a continuous simulation, watershed-scale, NPS pollution model, Annualized Agricultural Non-Point Source Pollution model (AnnAGNPS) to optimize the selection of best management practices (BMP) on a field-by-field basis for an entire watershed. To test the methodology, optimization analysis was performed for a U.S. Department of Agriculture experimental watershed in Pennsylvania to identify BMPs that minimized long-term (over a 4-year period) water quality degradation and maximized net farm return on an annual basis. Results indicate that the GA was able to identify BMP schemes that reduced pollutant load by as much as 56% and increased net annual return by 109%.

Point- and Nonpoint-Source Pesticide Contamination in the Zwester Ohm Catchment, Germany

Abstract: Reducing pesticide loads in surface waters implies identifying the pathways responsible for the pollution. The current study documents the pesticide contamination of the river Zwester Ohm, a 4917-ha catchment in Germany with 41% of the land used for crop production. Discharges and concentrations of 19 pesticides were measured continuously at three locations for 15 mo. The load detected at the outlet of the catchment amounted to 9048 g a.i. The losses represent 0.22% of the pesticides applied by the farmers. The contamination showed a seasonal pattern following the pesticide application times. The wastewater treatment plant system (WWTPS) in the catchment (two wastewater treatment plants [WWTP], 14 combined sewer overflows (CSO), four CSO tanks) emits during dry weather periods purified sewage and during storm events sewage mixed with stormwater runoff into the river. The contribution by the WWTPS to the pesticide load was defined as point-source pollution (PSP). The load was dominated by PSP with at least 77% of the total pollution. No significant interdependencies between intrinsic properties of the pesticides, hydrometeorological factors, and the loads occurring in the stream could be found. Therefore, it is not possible to predict PSP for other catchments based on the results from this study. Whereas 65% of the total load entered the river via the WWTP, a portion of 12% was attributed to the CSO. The study points out that the influence of CSO on PSP should be taken into account in future catchment studies in areas with comparable agricultural structure.

Predicting sediment and phosphorus loads in the rock river basin using swat

Abstract: The Rock River is considered degraded from excessive amounts of phosphorus. Individual programs are ongoing to reduce phosphorus from point and nonpoint sources. However, a comprehensive phosphorus management approach may prove more cost effective and beneficial. To be successful, such an approach must take into consideration phosphorus from all sources and seek geographically targeted, cost–effective, and holistic solutions. This study utilized the SWAT (Soil and Water Assessment Tool) model to quantify phosphorus sources throughout the basin and quantify impacts from the application of basin–wide BMPs. Results of this study indicate that, under existing land use and management conditions, an average annual phosphorus load of approximately 764,000 kg enters the Rock River and it tributaries. Point sources account for 41% of this value, and nonpoint sources account for 59%. Model results show that, under existing conditions, approximately 160,000 tons of sediment is delivered to the streams and surface water bodies on an average annual basis. Modeling results indicate that implementation of improved tillage practices (predominantly conservation tillage) can reduce sediment yields by almost 20%.

Sediment and Metals Modeling in Shallow River

Abstract: It is a challenge to apply coupled hydrodynamic, sediment process, and contaminant fate and transport models to the studies of surface water systems. So far, there are few published modeling studies on sediment and metal transport in rivers that simulate storm events on an hourly basis and use comprehensive data sets for model input and model calibration. The United States Environmental Protection Agency (USEPA) in 1997 emphasized the need for credible modeling tools that can be used to quantitatively evaluate the impacts of point sources, nonpoint sources, and internal transport processes in 1D/2D/3D environments. A 1D and time-dependent hydrodynamic, sediment, and toxic model, within the framework of the 3D Environmental Fluid Dynamics Code (EFDC), has been developed and applied to Blackstone River, Mass. The Blackstone River Initiative (USEPA) in 1996, a multiyear and multimillion-dollar project, provided the most comprehensive surveys on water quality, sediment, and heavy metals in the river, and serv...

Agricultural Pollution: Environmental Problems and Practical Solutions

Abstract: This comprehensive text provides a concise overview of environmental problems caused by agriculture, (such as pesticide pollution and increased nitrate levels) and offers practical solutions to them. It is well illustrated and contains a fully-referenced introduction to the main contemporary agricultural pollution issues in the UK. It will help pro

The Great Lakes' integrated atmospheric deposition network.

Abstract: The United States and Canada continue an effective partnership that measures nonpoint source pollution.

