Showing papers on "Nonpoint source pollution published in 1996"

Phosphorus Loads to Surface Waters: A Simple Model to Account for Spatial Pattern of Land Use

Abstract: Modeling nonpoint-source phosphorus (P) loading from land to surface wa- ters can be both complex and data intensive. Our goal was to develop a simple model that would account for spatial pattern in topography and land use using geographic information system (GIS) databases. We estimated areas of the watershed that strongly contributed to P loading by approximating overland flow, and modeled annual P loading by fitting three parameters to data obtained by stream monitoring. We calibrated the model using P loading data from two years of contrasting annual precipitation for Lake Mendota, a Wisconsin eutrophic lake in a watershed dominated by agriculture and urban lands. Land-use scenarios were developed to estimate annual P loading from pre-settlement and future land uses. As much as half of the Lake Mendota watershed did not contribute significantly to annual P loading. The greatest contribution to loading came from a heterogeneous riparian corridor that varied in width from 0.1 km to :6 km depending on topography and runoff conditions. We estimate that loading from pre-settlement land use was one-sixth of the loading from present land use. A future scenario, representing an 80% increase in existing urban land (from 9 to 16% of total watershed area, which would be reached in 30 yr with current land- use trends), showed only modest increases in annual P loading but possible significant effects on water quality. If the watershed were to become entirely urbanized, P loading to the lake would double and potential effects on water quality would be severe. Changes in P loading were strongest with conversions of undisturbed vegetated lands, especially ri- parian areas, to either urban or agricultural uses. Variability in total annual rainfall leads to variability in the riparian area that affects P loading, with implications for policies intended to control nonpoint nutrient inputs.

An examination of short-term variations in water quality at a karst spring in Kentucky

Abstract: Water quality at many karst springs undergoes very high amplitude but relatively brief degradation following influxes of runoff. Accurately recording transient variations requires more rigorous sampling strategies than traditional methods. A pilot study to determine the usefulness of high-frequency, flow-dependent sampling strategies, combined with coincidental quantitative dye tracer tests, was implemented in the Big Spring Ground-Water Basin in Mammoth Cave National Park, Kentucky. Data recorded following two separate runoff events showed that the concentrations of two nonpoint source pollutants, fecal coliform bacteria and suspended sediment, greatly exceeded prerunoff event values for very short periods of time. A phreatic conduit segment, calculated at 17 million liters in volume, instantaneously propagated head changes, caused by direct runoff entering the aquifer, from the ground-water inputs to Big Spring. A significant delay between the initial increases in discharge and the arrival of direct runoff, as indicated by a steady decrease in specific conductance, represented the time required to displace this volume of phreatic water. The delay showed that sampling a karst spring only during peak discharge would be an unreliable sampling method. Runoff from two different subcatchments was tagged with tracer dye and the timing of the passage of the resultant dye clouds throughmore » Big Spring were compared to water quality variations. Distinct lag times between the arrival of direct runoff at Big Spring and the bacteria and suspended sediment waveforms were shown through the concurrent quantitative tracer tests to be related to the areal distribution of land-cover type within the basin.« less

Answers-2000: runoff and sediment transport model

Abstract: A non-point source pollution management model, ANSWERS-2000, was developed to simulate long-term average annual runoff and sediment yield from agricultural watersheds. The model is based on the event-based ANSWERS model and is intended for use without calibration. The physically based Green-Ampt infiltration equation was incorporated into ANSWERS-2000 to improve estimates of infiltration. An evapotran­ spiration submodel was added to permit long-term, continuous simulation. The model was validated without calibration using data from the field-sized P2 and P4 watersheds in Watkinsville, Ga. Additional validation with limited calibration was done on the Owl Run watershed in Virginia. Model predictions of cumulative sediment yield were within 12% and 68% of observed values. Predicted cumulative runoff volumes ranged from 3% to 35% of observed values. Predictions of sediment yield and runoff volume for individual storms were less accurate, but generally within 200% of observed values. In a practical application, the use of the model in agricultural non-point-source pollution control planning was demonstrated.

