FOR IMMEDIATE RELEASE: August 2, 2005
CONTACT: Janet Byron, (510) 987-0668 and janet.byron@ucop.edu

Editors: High-resolution images of the Lassen and Willow Creek watersheds in Modoc County are available here.

July-September 2005 California Agriculture magazine

Studies show stream data helps to
restore cold-water fish habitat

Ten species of California salmon are currently listed as threatened or endangered, and the culprit is often increased stream temperatures linked to logging, agricultural discharges, irrigated pastures and other land uses. While regulators and watershed groups have collected reams of stream-temperature data, "in our experience the sheer volume of data collected can be overwhelming, and the data is often not analyzed," says Kenneth Tate, UC Davis rangeland watershed specialist.
Tate and his colleagues did case studies on two watersheds in Modoc County (in the northeasternmost corner of California) to illustrate how stream-temperature data can be collected from watersheds and irrigated pastures, graphically displayed, and analyzed in ways that are useful to land managers and regulators, yielding workable plans and contributing to the protection of cold-water fish habitat.
The three peer-reviewed studies are published in the July-September 2005 issue of the University of California‚s California Agriculture research journal, which is posted in full online at <http://californiaagriculture.ucop.edu> http://californiaagriculture.ucop.edu
"We used a statistical method often employed by epidemiologists. It is a good fit to the natural world, where events measured are not independent of each other, and where we cannot create a scientific 'control' for the purposes of comparison," Tate says. "This is the first study that I am aware of to bring this kind of analysis to bear on questions about the environment and stream management."
"We built a predictive model based on real, not theoretical data," Tate says. "Land managers can now analyze their stream data, prescribe a management method to improve stream health, and show that their interventions have improved water quality in a measurable, predictable way."
Cold-water habitat is critical for many salmonids and native fish. While extremely high temperatures (generally over 77°F) can kill fish outright, long-term exposure to sublethal but elevated temperatures can hamper their growth, reproduction and tolerance of pollutants and disease.
In the Central Valley, a state waiver allowing warm-water agricultural discharges into streams is likely to be replaced with regulations aimed at restoring cold-water fish habitat. Likewise, total maximum daily load (TMDL) plans, required under the federal Clean Water Act, are forcing California growers and ranchers to address temperature and other pollutants that impair water quality.
"Stream monitoring is critical to both identifying problems and developing solutions," Tate says. "With our studies, we show that good data is needed not only on stream temperature, but also on its interaction with variables such as riparian canopy cover, stream flow and air temperature."

The current issue of California Agriculture, including PDF versions of all peer-reviewed research articles, can be viewed in full online at: http://californiaagriculture.ucop.edu/0503JAS/toc.html

The July-September 2005 issue of California Agriculture also includes the following peer-reviewed research articles:

• Methyl bromide replacements for replanted orchards: A study of pre- and postplant soil treatments in a replanted peach-tree orchard found that soil solarization (with black plastic mulch) and organic-carbon amendments improved tree vigor as effectively as a chemical fumigant, while commercial microbial soil inoculants provided no measurable benefits.
• Weed mapping to reduce herbicide spraying: UC scientists demonstrated that weed maps developed at the time of the previous year's harvest can be used to guide variable-rate herbicide spraying during the next growing season; the map-driven spraying provided weed control similar to full-rate broadcast applications, yet reduced the amount of herbicide sprayed by 30% to 40%.
• Boron fertigation in vineyards: Boron, an essential plant nutrient, must be applied carefully in San Joaquin Valley vineyards, because the range between boron deficiency and toxicity is narrow. The authors showed that boron can be efficiently applied via drip irrigation systems ("fertigation"), but leaf blades should be monitored regularly to ensure that overfertilization does not occur.