Water Quality

Key EPA and State Decisions Limited by Inconsistent and Incomplete Data Gao ID: RCED-00-54 March 15, 2000

The Clean Water Act requires states to submit reports on the condition of their waters to the U.S. Environmental Protection Agency (EPA), which then compiles the data into a report entitled "National Water Quality Inventory." GAO examined several issues relating to EPA's report on water quality and water quality management. This reports discusses (1) the reliability of the data in the Inventory and whether the data are representative of water quality conditions nationwide and (2) whether the available data are sufficient to allow state officials to make key decisions on activities required by the act. GAO found that the Water Quality Inventory does not accurately portray water quality conditions nationwide. Consequently, the information in the Inventory cannot be meaningfully compared nationwide.

GAO noted that: (1) the National Water Quality Inventory does not accurately portray water quality conditions nationwide; (2) a major reason is that it would be cost-prohibitive to physically monitor all of the waters in the country, and, therefore, almost all states monitor a subset of their waters; (3) most monitoring is not done in a way that allows for statistically valid assessments of water quality conditions in unmonitored waters; (4) the Inventory is not reliable because wide variation exists in: (a) the way that individual states select their monitoring sites; (b) the kinds of tests they perform on their waters and how the results of these tests are interpreted; and (c) the methods they use to determine the causes and sources of pollution in waters that do not meet water quality standards; (5) as a result, the information in the Inventory cannot be meaningfully compared across states; (6) EPA used information from the Inventory as a basis for a number of important decisions and activities, such as deciding how to allocate federal funds for Clean Water Act programs to states and measuring and communicating EPA's and states' progress in implementing the act; (7) the dearth of the waters actually monitored, combined with the wide variation among states' monitoring and assessment approaches, make the national statistics unreliable and subject to misinterpretation and, therefore of limited usefulness for these purposes; (8) there is little doubt among experts that the remaining problems are considerable and that solutions will entail significant expenditures; (9) what is uncertain is the precise extent of water quality problems, where and what the most severe problems are, and the location of high-quality waters that need to be protected; (10) the limitations of the information in the Inventory extend well beyond the problems associated with the national uses of the report; (11) state-level activities, such as identifying water quality problems and setting priorities among them to obtain the most improvement in water quality for the dollar spent, are also affected by data limitations; (12) GAO's survey shows that data gaps limit states' abilities to carry out several key management and regulatory activities on water quality; (13) only six states reported that they have a majority of the data they need to assess whether their waters meet water quality standards; and (14) a vast majority of states reported that they have less than half the data they need to: (a) identify nonpoint sources that are causing waters not to meet standards; and (b) develop total maximum daily loads (TMDL) for those waters.


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