Photo of Lake Powell before and after 2002 drought.
Credit: John Dohrenwend
Monsoon thunderstorms breed intense, short-lived rains that can generate flash floods, transforming some roads into ragging torrents. Winter precipitation also occasionally overfills rivers and arroyos. Climate change may accentuate both winter and summer floods.
Groundwater accounts for nearly half of the water used for city and agricultural needs and also supports vital streamflows and wildlife habitat. Overuse of groundwater has forced managers to implement more sustainable strategies, but climate changes and population growth are placing new stresses on supplies.
Snowpack in the West is changing, largely the result of increasing temperatures. Rain is replacing snow, and water content in snowpack is declining. These changes are causing streamflows to peak earlier in the year. They may also elevate fire risk, expand the early summer dry period, and present new challenges for water storage.
Current observations suggest that climate change is altering streamflows in ways that negatively impact water supply for southwestern populations and wildlife. These changes may worsen as the climate warms, accentuating the natural variability inherent in river flows.