Possible Water Resource Impacts in North America

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In general, the Intergovernmental Panel on Climate Change (IPCC, 2007) concludes that climate change will strain many of North America’s water resources, increasing the competition for water. A warmer climate will affect the seasonable availability of water by increasing evaporation and reducing snowpacks. The Columbia River and other heavily used water systems of western North America are expected to be particularly vulnerable. Groundwater-based systems in the Southwest are also likely to be stressed by climate change. Heavier precipitation will very likely increase waterborne diseases and affect water quality, and higher variability of precipitation will make water management more difficult.

Potential water resource impacts for North America are listed below by region. (IPCC, 2001 and IPCC, 2007)

Alaska

The state is lightly settled and abundant in water resources. Potential ecological, hydropower, and flood impacts include:

Increased spring flood risks
Glacial retreat/disappearance in south, advance in north; impacts on flows, stream ecology
Increased stress on salmon, other fish species
Flooding of coastal wetlands
Changes in estuary salinity/ecology
Increased frequency of intense precipitation events - increased risk of flash floods

Northwest

The Pacific Northwest has a large and rapidly growing population, particularly along the coast; with lightly populated rural areas. Water abundance decreases from north to south. The region relies heavily on irrigation for agriculture and on hydropower for electricity production. These uses, along with endangered species issues, are increasing competition for water in the region.

Rise in snow line in winter-spring, possible increases in snowfall, earlier snowmelt, more frequent rain on snow, changes in seasonal streamflow, possible reductions in summer streamflow, reduced summer soil moisture
Possible increases in annual runoff in Cascades
Changes in lake and stream ecology - warmwater species benefiting; damage to coldwater species (e.g. trout and salmon)

West and Southwest

The West and Southwest have experienced rapid population growth but depend heavily on limited groundwater and surface water supplies. In the southern border region, there are also water quality concerns. Some rivers and canyons in the region are also subject to periodic flash flooding.

Likely reduction in snowpacks and seasonal shifts in runoff patterns
Possible declines in groundwater recharge - reduced water supplies
Increased water temperatures - further stress on aquatic species
Increased frequency of intense precipitation events - increased risk of flash floods
Possible summer salinity increase in San Francisco Bay and Sacramento/San Joaquin Delta

Midwest

America's agricultural heartland is mostly rainfed, with some areas relying heavily on irrigation.

Annual streamflow decreasing/increasing; possible large declines in summer streamflow
Increased likelihood of severe droughts
Possible increasing aridity in semi-arid zones
Increases or decreases in irrigation demand and water availability - uncertain impacts on farm-sector income, groundwater levels, streamflows, and water quality

Great Lakes

The states surrounding the Great Lakes are heavily populated. Variations in lake levels and flows would affect hydropower, shipping, tourism and recreation, municipalities, shoreline structures, and human health.

Possible lake-level declines
Reduced hydropower production; reduced channel depths for shipping
Decreases in lake ice extent - some years without ice cover
Changes in phytoplankton/zooplankton biomass, northward migration of fish species, possible loss of coldwater species in certain areas
Declines in water quality

Northeast

The Northeast states have a large, mostly urban population. The region has generally adequate water supplies, with a large number of small dams, but limited total reserve capacity. Floodplains in the region are heavily populated.

Decreased snow cover amount and duration
Possible large reduction in streamflow
Accelerated coastal erosion, saline intrusion into coastal aquifers
Changes in magnitude, timing of ice freeze-up/break-up, with impacts on spring flooding
Possible elimination of bog ecosystems
Shifts in fish species distributions, migration patterns

Southeast, Gulf, and Mid-Atlantic

These regions have experienced rapidly increasing population - especially in coastal areas. The region has some water quality and non-point source pollution problems, as well as stress on aquatic ecosystems.

Heavily populated coastal floodplains at risk to flooding from extreme precipitation events, hurricanes
Possible lower base flows, larger peakflows, longer droughts
Possible increases or decreases in runoff/river discharge, increased flow variability
Major expansion of northern Gulf of Mexico hypoxic zone possible - other impacts on coastal systems related to changes in precipitation/non-point source pollutant loading
Changes in estuary systems and wetlands extent, biotic processes, species distribution

References

IPCC, 2007: Climate Change 2007: Impacts, Adaptation, and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change [Parry, Martin L., Canziani, Osvaldo F., Palutikof, Jean P., van der Linden, Paul J., and Hanson, Clair E. (eds.)]. Cambridge University Press, Cambridge, United Kingdom, 1000 pp.
IPCC, 2001: Climate Change 2001: Impacts, Adaptation, and Vulnerability . Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change [McCarthy, James J., Canziani, Osvaldo F., Leary, Neil A., Dokken, David J., and White, Kasey S. (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1032pp.

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Possible Water Resource Impacts in North America

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