3.2.3 Adverse Effects on Essential Fish Habitat
The intent of EFH guidance is to enable regional development activities to avoid or minimize adverse effects by forward, informed planning. This is the essence of sustainable development. A measure of its success is the maintenance of properly functioning salmonid habitat conditions. A corollary is the restoration of diminished salmonid resources and their roles in regional economies, culture, and ecosystems through restoration of degraded or lost habitat. The highest benefit to cost ratios of mitigations are achieved with timely informed plans which detail likely resources to be affected and actions which can avoid or minimize adverse effects to properly functioning habitat.
Having established the elements of salmonid habitat and objectives for its proper functioning in Table 3-3, the likely adverse effects of common development-associated activities are outlined in Table 3-2. Table 3-2 shows the various types of actions that are likely to have either a direct, indirect, cumulative, or synergistic effect on salmon EFH. The check marks in Table 3-2 indicate the habitat elements, or pathways, that are likely to be altered by the specified action. In other words, this matrix cross-references habitat elements, or pathways, (e.g., channel condition and dynamics) with indicators for these components (e.g., flood plain connectivity or channel width/depth) with sixteen types of adverse actions likely to affect salmon EFH, and examples of activities which generate these actions (e.g., forestry, grazing, spoil disposal, etc.). Table 3-1 ("Examples of habitat alteration effects on Pacific Salmon") summarizes how habitat alterations listed in Table 3-2 can harm salmon. For example, if increased temperature results from grazing activities, altered adult migration patterns, accelerated egg development, parasite susceptibility in juveniles can be expected. The value of describing the effect on the behavior, physiology, and development of the fish, is in devising targeted, effective, useful mitigation.
Conservation and Enhancement Measures
Background - Section 600.815 (a) (7) of the interim final EFH regulations state that fishery management plans (FMPs) must describe options to avoid, minimize, or compensate for the potential adverse effects and promote the conservation and enhancement of EFH. Terrestrial activities may have adverse impacts on EFH. Activities that may result in significant adverse effects on EFH should be avoided where less environmentally harmful alternatives are available. Environmentally sound engineering and management practices should be employed for all actions which may adversely affect EFH. Disposal or spillage of any material (dredge material, sludge, industrial waste, or other potentially harmful materials) which would destroy or degrade EFH should be avoided. If avoidance or minimization is not possible, or will not adequately protect EFH, compensation for damage to, and/or mitigation to conserve and enhance EFH should be recommended. FMPs may recommend proactive measures to conserve or enhance EFH. When developing proactive measures, Councils may develop a priority ranking of the recommendations to assist Federal and state agencies undertaking such measures.
Measures - Established policies and procedures of the Council and NMFS provide the framework for conserving and enhancing essential fish habitat. Components of this framework include adverse impact avoidance and minimization, compensatory mitigation, and enhancement. New and expanded responsibilities contained in the Magnuson-Stevens Fishery Conservation and Management Act will be met through appropriate application of these policies and principles. In assessing the potential impacts of proposed projects, the Council and NMFS are guided by the following general considerations:
The range of potential conservation measures necessary to avoid, minimize and compensate for adverse effects needs to be suggested to project proponents and sponsors so they can plan their actions in a manner that maintains properly functioning salmonid habitat. Both land use and remedial actions need to promote achievement of the habitat objectives for properly functioning conditions listed in Table 3-3. The logic of the approach which employs the Tables described above is illustrated in Figure 3-1. A number of technically informed approaches and methods have been developed for mitigating the adverse effects of different project actions. Experience indicates the specific selection of conservation and enhancement measures, and, mitigation strategies and tactics must respond to the particular kinds of actions and site characteristics. More specific guidelines tailored to specific agency activities and category of threat can be developed during, or prior to, the consultation process in conjunction with federal and state agencies, tribes, and interested parties.
FIGURE 3-1. Example of logic train in the use of salmonid EFH conservation recommendations.
