There is no question but that the Clean Water Act has led to enormous improvements in water quality throughout the United States. Funding for publicly owned treatment works (POTWs) has largely eliminated the use of the nation's waterways for the disposal of raw sewage. Most point source discharges are now subject to permitting and technology-based and/or water-quality based effluent limitations.
There is also no question that the Clean Water Act is a statute that is still evolving to address water quality challenges that have become visible once the turbidity of sewage and point source discharges had been largely cleared away. The collection and discharge of stormwater, for example, has evolved from being largely unaddressed, to being the subject of much litigation and court decisions, to being incorporated explicitly into the Act through congressional amendments that imposed permitting requirements on significant stormwater discharges. Even so, stormwater details are still being worked out, and we'll see what the U.S. Supreme Court does regarding runoff from forest roads this term. Contamination of beaches with bacteria and viruses in upstream sewage discharges also emerged as a problem for coastal communities, and other amendments to the Act added water quality standard requirements to help keep the nation's beaches healthy.
But the task is clearly not done yet. The EPA and many states are now struggling to deal with nutrient pollution and the corollary to that task: how to incorporate traditionally exempt farming operations into the Act's divisions of regulatory authority, whether through state nonpoint source programs, state agricultural water quality programs, or increased use of state and multi-state total maximum daily loads (TMDLs), as seen with the Chesapeake Bay. Contamination of waters with waste pharmaceuticals—pollutants that POTWs largely don't (and maybe can't, at least not cheaply) treat—looms as one of the next major water quality problems.
All of the above, however, keeps us in the realm of "traditional" water quality problems—that is, the contamination of the nation's waters as a direct result of human activities. Moreover, while addressing some of these human activities might be technologically, politically, and even psychologically difficult, and while the solutions may be very expensive to achieve, agricultural runoff, nutrient pollution, and pharmaceutical pollution are not qualitatively different kinds of water quality problems than those that the Clean Water Act has been addressing since its creation.
Climate change is.
Climate change is a different kind of water quality problem because its impacts alter the very baseline characteristics of water bodies that ground the Clean Water Act's backstop regulatory mechanism: water quality standards. These baseline characteristics include water temperature, water pH, the total yearly flow within or into a water body, the timing of that flow, and the pulses in that flow (for example, relatively steady snowmelt versus alternating major storm events and relative drought). Changes in these baseline characteristics, in turn, affect water chemistry, biological processes, aquatic food webs, and the suitability of particular water bodies for particular uses. For example, many species of commercially and recreationally important fish, such as salmon and trout, need fairly cold water to survive; thus, increasing stream temperatures can effectively extirpate these species from their traditional habitat, as has already been starting in Montana and other places in the West. Increasing water temperatures also pose a threat to power plants—nuclear, coal-fired, and natural gas—that rely on withdrawals for cooling water. Droughts and heat waves in the Southeast have already threatened power plants' abilities to use native streams for cooling. Reduced water flows, the projected condition of most of the West, will similarly affect power plants' abilities to use water for cooling reliably; those reduced flows will also reduce hydropower production.
Thus, climate change poses a major challenge to the Clean Water Act's reliance on water quality standards as a regulatory backstop. Water quality standards are set by states and consist of designated uses, water quality criteria necessary to meet those uses, and an antidegradation policy that prevents states from easily adopting less stringent water quality standards. As a matter of federal law, water quality standards: (1) can require permitting authorities to impose more stringent water quality-based effluent limitations on point sources when technology-based effluent limitations are not sufficient to attain and maintain the relevant water quality standards; (2) are the measure of water quality impairment and hence of the need for a TMDL; and (3) allow states to impose conditions on federally permitted or licensed activities to ensure that those federally permitting activities do not unduly impair water quality in the state. As a matter of state law, violations of water quality standards are often what induce states to address agricultural and other nonpoint source pollution; they also often serve as a basis for states to allocate water quality improvement monies.
Because of climate change, the Clean Water Act's many mechanisms to reduce human contamination of waterways are more important than ever, because they reduce existing stressors to aquatic ecosystems and hence improve those ecosystems' resilience in the face of climate change impacts. However, the Act does not allow states to fully adapt to climate change through their water quality standards designations, particularly with regard to existing uses of waterways. Under the Act's antidegradation policy, it is impossible to eliminate a designated use if the use existed at the time of the Act's initial implementation—even if, as is likely to be increasingly the case, the use becomes physically, chemically, or biologically impossible as a result of climate change impacts. Interestingly, some local governments are already contemplating climate change-based futility defenses to violations of water quality standards that they foresee themselves as being unable to avoid.
While unbridled flexibility in the water quality standards provisions of the Clean Water Act would pose more dangers to the nation's water quality than we want, Congress and the EPA nevertheless need to think long and hard about how to cope with climate change impacts to baseline water quality conditions—alterations for which the only real solution is complete mitigation of climate change at the international level. It's time, in other words, for the Act to evolve again.