Second-Best Tax Policies to Reduce Nonpoint Source Pollution

Abstract: Control of nonpoint source pollution often requires regulation of inputs, but first-best solutions are unattainable. Because inputs are monitored by different agencies and regulatory coordination can be costly, it may be more practical to regulate single inputs. A cost-effectiveness approach to determining the best single-input tax policy is developed and applied to the question of reducing nitrate leaching from lettuce production in California. Water is the best single input to regulate, and efficiency losses from this second-best approach appear not to be great. Conditions for the welfare ranking of policies to be invariant to heterogeneity in production or leaching are identified.

Dominance of point source in heavy metal distributions in sediments of a major Sydney estuary (Australia)

Abstract: Size-normalized (<63 μm) distributions of Cu, Zn, and Pb in the surficial sediments of one of Sydneys' four major estuaries – the Georges River/Botany Bay estuary – are not facies or depositionally controlled, but rather their distribution is dominated by source. Point sources (waste dumps, sewage overflows, and discharge from a polluted river) are responsible for elevating sediment heavy-metal concentrations up to 50 times above background. Nonpoint sources contribute in raising baseline levels to four times background and comprise mainly stormwater and also marinas, moorings, and wharfs/jetties. Heavy metals disgorged from a point source (Cooks River) strongly impact the sediments in the lower estuary, which has implications for the construction of a new runway for Sydney airport.

Applications of GIS to the Modeling of NonPoint Source Pollutants in the Vadose Zone: A Conference Overview

Abstract: Because of their ubiquitous nature and potential chronic health effects, nonpoint source (NPS) pollutants have become a focal point of attention by the general public, particularly regarding pollution of surface and subsurface drinking water sources. The NPS pollutants pose a technical problem because of the areal extent of their contamination that increases the complexity and sheer volume of data far beyond that of point-source pollutants. The spatial nature of the NPS pollution problem necessitates the use of a geographic information system (GIS) to manipulate, retrieve, and display the large volumes of spatial data. This overview provides a brief introduction and review of the modeling of NPS pollutants with GIS and a brief discussion of some of the papers presented at the ASA-CSSA-SSSA 1995 Bouyoucos Conference entitled Applications of GIS to the Modeling of Nonpoint Source Pollutants in the Vadose Zone.

Characterization of metals and solids in urban highway winter snow and spring rainfall-runoff

Abstract: Urban highways are a nonpoint source of metal elements and solids. These constituents are generated from traffic activities, pavement degradation, roadway maintenance, and atmospheric deposition. Pavement degradation and abrasion generates solids ranging in size from submicron particles to gravel-size aggregates. These constituents accumulate on the highway until they are transported from the pavement by traffic-induced turbulence or precipitation-runoff processes. Total metal elements and solids concentration are higher in snow washoff from urban highways than rainfall runoff. One reason is the snow washoff volume is less than the volume generated during a rainfall-runoff event. Another reason is that the residence time of a highway snowbank can range from hours to months depending on weather conditions. In addition, porous snow banks act as repositories that trap metals and solids. Metal elements and solids in urban highway winter snow and spring runoff at one highway site located along I-75 in Cincinnati, Ohio, are described and compared. Both snow and rainfall-runoff samples were fractionated into particulate-bound and dissolved metals. Solids characterization included dissolved, inorganic, and organic fractions. Results from snow samples taken at daily intervals from late January through mid-February 1995 indicate a significant increase in metal elements and solids accumulation for several days after two snow events. Results from runoff events in April 1995 indicate that the particulate-bound metal element washoff response was a function of rainfall intensity. In contrast, the dissolved response exhibited a dependence on the solubility of the metal element. Metal elements in rainfall-runoff were predominately dissolved as compared with more particulate-bound metals in snowfall.

Charaterization of nonpoint sources and loadings to the Corpus Christi Bay National Estuary Program study area. Final report

Abstract: The report identified waterborne nonpoint sources of pollution (NPSP) contributing to pollutant loadings of receiving waters within the Corpus Christi Bay National Estuary Program (CCBNEP) study area. Literature and existing data was reviewed with respect to eight categories of land use and several pollutant parameters. Land use categories include: (1) industrial/commercial; (2) transportation; (3) urban; (4) residential; (5) agricultural cropland (dryland and irrigated); (6) rangeland; (7) undeveloped/open; and (8) marinas. The first phase (Year 1) portion of the assessment of nonpoint source pollutant loadings focussed on the derivation of Even Mean Concentrations (EMCs) of various pollutants associated with each of the above eight land use categories. It is envisaged that a Year 2 CCBNEP project will model the loadings of these pollutants based on variable conditions (e.g., wet/dry year, large/small storm) for watersheds and subwatersheds within the study area. The report includes a comprehensive geographic analysis of the contribution of NPS pollutants to the CCBNEP study area and an analysis of probable causes.

