Events & Media

Fellowship Enables PhD Student to Extend Bay-Delta Research

Bren PhD student Erin Bray was one of two doctoral students and five post-doctoral researchers to receive a 2011 Delta Science Fellowship from the Delta Science Program. The program is part of California Sea Grant, which supports science-based management, conservation, and enhancement of California's coastal and aquatic resources through research, extension, and education.

The Delta Science Program, formerly the CALFED Science Program, was established to develop scientific information and synthesis on issues critical to managing the Bay-Delta system. The first fellows were named in 2003. Since then, the pogram has paired graduate students and postdoctoral researchers with Bay-Delta agency scientists and senior research mentors. Fellows work on collaborative data analysis and research projects applicable to the California Bay-Delta system, defined broadly as the San Francisco Bay and the delta region where the Sacramento and San Joaquin rivers meet and flow into the bay.

Bray is studying the potential for restoring salmon habitats with flow releases in the Bay-Delta region.

"The Delta Science Fellowship is important to me because it allows me to study what I care about most — large rivers — in an interdisciplinary way at the intersection of stream hydrology and heat transfer,"Bray says. "And I get to do that with the goal of advancing our scientific understanding of the ecological stresses water temperature imposes at three different scales (local, meso, and macro) in a large river."

Water temperatures are driven by changes in water depth, flow velocity, and heat fluxes in the atmosphere and the river bed, with various river forms (meanders versus deep pools versus wide, shallow channels, for instance) responding differently to heating from radiation.  At smaller scales, the temperature of groundwater flowing into the river channel may be important for habitat. At larger scales, groundwater temperatures may be secondary to the local heat fluxes. Knowing how these elements work in combination can shed light on how thermal habitat in large rivers may be affected by dam operations.

Bray explains that a large-scale flow experiment began at Friant Dam in October 2009 to test the effects that alterations of streamflow have on abiotic elements, which are important non-living chemical and physical factors related to the overall health of the environment in which they are found.

Specifically, she says, "Few studies consider interactions of hydrology and heat in large rivers, and how those interactions change depending on the spatial scale.  Heating in rivers is affected by solar radiation, air temperature, wind, streamside vegetation, evaporation, and upstream temperatures — and can change with changes in flow.  The Friant Dam project provides timed releases of water and an opportunity to better understand the important physical processes governing stream temperatures in larger rivers below dams."

"The ongoing flow experiment in the San Joaquin River creates an irreplicable field experiment that is potentially both strong enough and long enough to elicit measureable abiotic responses," she says.

The Delta Science Fellowship provides a year of tuition and a stipend, which equates to paid support for research on priority issues for the San Francisco Bay-Delta, with a possibility of extension for a second year.

Read a summary of Bray's project, which examines the effect that releasing water from Friant Dam might have on physical properties that create salmon habitat. Her PhD advisor is Bren professor of river hydrology and geomorphology Tom Dunne, who has spent many years in a scientific advisory role to the Bay-Delta restoration project.