Spring grazing near riparian area – Table 3-2, column 2
Soil compaction, creation of impervious surfaces and soil erosion leading to increased sediment delivered to stream (Table 3-3, column 1), degradation to in-stream water quality (increased sediment/turbidity of > 12% fines) and degradation of stream habitat elements (reduced substrate gravel, cobble and > 20 % embeddedness), ) – Table 3-3, columns 1,2,3
Reduced egg and alevin survival, primary/secondary productivity, interference with feeding, behavioral avoidance and breakdown of social organization, pool filling (i.e., reduced spawning and incubation success) – Table 3-1, column 3
RESPONSE TO ACHIEVE PROPERLY FUNCTIONING HABITAT CONDITIONS
Conservation measures which reduce sediment loads to < 12% fines, lower turbidity, and reduce embeddedness to < 20% – Table 3-3, columns 1,2,3
Nonfishing Activities That May Affect Salmon EFH: Potential Effects and Conservation Measures
Section 600.815 (a) (5) of the draft interim EFH regulations pertain to identifying nonfishing related activities that may adversely affect EFH. The section states that fishery management plans (FMPs) must identify activities that have the potential to adversely affect, directly or cumulatively, EFH quantity or quality, or both. Broad categories of activities which can adversely affect salmonid EFH include, but are not limited to:
Artificial Propagation of Fish and Shellfish
Beaver Removal & Habitat Alteration
Dredging & Dredged Spoil Disposal
Habitat Restoration Projects
Irrigation Water Withdrawal, Storage and Management
Nonnative Species, Introduction/Spread of
Offshore Oil and Gas Exploration, Drilling & Transportation Activities
Road Building and Maintenance
Sand and Gravel Mining
Wetland & Floodplain Alteration
Woody Debris/Structure Removal From Rivers and Estuaries
Any of the above activities may eliminate, diminish, or disrupt the functions of salmonid EFH. These activities can potentially affect EFH through associated factors, including increased suspended solids, sedimentation, nutrient loading, toxic chemicals, high bacterial concentrations and physical disruption of habitat. While toxic contaminants, nutrient loading, oxygen depletion and eutrophocation, increased suspended solids, bacterial contamination, and hypoxia may not directly affect loss of physical habitat, all these factors are elements of water quality and hence EFH quality. The goals specified under Section 101(a)(2) of the federal Clean Water Act inherently address the EFH needs of aquatic organisms ----- "water quality which provides for the protection and propagation of fish, shellfish, and wildlife ...". Section 303(d) of the federal Clean Water Act used in conjunction with standards, provides the tools to manage water quality, and hence EFH quality. Under the mandate promulgated by the 1996 amendment to the Magnuson-Stevens Act, only Federal agencies are required to consult with Fishery Management Councils and NMFS regarding activities that may adversely affect EFH. Under the Clean Water Act, states, territories and tribes obtain approval of water quality standards from the EPA. Under EFH, EPA will have the opportunity to consult with NMFS prior to standards approval.
Each of these nonfishing related activities may directly or indirectly or cumulatively, temporarily or permanently, threaten the physical, chemical and biological properties of the habitat utilized by salmonid species and/or their prey. The direct results of these threats is that salmonid EFH may be eliminated, diminished or disrupted. The list includes common activities with known or potential impacts to salmonid EFH. The list is not prioritized, nor is it all-inclusive. Each of the above activities is described below along with conservation measures and management alternatives.
The conservation measures and management alternatives are not designed to be site-specific, but rather to be indicative of the spectrum of possible considerations for the conservation and enhancement of salmon EFH, and which might be applied to specific activities. This menu of suggested conservation options is based on the best scientific information available at this time. NMFS and the Council are not bound by these measures in the future. All of these measures are not necessarily applicable to each future project or activity that may adversely impact salmon EFH. More specific or different measures based on the best and most current scientific information may be developed during or prior to the consultation process and communicated to the appropriate agencies.
During agricultural activities, land surface alterations may be extensive because vegetation alteration and disturbances to the soil can occur several times per year. In addition, agriculture can take place on historical flood plains of river systems, where it has a direct effect on stream channels and riparian functions. Furthermore, irrigated agriculture frequently requires diversion of surface waters, which may decrease streamflow, lower water tables, and increase water quality problems, e.g., higher water temperatures. (See section on irrigation water withdrawal below).
