The Inevitability of Change: Water Law in Light of Climate Change

Climate change is routinely studied through the lens of air quality and air pollution.  However, climate change also has clear and often severe impacts on water quality and water law.  Those impacts include: rise in sea levels, changes in precipitation, extreme drought conditions, less snow pack during winter months, and increased likelihood of wildfires.  Accordingly, it is important to provide an overview of some of the impacts climate change has on water, and how water law may be required to adapt to the widespread and perhaps dramatic changes.

Water Quality and the Clean Water Act

One effect of climate change on water is that the average water temperature will increase.  Warmer water can cause an increase in algae, bacteria, and/or parasites.  The increased presence of microbes in warm water could have adverse impacts on human health.  As such, water quality laws, like the Clean Water Act may be required to account for the consequences and health effects that result from warmer water caused by climate change.

Additionally, scientists have noted that the increase of greenhouse gases that cause climate change have also contributed to ocean acidification by causing a shift in the pH of ocean water.  However slight the shift in ocean water pH may be, some species, like coral, cannot adapt to a more acidic environment.  As such, some marine ecosystems, like coral reefs, may be in danger of extinction.

The Clean Water Act may not be the most useful tool in combating climate change because it was designed to reduce and prevent direct pollution of water, which does not address the impacts of climate change.  Moreover, the act typically is used to address water quality issues on a local or regional level, and is not in a position to deal with climate change on a global level.  In short, the Clean Water Act could be used to help alleviate some effects of climate change, but it cannot necessarily be used to address the causes.

Water Use and Water Law

Climate change also has a direct impact on the amount of water available and the uses of water.  Wet climates will likely continue to see an increase in precipitation, and precipitation events will become more intense in those areas.  Conversely, dry climates will become even drier as a result of climate change.  Drought conditions will become pronounced and agricultural growing seasons will be shorter in those areas.  The upshot is that areas like the western United States will likely not have enough water to go around as what water there is will be subject to competing interests.  For example, will water be used to maintain agricultural production or will it stay in-stream in order to protect aquatic species and ecosystems?  In areas and regions where choices like this are already divisive and politically charged, it will only become worse as the effects of climate change increase.

Two major systems of water law are riparian rights and prior appropriation, neither of which is particularly well-equipped to deal with the effects of climate change.  First, under riparian rights systems, it may seem fair that less water means that each user is assigned a new share of water on pro rata basis.  However, in extreme drought conditions it is possible that the amount of water each user receives is not enough to be effectively used.  In that scenario, everyone loses, because while everyone has some water, no one has enough to do anything useful.  As such, riparian rights systems need to have some way to promote best-use decisions among competing users.  Meanwhile, under prior appropriation systems, senior users would be able to use the full amount of their water rights in drought conditions.  While this may make it so that at least some users have enough water to be effective, the problem is that senior users may not be the users that provide the most beneficial use of the water. Additionally, in prior appropriation systems, as long as they receive their portion, senior users are not incentivized to conserve water even during drought conditions.

Climate change and the resulting shifts in water supply could cause tensions between countries or regions that use common water resources.  Tensions could also occur between industries with competing interests in water.  For example, continued use in agriculture and irrigation during drought conditions could affect energy producers that rely on water flow.  Accordingly, there may be situations in which governments, particularly state governments, may be forced to step in and regulate the amount of water used among various users in order to mitigate the impacts of climate change.


Some agencies are already trying to find answers and come to grips with the changes that are taking place.  The Environmental Protection Agency released a report in 2012 that was the agency’s National Water Program’s “Response to Climate Change.”  The report explains the impact of climate change on water systems and sets out the ways in which the agency will seek to address those impacts going forward.  Additionally, state agencies have also started to address these same concerns.  In 2012, at the behest of California’s Energy Commission, the University of California, Berkeley completed a document titled, “Climate Vulnerability and Adaptation Study for California: Legal Analysis of Barriers to Adaptation for California’s Water Sector.”  The document outlines the impacts of climate change on California water supplies and the possible measures that the state can take to mitigate those impacts.  However, it is likely that there may not be a one-size-fits-all approach to addressing climate change impacts on water.  Ultimately, each country, region, or state will have to come to terms with how climate change affects their water resources and plan accordingly.



  • Robert W. Adler, Climate Change and the Hegemony of State Water Law, 29 Stan. Envtl. L.J. 1 (2010).
  • Robin Kundis Craig, Climate Change Comes to the Clean Water Act: Now What?, 1 Wash. & Lee J. Energy, Climate, & Env’t 9 (2010).
  • Envtl. Prot. Agency, Climate Change and Coastal Watersheds: Adaptation to Attain Clean Water Goals and Sustainable Coasts (Dec. 2012), available at
  • Envtl. Prot. Agency, National Water Program 2012 Strategy: Response to Climate Change (Dec. 2012), available at
  • Michael Hanemann, Deborah Lambe & Daniel Farber, University of California, Berkeley,  Climate Vulnerability and Adaptation Study for California: Legal Analysis of Barriers to Adaptation for California’s Water Sector (California Energy Commission, Publication number: CEC-500-2012-019, 2012), available at
  • Dan Tarlock, Takings, Water Rights, and Climate Change, 36 Vt. L. Rev. 731 (Spring 2012).