A similar picture of extensive water quality problems emerges from EPA's Index of Watershed Indicators. Only 16% of watersheds had good water quality, while 36% had moderate water quality problems and 21% had serious problems. Sufficient data were lacking to fully characterize the remaining 27%. In addition, 1 in 14 watersheds in all areas was vulnerable to further degradation from pollution, primarily from urban and rural runoff.

WHAT ARE THE MAJOR THREATS TO WATER QUALITY AND WATERSHED HEALTH?
Nonpoint source pollution (NPS) is the leading cause of water quality problems. NPS, unlike pollution from industrial and sewage treatment plants, comes from many diffuse sources. NPS pollution occurs when water runs overland or through the ground, picks up pollutants and deposits them in surface water or introduces them to groundwater. The effects of nonpoint source pollutants on specific waters vary and may not always be fully assessed. However, we know that these pollutants have harmful effects on drinking water supplies, recreation, fisheries, and wildlife. Runoff from agricultural lands and urban areas are the primary source of the leading pollutants threatening water quality: siltation, bacteria, the nutrients phosphorus and nitrogen, and metals. Major national efforts are clearly required to address this non-point pollution.

While substantial progress has been made under the Clean Water Act in reducing direct pollution from industry and public sewage treatment systems, many waterbodies continue to be polluted by large point sources. 25% of all major industrial and public wastewater dischargers in all states continue to operate with expired CWA permits, according to the Environmental Working Group's Clean Water Report Card. Without up-to-date permits, clean water laws cannot be enforced. When permits remain expired for years at a time, pollution can continue unchecked, water quality may deteriorate, and progress toward the Clean Water Act's ultimate goal of "zero discharge" of pollutants is brought to a standstill.

DATA LIMITATIONS
The official EPA sources that Scorecard uses for its water reports have important limitations and flaws. Most importantly:
1) not all water bodies or watersheds are included. In fact, EPA and the states have assessed only 1/3 of the nation's waterways. For example, if a report on Clean Water Act assessment indicates that "18% of reported surface waters with reported problems," that statistic covers only the surface waters that the state itself has chosen to include in its report to EPA.
2) The criteria for including water bodies are not uniform, so state-to-state comparisons can be misleading. For example, a state that has left out a major category of water bodies included by another state might report a comparatively low level of Clean Water Act problems, but might in fact show a comparatively high level of problems if the same types of water bodies had been assessed for both states.
3)The criteria for determining whether a problem exists also are not uniform, so what counts as an impaired or threatened use in one state may not count in another state.
4)The watershed index does not reliably capture some important indicators of poor water quality, is weak on biological and ecosystem indicators, and does not characterize either watershed condition (i.e., health) or watershed vulnerability as claimed, in the opinion of the EPA Science Advisory Board.

These serious limitations, which are inherent in the official data, mean that there is a constant risk of apples-to-oranges comparisons in comparing one state's reported Clean Water Act problems with another's, or in comparing one watershed's characterization with another. A high policy priority for EPA should be to require more uniform reporting from the states under the Clean Water Act reporting requirements. The user of this information should always keep in mind what percentage of a state's water bodies are actually included in that state's report to EPA (i.e., how much is left out), and what percentage of the water bodies being reported were actually assessed for the particular type of water quality impairment the reader is interested in (i.e., how thorough was the assessment).


DATA SOURCES
Scorecard's profiles of Clean Water Act status and watershed health are derived from three U.S. EPA sources: the 1998 TMDL Tracking System, the 1999 Index of Watershed Indicators, and the 1998 National Water Quality Inventory.

The TMDL Tracking System database contains information on the waters listed under section 303(d) of the Clean Water Act. The CWA requires states to identify all waters where required pollution controls are not sufficient to attain or maintain applicable water quality standards and rank the waters taking into account the uses of the water and severity of the pollution problem. Fifty-six states, territories, and tribes submitted 1998 303(d) lists to EPA for review and approval. Scorecard utilizes the database version of these lists as of December 10, 1999. States submitted updated information on Clean Water Act compliance status to EPA in 2000.