Replacing natural grasslands, forests, and wetlands with annual crops may leave areas unvegetated during part of the year and can change the function of plants and soil microbes in the tilled areas. Repeated tillage, fertilization, pesticide application and harvest can permanently alter soil character, resulting in reduced infiltration and increased surface runoff. These changes alter seasonal streamflow patterns by increasing high flows, lowering water tables, and reducing summer base flows in streams.
Agricultural land use can contribute substantial quantities of sediments to streams (Spence et al. 1996). Deposited sediment can reduce juvenile salmonid rearing and adult habitat by the filling of pools (Waters 1995), filling the interstitial spaces of bottom gravel, and by reducing the overall surface area available for invertebrates (i.e., prey) and fish production. Suspended sediment can decrease primary productivity, deplete invertebrate populations (by increasing downstream drifting) as well as interfere with feeding behavior (Waters 1995).
Agriculture can negatively affect stream temperatures by the removal of riparian forests and shrubs which reduces shading and increases wind speeds. In addition, bare soils may retain greater heat energy than vegetated soils, thus increasing conductive transfer of heat to water that infiltrates the soil or flows overland into streams (Spence et al. 1996). In areas of irrigated agriculture, temperature increases during the summer may be exacerbated by heated return flows (Dauble 1994). Warm water temperatures can harm fish directly through various mechanisms (see Table III-5) including oxygen depletion and increased stress and decreased survival.
Agricultural crops may require substantial inputs of water, fertilizer, and pesticides to thrive. Nutrients (e.g., phosphates, nitrates), insecticides, and herbicides are typically elevated in streams draining agricultural areas, reducing water quality and affecting fish and other aquatic organisms (Omernik 1977; Waldichuk 1993). These changes in water quality can cause ecosystem alterations that affect many biological components of aquatic systems including vegetation within streams, as well as the composition, abundance, and distribution of macroinvertebrates and fishes. These changes can affect the spawning, survival, food supply, and the health of salmon (Stober et al. 1979, NPPC 1986). Though currently used pesticides are not as persistent as previously used chlorinated hydrocarbons, most are still toxic to aquatic life. However, where biocides are applied at recommended concentrations and rates, and where there is a sufficient riparian buffer, the toxic effects to aquatic life may be minimal (Spence et al. 1996).
Chemicals such as some pesticides, phosphorus, and ammonium are transported with sediment in the adsorbed state. Changes in the aquatic environment, such as a lower concentration of chemicals in the overlying waters or the development of anaerobic conditions in the bottom sediments, can cause these chemicals to be released from the sediment. Phosphorus transported by the sediment may not be immediately available for aquatic plant growth but does serve as a long-term contributor to eutrophication, a form of pollution caused by over-enrichment (EPA 1993).
Agricultural practices may also include stream channelization, large woody debris removal, installation of rip-rap and revetments along stream banks, and removal of riparian vegetation (Spence et al. 1996). Natural channels in easily eroded soils tend to be braided and meander, creating considerable channel complexity as well as accumulations of fallen trees, which help create large, deep, relatively permanent pools, and meander cutoffs. These factors are important to salmon habitat.
Confined animal facilities (e.g., feed lots) may also adversely affect salmon habitat if the concentrated animal waste, process water (e.g., from that of a milking operation), and the feed, bedding, litter, and soil which comes intermixed with the fecal and urinary wastes is not properly contained and managed. If not properly treated, storm water run-off water and process water can carry nutrients, sediment, organic solids, salts, as well as bacteria, viruses, and other microorganisms into salmon habitat (EPA 1993). These pollutants can cause oxygen depletion, turbidity, eutrophication and other affects on the water quality and habitat quality for salmon.
Conservation Measures -- Agriculture
The restoration of natural vegetative communities and functions should be a goal of riparian restoration and management projects on agricultural lands. Once riparian areas have recovered, agricultural activities should strive to protect riparian vegetation and water quality through conservation practices and management plans. Conservation practices and management plans should include the measurement of water quality and the attainment of applicable federal and state water quality standards.
