This type of pollution is linked to an important problem of information and knowledge because of the impossibility of identifying the agent generating the emissions, the spatial location, and the amount of emission loads at the source. These problems explain the difficulties in the design and implementation of policies to control nonpoint pollution 1,2,3. Most of the current European pollution policies consist of using economic instruments to compensate the private benefits of agents causing pollution damages, or use public funds in financing investments in pollution abatement technologies.
These policies appear to be ineffective in curtailing the large nonpoint pollution loads in river basins around the world.
What might be more useful is the cooperation of stakeholders managing the water resources. The economic argument supporting this collective action approach is that water resources are mostly common-pool resources , thereby requiring cooperation rather than just economic instruments that are harder to implement in the case of public goods 4.
The analysis of water quality is an important issue in Europe given the large degradation of river basins in recent decades. The policy efforts to curb pollution have been considerable but results appear disappointing. However, the European data for the past 15 years on nitrate concentration indicate only a slight reduction in rivers and a large increase in aquifers 5.
Data from the Organisation for Economic Cooperation and Development 6 also found that most major European rivers show no abatement of nitrates, and some have even grown worse. The Nitrates Directive of was based initially on information and voluntary compliance; more recently farmers have been required to keep a nitrogen balance book.
Uncomplying farmers drawn by chance are penalised through their Common Agricultural Policy payments. The Nitrates Directive applies to cultivation over aquifers declared officially polluted. However, the Directive ignores cultivation over whole basins and highly polluting crops that are not receiving subsidies, such as greenhouses.
The Water Framework Directive of relies heavily on economic instruments to achieve the sustainable management of water resources. However, these water-based instruments to abate pollution do not seem to be good enough to curb nitrate pollution since the pollution driver is fertilizer rather than water.
Aquapedia background August 30, Point Source Pollution Point sources release pollutants from discrete conveyances, such as a discharge pipe, and are regulated by federal and state agencies. Nonpoint Source Pollution Nonpoint source pollution is a combination of pollutants from a large area rather than from specific identifiable sources such as discharge pipes. Print-friendly Layperson's Guide to California Wastewater. Referring Pages. Share this page. Related Links. Because trees grow slowly, this is usually not enough time for the multiple benefits of forest stewardship to accrue.
The WFP and similar initiatives around the United States are designed to counteract frequent turnover and substandard management to ensure source water protection. Short-term financial pressures obviously discourage long-term investments in silvicultural techniques to improve the value and condition of the forest, such as stand improvement, low-intensity thinning, or uneven-aged management Davis and Johnson, ; Smith et al.
The USDA Forest Service Stewardship Incentive Program, local conservation easements and current-use tax assessments, and education and outreach are expressly designed to counteract financial pressures and land turnover. In the absence of these types of programs, the gap between forestry expenses and revenues widens. This compels some landowners to cut only high-value trees such as black cherry, northern red oak, yellow birch, and sugar maple simply to maintain ownership of the larger parcel.
In the worst case, when high-value trees are continually removed ''high-grading" , biological diversity, tree health, and vigor are steadily reduced. Resistance and resilience to insects, diseases, and natural disturbances such as severe storms, as well as the ameliorative effect of forests in headwater areas, are gradually diminished.
In addition to economic pressures and land tenure issues, the ecological legacy of exploitative logging during the s clearcutting hemlock for tanbark and subsequent hardwood regeneration for charcoal and fuelwood described in an earlier chapter is a degraded, predominantly even-aged forest.
Exotic insects like gypsy moth can seriously damage oak stands. A woolly adelgid, accidentally introduced from Japan, threatens the few remnant stands of eastern hemlock.
Dutch elm disease and chestnut blight have virtually eliminated their host tree species from northeastern forests. More recently, atmospheric deposition has caused widespread mortality of high-elevation red spruce and balsam fir Lovett et al. In sum, there are substantial economic and ecological challenges that highlight the need for forest conservation and stewardship in the Catskills region.
The Watershed Forestry Program should continue its comprehensive efforts to promote sustainable forest management in the region. A spatially referenced database of forest lands, owners, management objectives, and activities should be developed to track on-the-ground progress and performance of forestry practices. The Geographic Information System GIS should be used to spatially link 1 databases with landowner information, forest resources inventory at the stand level , management objectives, and silvicultural prescriptions and treatments, 2 watershed characteristics e.
Its use would enable watershed managers to evaluate changes positive, negative, or non-detectable in the quantity, quality, and timing of streamflow as influenced by the WFP and other land or resource uses. The WFP is encouraged to merge landowner, management plan, and field assessment data with water quality data to evaluate program performance.
