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Restoration and the Clean Water Act

The objective of the Clean Water Act, as stated in Section 101, is to "restore and maintain the chemical, physical and biological integrity of the Nation's waters." Restoration is a tool for meeting some CWA requirements. The CWA provides the broad and flexible authority needed to realize the nation's water resource goals. Most importantly, the CWA recognizes that water resource quality is defined by all its components—the chemical, physical, and biological, and that water resource integrity depends on complex interactions among all three components.

Numerous CWA programs encompass the concept of restoration. Because widespread loss of ecological function and biological diversity jeopardizes the health of many water resources, CWA programs must address all elements of water resource integrity in a more integrated manner and cannot work in isolation if the goals of the Act are to be met. Figure 2-1 (not available electronically) illustrates EPA's emerging approach to harmonizing CWA programs and achieving the overall goal of aquatic ecosystem integrity. In addition, Table 2-1 on the following page provides some examples of restoration-related activities that have taken place within the framework of CWA programs.

Level 1 of the water quality pyramid represents a primary goal of water quality programs established to support the CWA. Watershed planning is a multi-objective process with many stakeholder goals that must share equal status with the water quality goals . However, functional aquatic ecosystems are not exclusive of other goals, and the water quality planning process can often support other goals as well. Level 2 represents the components of aquatic ecosystems, identified in Section 101 of the Clean Water Act, whose integrity must be maintained to support a functioning aquatic ecosystem. It is important to note that Section 101 of the CWA places equal emphasis on each of these components (i.e., chemical, physical, and biological). Water quality standards (level three of the pyramid) define specific objectives for restoring aquatic ecosystem integrity and are comprised of designated uses, numeric or narrative water quality criteria to protect these uses, and an antidegradation provision (Table 2-2). Ecological restoration techniques can be effective in addressing water resource quality impairments that are characterized by state water quality standards.

The relationship between impairment and restoration techniques is often direct and obvious; the connection between restoration techniques and particular stressors contributing to stream impairment, however, is not always apparent. Therefore, distinguishing between impairments and specific stressors and sources that cause impairments will help to identify the stressors that are amenable to control using various restoration techniques. Water quality impairment is often indicated by excursions of numeric criteria, which provide quantitative targets for particular stressors. However, water quality impairment may also be identified based on narrative criteria and designated uses, such as the ability to support a designated type of fishery. For example, if a river does not meet water quality standards because it fails to support adequate salmonid spawning, it is first necessary to identify the stressors that reduce spawning (such as loading of fine sediment, which reduces available spawning habitat) before selecting a control or restoration technique. Chapter 3 presents the linkages between certain ecological restoration techniques and a number of water quality parameters, thus illustrating how restoration can be used to address excursions of both numeric and narrative water quality criteria.

Depicted at the fourth level of the pyramid are the Watershed Protection Approach and the Total Maximum Daily Load (TMDL) process, in which several CWA programs cooperate to meet the primary goal of functional aquatic ecosystems. The Watershed Protection Approach encourages water program managers to solve water quality problems by following a watershed-based approach. The approach encompasses all or most of the landscape in a well defined watershed (or other ecological, physiographic, or hydrologic unit) and addresses dynamic relationships that sustain aquatic resources and their beneficial uses. Significant threats to water resource integrity are prioritized based on a comparative analysis of ecological, economic, and human health risks; managers can then direct resources to high-risk problems. Watershed approaches also prioritize stressors within watersheds using water quality data, biological monitoring and habitat suitability data, and information on land use and location of critical resources.

A key technical component of the Watershed Protection Approach is the TMDL process required under CWA Section 303(d) (1), which determines the maximum allowable load of a pollutant or stressor that a water resource can assimilate without violating a water quality standard. Planning restoration activities within the context of a TMDL is helpful, because the TMDL process links stressors and their sources to the condition of the watershed and water resource. The process quantifies relationships among stressors, stressor sources, recommended controls, and ecological conditions. For example, a TMDL may mathematically show how a specified percent reduction of a stressor (such as elevated temperature that prevents the maintenance of a cold water fishery) is necessary to meet a state water quality standard. Restoration is located at Level 5 of the pyramid, and is grouped with other key CWA activities that are implemented within the TMDL process. Restoration techniques can be applied in conjunction with traditional regulatory actions (such as point source permits) and voluntary programs (such as implementation of nonpoint source BMPs) in addressing any component of a water quality standard—a numeric or narrative criterion or a designated use. For example, if a stream does not meet the numeric criterion for unionized ammonia, the restoration of riparian vegetation can lower stream temperature, thereby indirectly reducing instream concentrations of the pollutant. Restoration can also address nonattainment of a designated use (e.g., a coldwater fishery) or a narrative criterion that refers explicitly to habitat quality or biological diversity. For example, in a water resource where elevated sediment loadings impair spawning habitat, a TMDL might establish a specific percent fines by weight for substrate as a measurable endpoint. The success of instream, riparian, or surrounding watershed restoration efforts could then be evaluated by the measurement of percent fine sediment. An optimal management strategy may combine some or all options involving point source load reductions, BMPs, and instream ecological restoration techniques.

Table 2-3 lists several recent publications on ecological restoration that emphasize the importance of comprehensive watershed-scale projects that address both specific instream conditions and stressors in the watershed that caused the impairment. These publications consistently warn that the application of instream or channel-related techniques (e.g., re-aeration structures and channel reconfiguration) should be limited until stressors that created the impaired condition are understood and can be controlled. This approach is entirely consistent with and supportive of the watershed protection approach and TMDL process.


  1. Under Section 303(d), states are required to identify waters not meeting water quality standards, even after the implementation of existing required control, such as traditional technology-based controls. States then prioritize the list and develop TMDLs for high-priority waters.  Return to text

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