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Assessing and Reporting Water Quality (Questions and Answers)
- How do states and other jurisdictions assess water quality?
- What is the difference between the "good," "threatened," and "impaired" categories of use support?
- What are "Causes of Impairment"?
- What are "Sources of Impairment"?
- What kinds of monitoring data are used to make water quality assessments?
- Who collects monitoring data?
- Is water quality getting worse compared to 2000?
- What is an Integrated Report?
- Why did EPA issue guidance to states to integrate their water quality reports?
- What is a Total Maximum Daily Load (TMDL)?
- What are the five Integrated Report categories?
- Why aren’t all states integrated?
- When will all the state reports be integrated?
- What is the advantage of the Water Quality Assessment and TMDL Information/ ATTAINS website compared to previous ways of depicting state information?
- Why are some states missing from the 2004 rollup in ATTAINS?
- Are data from Tribes and interstate commissions in ATTAINS?
- How do we determine trends in water quality?
1. How do states and other jurisdictions assess water quality?
Water quality assessment begins with water quality standards. States and other jurisdictions adopt water quality standards for their waters. EPA must then approve these standards before they become effective under the Clean Water Act.
Water quality standards have three elements: the designated uses assigned to waters (e.g., swimming, the protection and propagation of aquatic life, drinking), the criteria or thresholds that protect fish and humans from exposure to levels of pollution that may cause adverse effects, and the anti-degradation policy intended to prevent waters from deteriorating from their current condition.
After setting standards, states assess their waters to determine the degree to which these standards are being met. To do so, states may take biological, chemical, and physical measures of their waters; sample fish tissue and sediments; and evaluate land use data, predictive models, and surveys.
For more information on state water quality standards, visit the National Water Quality Standards Database (http://www.epa.gov/wqsdatabase/index.html).
2. What is the difference between the "good," "threatened," and "impaired" categories of use support?
Waters rated by the states as "good" fully support all of their designated uses.
Waters rated by the states as "threatened" currently support all of their designated uses, but one or more of those uses may become impaired in the future (i.e., water quality may be exhibiting a deteriorating trend) if pollution control actions are not taken.
Waters rated as "impaired" by the states cannot support one or more of their designated uses.
3. What are "Causes of Impairment"?
Where possible, states, tribes and other jurisdictions identify the pollutants or stressors causing water quality impairment. These causes of impairment keep waters from meeting the criteria adopted by the states to protect designated uses. Causes of impairment include chemical contaminants (such as PCBs, metals, and oxygen-depleting substances), physical conditions (such as elevated temperature, excessive siltation, or alterations of habitat), and biological contaminants (such as bacteria and noxious aquatic weeds).
4. What are "Sources of Impairment"?
Where possible, states, tribes and other jurisdictions identify where pollutants or stressors (causes of impairment) are coming from. These sources of impairment are the activities, facilities, or conditions that generate the pollutants that keep waters from meeting the criteria adopted by the states to protect designated uses. Sources of impairment include, for example, municipal sewage treatment plants, factories, storm sewers, modification of hydrology, agricultural runoff, and runoff from city streets.
5. What kinds of monitoring data are used to make water quality assessments?
State water quality assessments are normally based upon five broad types of monitoring data: biological integrity, chemical, physical, habitat, and toxicity. Each type of data yields an assessment that must then be integrated with other data types for an overall assessment. Depending on the designated use, one data type may be more informative than others for making the assessment. For example:
Biological integrity data are objective measurements of aquatic biological communities (usually aquatic insects, fish, or algae) used to evaluate the condition of an aquatic ecosystem. Biological data are best used when deciding whether waters support aquatic life uses.
Chemical data include measurements of key chemical constituents in water, sediments, and fish tissue. Examples of these measurements include metals, oils, pesticides, and nutrients such as nitrogen and phosphorus. Monitoring for specific chemicals helps states identify the causes for impairment and helps trace the source of the impairment.
Physical data include characteristics of water such as temperature, flow, dissolved oxygen, and pH. Physical attributes are useful screening indicators of potential problems, often because they can have an impact on the effects of chemicals.
Habitat assessments include descriptions of sites and surrounding land uses; condition of streamside vegetation; and measurement of features such as stream width, depth, flow and substrate. They are used to supplement and interpret other kinds of data.
Toxicity testing is used to determine whether an aquatic life use is being attained. Toxicity data are generated by exposing selected organisms such as fathead minnows or daphnia ("water fleas") to known dilutions of water taken from the sampling location. These tests can help determine whether poor water quality results from toxins or degraded habitat.
6. Who collects monitoring data?
Hundreds of organizations around the country conduct some type of water quality monitoring. These include federal agencies such as the EPA and the U.S. Geological Survey. They also include state, interstate, tribal and local water quality agencies; research organizations such as universities; industries and sewage and water treatment plants; and citizen volunteer programs. They may collect water quality data for their own purposes or to share with government decision makers. States evaluate and use much of these data when preparing their water quality reports.
The states, territories, and tribes maintain monitoring programs to support several objectives, including assessing whether water is safe for drinking, swimming, and fishing. States also use monitoring data to
- review and revise water quality standards,
- identify impaired and threatened waters under Clean Water Act Section 303(d),
- develop pollutant-specific total maximum daily loads or TMDLs (calculations of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards and an allocation of that amount to the pollutant's sources),
- determine the effectiveness of control programs,
- measure progress toward clean water, and
- respond to citizen complaints or events such as spills and fish kills.
7. Is water quality getting better or worse?
It is not appropriate to use the information in this database to make statements about national trends in water quality. The methods states use to monitor and assess their waters and report their findings vary from state to state and even over time. Many states target their limited monitoring resources to waters they suspect are impaired and, therefore, assess only a small percentage of their waters. These may not reflect conditions in state waters as a whole. States often monitor a different set of waters from cycle to cycle. Even weather conditions - such as prolonged drought - can have an impact on whether waters meet their standards from one year to the next.