The 1996 reauthorization of the Farm Bill (the "Federal Agricultural Improvement and Reform Act") included several conservation programs that provide potential benefit to EFH. They are the Environmental Quality Incentives Program, the Wetlands Reserve Program, and the Conservation Reserve and Enhancement Programs . These programs provide farmers assistance for idling erosion-prone land, preserving wetlands, and undertaking land management conservation practices. Land owners are encouraged to contact their local agricultural extension agents to find out further information about these programs.
Below are the types of measures that can be undertaken by the action agency on a site-specific basis to conserve salmon habitat to conserve, enhance, or restore EFH adjacent to agricultural lands that have the potential to be adversely affected by agricultural activities. Not all of these suggested measures are necessarily applicable to any one project or activity that may adversely affect salmon EFH. More specific or different measures based on the best and most current scientific information may be developed prior to, or during the EFH consultation process, and communicated to the appropriate agency. The options listed below represent a short menu of general types of conservation actions that can contribute to the restoration and maintenance of properly functioning salmon habitat. The following suggested measures are adapted from EPA (1993).
2. Artificial Propagation of Fish and Shellfish:
Public and private hatcheries, acclimation sites, and net pens producing Pacific salmon (coho, chinook, chum, pink, kokanee, sockeye salmon, steelhead, and cutthroat), trout (Atlantic salmon, brown, rainbow, and golden), char (eastern brook, and lake trout), sturgeon, and several species of warmwater fish operate in and adjacent to salmon EFH in fresh and sea water (NRC 1995-1996; WDFW 1998). Additionally, captive breeding of threatened or endangered stocks of sockeye and spring chinook salmon occurs in Idaho, Oregon, and Washington, and of endangered winter chinook salmon in California (Flagg et al. 1995). Shellfish culture in salmon EFH consists primarily of oyster culture, although clams, mussels and abalone are grown as well.
Currently, there are several hundred public facilities (federal, tribal and state-operated) producing Pacific salmonids for release into fresh and sea water salmon EFH (NRC 1995-1996). In addition, hundreds of private hatcheries in salmon EFH produce various salmon and trout species, as well as catfish and tilapia, for commercial sale.
The artificial propagation of native and nonnative fish and shellfish species in or adjacent to salmon EFH has the potential to adversely affect that habitat by altering water quality, modifying physical habitat, and creating impediments to passage. Artificial propagation may also adversely impact EFH by predation of native fish by introduced hatchery fish, competition between hatchery and native fish for food and habitat, exchange of diseases between hatchery and wild populations, the release of chemicals in natural habitat, and the establishment of nonnative populations of salmonids and nonsalmonids. Many of these potential adverse affects have been summarized by Fresh (1997). These concerns have lead to revision of many hatchery policies to eliminate or reduce impacts on wild fish (USFWS 1984; ODFW 1995; WDF 1991; NWIFC/WDFW 1998).
Various methods of shellfish culture and harvest also have the potential to adversely impact salmon EFH, such as dredging in eel grass beds, off-bottom culture, raft and line culture, and the use of chemicals to control burrowing organisms detrimental to oyster culture. To control burrowing shrimp, for example, Washington state has used the pesticide carbaryl since 1963. About 800 acres are treated with carbaryl annually in Grays Harbor and Willapa Bay, with a given oyster bed sprayed about every 6 years. Nontarget effects of carbaryl use include short-term decreases in the density of prey species for salmon as well as the mortality of nontarget benthic invertebrates and nonsalmonid fish (Pozarycki et al. 1997, Simenstad and Fresh 1995). Concerns over such potential adverse impacts have led to the development of regulations for the use of chemicals in natural habitat and policies for offseting losses to eelgrass beds (WDF 1992). On a positive note, some methods of mollusc culture have been shown to create beneficial habitat for salmonids (Johnson 1998, pers com).
Treated wood structures in salmon EFH (e.g., creosote, chromated copper arsenate) used for docks, pilings, raceway separators, fish ladders etc., and other structures can release toxic heavy metals and persistent aromatic hydrocarbons into the aquatic environment (see estuarine section).