The Watershed Forestry Program should foster the movement toward third-party green certification of forest management Forsyth et al. Resource manager and public land certification in New York, Pennsylvania, Massachusetts, and other New England states can serve as a model for consulting foresters.
It is recommended that New York State consider tax policy changes that would promote sustained management of private forest land including forests on relatively small parcels that are suitable for development.
Because of the benefits of such programs extend beyond the local political boundaries, impacts on town revenues should be evaluated, and mitigation payments to local governments by the State should be made as an integral part of the program.
Urban stormwater is the final type of NPS pollution considered in this chapter. SPPPs specify best management practices that will prevent erosion and sedimentation during construction and any increase in the rate of pollutant loading in stormwater after construction.
These plans must include a quantitative analysis demonstrating that runoff quantity and quality from postconstruction conditions will be less than or equal to that of preconstruction conditions. Whether or not an SPPP or some other type of stormwater plan is developed depends on a number of factors, including the proximity of the project to nearby waterbodies. For detailed information on the multiple types of stormwater plans and the activities that require them, see NYC DEP, b.
An SPPP must include a description of the proposed construction activities. An estimate of pre-and postdevelopment runoff is required, considering both the quantity and quality of stormwater. Pollutants of concern vary, but often include biological oxygen demand, phosphorus, nitrogen, total suspended solids, organic matter, and bacteria. Measures that might be undertaken to reduce runoff rates and pollutant loading from stormwater are then presented. These measures are committed to a Stormwater Management Plan, which describes the specific BMPs that will be used to ensure that the postdevelopment runoff rates will not exceed predevelopment runoff rates for the 2-year, year, and year hour storms.
To prevent pollutant loadings, the Stormwater Management Plan must control the "first flush"—the first half inch of runoff from the 1-year, hour storm event. However, there are no numeric standards requiring a certain amount of pollution to be removed by stormwater BMPs. These contain a complete description of the BMPs that will be used to control erosion during each phase of construction. The methods,. The requirement is stated by the following: "Regulations require that pre- and postconstruction runoff characteristics not be substantially altered.
Unfortunately, there is little basis for confidence that the current generation of urban stormwater BMPs can reduce pollutant loads to levels that approach predevelopment conditions. Table provides a summary of reported nutrient removal rates for stormwater BMPs. Although their removal rates are variable, most BMP groups have median annual removal rates in the 30 percent to 50 percent range for both soluble and total phosphorus Table Dry extended detention ponds and open channels.
Notes: n is a number of performance monitoring studies. The actual number for a given parameter is likely to be slightly less. Sol P is soluble phosphorus, measured as orthophosphate, soluble reactive phosphorus, or biologically available phosphorus. Source: Brown and Schueler Reprinted, with permission, from Center for Watershed Protection, Interestingly, several BMP groups—wetlands, water quality swales, and sand filters—exhibit very wide variation in phosphorus removal, suggesting internal nutrient cycling can be an important factor in determining BMP effectiveness.
Some BMPs, such as sand filters, actually increase soluble phosphorus concentrations via desorption, dissolution, or extraction of phosphorus into the aqueous phase. These removal rates are average annual load reductions, and the removal rates do not account for diminished removal related to poor design or construction, age, or lack of maintenance. It is also important to remember that trapping of phosphorus within a stormwater BMP is only a temporary form of removal; ultimate removal is dependent on the cleanout, removal, and safe disposal of trapped sediments through periodic maintenance.
For stormwater wetlands, continued phosphorus removal may require periodic replacement of wetland media as adsorption sites diminish over time Oberts, The moderate phosphorus removal of stormwater BMPs needs to be balanced against the sharp rise in phosphorus loads produced by new development.
The effect of stormwater BMPs on phosphorus load as a function of impervious cover is shown in Figure At a low density of development 5 percent to 25 percent site impervious cover , the reduction in phosphorus load by stormwater BMPs keeps pace with the increased load produced by impervious cover.
After that point, however, stormwater BMPs can no longer achieve predevelopment phosphorus loads. To date, studies evaluating the performance of stormwater BMPs in removing microbial pathogens have focused on bacteria. The limited research conducted to date indicates that current BMPs cannot meet this standard on a reliable basis. Only 24 BMP performance-monitoring studies have measured the input and output of fecal coliform bacteria from stormwater BMPs during storm events.
