Climate change projections for California indicate a future characterized by warmer temperatures, reduced snowfall, greater rainfall, and drier summer conditions. While the future of annual precipitation is uncertain, there is a widespread projection of drier, more drought-prone conditions interspersed with occasional intense storms.
At the February meeting of the Delta Stewardship Council, Interim Delta Lead Scientist Lisamarie Windham-Myers presented an essay that argues that rather than focusing on the uncertain changes in annual precipitation, water managers should prioritize preserving water in the headwaters for more extended periods.
The graphics on the slide, provided by the lead author Mike Dettinger with the USGS, show the historical precipitation record up to 2020 and projected precipitation to 2100. While the total amount is not projected to change much, what is changing is the size of the storms; we’re losing the middle-sized storms, but we’re going to have more of the small, unimportant storms and the large atmospheric rivers, said Dr. Windham-Myers.
“As you can see from the second two graphics, all of these ten global climate models are predicting that there’s going to be about a 30% increase in atmospheric rivers and a 30% decrease of the non-atmospheric rivers,” said Dr. Windham-Myers. “That’s where we’re headed. And so rather than focus on what we are going to do with less water, the idea in this essay was, what can we do to hold on to this water we’re getting? How can we move forward and leverage what we have currently?”
The paper points out that over the last 100 years, peak runoff has already shifted to earlier in the year. “What we’re losing is that slow water, the water that moves slowly through the landscape,” she said. “We’ve tended to channelize water for use, and then it leaves the system earlier. But if you’re thinking about future base flow conditions and trying to provide some colder water, these are ways to promote that upstream and have slower water, colder water coming out in a more even distribution rather than peaks that are hard to catch and utilize.”
So, rather than focusing on the uncertain changes in annual precipitation, it is recommended to prioritize preserving water in the headwaters for more extended periods. The essay suggests three potential techniques to do this: forest management, beaver reintroduction, and holding water in upstream dams.
“We’re already going to be doing a lot of forest management because of wildfires, so there are some opportunities there in terms of forest thinning and soil improvements such as increasing retention of organic matter in that soil that can help retain water,” Dr. Windham-Myers aid. “Another thing we can do is enhance meadow restoration and beaver reintroductions … Right now, Shasta is getting dumped out to prevent flooding. However, with Forecast-Informed Reservoir Operations, there are a lot of little upstream dams above these large reservoirs that could be held for longer to enhance infiltration and so on. So instead of thinking about them just for hydropower production, we can think about the other things as well.”
Climate change is a stressor that will influence many climate, hydrology, and ecosystem variables of the Delta and the Delta’s watershed, primarily through enhanced extreme events in this century. “The paper is really more of a thought process,” said Dr. Windham-Myers. “It’s important for us to start thinking about this as an integrated system and not as just independent pieces of an overall environmental management plan … this paper was trying to point out things that are already happening on the landscape that we could optimize for enhanced retention of waters that are upstream in non channelized situations. So that is really the point of this paper.”
READ IT HERE: Keeping Water in Climate-Changed Headwaters Longer
DELTA SCIENCE ACTIVITIES:
Review of the Long-Term Operations of the Central Valley Project and the State Water Project: The National Academies of Sciences, Engineering, and Medicine has convened a committee to conduct a biennial review of the monitoring, modeling, and other relevant scientific activities that support the long-term operations of the Central Valley Project (CVP) and the State Water Project (SWP). The committee held its first public meeting on January 30 – February 1. The review focuses specifically on Old and Middle River (OMR) flow management, Shasta cold water pool management, summer-fall Delta Smelt habitat, and recommendations on improving modeling and monitoring strategies and decision-support tools. The committee subsequently met on February 28 – March 1, 2024. The committee is expected to complete its report in 2025.
March 26-27, 2024: Salinity Management Workshop: Registration is now open for the Salinity Management Workshop on March 26 and 27. This two-day virtual workshop is being hosted by the Delta Science Program to discuss tools and strategies, identify knowledge gaps, and build shared goals for adaptively managing ocean saltwater intrusion in the Sacramento-San Joaquin Delta. Day One of the workshop will focus on tradeoffs involved with salinity management and who is impacted. Day Two will focus on modeling results that compare scenarios with different management actions and amounts of sea level rise. Here is the agenda. Register to attend Day 1 on March 26. Register to attend Day 2 on March 27.