Conservation Measures -- Artificial Propagation of Fish and Shellfish:
Below are the types of measures that can be undertaken by the action agency on a site-specific basis to conserve salmon EFH in areas that have the potential to be adversely affected by the artificial propagation of fish and shellfish. Not all of these suggested measures are necessarily applicable to any one project or activity that may adversely affect salmon EFH. More specific or different measures based on the best and most current scientific information may be developed prior to, or during the EFH consultation process, and communicated to the appropriate agency. The options listed below represent a short menu of general types of conservation actions that can contribute to the restoration and maintenance of properly functioning salmon habitat.
3. Bank Stabilization:
The extent and magnitude of stream bank erosion has been greatly increased by human activities that remove riparian vegetation, increase sediment inputs, relocate and straighten channels, or otherwise cause channel down-cutting. Vessel traffic and the resulting wakes can also create bank scour.
Attempts to deal with the bank erosion resulting from these activities often involve the use of adding adamantine-like materials. In smaller streams, particularly those that seasonally become dry or nearly dry, bulldozing of streambed gravel against the banks has been a common practice to retard erosion. In larger streams (and rivers) the dumping or placement of rock (rip-rap), broken concrete, and mixtures of materials (i.e., rocks, dirt, branches) along the banks is a common practice (OWRRI 1995). Additionally bulkheads and concrete walls have been used on lake and estuarine shores. Concerns for salmon that are associated with shoreline stabilization include loss of shallow edgewater rearing habitat, changes to benthic vegetation, impacts to eelgrass and other vegetation important for herring spawning, loss of shoreline riparian vegetation and reduction in leaf fall, loss of wetland vegetation, alteration of groundwater flows, loss of large woody debris, changes in food resources, and loss of migratory corridors (PSWQAT 1997, Thom and Shreffler 1994).
The installation of riprap or other streambank stabilization devices can reduce or eliminate recruitment of crucial spawning gravel by eliminating lateral erosion, as has occurred in the Sacramento River (Council 1988). By confining the stream or shoreline with hard materials, the development of side channels, functioning riparian and floodplain areas, and off-channel sloughs are precluded (WDFW 1997).
Another concern is the use of chemicals (e.g., creosote, chromated copper arsenate, copper zinc arsenate) on bulkheads or other wood materials used for bank stabilization. These chemicals can introduce toxic substances into the water, injure or kill prey organisms and salmon directly, or concentrate in the food chain (WMOA 1995). Their use is generally prohibited. In freshwater, copper concentrations are acutely toxic to yearly coho salmon at 60-74 micrograms per liter in freshwater, but affect smoltification, migration, and survival at 5 to 30 micrograms/liter (Lorz and McPherson 1976).
Conservation Measures -- Bank Stabilization:
Below are the types of measures that can be undertaken by the action agency on a site-specific basis to conserve salmon EFH in areas that have the potential to be affected by bank stabilization activities. Not all of these suggested measures are necessarily applicable to any one project or activity that may adversely affect salmon EFH. More specific or different measures based on the best and most current scientific information may be developed prior to, or during the EFH consultation process, and communicated to the appropriate agency. The options listed below represent a short menu of general types of conservation actions that can contribute to the restoration and maintenance of properly functioning salmon habitat. The following suggested measures are adapted from Streif (1996) and Meyer (1997 personal communication).
4. Beaver Removal & Habitat Alteration:
Beavers have long co-existed with salmon, and were once much more abundant in the region. Beavers have multiple effects on water bodies and riparian ecosystems, altering hydrology, channel morphology, biochemical pathways, and the productivity of a stream system (Olson and Hubert 1994). Their presence can have both positive and negative influences on salmon habitat, but overall, beavers are considered to impart a significant positive benefit to both water quality and salmon, particularly juvenile coho. The removal of beavers has fundamentally altered natural aquatic ecosystem processes.
Beaver dams can cause channel obstruction, the redirection of channel flow, and the flooding of streambanks and side channels. By ponding water, beaver dams create enhanced rearing and over-wintering habitat that offer juvenile salmonids protection from both freezing and high winter flows (NRC 1996).
