Snake River Reservoirs Research Articles

Hydropower peaking and stalled salmon migration are linked by altered reservoir hydraulics: A multidisciplinary synthesis and hypothesis

AbstractAdding variable renewable energy (solar, wind) in electricity portfolios will increase need for fast grid responses through hydropower peaking. Over 60 years of daily hydropeaking by four dams on the lower Snake River, United States of America provide an example of long‐term environmental impacts. Downstream‐migrating Chinook salmon (Oncorhynchus tshawytscha) subyearlings that normally transit the dammed river in summer slowed their migration into autumn with about one‐third of those delayed overwintering in the reservoirs. Specific cause for stalled migration is controversial, with options including evolution of a new migratory strain and action of environment on individual migrants. Analysis of archived dam data shows evidence of reservoir seiches (standing waves of waterbody oscillations) caused by within‐day hydropower peaking during the October–February period of stalled migration. Analyses of limnological literature identified typical water movements in seiches and analyses of biological literature identified typical effects on fish kinematics (shape, motion) of changing flows in a fish's immediate proximity. Process‐focused inference predicts anomalous fish‐migration behavior in seiche hydraulics, which matches fish‐tracking data obtained by others in Lower Monumental Reservoir. Fish tracks include upstream swimming (‘downstream’ in reverse seiche flows) and periods of disoriented movements typical of responses to repeatedly changing flows. This multi‐disciplinary, process‐focused synthesis yields a testable hypothesis that seiche‐flow hydraulics in the lower Snake River reservoirs from hydropower peaking contribute to known out‐migration delay and overwintering of late‐migrating fall Chinook salmon subyearlings. As hydropower peaking causes seiches in downstream reservoirs elsewhere in North America and Europe, migratory species elsewhere may be susceptible to similar migration delays with long‐term population effects.

Watershed water balance changes as furrow irrigation is converted to sprinkler irrigation in an arid region

Irrigation is the largest water use in the western United States. The Upper Snake Rock Conservation Effects Assessment Project in southern Idaho began in 2005 to quantify the impacts of conservation practices in this irrigated watershed. The objective of this study was to determine the changes in the watershed water balances as farmers converted furrow irrigated fields to sprinkler irrigation from 2006 to 2016. More than 75% of annual watershed inflow was irrigation water diverted into the watershed from the Snake River and distributed through canals to 82,000 ha of cropland, while annual precipitation was only 10% to 23% of the annual inflow. Approximately 30% of the annual watershed inflow flowed back to the Snake River as irrigation return flow. Water balances showed that irrigation exceeded evapotranspiration (ET) in the spring and fall, indicating that irrigation diversions could be reduced early and late in the irrigation season. Annual irrigation project efficiency, defined as ET divided by the amount of diverted irrigation water, varied from 61% to 73%, but project efficiency did not increase as the amount of cropland that was sprinkler irrigated increased from 46% in 2006 to 59% in 2016. The only significant trends indicating that increasing sprinkler irrigation impacted the water balances were increasing irrigation project efficiency in July and increasing irrigation return flow during the irrigation season. Farmers may be applying less irrigation water with sprinkler irrigation compared to furrow irrigation, which could have caused return flow to increase since irrigation diversions did not change with the supply-based water allocation. Irrigation scheduling based on soil moisture measurement or daily ET would help irrigation application match crop water needs on individual fields. For the entire irrigation project, irrigation efficiency could improve if irrigation diversions into the watershed could be adjusted to more closely match ET in the spring and fall, which may require structural changes to the canal system and policy changes for the Snake River reservoir system.

Juvenile Chinook Salmon Mortality in a Snake River Reservoir: Smallmouth Bass Predation Revisited

AbstractPredation by nonnative fishes has been identified as a contributing factor in the decline of juvenile salmonids in the Columbia River basin. We examined the diet composition of Smallmouth Bass Micropterus dolomieu and estimated the consumption and predation loss of juvenile Chinook Salmon Oncorhynchus tshawytscha in Lower Granite Reservoir on the Snake River. We examined 4,852 Smallmouth Bass stomachs collected from shoreline habitats during April–September 2013–2015. Chinook Salmon were the second most commonly consumed fish by all size‐classes of Smallmouth Bass (≥150 mm TL) throughout the study. Over the 3 years studied, we estimated that a total of 300,373 Chinook Salmon were consumed by Smallmouth Bass in our 22‐km study area, of which 97% (291,884) were subyearlings (age 0) based on length frequency data. A majority of the loss (61%) occurred during June, which coincided with the timing of hatchery releases of subyearling fall Chinook Salmon. Compared to an earlier study, mean annual predation loss increased more than 15‐fold from 2,670 Chinook Salmon during 1996–1997 to 41,145 Chinook Salmon during 2013–2015 (in reaches that could be compared), despite lower contemporary Smallmouth Bass abundances. This increase can be explained in part by increases in Smallmouth Bass consumption rates, which paralleled increases in subyearling Chinook Salmon densities—an expected functional response by an opportunistic consumer. Smallmouth Bass are currently significant predators of subyearling Chinook Salmon in Lower Granite Reservoir and could potentially be a large source of unexplained mortality.

