NEWS RELEASE

Water district begins streamflow experiments
Improvements in fish habitat sought

Were conditions better for fish in local creeks before there were reservoirs? How do water and air temperatures affect fish in local creeks? Do greater streamflows always mean better conditions for fish? If you walk along sections of Guadalupe, Alamitos, Los Gatos and Stevens creeks this summer, you may observe water level changes as the Santa Clara Valley Water District works to find answers to these and other fish-habitat questions.

From July 20 to October 15, the water district will be conducting an experimental streamflow study, part of a larger project to improve conditions for local fish, particularly steelhead and Chinook salmon. That project is the Fisheries and Aquatic Habitat Collaborative Effort (FAHCE), a multi-agency endeavor convened by the water district and the Department of Fish and Game to develop an interim fisheries and aquatic habitat management plan by December 2000. FAHCE participants include the water district, the Department of Fish and Game, the U.S. Fish and Wildlife Service, the National Marine Fisheries Service, the Natural Heritage Institute, the Guadalupe-Coyote Resource Conservation District and the city of San Jose.

Why is the study being conducted now?

Normally, the district releases some water from its reservoirs for recharge into the underground water basin; this groundwater is then pumped and treated for drinking and general use. The 1998 hydrologic year--one of the wettest on record--offers an excellent opportunity to utilize water usually reserved for recharge for study purposes, as groundwater and reservoir reserves are full. "This is the positive side to El Nino," said Stan Williams, water district general manager. "We're pleased to have sufficient water to be able to use some for this important project."

The Guadalupe and Alamitos creeks study will be completed in early August to avoid attracting fall-run, adult Chinook salmon upstream during the high-flow test. Once upstream, the fish could be put at risk during the low-flow test, as water recedes.

What areas are involved?

Guadalupe and Alamitos creeks (Guadalupe Watershed). Both a high-flow and a low-flow test will take place. In the high-flow test, scheduled from July 20 to August 8, water will be released from Guadalupe Reservoir into Guadalupe Creek, and from Almaden Reservoir into Alamitos Creek, at a rate of 10 cubic feet per second. During the low-flow test, scheduled from August 8-22, water released to the creeks will equal the same amount/rate of water that flows into the reservoir. If downstream test areas become too dry, additional water will be released to avoid harm to fish.

Los Gatos Creek (Guadalupe Watershed) and Stevens Creek (Permanente Watershed). A low-flow test will be conducted from July 15 to October 15, in which water released from the Lexington/Vasona Reservoir system to Los Gatos Creek, and from Stevens Creek Reservoir to Stevens Creek, will be released at a rate comparable to reservoir inflow. Additional water will be released if necessary to avoid stranding juvenile steelhead in areas downstream of the reservoirs.

What are the study objectives?

Among numerous study objectives are:

· Document summer water temperatures within various stream segments in relation to the two experimental streamflow conditions, the temperature of water upstream of the reservoirs, and the air temperature;

· Map habitat within Guadalupe Creek; measure changes in conditions in relation to summer flow;

· Evaluate summer water temperatures with respect to juvenile steelhead summer rearing conditions;

· Evaluate existing fish passage barriers under different flow conditions; and

· Monitor attraction of adult upstream migrant Chinook salmon into the lower Guadalupe River during the summer release program.

Does the study consider historical streamflow data?

The study is attempting to mimic a range of "natural" summer streamflows, a difficult task in an urban environment. To accomplish this, FAHCE is using historical data from the U.S. Geologic Service consisting of pre-dam stream gauge information. "With these tests, we're trying to mimic wet-year, pre-reservoir conditions to the best of our ability," said Melanie Tucker, district executive project manager on FAHCE. "We have to remember, however, that many changes have occurred within the creeks in the last 60 to 70 years that cannot be reversed."

Habitat mapping: assessing streamflow, temperature influence

A key part of the study is habitat mapping. On Guadalupe creek, fisheries biologists will "map," or assess, six miles of habitat to determine the effects of high and low flows. "In studying the relationship of streamflow to habitat, one question is: Is the habitat suitable for steelhead/rainbow trout?" said David Salsbery, a district fisheries biologist. "If not, what types of fish does the habitat favor?" Biologists will be looking at the area from Almaden Expressway to the base of Guadalupe Reservoir to determine numerous factors, including: fish cover (rocks, vegetation), both instream and on the banks; length and width of habitat areas, such as pools; type of creek bottom; potential for steelhead spawning gravel areas; evidence of fish passage barriers; and quality for different steelhead life phases.

Working collaboratively toward a successful outcome

In addition to providing information critical to aquatic habitat preservation, the experimental streamflow study offers a unique opportunity for FAHCE representatives to work together towards a common goal. Water district staff will be joined by staff from the Department of Fish and Game, the U.S. Fish and Wildlife Service and the Natural Heritage Institute on several aspects of the project. "I'm extremely pleased that our collaborative effort will generate new knowledge about the relationship between streamflow and habitat," said Mark Wolfe, staff attorney with the Natural Heritage Institute. "I'm confident that the study will create positive benefits for the local environment."

If you'd like more information on the experimental flow study or on FAHCE, please call Melanie Tucker at (408) 265-2607, extension 2035, or Scott Akin at (408) 265-2607, extension 2060.