The increase in demand for water by agriculture, domestic, municipal,industrial, and recreational users has jeopardized the existence of manyspecies of fish and wildlife. Fish and wildlife depend on water for theirsurvival. People also depend on water for survival. Water removal, or waterdiversion, from public waterways sometimes removes more than just water. Alllife stages of fish that depend on water for their survival are also vulnerableto these water diversions. The need for fish screens on water diversions isbecoming more prevalent to prevent losses to the fishery resource, otherwise,many may end up in agricultural fields, settling ponds, power plants, or whoknows where.
Since several fish species, such as the winter-run chinook salmon, the Deltasmelt, the Sacramento split-tail (currently being petitioned), have been listedunder the Federal Endangered Species Act (ESA), or the California EndangeredSpecies Act (CESA), state law provides the authority for the installation offish screens. This authority is described in several sections of theCalifornia Fish and Game Code (Appendix A).
Similar requirements for screening to protect anadromous fish are in effect inother states including Oregon, Washington, Alaska, Idaho, and Montana.
Fish screens are designed to keep fish from being taken out of their normalenvironment by water diversions. Presently, their are two types of fishscreens. The "positive barrier" fish screen, which physically prevents fishfrom passing through the barrier, and the "behavioral barrier" fish screen,which attempts to keep fish out of the diversion by causing the fish to swimaway from the site.
Presently, "positive barriers" are the only fish screens that meet Departmentof Fish and Game (DFG) fish screen criteria (Appendix B). A variety of fishscreens are being used which include flat plate (Fig. 1), rotary drum screen(Fig. 2), perforated pipe (Fig. 3), and fixed cylinder screen (Fig. 4).Commonly used materials include perforated plate, slotted plate, woven wiremesh, and welded wedge wire (Fig. 5), made of a non-corrosive type materialsuch as stainless steel.
Click here for Figure 1.
Click here for Figure 2.
Click here for Figure 3.
Click here for Figure 4.
Click here for Figure 5.
"Behavioral barriers" fish screens are devices that attempt to create astimulus in the water that the fish tries to avoid. Examples include louvers,sound, electricity, lights, and air bubbles. None of these devices currentlymeet DFG's fish screen criteria.
It is the policy of the Department of Fish and Game to provide all necessarymeasures to minimize fish losses caused by entrainment or other hazardsassociated with water diversion. These measures may include the installationof fish screens, the cessation of diversion during critical periods of fishmigration, or the relocation or consolidation of diversions.
In certain situations, screening a water diversion may be as simple aspurchasing an off-the-shelf type screen, or as complicated as a full-scale,civil engineering project. Screening a water diversion is based on theuniqueness of each and every individual diversion.
Cost estimates vary depending on the size of the diversion and the complexityof the fish screen system. There are three general categories for estimatingfish screening costs:
For diversions constructed or modified after 1972, screening costs are to bepaid entirely by the diverter (Fish and Game Code, Section 6100). The costs ofscreening older diversions, constructed prior to 1972 and greater than 250cubic feet per second, are to be shared equally by the diverter and DFG (Fishand Game Code 6020). For older diversions, less than 250 cubic feet persecond, the costs may be paid by DFG (Fish and Game Code 6020).
Diversions affecting threatened or endangered species are treated differentlysince they involve the "take" of a listed species. These are treated on acase-by-case basis in consultation with the National Marine Fisheries Service,the U.S. Fish and Wildlife Service, and DFG.
The Central Valley Project Improvement Act (CVPIA), provides funding for up tohalf the cost of installing fish screens on water diversions in the CentralValley. The balance of the cost must be paid from non-federal funds. TheCVPIA also provides funding for impacts from Central Valley Project operations,in which some diversions might qualify.
To assist diverters in their design and planning efforts, the CaliforniaDepartment of Fish and Game has developed a "General Fish Screen Criteria"(Appendix B). These criteria present a set of guidelines that will help assurediverters approval from the Department.
This fish screening policy is structured to comply with existing fish screeningstatutes, the National Environmental Policy Act (NEPA), the CaliforniaEnvironmental Quality Act (CEQA), the Federal Endangered Species Act (ESA), theCalifornia Endangered Species Act (CESA), and court decisions in place at thetime of its adoption. All diversions shall be dealt with uniformly on astatewide basis.
