Water in the West
This week, we explain how exceptional drought and our warming climate put western water supplies at risk.
There are several different types of drought, characterized by a deficit of precipitation (meteorological), soil moisture (agricultural), or runoff (hydrological).
The U.S. has experienced significant meteorological, agricultural, and hydrological droughts since 2011. Drought can lead to short- and long-term impacts on water supplies, agriculture, ecosystems, wildfire risk, public health and more.
Warming air increases the potential evaporation from the land and transpiration from plants. This process increases the water available for precipitation in some areas but contributes to drying in other areas—such as the southwestern U.S.
The recent southwestern megadrought (2000-2021) is the most severe of the past 1,200 years, and over 40% of the drought’s severity is attributed to human-caused climate change. Risks of severe and prolonged megadroughts in the Southwest are projected to intensify over this century with continued warming.
As the climate continues to warm, the western U.S. also faces increasing risks of hydrological drought due to declining snowpack and earlier spring melt.
Overall, human-caused warming is projected to result in dryer soils and less runoff in the long term. According to the latest IPCC reports, warming since the 1950s has also increased the frequency of concurrent heatwaves and droughts on a global scale.
Updated: July 2023
These resources explore the science, trends, and local impacts of droughtSearch our resource library