Basic Information

Water & Climate Change
Water is at the center of life. Earth's abundant waters have allowed life to exist and flourish in almost every corner of the globe, from the hot, humid depths of the rainforest to the most arid deserts. But beyond its biological importance, water is fundamental to many traditional Native American narratives-the sacred stories that give meaning and understanding to life and a connection to the past. Water gives life to salmon of the Northeast, the sturgeon of the Great Lakes, and the wild rice harvests of Minnesota. In other places, water is the domain of the divine on Earth, like the Zuni Salt Lake of New Mexico. The lake is inhabited by the great Salt Mother, called Ma'l Oyattsik'i by the Zuni people, keeper of the salt that nourishes life.

Yet freshwater availability, and the frequency and intensity of floods and droughts are changing. Water is highly sensitive to changes in weather and climate, and thus highly susceptible to the impacts of climate change. A shifting climate may threaten Earth's ability to supply adequate sources of water to support life. While climate change is expected to bring some benefits, scientists predict that climate change impacts on water resources will be negative overall.

The Intergovernmental Panel on Climate Change reports that Earth's temperature has risen about 1° F since the mid-1970s. Higher air temperatures will result in increased water temperatures in rivers, lakes, springs, and other freshwater sources. The panel reports that "[s]imulated future surface and bottom water temperatures of lakes, reservoirs, rivers, and estuaries throughout North America have consistently increased from 2 to 7°C [3.6 to 12.6°F] ...with summer surface temperatures exceeding 30°C [86°F] in Midwestern and southern lakes and reservoirs."

Higher air temperatures will also increase evaporation rates and cause water levels to drop in many regions. This issue will be compounded by lower levels of precipitation expected in most areas of North America. Amongst other impacts, lower water levels will contract habitats, many of which already face anthropogenic degradation.

Even a minor temperature rise may substantially reduce water quality and threaten freshwater fisheries. In large or deep bodies of water, such as northern lakes, warmer water temperatures are expected to extend and intensify summer thermal stratification. Thermal stratification refers to layers of temperatures that occur in deep bodies of water: warmer, less dense layers of water overlay cooler, denser layers. Extending this process may lead to oxygen depletion during the summer months. However, less ice cover during winter months may actually increase oxygen levels, thus decreasing typical winter fish mortality.

Higher water temperatures may also affect fish survival and spawning, although the impacts will vary across regions. Warm water fisheries may be able to expand their ranges, while coldwater species will be forced to migrate northward or decline as habitats become unsuitable.

Increasing water temperatures and lower volumes will most likely lead to higher concentrations of phosphorous, a highly toxic compound found in fertilizers and sewage effluent. Phosphorous concentrations can swell in an ecosystem and cause eutrophication-a build-up of chemical nutrients-that often leads to a substantial reduction in water quality. Eutrophic conditions promote rapid plant growth and decay. Excessive growth of phytoplankton, or algae bloom, disrupts normal ecosystem functioning and reduces oxygen availability for aquatic species. Eutrophication also interferes with normal water treatment procedures, posing a health risk to some communities. Higher water temperatures are also expected to increase bacteria and fungi content, exacerbating this risk.

Most climate scientists agree that North America will witness lower overall levels of precipitation with a concurrent increase in the intensity of precipitation events, especially at lower latitudes. The West is expected to undergo the most extreme change, while the northeastern U.S. may only experience more rainfall without periods of drought. Winter snowpack, too, will decrease. In turn, peak spring runoff will occur earlier and more rapidly than in the past. Communities and ecosystems dependant on snowmelt-fed rivers will likely experience water shortages during dry summer months. Glacial melt is expected to continue, and many small glaciers will disappear entirely. Scientists warn that communities already under water stress will likely face more severe shortages in the future. Such shortages could slow economic development on tribal lands in arid and semi-arid regions.

The impacts of intense precipitation events, including tropical storms and hurricanes, may stress water management infrastructure, like dams and levees. The IPCC warns that high volumes of water can overburden infrastructure, raise the potential for flooding, and "create new design challenges and costs for storm water management." Flooding can carry contaminants into bodies of water, like pesticides, sewage, salt, and other chemicals. Heavy precipitation and flooding will also accelerate shore erosion, further threatening water quality.

Groundwater recharge rates may also be affected by climate change, which will have the most serious consequences for tribes in arid and semi-arid regions of the country. Scientists admit that such impacts are poorly understood and further studies are necessary to predict changes in aquifer levels as the climate shifts. Scientists do know that aquifer recharge is influenced by a variety of factors, including the characteristics of overlying rocks and soils, duration of rainfall events, and rainfall season. In regions where rainfall occurs during the winter months, aquifer recharge is expected to increase, as less water is lost to evaporation. Conversely, summer rainfall typically undergoes higher rates of evaporation, and thus less water is available to the aquifers. Aquifer recharge is also affected by changes in rainfall duration. Studies suggest that even a moderate decrease in rainfall could have a substantial affect on aquifer levels. Streams and lakes also provide water to groundwater sources; thus, altered stream flow or water levels will reduce aquifer levels. In coastal areas, sea level rise and saltwater encroachment could seriously decrease freshwater quality as ocean water seeps into groundwater sources. Aquifers recharged by distant water sources and characterized by an impermeable rock overlay (known as confined aquifers) are less impacted by short-term changes in surface waters, and are thus less susceptible to the overall effects of climate change.

For many tribes, these impacts spell an uncertain future. This uncertainty is no more obvious than for the Tribes of the Pacific Northwest fighting for the restoration of salmon habitat, a species inextricable from their lives and cultures. Seven species of salmon must compete with the demands of hydropower, navigation, flood control, irrigation, and municipal uses for enough water to reach inland estuaries to reproduce. Reliant on snowmelt, many streams and rivers will undergo a shift in runoff patterns and higher water temperatures-both leading to an unclear future for the salmon. Already stressed by degraded freshwater streams and estuaries, some species of Pacific Northwest salmon may now be pushed even closer to the edge of extinction.

  1. LaDuke, Winona. 2002. Recovering the Sacred: The Power of Naming and Claiming. Cambridge, MA: South End Press. p. 33-34.

  2. Bates, B.C., Z.W. Kundzewicz, S. Wu and J.P. Palutikof (Eds.). 2008. "Climate Change and Water." Technical Paper of the Intergovernmental Panel on Climate Change, IPCC Secretariat, Geneva, 210 pp.

  3. Field, C.B., L.D. Mortsch,, M. Brklacich, D.L. Forbes, P. Kovacs, J.A. Patz, S.W. Running and M.J. Scott. 2007. "North America. Climate Change 2007: Impacts, Adaptation and Vulnerability." Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, {Eds.}. Cambridge University Press, Cambridge, UK, 617-652. p. 629.

  4. U.S. Environmental Protection Agency, Office of Water. 2008 March. "National Water Program Strategy: Response to Climate Change." Available online at [accessed 14 November 2008].

  5. Field et al., 633.

  6. U.S. Environmental Protection Agency, 10.