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Draft Fish Screens White Paper

Category: Habitat - Habitat Conservation Plans

Date Published: March 2008

Number of Pages: 205

Author(s): Herrera Environmental Consultants, Inc., Kozmo Ken Bates


In 2006 and 2007, WDFW contracted with Anchor Environmental, Herrera Environmental Consultants, Jones & Stokes Associates, and R2 Resource Consultants to develop a series of “white papers” documenting the state of the science on a range of topics related to HPAs. The original white papers were peer-reviewed by a panel of experts outside of WDFW.

In developing the white papers, the consultants were working under specific time, scope, and cost constraints established by WDFW. These constraints were designed to further WDFW's specific goal of building a scientific foundation for a Habitat Conservation Plan for hydraulic projects that receive HPAs.

The white papers provide a solid scientific foundation upon which to build conservation measures for avoiding potential impacts, but they are not an exhaustive review of every potential impact of hydraulic projects. Rather, they reflect WDFW’s goal of establishing a solid scientific foundation for the HCP with limited time and financial resources.

Despite these constraints, WDFW is confident that a large proportion of the current scientific literature has been incorporated into the white papers. As WDFW continues to develop the Habitat Conservation Plan, we will also continue to assess new science, fill data gaps, and listen to the advice of scientists and hydraulic project construction specialists.


The Revised Code of Washington (RCW) directs the Washington Department of Fish and Wildlife (WDFW) to “preserve, protect, perpetuate, and manage” the fish and wildlife species of the state as its paramount responsibility (RCW 77.04.012). Under RCW 77.55, any construction or work that uses, diverts, obstructs, or changes the natural bed or flow of state waters requires a Hydraulic Project Approval (HPA) issued by WDFW. The purpose of the HPA program is to ensure that hydraulic projects are completed in a manner that prevents damage to public fish and shellfish resources and their habitats. To ensure that the HPA program complies with the Endangered Species Act (ESA), WDFW is developing a programmatic multispecies Habitat Conservation Plan (HCP) to obtain an Incidental Take Permit (ITP) from the U.S. Fish and Wildlife Service (USFWS) and the National Oceanic and Atmospheric Administration (NOAA) Fisheries Service (also known as NOAA Fisheries), in accordance with Section 10 of the ESA. For WDFW, the objective is to ensure that activities conducted under an HCP avoid and/or minimize the incidental take of those aquatic species potentially considered for coverage under the HCP (referred to in this white paper as “HCP species”) resulting from activities conducted under an HPA.

The HCP will address the impacts, potential for take, and mitigation measures for effects on HCP species from hydraulic projects that require HPAs. WDFW’s intent is to build the scientific foundation for the effort to prepare an HCP for hydraulic projects that receive HPAs. To accomplish this, WDFW is compiling the best available scientific information related to the impacts, potential for incidental “take” of species that may be covered in the HCP (as defined in the ESA; see Section 9 of this white paper for a definition of “take”), and possible management directives and mitigation measures to avoid and/or minimize potential take to the maximum extent practicable. Because the HPA authority covers all waters of the state, this white paper considers hydraulic project impacts in both freshwater and marine environments.

This white paper is one of a suite of white papers prepared to establish the scientific basis for the HCP and to assist WDFW decision-making on what specific HPA activities should be covered by the HCP. This particular white paper compiles and synthesizes existing scientific information on fish screen structures and operations which, for the purpose of this effort, include in-channel and off-channel screen designs.

The objectives of this white paper are to:

  • Compile and synthesize the best available scientific information related to the potential human impacts on HCP species, their habitats, and associated ecological processes resulting from the construction, operation, and maintenance of fish screens.
  • Use this scientific information to estimate the circumstances, mechanisms, and risks of incidental take potentially or likely to result from the construction, operation, and maintenance of fish screens.
  • Identify appropriate and practicable measures, including policy directives, conservation measures, and best management practices (BMPs), to avoid, minimize, or mitigate the risk of incidental take of HCP species.

For the purpose of this white paper, the effects of fish screens are considered limited to those effects imposed by the screen only. The effects of flow control structures and/or channel modifications associated with the diversion or intake system requiring the screen are not considered in this analysis. The effects of these actions or activities have been addressed in companion white papers. The effects of water withdrawals are also not considered. The Washington State Department of Ecology (Ecology) has lead responsibility for water rights and withdrawal determinations, and is therefore responsible for identifying related effects. On this basis, the literature review conducted for this white paper identified five impact mechanisms that could potentially affect HCP species. These mechanisms of impact are both direct and indirect and can have temporary, short-term effects or permanent, long-term effects. The impact mechanisms analyzed in this white paper are:

  • Construction and maintenance activities
  • Operations
  • Water quality modifications
  • Hydraulic and geomorphic modifications
  • Ecosystem fragmentation.

This white paper presents an overview of what is known about the potential impact mechanisms in relation to the 52 HCP species. Based on a separate analysis conducted using exposure-response matrices for each species, the risks of direct and indirect impacts on these species and their habitats are identified and described. This white paper also reviews data gaps and estimates the risk of take. In addition, habitat protection, conservation, mitigation, and management strategies that could avoid, minimize, or mitigate the identified potential impacts are also provided. The key goals of this white paper are to:

  • Identify the distribution of the 52 HCP species (i.e., whether they use fresh water, marine water, or both) and their habitat requirements.
  • Identify the risk of take associated with each of the identified impact mechanisms based on the distribution information.
  • Identify cumulative impacts.
  • Identify data gaps.
  • Identify habitat protection, conservation, and mitigation strategies for each species.