|Watershed approach to water quality managment|
What is a watershed?
A watershed is the land area that drains into a stream; the watershed for a major river can encompass smaller watersheds that ultimately combine at a common point. A watershed includes all surface water and groundwater, soils, vegetation and animals, and human activities contained within its area.
What is the Watershed Management Approach?
Watershed Management is a holistic approach to managing water resources for quantity and quality within a watershed. Watershed management is also a useful, proactive approach in areas without immediate problems. The figure below demonstrates the Watershed Approach to Water Quality Management. By looking at watersheds, the state can evaluate all the sources of pollution that may be affecting the water quality and quantity.
The Watershed Approach is an ongoing cycle of tasks: setting standards for surface water quality; taking measurements of the conditions; assessing the data and identifying the impairments including establishing priorities; verifying the pollution sources and developing plans for restoring water quality; and implementing pollution source controls. Pollution source controls can be things such as permits, rules, and nonpoint source management practices.
Specific steps to this approach include:
During the planning phase, you must identify the watershed planning unit, and identify stakeholders and resource personnel.
Determine the watershed planning unit. Watershed units vary from mainline portions of large river basins to small areas discharging excess flows into ponds. Watershed size influences stakeholder roles in all steps of the watershed management cycle.
Although watershed units are usually based on geographic boundaries, they also may be defined according to which government unit exercises authority over a particular land area. For example, a state or federal agency may be the lead stakeholder in a large river basin (1,000 to 10,000 square miles), but local government agencies may play the larger role in a subwatershed (1 to 10 square miles).
Watershed unit size also generally determines (1) influence of impervious ground cover due to urban growth and (2) management focus from site-specific design to planning for the entire river basin.
Resource personnel are individuals or groups who bring specific technical expertise to the stakeholders and decision makers. Resource personnel might include scientists, engineers, conservationists, policy experts, or attorneys that can advise stakeholders on specific issues and questions. In some cases, resource personnel may be contracted from the private sector and in other cases may be part of the stakeholder group.
Stakeholders may include:
During the data collection phase, routine water quality and quantity data is collected at specific locations.
Degrading water quality or limited water supply is usually the reason a watershed management plan is developed. Sources that contribute to water quality include two main categories: point and nonpoint.
In fact, the total pollutant load to a lake or stream is generally expressed in the following form:
Total Pollutant Load = Total Point Source Load + Total Nonpoint Source Load
Point Source Pollution. Point source pollution comes from the collection of pollution and the discharge of that pollution at a defined point.
Examples of point sources include:
Point sources are typically monitored and regulated for quality and quantity standards by a state or federal environmental agency. Although costly at times, implementing tougher standards at point sources is typically easier because the pollution is delivered to one area for treatment.
Nonpoint Source Pollution: Nonpoint source pollution comes from diffuse sources that are not easy to collect or treat. According to the Environmental Protection Agency (EPA), the most common nonpoint source pollutants are sediment and nutrients.
Examples of nonpoint sources include:
Depending on the specific problem, nonpoint source pollution is generally controlled through the design, construction and maintenance of best management practices. Nonpoint source pollution is generally more difficult to control because it is not centrally collected and can be a result of numerous factors. These factors are not always specific to land areas adjacent to streams and could be a result of secondary impacts.
The next step in the watershed management approach is the assessment and targeting phase. This portion involves a comparison of the current water quality to state and federal standards.
Water quality has continued to increase in evaluation and concern from both federal and state perspectives. In Texas, state surface water quality standards are outlined in Title 30, Chapter 307 of the Texas Administrative Code.
According to Texas Commission on Environmental Quality (TCEQ), the Texas Surface Water Quality Standards are rules designed to:
All standards are protective; that is, they signal a situation where there is some possibility that water quality may be inadequate to meet its designated uses. There are instances, for example, in which a water body fails to meet the standard for aquatic life use, yet no fish kills are observed. However, a decline in the variety or number of aquatic species and an increased probability of fish kills may be observed.
Four general categories for water use are defined in the Texas Surface Water Quality Standards:
Aquatic life use: The standards associated with aquatic life use are designed to protect plant and animal species that live in and around the water. They establish optimal conditions for the support of aquatic life and define indicators used to measure whether these conditions are met.
Some pollutants or conditions that may violate this standard include low levels of dissolved oxygen, or toxic substances such as metals or pesticides.
Contact recreation: The standard associated with contact recreation measures the level of certain bacteria in water to estimate the relative risk of swimming or other water sports involving direct contact with the water. It is possible to swim in water that does not meet this standard without becoming ill; however, the probability of becoming ill is higher than it would be if bacteria levels were lower.
