The primary objective of the Clean Water Act is to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” As authorized under the act, states have primary responsibility for implementing programs to manage water quality. As a first step, states set water quality standards to achieve designated (or beneficial) uses for waters, such as recreational, agricultural, industrial, or other uses. These standards are then used to determine whether the states’ waters are impaired, among other things. In addition to establishing water quality standards, states are also responsible for monitoring the quality of their waters, assessing all readily available water quality data to determine whether the criteria for particular waters are being met, and reporting on the quality of their waters to EPA. Generally, to monitor water quality, states select the rivers, lakes, and other waters for which they plan to collect data during a specific period of time and collect water samples from them. After the data are collected, the states analyze the data and compare the results to their standards to assess whether the water bodies are meeting standards. In assessing their waters, state agencies responsible for water quality programs can also use data collected by other state agencies, federal agencies, volunteer or academic groups, and other entities. For example, one source used by many states is the U.S. Geological Survey (USGS) within the Department of the Interior, which has a large program for monitoring water quality. Under section 305(b) of the act, states are responsible for reporting biennially on the quality of their waters, and EPA is responsible for compiling these reports into the National Water Quality Inventory. As part of this effort, EPA provides guidance to states on monitoring and assessing their waters. In addition to reporting on the overall quality of their waters, the Clean Water Act requires states to identify waters that do not meet applicable water quality standards. Specifically, section 303(d) of the act requires states to list the waters within their state boundaries for which certain technological controls required under the act are not stringent enough to implement applicable standards. Under the act, EPA must approve the states’ lists. The 303(d) lists identify waters in which pollutants need to be reduced. States are required to develop a TMDL for each of the pollutants affecting each impaired body of water. Under the act, if states do not establish TMDLs for impaired waters, EPA must do so. While the states are primarily responsible for managing water quality, EPA is responsible for developing regulations and guidance implementing the act. In 1985, EPA issued water quality regulations requiring states to provide a list of impaired waters. In 2000, EPA finalized major revisions to these regulations that would have required the states to develop more comprehensive lists of impaired waters and would have clarified the required elements of a TMDL. However, Congress postponed implementation of these revisions, in part because of widespread concerns among a variety of groups. Because the regulations were in flux during 2000, EPA waived the requirement for states to submit their lists that year; instead, states are required to submit their next list by October 1, 2002. In October 2001, EPA further postponed the effective date of the revised regulations to April 30, 2003. Prior to that time, EPA plans to develop a second set of revised regulations. Concern over the impaired waters program has led to years of litigation among states, EPA, and interest groups. Lawsuits in 38 states have resulted in almost two dozen consent decrees requiring states to develop TMDLs or requiring EPA to develop them if states fail to do so. At congressional hearings in 2000, we and other organizations raised concerns over the ability of states to gather the data needed to monitor their waters, and in particular to support the identification of impaired waters needing TMDLs. As a result of these concerns, Congress requested the National Academy of Sciences’ National Research Council to study the scientific basis for the TMDL program. The council issued a report in June 2001 that expressed support for the TMDL program but called for improvements in how impaired waters are identified and how TMDLs are developed. While the general process that states follow to identify impaired waters is similar, the specific approaches they use vary considerably among states. Generally, the process involves establishing water quality standards, gathering data on water quality through monitoring, and assessing the data to determine whether the criteria and standards are being met or whether a body of water is impaired (see fig. 1). If a state determines that a previously listed body of water is no longer impaired, then it can seek EPA’s approval to remove that body of water from its list. Variation in the approaches that states use occurs at each step in the process and causes inconsistencies in the listing of impaired waters. These inconsistencies are particularly apparent in cases of interstate waters. EPA published one set of guidance in November 2001 that it believes will address some of these inconsistencies. It plans to issue a second set in early 2002 to address other causes. However, EPA officials stated that the underlying causes of inconsistent listings require long-term action. Water quality standards can vary significantly among states. Variations in water