As the climate warms, sources of the water so critical to life everywhere on Earth are drying up.
By the end of this century, communities dependent on fresh water from mountain-fed rivers could see significantly less water, according to a new climate model recently released by University of California researchers.
For example, people who get fresh water from the Kings River could see a 26 percent decrease in river flow.
Why? Think of the environment to which humans are accustomed as a huge jigsaw puzzle.
Sign Up and Save
Get six months of free digital access to The Sacramento Bee
You can look at any one piece to see how it fills out the picture of climate change, but you cannot ignore the surrounding pieces and the chain reactions set off by the warming climate’s influences on the original piece.
UC Merced professor Roger Bales and UC Irvine professor Michael L. Goulden have been looking into how climate change affects certain plant functions in upper elevations of the Sierra Nevada.
The results of their work, “Mountain Runoff Vulnerability to Increased Evapotranspiration with Vegetation Expansion,” were published recently in the Proceedings of the National Academy of Sciences of the United States of America.
The research is another way UC Merced seeks to add to the base of knowledge about climate change and the development of solutions to the challenges it presents.
Bales and Goulden examined the evapotranspiration of plants in the mountains. Evapotranspiration is water evaporation from the land plus the loss of water through plant leaves during transpiration. The more evapotranspiration, the less water remaining in drainage basins, such as meadows, where it runs off to rivers.
As the climate warms, higher elevations that are usually snow-dominated see milder temperatures, with plants that normally go dormant during the winter snows remaining active longer.
Higher-elevation plants usually evapotranspire less than plants with year-round growing seasons because they rest for part of the year.
But if they are not resting, they are using up more of the water that people and animals downstream rely on.
“The dramatic changes that Goulden and Bales found in forest water use and runoff could not have been made without having made the necessary measurements to make the forest-water-climate linkage,” UC Merced engineering professor Martha Conklin said. “Expanding their approach throughout the state’s source-water area would provide a scientific basis for managing these areas.”
Using water-vapor emission rates and remote-sensing data, Bales and Goulden determined relationships between elevation, climate and evapotranspiration.
The data shows that freshwater mountain runoff is highly sensitive to changes in temperature and vegetation growth. With a 4.1 degree Celsius increase in the Sierra Nevada, which is projected by climate models for 2100, vegetation growth would result in a 28 percent increase in evapotranspiration.
The researchers’ work shows the relationships between evapotranspiration, temperature and vegetation growth were similar across a broader area of the Sierra Nevada, suggesting that the impact of climate change on evapotranspiration and fresh water availability could be widespread.
Student researchers needed on Global Food Initiative
UC Merced is recruiting three students to be part of the UC Global Food Initiative, which aims to address how to sustainably and nutritiously feed a world population expected to reach 8 billion by 2025.
The campus has three $2,500 food fellowships open to undergraduate and graduate students, and applications are being accepted through Sept. 30 on Chancellor Dorothy Leland’s website. The recipients will be announced in mid-October. The proposals will be evaluated on how they can advance the UC Global Food Initiative.
Leland touted the opportunities during a meeting last week with UC President Janet Napolitano and area food and agriculture leaders.
“We are excited about this opportunity to recognize and support student research, service learning projects, internships and humanitarian efforts connected to the Global Food Initiative,” Leland said. “We have graduate students researching plant ecology, others who are engineering creative solutions to agricultural challenges, and those students who are volunteering their time to develop sustainable practices and address food scarcity.”