Early detection monitoring for larval dreissenid mussels: how much plankton sampling is enough?

The development of quagga and zebra mussel (dreissenids) monitoring programs in the Pacific Northwest provides a unique opportunity to evaluate a regional invasive species detection effort early in its development. Recent studies suggest that the ecological and economic costs of a dreissenid infestation in the Pacific Northwest of the USA would be significant. Consequently, efforts are underway to monitor for the presence of dreissenids. However, assessments of whether these efforts provide for early detection are lacking. We use information collected from 2012 to 2014 to characterize the development of larval dreissenid monitoring programs in the states of Idaho, Montana, Oregon, and Washington in the context of introduction and establishment risk. We also estimate the effort needed for high-probability detection of rare planktonic taxa in four Columbia and Snake River reservoirs and assess whether the current level of effort provides for early detection. We found that the effort expended to monitor for dreissenid mussels increased substantially from 2012 to 2014, that efforts were distributed across risk categories ranging from high to very low, and that substantial gaps in our knowledge of both introduction and establishment risk exist. The estimated volume of filtered water required to fully census planktonic taxa or to provide high-probability detection of rare taxa was high for the four reservoirs examined. We conclude that the current level of effort expended does not provide for high-probability detection of larval dreissenids or other planktonic taxa when they are rare in these reservoirs. We discuss options to improve early detection capabilities.

Ecology of the Opossum Shrimp (Neomysis mercedis) in a Lower Snake River Reservoir, Washington

The opossum shrimp Neomysis mercedis has expanded its range from the lower Columbia River upstream 695 kilometers into Lower Granite Reservoir where it is now very abundant. We studied Neomysis ecology in the reservoir during 2011–2015 to better understand the physical and biological factors that shape their distribution as well as their potential role in the food web. Benthic densities in offshore habitats ranged from 19 to 145 mysids m-2 in shallow (2–12 m) water and from 3 to 48 mysids m-2 in deep (> 12 m) water. Water velocity, depth, substrate, and seasonal interactions were important variables for explaining variation in Neomysis densities in offshore habitats. During spring, daytime densities in shoreline habitats (< 2 m deep) were variable, but nighttime densities generally decreased in summer following reproduction and as temperatures approached 23 °C. Neomysis were mainly collected from the water column during nighttime vertical tows in the downstream end of the reservoir when water velocities were low during summer and autumn. Reproduction occurred mainly in spring and early summer, but a second, smaller reproductive event was observed during autumn. The diet of Neomysis consisted primarily of detritus, rotifers, and copepods, but cladocerans were more prominent during summer and autumn. Physical factors like water velocity may have limited vertical migrations of Neomysis to feed in the water column and influenced use of different habitats in the reservoir. Neomysis are prey for a number of species, including juvenile salmon, but their relations are still largely unknown, and continued monitoring and research is warranted.

Assessing Juvenile Salmon Rearing Habitat and Associated Predation Risk in a Lower Snake River Reservoir