Bank dens and channels can increase erosion potential, but ponds can lessen bank erosion by reducing the channel gradient during high flows as well as by settling out and trapping sediment. Beaver ponds also provide a sink for nutrients from tributary streams, and create conditions that promote anaerobic decomposition and de-nitrification. Anaerobic decomposition and de-nitrification results in nutrient enrichment and increased primary and secondary production downstream from the pond and increased nutrient retention time and enhanced invertebrate prey production (NRC 1996).
Although beaver dams can occasionally block the upstream migration by adult and juvenile salmonids, studies on trout movement indicate that fish not only can pass over dams during high water, but also can travel upstream and downstream through most beaver dams during all seasons (Olson and Hubert 1994).
Beaver ponds increase the surface to volume ratio of the impounded area, which can result in increased summer temperatures (Spence et al. 1996). However, beaver ponds also cause increased storage of water in the banks and flood plains. This increases the water table, enhances summer flows, adds cold water during summer, and causes more even stream flow throughout the year. During winter, beaver ponds in cold environments prevent anchor ice from forming and prevent super-cooling of the water. By storing spring and summer storm run-off, beaver ponds help to reduce downstream flooding and the damage from rapid increases in stream flows (Olson and Hubert 1994).
Beavers also help shape riparian habitat. Beaver ponds increase the surface area of water several hundred times and thereby enhance the overall riparian habitat development. They also enhance vegetation growth by increasing the amount of groundwater for use by riparian plants. They also create and expand wetland areas (Olson and Hubert 1994).
Conservation Measures -- Beaver Removal & Habitat Alteration:
Below are the types of measures that can be undertaken by the action agency on a site-specific basis to conserve salmon EFH in areas that have the potential to be affected by beaver removal/habitat alteration. Not all of these suggested measures are necessarily applicable to any one project or activity that may adversely affect salmon EFH. More specific or different measures based on the best and most current scientific information may be developed prior to, or during the EFH consultation process, and communicated to the appropriate agency. The options listed below represent a short menu of general types of conservation actions that can contribute to the restoration and maintenance of properly functioning salmon habitat. The following suggested measures are adapted from Olson and Hubert (1994) and Buckman (1998 personal communication).
Activities associated with urbanization (e.g., building construction, utility installation, road and bridge building, storm water discharge) can significantly alter the land surface, soil, vegetation, and hydrology and adversely impact salmon EFH through habitat loss or modification. Construction in and adjacent to waterways can involve dredging and/or filling activities, bank stabilization (see other sections), removal of shoreline vegetation, waterway crossings for pipelines and conduits, removal of riparian vegetation, channel re-alignment, and the construction of docks and piers. These alterations can destroy salmon habitat directly or indirectly by interrupting sediment supply that creates spawning and rearing habitat for prey species (e.g., sand lance, surf smelt, herring), by increasing turbidity levels and diminishing light penetration to eelgrass and other vegetation, by altering hydrology and flow characteristics, by raising water temperature, and by re-suspending pollutants (Phillips 1984).
Projects in or along waterways can be of sufficient scope to cause significant long-term or permanent adverse affects on aquatic habitat. However, most waterway projects and other projects associated with growth, urbanization and construction within the region are small-scale projects that individually cause minor losses or temporary disruptions and often receive minimal or no environmental review. The significance of small-scale projects lies in the cumulative and synergistic effects resulting from a large number of these activities occurring in a single watershed.
Construction activities can also have detrimental effects on salmon habitat through the run-off of large quantities of sediment, as well as the nutrients, heavy metals, and pesticides. Run-off of petroleum products and oils from roads and parking lots and sediment, nutrients, and chemicals from yards as well as discharges from municipal sewage treatment plants and industrial facilities are also associated with urbanization (EPA 1993). Urbanized areas also alter the rate and intensity of run-off into streams and waterways. Urban runoff can cause immunosuppression by organic contaminants (Arkoosh et al. 1998).