quality standards arise from differences among states in two components of the standard-setting process: (1) the identification of designated (or beneficial) uses for a particular body of water and (2) the development of water quality criteria to protect each use. According to EPA, some of these variations are appropriately based on different ecological conditions but others are not. For example, states with coastal plains could appropriately have lower standards for dissolved oxygen than states with high mountain streams. The agency also notes that other variations are often not appropriate. Inappropriate variations may arise if states with shared or immediately adjacent water bodies designate them for different uses. For example, one may consider the water suitable for swimming and therefore have more stringent water quality criteria, while a neighboring state may consider the same water to be used for wading, which requires less stringent criteria. Designated uses are the beneficial uses established by states, based on social and environmental factors that waters are intended to support. For example, a water may be designated for use as a public water supply or to support aquatic life, irrigation, or contact recreation. Officials in some states said that the designated uses in their states are appropriate while others did not. Of the 15 state officials that we interviewed, 8 acknowledged that designated uses in their states need to be revised. For example, all waters in Virginia are designated for swimming even though some of the waters are inaccessible and too shallow for swimming purposes. Other waters in Virginia are impaired by bacteria from wildlife sources and cannot achieve the primary contact use. As a result, these waters do not meet the water quality standard set for them. In other states, in some cases where designated uses are inappropriate and need revision, waters may be considered impaired by natural water quality conditions. Yet, one state may list such waters as impaired, while another might not. For example, according to their 1998 303(d) listing methodologies, Arizona precludes the listing of waters impaired by naturally-occurring conditions while California includes such waters on its list. One explanation for the problems with many designated uses is that states established many of them en masse in the early 1970s in order to meet the requirements of the Clean Water Act. States had 180 days to put designated uses in place, and many used the highly general goals of the Clean Water Act—fishable-swimmable waters—as their designated uses. In addition, implementation of the act initially focused on installing controls on individual point sources of pollution and little attention was paid to whether overall water quality met specific standards. Reflecting these concerns, the National Research Council’s recent report states that many designated uses are too broad and need to be refined in order to incorporate the range of scientific data and social needs for water quality. The Council’s report recommended that states’ designated uses should be divided into several tiers to more adequately represent water quality conditions and that water quality criteria should have a more logical link to the designated use to sufficiently measure attainment. According to responses from our 15-state survey, such a refinement in states’ designated uses and water quality criteria would most likely result in different waters being listed. Water quality criteria provide thresholds for determining whether bodies of water can support their designated uses. As with designated uses, criteria used by states vary and in many states need updating. Variation among states is primarily caused by different states focusing on different pollutants, mainly because of differences in water quality criteria. Illinois, for example, has numeric water quality criteria for two pollutants— sediment and nutrients—for which neighboring Indiana does not have numeric criteria. As a result, Illinois listed 32 percent of its waters as impaired by sediment, while Indiana listed none. Similarly, Illinois listed 22 percent of its waters as impaired by nutrients, but Indiana listed less than 1 percent as so impaired. In some instances, neighboring states may both have numeric criteria for a given pollutant, but the criteria may differ significantly. Connecticut and New York on the Long Island Sound have different criteria for dissolved oxygen and, therefore, list the Sound differently. States also vary in the extent to which they use narrative criteria versus numeric criteria to make a listing determination. For example, Nevada focuses its listing determinations on violations of numeric water quality criteria. On the other hand, Massachusetts used narrative criteria to list approximately one-third of its reported impairments because it felt that the designated use was impaired. With the criteria, Massachusetts considered a lake to be impaired (for swimming) if noxious aquatic plants covered over 50 percent of its area. Massachusetts’ officials conceded that their narrative criteria may not correctly identify when a lake is impaired for various uses, and they are currently working on revising the water quality standards. Other states also discussed the need to revise criteria that are difficult to use in identifying impairments. Officials in 14 of the 15 states represented in our interviews believe that water quality criteria in their states need to be revised.