Phosphorus indexing for cropland: Overview and basic concepts of the Iowa phosphorus index

Abstract: Excessive phosphorus (P) loss from soils impairs surface water resources. An assessment tool or index has been proposed to identify fields with high potential risk of P delivery. The P index integrates P source and transport factors into a decision making process that may lead to changes in current P management and soil conservation practices. The index recognizes that a single soil P threshold alone is not an appropriate evaluation factor because of the varying conditions across fields. Although most indices being developed in the United States include similar factors, source and transport characteristics are considered in various ways to best address the variable conditions across regions. The Iowa P index reflects conditions that predominate under grain-crop production systems, considers source factors in a multiplicative manner within three main transport mechanisms, and approximates loads of P likely to enter and become available to aquatic ecosystems. An erosional component considers sheet and rill erosion, P enrichment, total soil P, buffers, sediment delivery, distance to a stream, and the long term biotic availability of particulate P in lake ecosystems. A runoff component considers water runoff based on a modification of the runoff curve number (RCN), soil-test P (STP), rate, time, and method of P application. An internal drainage component considers the presence of tiles, water flow to tile lines, subsurface recharge from subsurface flow, and soil-test P. When the erosion risk is high, the index weighs particulate P loss heavily compared with dissolved P loss, and emphasizes long-term processes comparatively more than short-term processes. This P assessment tool helps identify alternative P and soil conservation management options for reducing total P delivery from fields to surface water resources.

Setting priorities for research on pollution reduction functions of agricultural buffers

Abstract: The success of buffer installation initiatives and programs to reduce nonpoint source pollution of streams on agricultural lands will depend the ability of local planners to locate and design buffers for specific circumstances with substantial and predictable results. Current predictive capabilities are inadequate, and major sources of uncertainty remain. An assessment of these uncertainties cautions that there is greater risk of overestimating buffer impact than underestimating it. Priorities for future research are proposed that will lead more quickly to major advances in predictive capabilities. Highest priority is given for work on the surface runoff filtration function, which is almost universally important to the amount of pollution reduction expected from buffer installation and for which there remain major sources of uncertainty for predicting level of impact. Foremost uncertainties surround the extent and consequences of runoff flow concentration and pollutant accumulation. Other buffer functions, including filtration of groundwater nitrate and stabilization of channel erosion sources of sediments, may be important in some regions. However, uncertainty surrounds our ability to identify and quantify the extent of site conditions where buffer installation can substantially reduce stream pollution in these ways. Deficiencies in predictive models reflect gaps in experimental information as well as technology to account for spatial heterogeneity of pollutant sources, pathways, and buffer capabilities across watersheds. Since completion of a comprehensive watershed-scale buffer model is probably far off, immediate needs call for simpler techniques to gage the probable impacts of buffer installation at local scales.

Assessment of runoff and sediment yield using remote sensing, gis, and agnps

Abstract: A model that can predict runoff and soil loss from a watershed is an important tool that can be used for planning and for watershed assessment and management. An application that combined the capabilities of remote sensing, Geographic Information Systems (GIS), and the Agricultural NonPoint Source Pollution (AGNPS) model was used to assess runoff and sediment yield from various sub-watersheds above Cheney Reservoir in Kansas. Remotely sensed Landsat thematic mapper (TM) images were used to obtain land cover and associated AGNPS model input parameters, including the Universal Soil Loss Equation9s (USLE) cropping factors (C-factor), based on estimates of vegetative cover for rangeland and crop residue. Several input parameters of the AGNPS model were extracted from GIS layers using the AGNPS-ARC/INFO interface. C-factors and curve numbers (CNs) of agricultural crops were adjusted on the basis of management practices and hydrologic conditions of the watershed during various runoff events. Surface-water quantity and quality data, including total suspended solids (TSS) for major runoff events, were obtained from United States Geological Survey (USGS) gaging stations in the watershed and were used for evaluation of this AGNPS modeling process. Base-flow separation was done so that measured runoff and TSS levels could be compared directly with the AGNPS model output. Use of remote sensing along with GIS reduced the time to obtain input for the modeling process and added to the confidence in the representation of watershed conditions. The modeling process was effective for small watersheds (up to 145 sq km [56 sq mil) with adequate available rainfall data. However, for larger watersheds with substantial variations of rainfall, this process was less satisfactory.

Predicting the fate of sediment and pollutants in river floodplains.

Abstract: Geological processes such as erosion and sedimentation redistribute toxic pollutants introduced to the landscape by mining, agriculture, weapons development, and other human activities. A significant portion of these contaminants is insoluble, adsorbing to soils and sediments after being released. Geologists have long understood that much of this sediment is stored in river floodplains, which are increasingly recognized as important nonpoint sources of pollution in rivers. However, the fate of contaminated sediment has generally been analyzed using hydrodynamic models of in-channel processes, ignoring particle exchange with the floodplain. Here, we present a stochastic theory of sediment redistribution in alluvial valley floors that tracks particle-bound pollutants and explicitly considers sediment storage within floodplains. We use the theory to model the future redistribution and radioactive decay of 137Cs currently stored on sediment in floodplains at the Los Alamos National Laboratory (LANL) in New Me...

Nitrogen contamination in the Yellow River basin of China.