AbstractSubyearling fall Chinook salmon (Oncorhynchus tshawytscha) in the Columbia River basin exhibit a transient rearing strategy and depend on connected shoreline habitats during freshwater rearing. Impoundment has greatly reduced the amount of shallow‐water rearing habitat that is exacerbated by the steep topography of reservoirs. Periodic dredging creates opportunities to strategically place spoils to increase the amount of shallow‐water habitat for subyearlings while at the same time reducing the amount of unsuitable area that is often preferred by predators. We assessed the amount and spatial arrangement of subyearling rearing habitat in Lower Granite Reservoir on the Snake River to guide future habitat improvement efforts. A spatially explicit habitat assessment was conducted using physical habitat data, two‐dimensional hydrodynamic modelling and a statistical habitat model in a geographic information system framework. We used field collections of subyearlings and a common predator [smallmouth bass (Micropterus dolomieu)] to draw inferences about predation risk within specific habitat types. Most of the high‐probability rearing habitat was located in the upper half of the reservoir where gently sloping landforms created low lateral bed slopes and shallow‐water habitats. Only 29% of shorelines were predicted to be suitable (probability &gt;0.5) for subyearlings, and the occurrence of these shorelines decreased in a downstream direction. The remaining, less suitable areas were composed of low‐probability habitats in unmodified (25%) and riprapped shorelines (46%). As expected, most subyearlings were found in high‐probability habitat, while most smallmouth bass were found in low‐probability locations. However, some subyearlings were found in low‐probability habitats, such as riprap, where predation risk could be high. Given their transient rearing strategy and dependence on shoreline habitats, subyearlings could benefit from habitat creation efforts in the lower reservoir where high‐probability habitat is generally lacking. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Seasonal dynamics of zooplankton in Columbia–Snake River reservoirs, with special emphasis on the invasive copepod Pseudodiaptomus forbesi

The Asian copepod Pseudodiaptomus forbesi has recently become established in the Columbia River. However, little is known about its ecology and effects on invaded ecosystems. We undertook a 2-year (July 2009 to June 2011) field study of the mesozooplankton in four reservoirs in the Columbia and Snake Rivers, with emphasis on the relation of the seasonal variation in distribution and abundance of P. forbesi to environmental variables. Pseudodiaptomus forbesi was abundant in three reservoirs; the zooplankton community of the fourth reservoir contained no known non-indigenous taxa. The composition and seasonal succession of zooplankton were similar in the three invaded reservoirs: a bloom of rotifers occurred in spring, native cyclopoid and cladoceran species peaked in abundance in summer, and P. forbesi was most abundant in late summer and autumn. In the uninvaded reservoir, total zooplankton abundance was very low year-round. Multivariate ordination indicated that temperature and dissolved oxygen were strongly associated with zooplankton community structure, with P. forbesi appearing to exhibit a single generation per year. The broad distribution and high abundance of P. forbesi in the Columbia– Snake River System could result in ecosystem level effects in areas intensively managed to improve conditions for salmon and other commercially and culturally important fish species.

Three approaches to time valuation in recreation demand: A study of the Snake River recreation area in eastern Washington

Three travel cost models are used to estimate non-fishing recreation demand at the Snake River reservoirs recreation area in eastern Washington. The opportunity cost of time is specified in the “traditional” and McConnell–Strand models as a fraction of the exogenous market wage rate and in the two-step decision model as a function of socioeconomic attributes of the recreationists. Benefits per person per trip were $90, $35, and $46 respectively, for the three models. Boaters visit the site more than three times as often as non-boaters resulting in higher annual benefits for boaters.

Downstream Movement of Fall Chinook Salmon Juveniles in the Lower Snake River Reservoirs during Winter and Early Spring

AbstractWe conducted a 3‐year radiotelemetry study in the lower Snake River to (1) determine whether juvenile fall Chinook salmon Oncorhynchus tshawytscha pass dams during winter, when bypass systems and structures designed to prevent mortality are not operated; (2) determine whether downstream movement rate varies annually, seasonally, and from reservoir to reservoir; and (3) identify some of the factors that contribute to annual, seasonal, and spatial variation in downstream movement rate. Fall Chinook salmon juveniles moved downstream up to 169 km and at a sufficiently fast rate (7.5 km/d) such that large percentages (up to 93%) of the fish passed one or more dams during the winter. Mean downstream movement rate varied annually (9.2–11.3 km/d), increased from winter (7.5 km/d) to spring (16.4 km/d), and increased (from 6.9 to 16.8 km/d) as fish moved downstream from reservoir to reservoir. Fish condition factor at tagging explained some of the annual variation in downstream movement rate, whereas water particle velocity and temperature explained portions of the seasonal variation. An increase in migrational disposition as fish moved downstream helped to explain the spatial variation. The potential cost of winter movement might be reduced survival due to turbine passage at a time when the bypass systems and spillway passage structures are not operated. Efforts to understand and increase passage survival of winter migrants in large impoundments might help to rehabilitate some imperiled anadromous salmonid populations.