These data, collected for fecal coliform, fecal streptococcus, and E. For stormwater ponds, the mean fecal coliform removal efficiency was about 65 percent range was from —5 percent to 99 percent. The mean removal efficiency calculated for sand filters was lower about 50 percent , but these practices had a wider range in reported removal —68 percent to 97 percent.
Grass swales and biofilters were found to have no ability to. The grey band indicates typical "background" phosphorus loads from undeveloped watersheds. The BMP-Lo indicates a 40 percent removal rate. It should be noted that actual curves in individual watersheds may be different. For example, the contribution of new septic systems that accompany development to overall phosphorus loading is not represented by these curves. Source: Schueler Pet wastes and in situ multiplication of bacteria were cited as the primary reason for the poor performance.
No performance monitoring data are available to assess the capability of infiltration or wetland BMPs to remove coliforms. The limited data on fecal streptococcus and E.
Based on the mediocre effectiveness of BMP removal mechanisms for fecal coliforms, and the survivability of cysts and oocysts in sediments, the committee expects that it will be difficult to reliably remove the protozoan pathogens from urban runoff using traditional stormwater BMPs.
If no net increase in bacterial concentrations in postdevelopment runoff is desired, it may be necessary to install stormwater BMPs at both current development projects as well as at older, neighboring development sites.
As written, the SPPPs call for a level of BMP performance that simply cannot be met with current stormwater techniques at most highly developed sites. As discussed in detail in Chapter 8 , the use of multiple BMPs in series at individual sites cannot reduce postdevelopment loadings below predevelopment levels. With some exceptions, the Watershed Rules and Regulations exempt development projects of less than five acres in size from the stormwater pollution prevention plan requirements 4.
Many kinds of small-scale industrial and commercial development are thus allowed to produce phosphorus and bacteria loads without treatment. Most states and localities that currently regulate stormwater discharges have a much lower threshold for stormwater requirements usually less than one acre Watershed Management Institute, Although it is true that even very low-acreage thresholds 30, ft 2 have been found to allow as much as 25 percent of stormwater to pass through untreated Booth and Jackson, , the efficacy of stormwater management will be markedly improved by lowering the current threshold from five acres to one acre.
A one-acre threshold. SPPPs are also required, regardless of acreage, for construction of a subdivision; construction of an industrial, commercial, multifamily, or municipal project where more than 40, sq. The SPPPs contain three different sizing criteria that must be considered when designing stormwater treatment facilities. The chosen BMPs must treat the greater of 1 the first half inch of runoff from impervious areas of the site or 2 the runoff produced by the one-year, hour storm event approximately 2.
In phosphorus- and coliform-restricted basins, the BMPs must treat the runoff produced by the two-year, hour storm event approximately 3—4 inches of rainfall. The latter two sizing criteria are among the largest sizing criteria for stormwater runoff in the United States. The regulations, however, provide no guidance for designing BMPs that can fulfill these requirements, either in terms of the hydrologic models that should be employed or standardized parameters.
Consequently, design engineers and state and local regulatory agencies are in frequent conflict as to how SPPPs should be interpreted and applied. It should be noted that the larger stormwater treatment volumes do not necessarily lead to proportionately greater levels of pollutant removal. For example, a BMP designed to capture runoff from the one-year storm is able to treat 90 percent of the annual stormwater runoff volume each year MDE, A BMP designed to capture runoff from the two-year storm is able to treat only 95 percent to 97 percent of the annual runoff volume produced each year, even though it is four times larger in size and cost.
BMP research has shown that treatment volume alone is not a reliable predictor of pollutant removal performance. Other design variables, such as internal geometry, pretreatment, conveyance, and multiple treatment pathways, are very important in determining pollutant removal. Yet the SPPP requirements offer minimal guidance on these other important design parameters.
The lack of a stormwater design and engineering manual and of performance criteria for individual BMPs for the New York City watersheds is a major impediment to achieving higher and more consistent pollutant removal. Other states such as Maryland have recently produced detailed and useful manuals to assist engineers in designing and building more effective BMPs MDE, The Watershed Rules and Regulations of the MOA have introduced stormwater control technologies into a region of the country that had little or no prior experience with stormwater management.
The regulations emphasize a. That is, an SPPP relies strongly on quantitative and highly theoretical calculations, rather than on performance monitoring or strict requirements for BMP size and treatment efficiency. The SPPP program does not currently have the basic support needed to foster success in the areas of training, engineering manuals, performance monitoring, review staffing, program financing and demonstration projects, maintenance requirements, design methods, BMP feasibility guidance, construction and maintenance inspection criteria, or BMP specifications.