Similarly, effects on run-off rates can be much greater than in any other type of land use because of the amount of impervious surfaces associated with urbanization. Buildings, rooftops, sidewalks, parking lots, roads, gutters, storm drains, and drainage ditches, in combination, quickly divert rainwater and snow melt to receiving streams, resulting in an increased volume of runoff from each storm, increased peak discharges, decreased discharge time for runoff to reach the stream, and increased frequency and severity of flooding (EPA 1993). Flooding reduces refuge space for fish, especially where accompanied by loss of instream structure, off-channel areas, and habitat complexity. Flooding can also scour eggs and young from the gravel. Increases in streamflow disturbance frequencies and peak flows also compromises the ability of aquatic insects and fish life to recover (May et al. 1997)
The amount of impervious surfaces also can influence stream temperatures. Summer time air and ground temperatures in impervious areas can be 10 to 12 degrees warmer than in agricultural and forested areas (Metro 1997). In addition, the trees that could be providing shade to offset the effects of solar radiation are often missing in urban areas. The alteration in quantity and timing of surface run-off also accelerates bank erosion and the scouring of the streambed, as well as the downstream transport of wood. This results in simplified stream channels and greater instability, all factors harmful to salmon (Spence et al. 1996). The lack of infiltration also results in lower stream flows during the summer by reducing the interception, storage, and release of ground water into streams. This affects habitat availability and salmonid production, particularly for those species that have extended freshwater rearing requirements (e.g., coho). Generally, it has been found that instream functions and value begin to seriously deteriorate when the levels of impervious surfaces exceed 10% of a sub-basin (WDFW 1997).
Conservation Measures -- Construction/Urbanization:
Existing urban and industrial sites, highways, and other permanent structures will prevent restoration of riparian zones in heavily developed areas. In these areas, generally along major river systems, buffers will not be continuous and riparian areas will remain fragmented. Habitat improvement plans will need to identify locations of healthy riparian zones and opportunities for re-establishing corridors of riparian vegetation between them, so that nodes of good quality habitat can be maintained and managed in ways that protect salmon habitat (Sedell et al. 1997).
Below are the types of measures that can be undertaken by the action agency on a site-specific basis to conserve salmon EFH in areas that have the potential to be affected by construction and urbanization activities. Not all of these suggested measures are necessarily applicable to any one project or activity that may adversely affect salmon EFH. More specific or different measures based on the best and most current scientific information may be developed prior to, or during the EFH consultation process, and communicated to the appropriate agency. The EPA (1993) publication "Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters" extensively describes best management practices for control of runoff from developing areas, construction sites, roads, highways and bridges affecting salmon EFH. In addition to the above guidelines, the options listed below represent a short menu of general types of conservation actions that can contribute to the restoration and maintenance of properly functioning salmon habitat. The following suggested measures are adapted from Metro (1997), ODFW (1989), and EPA (1993).
6. Dam Construction/Operation:
Dams built to provide power, water storage and flood control have significantly contributed to the decline of salmonids in the region. Potential adverse effects include impaired fish passage (including blockages, diversions), alterations to water temperature, water quality, water quantity, and flow patterns, the interruption of nutrient, large woody debris, and sediment transport which affect river, wetland, riparian, and estuarine systems, increased competition with nonnative species, and increased predation and disease.
The construction of dams without fish passage facilities has blocked salmon from thousands of miles of mainstream and tributary stream habitat in the Columbia River basin, Sacramento-San Joaquin system, and other streams throughout the western United States (Council 1988). While technology exists for providing fish passage around dams, it has not always been successful, and migration delays and increased mortality may still occur at some projects under certain water temperatures and flows. Poorly designed fishways, or fishways that are improperly operated and maintained can inhibit movement of adults upstream, causing migration delays and unsuccessful spawning. Additionally, the fallback of adult salmon through spillways and turbines contribute to migration delays and increased mortality. Increased vulnerability to predation is also an impact of dams and fish passage structures.