Modeling prevention alternatives for nonpoint source pollution at a Wellfield in Florida

Abstract: Agricultural and urban activities in the West Wellfield Interim Protection Area (WWIPA), located in West Dade County in South Florida, have the potential to impact both the environmentally sensitive Everglades and the Biscayne Aquifer. The Hydrological Simulation Program-FORTRAN (HSPF) is used to simulate surface runoff, ground water recharge, and transport of sediments, nutrients, and pesticides in the WWIPA, as a basis to quantify impacts and evaluate alternatives. Presented are four model test runs that consider current conditions, the effect of future urbanization of the agricultural land, as well as two preventive actions to minimize pollution levels. Preventive actions include application of minimum required rates of fertilizers and replacement of fertilizers by sewage sludge. Model results show that under current practices, sediments, nutrients, and pesticides are present in surface runoff and nutrients enter the ground water, and that both urbanization and preventive actions result in pollutant reductions.

Non point source pollution

Abstract: Non Point Source (NPS) pollution is a major contributor to the degradation of surface water quality. NPS pollution is caused by water movement over and through the surface of the land. The runoff picks up and transports natural and man-made pollutants. The pollutants are transported into rivers, streams, lakes, wetlands, coastal waters, and ground water. Federal and state governments have targeted the identification and control of non point source runoff as major pollution minimization goals. Location of NPS pollution runoff, types of areas drained, and drainage channels are data vital to leaders in agricultural, forestry, and urban planning industries. State and federal agencies can use these data for planning purposes and for prioritizing allocation of resources. The objective of the present study is to identify areas of prime NPS pollution concern using remotely sensed imagery and GIS modeling techniques. A model was designed to identify, quantify and prioritize areas of NPS contribution potential within a water quality basin area.

Poultry Litter-treated Length Effects on Quality of Runoff from Fescue Plots

Abstract: Using experimental data and/or mathematical simulation models to identify practices that reduce pollution from manure-treated areas is sometimes perceived as limited by the unknown validity of extrapolating plot-scale data to larger areas and by uncertainties in modeling transport of various pollutants. The objectives of this study were to assess the effect of length of manure treatment on runoff concentrations of poultry litter constituents and to define the modes of transport (particulate versus soluble) for nitrogen (N), phosphorus (P), carbon (C), and solids. Poultry litter was applied to three 1.5- ¥ 18.3-m fescue (Festuca arundinacea Schreb.) plots with runoff collection gutters installed at 3.0-m intervals along the lengths of the plots. Runoff was generated from simulated rainfall (50 mm/h for 1 h of runoff), and samples were analyzed for total Kjeldahl N (TKN), organic N (Org-N), ammonia N (NH3-N), nitrate N (NO3-N), total P (TP), total organic C (TOC), and total suspended solids (TSS). Soluble fractions of TKN, Org-N, NH3-N, TP, and TOC were also determined. Manure-treated length had no effect on runoff concentration of any parameter, indicating that a manure-treated length of only 3.0 m would have been sufficient to simulate runoff quality associated with longer manure length treatments. Proportions of TKN, Org-N, NH3-N, and TP transported in soluble form were high (= 74%), and over half of the TOC in the runoff was in soluble form. These results indicate that for conditions similar to those of this study, extrapolation with respect to runoff concentrations might be possible with little adaptation of the data and might simplify the design of management practices that key on edge-of-field runoff concentrations. The results with regard to modes of transport can help to better model losses of N, P, and COD and suggest that losses of these parameters will be most effectively controlled through practices that focus on reducing soluble losses rather than simply reducing erosion.

