Water resources are important to both society and ecosystems. We depend on a reliable, clean supply of drinking water to sustain our health. We also need water for agriculture, energy production, navigation, recreation, and manufacturing. Many of these uses put pressure on water resources, stresses that are likely to be exacerbated by climate change.
Related Links
EPA:
Climate Change and Water
Climate Change and Water: Planning and Management
Learn About Water
Climate Ready Water Utilities
Other:
National Climate Assessment: Water
USGCRP: Climate Change and Agriculture, Land Resources, Water Resources, and Biodiversity
IPCC: Fifth Assessment Report EXIT
IPCC: Technical Paper on Climate Change and Water EXIT
NAS: America's Climate Choices EXIT
USGS: Water Resources of the United States
USGS: The Water Cycle
Energy.gov (Information about renewable energy production, including hydroelectricity, by state)
In many areas, climate change is likely to increase water demand while shrinking water supplies. This shifting balance would challenge water managers to simultaneously meet the needs of growing communities, sensitive ecosystems, farmers, ranchers, energy producers, and manufacturers.
In some areas, water shortages will be less of a problem than increases in runoff, flooding, or sea level rise. These effects can reduce the quality of water and can damage the infrastructure that we use to transport and deliver water.
Top of Page
Water Cycle and Water Demand
The water cycle (shown in the following figure) is a delicate balance of precipitation, evaporation, and all of the steps in between. Warmer temperatures increase the rate of evaporation of water into the atmosphere, in effect increasing the atmosphere's capacity to "hold" water.[1] Increased evaporation may dry out some areas and fall as excess precipitation on other areas.
Changes in the amount of rain falling during storms provide evidence that the water cycle is already changing. Over the past 50 years, the amount of rain falling during very heavy precipitation events has increased for most of the United States. Â This trend has been greatest in the Northeast, Midwest, and upper Great Plains, where the amount of rain falling during the most intense 1% of storms has increased more than 30%.[1] Â Warming winter temperatures cause more precipitation to fall as rain rather than snow. Furthermore, rising temperatures cause snow to begin melting earlier in the year. This alters the timing of streamflow in rivers that have their sources in mountainous areas.[1]
As temperatures rise, people and animals need more water to maintain their health and thrive. Many important economic activities, like producing energy at power plants, raising livestock, and growing food crops, also require water. The amount of water available for these activities may be reduced as Earth warms and if competition for water resources increases.[1]