The science of monitoring and assessment itself changes. We know that a number of states have increased the amount of fish tissue sampling they conduct and, as a result, are issuing more protective fish consumption advisories. We don't think this means necessarily that there are new pollution problems; it's likely that states are able to identify them better as monitoring and analytical methods progress. States may also, over time, change how they issue or count fish consumption advisories.
Another fact to consider is that, for this reporting cycle and beyond, EPA has dramatically changed its monitoring and assessment guidance to the states. For the first time in November 2001, we encouraged states to combine water quality reporting under Section 305(b) of the Clean Water Act with Section 303(d) (which requires identification of impaired waters and implementation of pollution controls for those waters) into one Integrated Report. States were also to submit their reports electronically using either the Assessment Database developed by EPA or a compatible database. Some states followed this guidance, others did so only partially, and others could not change their reporting systems in time for the 2002 submissions.
8. What is an Integrated Report?
An Integrated Report is a biennial state submittal that includes the state’s findings on the status of all its assessed waters (as required under Section 305(b) of the Clean Water Act), a listing of its impaired waters and the causes of impairment, and the status of actions being taken to restore impaired waters (as required under Section 303(d)).
EPA first issued guidance to the states in 2001 encouraging them to integrate their water quality assessment information into one report. Before the issuance of this guidance, these were separate state 305(b) and 303(d) reports, and in many cases the findings and assessment data in them did not agree. EPA has issued additional guidance on Integrated Reporting in subsequent years.
9. Why did EPA issue guidance to states to integrate their water quality reports?
The purpose of this guidance was to streamline and reduce the reporting burden to the states and improve the information needed to make water quality management decisions. Information on Integrated Reporting, including the guidance issued by EPA, is available at http://www.epa.gov/owow/monitoring/repguid.html and http://www.epa.gov/owow/tmdl/policy.html.
10. What is a Total Maximum Daily Load (TMDL)?
A Total Maximum Daily Load, or TMDL, is a calculation of the maximum amount of a pollutant that can be present in a segment and still allow attainment of water quality standards, and an allocation of that amount to the pollutant’s sources. The TMDL calculation is TMDL = WLA + LA + MOS, where, WLA is the sum of wasteload allocations (point sources), LA is the sum of load allocations (nonpoint sources and background), and MOS is the margin of safety.
The MOS accounts for any lack of knowledge concerning the relationship between load and wasteload allocations and water quality. The TMDL analysis must take into account critical conditions such as high and low flows and seasonal variations in water quality. The waste load allocation in a TMDL is implemented through NPDES permits, but there is no federal regulatory requirement to implement the allocation to nonpoint sources.
11. What are the five Integrated Report categories?
States are required to place their assessed waters in one of five categories, as follows:
| Category | Description |
|---|---|
| 1 | All designated uses (DU) met |
| 2 | Some, but not all, DUs met |
| 3 | Can not determine if any DUs met |
| 4 | Impaired/threatened - TMDL not needed |
| 4a | TMDL completed |
| 4b | TMDL alternative |
| 4c | Non-pollutant causes |
| 5 | Impaired/threatened by pollutant - TMDL needed * Also known as the 303(d) list |
12. Why aren’t all the states integrated?
States are as a whole moving toward improved integration of their 305(b) and 303(d) reports. However, EPA guidance on integration is relatively new, and states are not required to integrate their reports. Because 303(d) lists require public comment and EPA approval, this process may delay the development of the 305(b) report, so states may prefer to prepare separate 303(d) and 305(b) reports.
13. When will all the state reports be integrated?
Since states are not REQUIRED to integrate their 305(b) and 303(d) reports, there may always be some states that do not prepare integrated reports. However, most states are working toward integration.
14. What is the advantage of the Water Quality Assessment and TMDL Information/ ATTAINS website compared to previous ways of depicting state information?
ATTAINS provides one dynamic, continuously updated website where water quality managers and the public can go to view a wide range of state-reported water quality information. ATTAINS for the first time allows the user to view tables and charts that summarize state-reported data for the nation as a whole, for individual states, for individual waters, and for the ten EPA regions. It gives the “full story” showing which waters have been assessed, which are impaired, and which are being (or have been) restored. The user can select the most recent available information or sort by reporting cycle. By displaying Integrated Report data in one location, ATTAINS will allow for a more informed summary of the quality of state waters and will provide decision makers with better information on the actions necessary to protect and restore the waters of the U.S.
15. Why are some states missing from the 2004 rollup in ATTAINS?
Some states are missing from the 2004 rollup in ATTAINS because they either did not submit electronic data for the 2004 cycle by November 30, 2007, or submitted data in a format EPA could not use. You may be able to find water quality information on that state by visiting the state water quality assessment website.
16. Are data from Tribes and interstate commissions in ATTAINS?
No. Neither tribes nor interstate commissions are required to submit 305(b) or 303(d) reports to EPA. However, they may have similar information posted on their own websites.
17. How do we determine trends in water quality?
National water quality trends are best determined using scientifically-based studies designed to sample water quality conditions at randomly-selected sites that are statistically representative of the Nation's many distinct ecological regions. EPA and the states have embarked on such probability-based studies of near coastal conditions (see the National Coastal Condition Report II or NCCR; http://www.epa.gov/owow/oceans/nccr/index.html) and the biological health of wadeable streams. The NCCR uses nationally consistent methods and probability-based design to assess five key indicators of coastal water health. The Wadeable Streams Assessment (http://www.epa.gov/owow/monitoring/wsa/index.html) will provide a scientific baseline of stream water quality based on 1,100 randomly-selected sites across the country.