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Sierra Snowpack: Past Won’t Necessarily Predict the Future

March 2014

Providing a reliable water supply for all Californians, one of the state’s coequal goals for the Delta, is more than just maintaining a proper water transport system or the delegation of who gets what and how much. Dr. Martha Conklin, a hydrologist with UC Merced says it’s also about understanding the amount of water that may be available from year to year and where that water will be coming from, such as snowpack, headwaters, or aquifers.

“In recent years our precipitation patterns have been changing,” said Conklin. “We may receive less during the winter (resulting in snowpack) and a little more in the spring (resulting in more rain).”

This pattern change, often attributed to climate change, has created a new challenge for Dr. Conklin and her team of scientists who study the Sierra Nevada snowpack. She says using statistical patterns of water availability based on historical precipitation patterns in no longer considered reliable. Their goal now is to make more precise measurements of snowmelt because knowing how much actual runoff the State can expect in any given season can provide the information necessary to help water managers with their allocations of water resources.

Dr. Conklin offered her research during a Feb. 14 Brown Bag seminar hosted by the Council’s Delta Science Program, the Ecosystem Restoration Program and the Surface Water Ambient Monitoring Program. Part of her presentation included a Power Point that focused on the study of the Southern Sierra Critical Zone Observatory near Shaver Lake in Fresno County.

The observatory has been outfitted with a system of wireless sensors strategically clustered around watershed locations in that region. The sensors measure in real time both precipitation and the distribution of precipitation. The data allow the scientists to track, among other things, the rate of the snowmelt, the amount that runs off or percolates into the soil, what the soil water content is, and how the water moves from the soil into local streams.

“These information systems will be useful for better water resource decisions,” said Dr. Conklin. “We’ll provide the information to State officials allowing them to meet our changing snowpack patterns and adapt our water management system accordingly.”

Flux towers located near the observatory, as well as satellites in space, will also be tracking the fluctuation of the water exchange during evapotranspiration where water from the snowpack, the surrounding vegetation, and the soil moves into the air removing itself from the critical zone.

“If you can’t measure it, you can’t manage it,” said Garrett Liles, an environmental scientist in the Delta Stewardship Council’s Delta Science Program. Liles says Dr. Conklin’s work allows for a better understanding of how nature works, thus providing the best available science when determining a hydrological management plan for the State’s water system.

“It allows us to better quantify the relative value of the various resources in a given region,” said Liles. “The information will aid decision-makers in making better choices about the water supply.”

Dr. Conklin’s work is expanding to include the American River Hydrologic Observatory in the American River Basin. Automated wireless sensor networks will again provide real time information from headwater locations, but also stretch throughout the watershed offering data on water flows, fluxes, and storage. As the number of stations increase, the predictability of future water availability will become more accurate hopefully eliminating shortages when allocating water among competing interests.

Coequal goals

The Delta Stewardship Council was created in legislation to achieve the state mandated coequal goals for the Delta. "'Coequal goals' means the two goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem. The coequal goals shall be achieved in a manner that protects and enhances the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place." (CA Water Code §85054)