Public water supply: Standards associated with public water supply indicate whether water from a lake or river is suitable for use as a source for a public water supply system. Source water is treated before it is delivered to the tap; a separate set of standards govern treated drinking water.
Indicators used to measure the safety or usability of surface water bodies as a source for drinking water include the presence or absence of substances such as metals or pesticides. Concentrations of salts, such as sulfate or chloride, are also measured, because treatment to remove high levels of salts from drinking water is expensive.
Fish consumption: The standards associated with fish consumption are designed to protect the public from consuming fish or shellfish that may be contaminated by pollutants in the water. The standards identify levels at which there is a significant risk that certain toxic substances dissolved in water may accumulate in the tissue of aquatic species.
However, these levels do not always predict when toxic substances will accumulate in fish in unsafe concentrations. As a result, the state also conducts tests on fish and shellfish tissue to determine if there is a risk to the public from consuming fish caught in state waters. The standards also specify bacterial levels in marine waters to ensure that oysters or other shellfish that may accumulate bacteria from the water are safe for commercial harvest, sale, and consumption by the public.
Surface Water Quality Inventory: Texas has a formal process for evaluating surface water quality called the Surface Water Quality Inventory that is conducted every two years.
This same report identifies impaired waterbodies (known as the 303(d) list) and is used to establish Total Maximum Daily Load Programs.
A total maximum daily load (TMDL) is established for a body of water found to exceed state standards for a particular contaminant.
The goal of the TMDL Program is to restore water quality to rivers, lakes, and bays that have substandard water quality. A TMDL is like a budget for pollution. It is a scientific model that:
An implementation plan puts the TMDL into action by outlining the steps necessary to reduce pollutant loads through regulatory and voluntary activities.
The next step in the watershed management approach is strategy development. This phase involves the development of goals and strategies to maintain, or achieve water quality standards and meet future demands.
Setting and prioritizing goals is the key step at which stakeholders, both direct and indirect, become key players in identifying strategies and designing the actual watershed management plan. In addition to direct and indirect stakeholders, there exists a need to involve interest groups, policy makers and experts in this process so that decisions can be made with full access to policy and practical implications. Experts may include private or public engineers and scientists. Public policy participants may include local, regional, state and federal personnel who may be responsible or have interest in planning.
Outlining specific goals will enable stakeholders to more easily achieve a desired result. For example, instead of setting a goal to improve water quality, a more specific goal might be to reduce phosphorus loading in your watershed by 25 percent. Another example would be to develop a computer model that accurately predicts nitrogen and phosphorus loadings at a specific lake.
Water quality models are tools that allow users (managers, engineers, planners, etc.) to mathematically simulate natural processes in a watershed using a personal computer. Models generally require information on topography, land use, climate, and soils. A model can assist stakeholders in evaluating the impacts of various management strategies and land use changes on the watershed. In short, water quality models allow "what-if" scenarios to be developed and evaluated.
Although models can be a very useful tool, they have limitations due to scale (size of the watershed) and available data (stream flow, water quality parameters, etc.). In addition, modeling efforts need to be combined with social acceptability to achieve successful results.
Implement goals and strategies: To fit their watershed's needs, stakeholders and decision makers may customize the tools that exist for putting watershed management plans into practice. Three of those tools are permits, best management practices (BMPs) and educational programming. Each watershed management plan will have site-specific needs requiring different combinations of these three tools:
Permits: Regulatory permits are used most often to control point sources. Such permits are issued by the government and specify discharge levels for pollutants. Point sources may not exceed these permitted levels. Point source contributors might address water quality issues by modifying permits to change certain pollutants' allowed discharge quantities.
However, putting such permit changes into practice may require plant expansion and new processes that will increase treatment costs for a facility's users or consumers. A watershed management approach that uses permits as its sole tool will be effective only if point sources are the dominant contributors to water quality problems.
BMPs: BMPs are the preferred approach to managing nonpoint source pollution. Although BMPs are often voluntary, some regulatory agencies require their inclusion in watershed management plans.
For example, the National Pollutant Discharge Elimination System (NPDES) combines construction permits with BMPs for erosion and run-off control. A watershed management strategy that uses BMPs as its sole tool will be effective only if nonpoint sources are the dominant contributors to water quality problems.
Educational Programming: Education is key to a successful watershed management plan. Education programs can alert stakeholders to watershed problems and can help involve them in decision making.
Educational programs also draw the attention of both agency employees and stakeholders to the need for a proper strategic balance between permits and BMPs. Such balance leads to management plans that address pollution from both point and nonpoint sources.
The Watershed Management Approach, Russell A. Persyn, Molly Griffin, Amy T. Williams and Clint Wolfe