Abstract: Nitrogen contamination is one of the most serious problems in the Yellow River of China. This study was conducted to analyze monitoring data on nitrogen contamination for the Yellow River basin in the years 1980, 1990, 1997, and 1999. Several significant results have arisen from the study. First, in conjunction with an increase in economic indexes from the Yellow River's upper basin to its lower basin, the nitrogen concentration in the tributaries also showed an increasing trend from the upper to the lower basin, which, in turn, led to an increase in the nitrogen concentration of the mainstream from the upper to the lower reaches. Second, nitrogen in the river water in the mainstream and the tributaries of the Yellow River was attributed mainly to point sources. In spite of the fact that the ratio of point to nonpoint sources decreased from 2.7 in 1990 to 1.8 in 1997 for total inorganic nitrogen in river water at the Tongguan Station in the lower basin, point sources increased more than nonpoint sources. Third, the ammonium nitrogen and total inorganic nitrogen content of the river water increased significantly in the mainstream and the tributaries during the 1980-1999 period, a change caused by an increase in wastewater discharge and nitrogenous fertilizer application in the Yellow River catchment.

Point-nonpoint nutrient trading in the Susquehanna River basin

Abstract: [1] There is considerable interest in the use of pollution trading between point and nonpoint sources to improve the cost-effectiveness of water pollution control but little literature to guide the design of trading systems involving nonpoint sources. Expanding on prior theoretical work, this paper provides empirical evidence about design and performance issues for two types of trading systems that would allow nutrient trading among and between point and nonpoint sources in the Susquehanna River basin in Pennsylvania.

Impact source determination with biomonitoring data in New York State: Concordance with environmental data

Abstract: An Impact Source Determination method, used to identify point and nonpoint sources of impacts to stream water quality on the basis of benthic macroinvertebrates, was examined for concordance with impairment sources inferred from chemical and physical site characteristics, watershed characteris- tics, and biomonitoring results collected from 26 sites in the Hudson River Basin during 1993-94. Most classifications agreed with the resulting interpreta- tions; site locations on Canonical Correspondence Analysis triplots corre- sponded with interpretation of environmental gradients as (1) overall pollution including organic enrichment and contaminants from point and nonpoint sources, (2) nonpoint nutrients from both agricultural and urban sources, and (3) sediment and suspended organic carbon from agricultural runoff. High-level taxonomic resolution was important in identifying the environmental gradients, and may be necessary for impairment source identification.

Influence of a riparian wetland on nitrate and herbicides exported from an agricultural field.

Abstract: Agrochemicals are a major source of nonpoint pollution. Forested corridors along stream channels (riparian zones) are thought to be potential sites for removal of agricultural contaminants from ground and surface waters. First-order riparian wetlands are reputed to be especially effective at groundwater remediation. The study site is a fairly typical (for eastern Maryland) small, first-order stream in an agricultural watershed. Preferential flow supplies most of the stream water within the riparian headwater wetland. This upstream area also contains the highest average stream N and pesticide loads in the entire first-order riparian system. Zones of active groundwater emergence onto the surface display high concentrations of nitrate throughout the soil profile and in the exfiltrating water, whereas inactive areas (where there is no visible upwelling) show rapid attenuation of nitrate with decreasing depths. Atrazine degradation products appear to penetrate more readily through the most active upwelling zones, and there is a correlation between zones of high nitrate and high atrazine metabolite levels. Deethylatrazine/atrazine ratios (DAR) seem to indicate that stream flow is dominated by ground water and that much of the ground water may have reached the stream via preferential flow. Remediative processes appear to be very complex, heterogeneous, and variable in these systems, so additional research is needed before effective formulation and application of riparian zone initiatives and guidelines can be accomplished.

Calibration of Storm Loads in the South Prong Watershed, Florida, Using Basins/hspf

Abstract: The South Prong watershed is a major tributary system of the Sebastian River and adjacent Indian River Lagoon. Continued urbanization of the Sebastian River drainage basin and other watersheds of the Indian River Lagoon is expected to increase runoff and nonpoint source pollutant loads. The St. Johns River Water Management District developed watershed simulation models to estimate potential impacts on the ecological systems of receiving waters and to assist planners in devising strategies to prevent further degradation of water resources. In the South Prong system, a storm water sampling program was carried out to calibrate the water quality components of the watershed model for total suspended solids (TSS), total phosphorous (TP), and total nitrogen (TN). During the period of May to November 1999, water quality and flow data were collected at three locations within the watershed. Two of the sampling stations were located at the downstream end of major watercourses. The third station was located at the watershed outlet. Five storm events were sampled and measured at each station. Sampling was conducted at appropriate intervals to represent the rising limb, peak, and recession limb of each storm event. The simulations were handled by HSPF (Hydrologic Simulation Program-Fortran). Results include calibration of the hydrology and calibration of the individual storm loads. The hydrologic calibration was continuous over the period 1994 through 1999. Simulated storm runoff, storm loads, and event mean concentrations were compared with their corresponding observed values. The hydrologic calibration showed good results. The outcome of the individual storm calibrations was mixed. Overall, however, the simulated storm loads agreed reasonably well with measured loads for a majority of the storms.