A GIS-based index for relating landscape characteristics to potential nitrogen leaching to wetlands

Abstract: We developed a spatially-explicit, quantitative Nitrogen Leaching Index to assess the potential for non-point source subsurface nitrogen pollution to wetlands. The index was based on the leaching potential of the watershed soils, the amount of nitrogen available for leaching, and the spatial position of nitrogen sources in the watershed. A raster or cell-based geographic information system (GIS) was used to estimate the necessary data inputs for calculating the index, such as soil hydrologic group, land use/soil type combination, groundwater residence time, and location of septic systems. The Total and Average Watershed Nitrogen Leaching Index (TWNLI and AWNLI) were calculated by summing and averaging, respectively, individual cell contributions over a watershed. Analysis of nine wetland watersheds in central New York state, USA, with mixed forest and agricultural land uses illustrated the use of the index for identifying and ranking wetlands with potential nitrogen pollution. Results showed that the spatial characteristics of a watershed potentially can effect subsurface nitrogen delivery to groundwater-dominated wetlands. The use of an index based on watershed soils, topography, and land use may be useful for assessing potential nitrogen pollution to wetlands at a regional scale.

Contracting for Non-Point-Source Pollution Abatement

Abstract: This study presents an incentive scheme to control agricultural nonpoint-source pollution. The analysis is based on a principal-agent framework with two parties: farmers and a regulating authority. Our incentive scheme proposes collective penalties as a way to control pollution. Unlike previous analyses of incentive schemes to control agricultural pollution, we suggest nonindividual contracts between farmers and a regulating authority, where farmers can trade pollution abatement efforts. Findings show that the information requirement of a regulatory agency can be substantially reduced if contracts can be made nonindividual.

Vegetative Filter Strip Design for Grassed Areas Treated with Animal Manures

Abstract: Vegetative filter strips (VFS) are a low-cost management option that have been demonstrated to be effective in reducing runoff transport of fertilizer constituents applied to grassed areas (pasture or meadow). Runoff quality studies involving fertilizers applied to grassed areas suggest that VFS can be designed by assuming that (1) only infiltration is responsible for pollutant removal, (2) the first post-application runoff event is most important from a water quality perspective (enabling a design event approach), and (3) no pollutant build-up that degrades VFS performance will occur. The purpose of this study was to develop a VFS design algorithm for grassed areas that uses available information on the water quality dynamics of these systems to simplify the design process to the greatest degree practical. The design algorithm consists of the SCS (1972) Curve Number method for runoff estimation and the Overcash et al. (1981) equation for predicting concentrations of pollutants exiting a VFS as a function of VFS and runoff parameters. The procedure can be used to determine the VFS length required to meet either an allowable pollutant runoff concentration or allowable pollutant mass transport. As an alternative, the process can be used to determine VFS length required to achieve given relative reductions in incoming pollutant runoff concentrations and mass transport. This algorithm can be used quickly and with minimal data to determine the VFS length requirement necessary to provide any desired degree of effectiveness given inputs such as incoming pollutant runoff concentration, background pollutant runoff concentration, soil hydrologic properties, and design storm parameters. Charts are presented that eliminate the need for computations in selected cases.

Increasing regulators' confidence in point-nonpoint pollutant trading schemes

Abstract: One of the principal stumbling blocks to regulatory agencies' adopting pollutant trading schemes is the complex of uncertainties surrounding any change in institutions. This is especially true if nonpoint pollution sources are to be involved along with point sources. Regulators are understandably reluctant to switch from tried-and-true point source permit systems, even if trading schemes can be shown (on paper, at least) to result in lower public expenditures. We propose a set of practical criteria for point-nonpoint pollutant trading systems that promise to increase regulators' confidence that the new system will be equally effective in controlling pollution and at the same time more likely to capture efficiencies in pollution reduction practices.

Risk Analysis of Total Maximum Daily Loads in an Uncertain Environment Using EUTROMOD

Abstract: A two-phased Monte Carlo procedure is presented for estimating the probability distribution of annual phosphorus load to a lake and the response of the lake to the load. A watershed-level nutrient loading and lake response model, EUTROMOD, and a geographic information system (GIS) were used. The uncertainty in loading and lake response due to natural variability and parameter uncertainty were propagated separately throughout the analysis. The methodology was applied to Wister Lake in Oklahoma with the lake and its trophic state as the endpoint for total maximum daily load (TMDL) analysis. The watershed contributing to Wister Lake covers approximately 260,000 ha and contains a variety of point and nonpoint sources of pollution contributing to the degradation of the lake. Model results compared well with measured water quality data. EUTROMOD simulations indicated that the lake is eutrophic under current land use and management conditions. Nonpoint source (NPS) pollution was estimated to contribute ...