EPA believes that the CWA list provides a comprehensive public accounting of all impaired or threatened waterbodies, but several data quality problems effect comparisons across geographic areas. The l998 figures reflect the states' assessment of only one third of the nation's waterways. States assessed almost 25% of the nation's total river and stream miles; 40% of its lake, pond and reservoir acres; and 30% of its estuarine square miles. Not all states and territories report the same types of information on their lists (e.g., some report the potential sources of the impairment while others do not). The information in the database for Idaho and Lousiana are based on lists that are not complete and fully approved. Also, data in the TMDL tracking system may change as states have an opportunity to review the interpretation of their list submission as compared to the Tracking system.

The Index of Watershed Indicators (IWI) characterizes the condition and vulnerability of aquatic systems in each of the 2,262 watersheds in the 50 states and Puerto Rico. The Index is based on the June 1996 Indicators of Water Quality in the United States, developed by EPA in partnership with states, tribes, private organizations, and other federal agencies. Scorecard utilizes version 1.4 of the IWI database (September, 1999). Note that the data used to construct different indicators was compliled over the period 1990-1999.

EPA created the IWI to focus the attention of the public and decision makers on watershed health, but there are important limitations to the data. For each watershed, the Index evaluates condition (water quality), vulnerability, and data sufficiency. Extensive professional judgement is used to integrate water quality indicators and watershed vulnerability indicators into an overall watershed health indicator. EPA's Science Advisory Board has noted that the data available to EPA for constructing its indicators do not provide good measures of ecological health, and warns that differences in IWI indicator scores may not correspond to meaningful differences in environmental quality.

The Index of Watershed Indicators makes use of data collected by a wide variety of regulatory and scientific agencies at specific sites across the country. More data are available in some watersheds than others. In order to ensure that sufficient data exist to make a valid judgment of aquatic resource health, U.S. EPA set threshold levels for the number of indicators needed to categorize watersheds. For the condition assessment, watersheds must have information for at least four of the seven indicators. For the vulnerability assessment, at least six of the eight indicators are required. In watersheds which fall short of these threshold requirements, the IWI categorizes them as having "insufficient data." Note that this categorization does not necessarily mean that there are no data available for the watershed. Information for those indicators with data is reported in Scorecard's county reports.

The National Water Quality Inventory: 1998 Report to Congress is a biennial report to Congress prepared under Section 305(b) of the Clean Water Act. It contains information from each state on the quality of its rivers, lakes, wetlands, estuaries, coastal waters, and ground water, along with information on public health and aquatic life concerns. It serves as a snapshot of water quality conditions across the country. Scorecard uses NWQI as its source of information about the percent of waterbodies in an area that have been asssessed by state agencies and can therefore be evaluated for Clean Water Act compliance.

To produce the NWQI, EPA combines information reported by states under two Clean Water Act reporting requirements. To assess water quality, states compare their monitoring results to the water quality standards they have set for their waters. Under Section 303(d) of the Clean Water Act, states provide lists of all of their impaired waters to support the development of Total Maximum Daily Loads (TMDLs). These different sources of state water quality data are generally consistent, although the 303(d) lists often include specific information from more targeted monitoring activities.

Scorecard's data on the percentage of particular types of waterbodies assessed by each state are derived from the state’s own accounting as complied in the appendices of the 1998 NWQI. Data on the number of impaired waterbodies in a particular geographic area are derived from EPA's TMDL Tracking System. In some cases these two statistics can be inconsistent - even though the same state provides both pieces of information. The reader should not assume that the percentage of assessed waterbodies is always a limit on the number of impaired waterbodies, or vice versa. This is a weakness of the existing data as reported by U.S. EPA. No other data are available to the public that would make it possible to eliminate these possible inconsistencies.