Dams are also a barrier to downstream passage of juveniles. Reservoirs and water diversions (see section on irrigation water withdrawal) reduce water velocities and change current patterns, resulting in increased migration times (Raymond 1979), exposure to less favorable environmental conditions, and increased exposure to predation. At dams, injury and mortality to juveniles occurs as a result of passage through turbines, sluiceways, juvenile bypass systems, and adult fish ladders. Encounters with turbine blades, rough surfaces, or solid objects can cause death or injury. Changes in pressure within turbines or over spillways also can result in death or injury. Juveniles, frequently stunned and disoriented as they are expelled at the base of the dam, are particularly vulnerable to predation (Council 1988). Dams also result in changes in concentrations of dissolved oxygen and nitrogen. Above the dams, slow-moving water has lower dissolved oxygen levels than faster, turbulent waters, a factor that may stress fish (Spence et al. 1996). Below hydroelectric facilities, nitrogen supersaturation may also negatively affect migrating as well as incubating or rearing salmon, by causing gas-bubble disease. Gas bubble disease increases in years of high flow and high spill.
Hydrologic effects of dams include water-level fluctuations, altered seasonal and daily flow regimes, reduced water velocities and reduced discharge volume. These altered flow regimes can affect the migratory behavior of juvenile salmonids. Water-level fluctuations associated with hydro power peak operations may reduce habitat availability, inhibit the establishment of aquatic macrophytes that provide cover for fish, and in some cases strand fish or allow desiccation of spawning redds. Drawdowns reduce available habitat area and concentrate organisms, potentially increasing predation and transmission of disease (Spence et al. 1996). Drawdown in the fall for flood control produces high flows during spawning which allow fish to spawn in areas which may not have water during the winter and spring, resulting in loss of the redds.
Impoundments may also change the thermal regimes of streams causing effects on salmon. Temperatures may increase in shallow reservoirs to the detriment of salmon. Below deeper reservoirs that thermally stratify, summer temperatures may be reduced, but fall temperatures tend to increase as heated water stored during the summer is released. These changes in water temperatures affect development and smoltification of salmonids, decreasing survival. Water temperatures also can affect adult migration (Spence et al. 1996). Water temperature changes also influence the success of predators and competitors and the virulence of disease organisms. Additionally, in winter, drawdown of impoundments may facilitate freezing, which diminishes light penetration and photosynthesis, potentially causing fish kills through anoxia (Spence et al. 1996).
In watersheds where temperatures and flows may limit salmon production, dams can sometimes be operated to have positive benefits such as lowering water temperatures during the summer, providing stable flows and temperatures which may benefit both salmonid spawning and rearing and invertebrate production.
Dam impoundments alter natural sediment and large woody debris transport processes. Water storage at dams may prevent the high flows that are needed to scour fine sediments from spawning substrate and move wood and other materials downstream. Behind dams, suspended sediments settle to the bottoms of reservoirs, depriving downstream reaches of needed sediment inputs, leading to the loss of high quality spawning gravels (as substrate becomes dominated by cobble unsuitable for spawning) as well as to changes in channel morphology (Spence et al. 1996).
Dams can also affect the health and extent of downstream estuaries. Reservoir storage can alter both the seasonal pattern and the characteristics of extremes of freshwater entering the estuary. Flow damping has also resulted in a reduction in average sediment supply to the estuary. Except for times of major floods, residence time of water in estuaries has increased with decreasing salinity. Estuaries have also been converted into a less-energetic microdetritus-based ecosystem with higher organic sedimentation rates. Detritus and nutrient residence has increased; vertical mixing has decreased, likely increasing primary productivity in the water column, and enhancing conditions for detritivorous, epibenthic and pelagic copepods (Sherwood et al. 1990). The effects of these changes have not been evaluated as yet, though there are concerns about possible affects on fish and other resources which depend on a highly co-evolved and biologically diverse estuarine environment (NRC 1996).
Conservation Measures -- Dam Construction/Operation:
Below are the types of measures that can be undertaken by the action agency on a site-specific basis to conserve salmon EFH in areas that have the potential to be affected by dam construction and operation activities. Not all of these suggested measures are necessarily applicable to any one project or activity that may adversely affect salmon EFH. More specific or different measures based on the best and most current scientific information may be developed prior to, or during the EFH consultation process, and communicated to the appropriate agency. The options listed below represent a short menu of general types of conservation actions that can contribute to the restoration and maintenance of properly functioning salmon habitat. The following suggested measures are adapted from Spence et al. (1996), NMFS (1997a).