When reviewing projects, the Department of Fish and Game shall make everyeffort to require the installation of fish screens on all unscreened diversionswhere other measures cannot reasonably prevent entrainment of fish. Further,the Department of Fish and Game shall make every effort to require themodernization of fish screens which do not meet the present fish screeningcriteria. This effort shall include the Streambed Alteration Agreement process(Section 1600 et seq. of the Fish and Game Code). Variations from the fishscreening policy shall be treated on a case-by-case basis.
Under the provisions of this federal act, the Department of Fish and Game shallrequire installation of fish screens on all unscreened diversions where fishare present. Further, the Department of Fish and Game shall make every effortto require the improvement of existing fish screens which do not meet thepresent fish screening criteria. For example, opportunities are provided bythe U.S. Army Corps of Engineers' permit process under the federal Rivers andHarbors Act and Clean Water Act.
The Department of Fish and Game shall require the installation of fish screensunder Section 6100 et seq. of the Fish and Game Code on any new diversion, oron the intake of any existing diversion that is either enlarged, relocated, orat which the season of use is changed, in salmon and steelhead (anadromous)waters of the State.
In addition, all diversions covered by this section which are located withinthe essential habitat of a state (CESA) listed species or the critical habitatof a federally (ESA) listed species shall be deemed to require screening.
Variances from these requirements shall be supported by a report, prepared bythe diverter, which includes data from onsite monitoring and a review ofhistorical entrainment and diversion data. The scope of the report and thesampling effort shall be approved by the Department of Fish and Game prior tothe initiation of work.
Both the approval of the scope of the report and the approval of an exceptionto this policy shall include the concurrence of the appropriate RegionalManager, the Chief of the Inland Fisheries Division, and the Chief of theEnvironmental Services Division.
The final exception notice shall be issued by the Deputy Director, Fisheries.
The Department of Fish and Game shall investigate, and where necessary, orderfish screens installed on all diversions with a capacity greater than 250 cfs,which affect fishery resources. Diversions in anadromous waters of the Stateshall be deemed to require screening unless onsite sampling demonstratesotherwise.
In addition, all diversions covered by this section which are located withinthe essential habitat of a state (CESA) listed species or the critical habitatof federally (ESA) listed species shall be deemed to require screening.
Variance from these requirements shall be supported by a report, prepared bythe diverter, which includes data from onsite monitoring and a review ofhistorical entrainment and diversion data. The scope of the report and thesampling effort shall be approved by the Department of Fish and Game prior tothe initiation of work.
Both the approval of the scope of the report and the approval of an exceptionto this policy shall include the concurrence of the appropriate RegionalManager, the Chief of the Inland Fisheries Division, and the Chief of theEnvironmental Services Division. The final exception notice shall be issued bythe Deputy Director, Fisheries.
The Department of Fish and Game may consider for screening any diversion withthe capacity of 250 cfs or less. Activities in this category should beassigned a lower priority than those covered by provisions of Section 5980until all of the Department of Fish and Game obligations for both its owndiversions, and for those diversions greater than 250 cfs, have beenfulfilled.
In addition, all diversions covered by this section which are located withinthe essential habitat of a state (CESA) listed species or the critical habitatof a federally (ESA) listed species shall be deemed to require screening.
Variances from these requirements shall be supported by a report, prepared bythe diverter, which includes data from onsite monitoring and a review ofhistorical entrainment and diversion data. The scope of the report and thesampling effort shall be approved by the Department of Fish and Game prior toinitiation of work.
Both the approval of the scope of the report and the approval of an exceptionto this policy shall include the concurrence of the appropriate RegionalManager, the Chief of the Inland Fisheries Division, and the Chief of theEnvironmental Services Division. The final exception notice shall be issued bythe Deputy Director, Fisheries.
1. Structure Placement
A. Streams and Rivers (flowing water)
The screen face shall be parallel to the flow and adjacent bankline with thescreen at or streamward of the annual low flow water's edge. The banklineshall be warped to match the screen structure, eliminating eddies in front,upstream, and downstream of the screen.