As the Watershed Management Institute notes, strong program support in these areas has been the critical ingredient in effective implementation of stormwater requirements in other localities. It will be critical to the success of stormwater management in the New York City watersheds as well. The SPPP approach relies heavily on the use of structural stormwater practices such as ponds, wetlands, filters, and infiltration. Although these practices are an essential component of an effective stormwater quality strategy, they need to be combined with site design practices that reduce the amount or impact of impervious cover created by land development.
Recent modeling work has indicated that widespread application of better site design techniques can provide stormwater pollutant reduction equivalent to that achieved by structural stormwater practices Caraco et al. When better site design techniques and structural practices are combined, nutrient loadings are projected to decline to levels 30 percent to 50 percent lower than what can be achieved using conventional subdivision designs.
The Watershed Rules and Regulations and the SPPP requirements provide no incentives for developments that employ better site design techniques. Recently, the state of Maryland provided a series of stormwater quality credits for developments that use better site design MDE, These credits could be adapted for developments in the New York City watersheds. For phosphorus, current stormwater best management practices are only moderately effective.
In almost all cases, they cannot reduce postdevelopment loadings to predevelopment levels. Most current practices show some ability to remove bacteria but not enough to meet current water quality standards. Swales are capable of no net. Because urban areas are a source of Cryptosporidium oocysts see Chapter 5 , this deficiency is particularly notable.
Stormwater Pollution Prevention Plans should be required for activities greater than one acre, rather than for those greater than five acres. The five-acre measure was likely derived from the fact that activities that affect less than five acres are generally not required to obtain an NPDES permit for stormwater. However, most communities have recognized that one acre is a more appropriate lower limit. NYC DEP should develop guidance material for designing stormwater BMPs that can meet the one-year, hour storm event and the two-year, hour storm event.
Among other things, guidance material for such a new approach should include information on performance monitoring of stormwater BMPs for a variety of pollutants, including Cryptosporidium , and on long-term maintenance of stormwater BMPs.
The Stormwater Pollution Prevention Plans should encourage the use of nonstructural BMPs that limit the amount and the adverse effects of impervious surfaces. Excellent examples of good site design practices using such BMPs are found in Maryland. Arendt, R. Designing Open Space Subdivisions. Auer, M. Tomasoski, M.
Babiera, M. Needham, S. Effler, E. Owens, and J. Phosphorus bioavailability and P-cycling in Cannonsville Reservoir. Journal of Lake and Reservoir Management 14 Barten, P. Conservation of soil, water, and aquatic resources of the NorSask Forest.
Prepared for Mistik Management, Ltd. Kyker-Snowman, P. Lyons, T. Mahlstedt, R. O'Connor, and B. Managing a watershed protection forest. Journal of Forestry 96 8 Bentley, W.
Booth, D. Urbanization of aquatic systems—degradation thresholds, stormwater detention, and limits of mitigation. Journal of American Water Resources Association 33 5 Brown, M. Rafferty, P. Robillard, M. Walter, D. Haith, and L.
Brown, W. Campbell, S. Application of an ecosystem-based approach to management on multiple NIPF ownerships: A pilot project. Journal of Forestry 94 2 Caraco, D. Zieluski, and R. Site Planning Roundtable. Review of the Watershed Agricultural Program. Sediment: Sediments are soil particles dislodged by precipitation and deposited in streams, lakes, and rivers.
While erosion of soil is a naturally occurring process, accelerated erosion from degraded streams and poor construction practices creates excess sediment. Sediments accumulate in waterbodies and destroy feeding grounds for aquatic life, clog fish gills, block light, and increase water temperature.
Nutrients and Organic Debris: Nutrients are essential to water life, but too much can harm more than help. Phosphorous, nitrogen, and potassium are nutrients that help plants and animals grow.
Found in fertilizer, leaves, grass clippings, sewage, detergents, and animal wastes, these elements are not harmful to the environment in low doses. However, excess nutrients in an already healthy environment can be dangerous. Decaying organic matter depletes oxygen needed by aquatic life, leaving fish and shellfish to suffocate. Trash: Garbage, construction debris, and animal waste become part of the runoff entering storm drains and local waterways and clogging the system.
Toxins: Toxins are chemicals that can cause human and wildlife health problems. They include organic chemicals and metals, pesticides, herbicides, household chemicals, paint, paint cleaners, gasoline, motor oil, battery acid, antifreeze, and roadway salt.
0コメント