In-sewer treatment of domestic wastewater

Abstract: Urban sewerage systems, which are normally used for the transport of wastewater from its origin to a wastewater treatment plant (WWTP), could be used as a treatment facility because (i) they contain heterotrophic bacteria capable of oxidising organic matter both suspended within the body of the flowing wastewater and attached to the surface of the wetted perimeter, and (ii) they provide retention times which are often comparable to those in a conventional activated sludge aeration tank and which, in some cases, may be equal to the hydraulic retention time in a WWTP. Using sewers as a treatment facility could be an economical method of alleviating the load on an existing WWTP or reducing the size of the proposed WWTP. The current study was undertaken to investigate the feasibility of using urban sewerage systems as suspended growth biological reactors for the treatment of domestic wastewater. The flow in a linear gravity sewer was simulated using a batch reactor fed with raw domestic wastewater. A comparison of simulated aerobic and anaerobic gravity transport indicated that aerobic treatment would be the most favoured method of in-sewer biological treatment. The soluble COD (SCOD) removal efficiencies over a retention period of 8 hours averaged 36 and 6% under aerobic and anaerobic conditions, respectively, at an average temperature of 22°C. The corresponding total COD removal averaged 8 and 11%, respectively. When the effluent samples, taken from the batch reactors after a retention period of 6 hours, were settled in a bench-scale settling column for one hour, the average suspended solids removal under aerobic conditions was 29% greater than those under anaerobic conditions.

Integrating Economic and Physical Models for Analyzing Water Quality Impacts of Agricultural Policies in the High Plains

Abstract: Agency estimated in 1992 that 52.1 percent of all community water systems contained nitrates and 10.4 percent contained pesticides. A study by the Water Quality Task Force of the Great Plains Agricultural Council concluded that agriculture was the largest contributor of nonpoint source pollution in the Great Plains and throughout the nation. Increased public awareness of these issues continues to put significant pressure on policy makers to consider water quality impacts in agricultural legislation. The impact of government commodity programs on agricultural production has been well documented (e.g., Houck and Ryan; Houck et al.; Lidman and Bawden; Chavas, Pope, and Kao; Johnson, Wolcott, and Aradhyula). For example, Houck and Ryan found that more than 95 percent of the variation in U.S. corn acreage during 1948 to 1970 could be attributed to selected policy variables. The resulting changes in agricultural production may in turn affect water quality. Several studies have discussed possible conflicts in the objectives of agricultural and environmental policies (Just and Antle; Johnson, Wolcott, and Aradhyula; Miranowski, Hrubovcak, and Sutton). Just and Antle found that existing agricultural policies can have either positive or negative effects on nonpoint source pollution; however, they did not provide any measure of the aggregate effect because no empirical investigation was conducted. Johnson, Wolcott, and Aradhyula examined the impact of commodity programs on output supply and input demand in the U.S. agricultural sector and illustrated possible tradeoffs between agricultural and environmental policies. Miranowski, Hrubovcak, and Sutton used a general equilibrium model of the U.S. agricultural sector to examine the impact of the Acreage Reduction Programs (ARP) and the Conservation Reserve Program (CRP) on chemical use and soil erosion. The results

Economic analysis of best management practices in the Gum Creek Watershed water quality program

Abstract: Crop growth and agricultural nonpoint pollution levels were simulated under stochastic weather and market observations to predict farmers9 expected net returns and the environmental effects of implementing best management practices (BMPs) under risky and uncertain conditions. Stochastic dominance analysis reveals economically preferred BMPs, the trade-offs relative to the production and market uncertainties, and the opportunity costs of altering current practices to meet prospective regulatory limits for nitrogen runoff and leaching. Our simulations provide evidence that the control of nonpoint source pollution in this area through crop production and water management practices alone appears to be expensive and very limited. A federal cost-share program could provide incentives to farmers for voluntary adoption of economically efficient and environmentally acceptable BMPs. Simulation of expected returns may also allow the identification of those producers who could most efficiently reduce N leaching/runoff and woidd be superior to an alternative scenario of regulating/penalizing all producers in the watershed.