Intake structures shall not be constructed shoreward from the normal banklinein locations where parallel velocities pas the screen cannot be provided.
B. Lakes and Reservoirs (non-flowing waters)
Diversion structures and/or intakes shall be constructed offshore to minimizefish contact with the diversion. Velocities from any direction toward thescreen shall not exceed the approach velocities in No. 2 below.
2. Approach Velocity (local velocity component perpendicular to screenface)
A. The approach velocity shall be uniformly distributed across the face of thescreen.
B. For continually cleaned screens, the approach velocity shall not exceed0.33 feet/second. Fish screens shall be considered continually cleaned when acleaning cycle can be completed in five-minute intervals or less.
C. Screens which are not continually cleaned shall be designed with an approachvelocity of 0.0825 feet/second and shall be cleaned before the approachvelocity becomes 0.33 feet/second.
D. Fish screens will be cleaned as frequently as necessary to prevent impedanceof flow and violation of the approach velocity criteria.
E. The actual wetted screen area, affected by structural components, requiredat the minimum stream stage is calculated by dividing the maximum diverted flowby the allowable approach velocity.
3. Sweeping Velocity (velocity component parallel to screen face)
In streams, the sweeping velocity shall be at least the allowable approachvelocity. Screen faces shall be placed flush with any adjacent screen baypiers or walls to allow an unimpeded flow of water parallel to the screenface.
4. Screen Openings
A. The screen surface shall have a minimum open area of 1/2 square foot persquare foot of screen (50% or greater porosity).
B. Round openings in screening shall not exceed 5/32 inch.
C. Square openings in screening shall not exceed 5/32 inch measureddiagonally.
D. Slotted openings shall not exceed 3/32 inch in width.
5. Screen Construction
A. Screens may be constructed of any rigid material that is perforated, woven,or slotted that provides water passage while physically excluding fish.
B. Stainless steel or other corrosion resistant material is recommended for thescreening fabric to reduce clogging due to corrosion.
C. Plans shall be provided to the Department which show that all the applicablescreening criteria have been met before written approval can be granted by theRegional Manager.
D. All fish screens constructed after 1982 shall be designed and constructed tosatisfy the current criteria. Owners of existing screens approved by theDepartment prior to 1982 shall be required to upgrade their facilities tosatisfy current criteria as 1) the screen components deteriorate and requirereplacement (i.e., change mesh size or mesh orientation when the mesh on panelsor rotary drum sections needs replacing), or 2) during modification orreconstruction of the intake facilities (i.e., change screen alignment orincrease screen area to satisfy approach velocity requirement) or, 3) when theowner proposes to increase the rate of diversion which would result inviolation of the approach velocity criteria without the construction ofadditional screen area.
E. Supplemental criteria may be issued by the Department to accommodate newfish screening technology or to address species specific or site specificcircumstances.
F. Written variances to these screening criteria may be granted with theapproval of the Regional Manager and concurrence with the EnvironmentalServices Division and Inland Fisheries Division Chiefs.
Flosi, G. and F.L. Reynolds. 1991. California Salmonid Stream HabitatRestoration Manual. California Department of Fish and Game.
Odenweller, D.B. 1994. Screens Protect Fish from Diversions. OutdoorCalifornia. Vol. 55, No. 5.
Prepared by: Spencer Kawasaki, Fishery Biologist, and Paul F. Raquel,Associate Fishery Biologist California Department of Fish and Game.
The National Fish and Wildlife Foundation, Hofmann Foundation and WildlifeConservation Board provided the generous funding for this issue of ValleyHabitats.
Valley Habitats is produced by Ducks Unlimited's Western Regional Office.Items contained herein may be reproduced with permission. Copyright, DucksUnlimited, Inc., 1995.
Valley Habitats is published as part of Ducks Unlimited's VALLEY CARE Programto provide information to private land managers who wish to integrate wildlifemanagement into their existing operations.
For more information regarding conservation related land management practicescontact: Ducks Unlimited, Western Regional Office 9823 Old Winery Place, #16Sacramento, CA 95827 TELEPHONE: (916) 363-8257 FAX: (916) 363-9849