Willingness to Pay for Non Angler Recreation at the Lower Snake River Reservoirs

This study applied the travel cost method to estimate demand for non angler recreation at the impounded Snake River in eastern Washington. Net value per person per recreation trip is estimated for the full non angler sample and separately for camping, boating, water-skiing, and swimming/picnicking. Certain recreation activities would be reduced or eliminated and new activities would be added if the dams were breached to protect endangered salmon and steelhead. The effect of breaching on non angling benefits was found by subtracting our benefits estimate from the projected non angling benefits with breaching. Major issues in demand model specification and definition of the price variables are discussed. The estimation method selected was truncated negative binomial regression with adjustment for self selection bias.

Quantification of Oxygen Depletion in Lakes and Reservoirs with the Hypoxic Factor

ABSTRACT The amount of dissolved oxygen (DO) in lake water has biological and chemical implications. There are no easy ways to quantify exeedences of important thresholds of DO in lakes, except the complete lack of DO, quantified as an annual or seasonal anoxic factor (Nürnberg 1995a, b). Here an analogous concept, the “Hypoxic Factor” (HF) is introduced. According to specific water quality standards, certain levels of oxygen depletion can be quantified, e.g., DO concentrations below 5 mg L−1 or 6.5 mg L−1. The HF is computed from the duration and extent of hypoxia by using DO profiles and hypsographic data. It is expressed in such a way that a value of 365 d yr−1 would mean the whole lake has a DO concentration below the specified level at all times. The application to a TMDL project, where DO standards are to be employed in a large Snake River reservoir, demonstrates the potential usefulness of HF. This quantification of hypoxia allows the testing of hypotheses, e.g., the dependency of hypoxia on stage height, flow and nutrients. Significant relationships were found between annual expressions of hypoxia and hydrological variables (seasonal flows, water retention time) and a climatic index.

TMDLS: Statistical Correlations or Mechanistic Modeling?

In developing TMDL waste-load allocations for the Snake River-Reservoir system in Western Idaho and Eastern Oregon, determinations of the assimilative capacity of the system and the impact of pollutant reduction strategies has been performed using both a statistical-correlation approach and a mechanistic modeling approach. The system included the Lower Snake River, Brownlee Reservoir, Oxbow Reservoir, and Hells Canyon Reservoir with the focus was on Brownlee Reservoir. The statistical approach used on Brownlee Reservoir divided the system into riverine and lacustrine zones. Field data were then averaged over season and location to provide statistical correlations, such as between total phosphorus (TP) and chlorophyll a (chl a), between an anoxic factor (AF) and TP, and between a hypoxic factor (HP) and TP. The anoxic factor is defined as the number of days when dissolved oxygen was less than 2 mg/l and the hypoxic factor was defined as the number of days when dissolved oxygen was less than 6.5 mg/l. The mechanistic approach used a two-dimensional, unsteady, hydrodynamic and water quality model called CE-QUAL-W2. The model was calibrated to field data over a three year period for 1992 (a low flow year), 1995 (an average flow year), and 1997 (a high flow year). Some of the important questions that the TMDL process was to answer included the following. What level of TP is necessary in the river coming into Brownlee Reservoir to reduce the number of days of hypoxia in the reservoir? What are the causes of low-

Variability in Biological Characteristics of Northern Squawfish in the Lower Columbia and Snake Rivers

Abstract We described and compared population structure, growth, mortality, and reproduction of northern Squawfish Ptychocheilus oregonensis among four reservoirs of the lower Columbia River and among four reservoirs of the lower Snake River. We also pooled data for comparisons among three larger areas: Columbia River reservoirs, Snake River reservoirs, and the unimpounded Columbia River downstream from Bonneville Dam. Females made up 76–100% of northern squawfish 380 mm fork length or greater in individual reservoirs, and 87–99% of fish 380 mm or greater in the three combined areas. Females lived longer and grew faster than males in all reservoirs and areas and had lower annual mortality rates in all but two reservoirs. Proportional stock density was highest and annual mortality rates were generally lowest in Columbia River reservoirs. Northern Squawfish downstream from Bonneville Dam had a lower mean relative weight and higher relative fecundity (eggs per unit fish weight) than populations in impoundmen...

A stochastic, compartmental model of the migration of juvenile anadromous salmonids in the Columbia River Basin

A probabilistic model is developed which describes the juvenile migration of Pacific salmon and steelhead trout ( Oncorhynchus sp.) in the Columbia River Basin in western North America. The downstream passage of smolts through a series of reservoirs or river reaches is modeled as an irreversible particle diffusion process through a series of compartments. The probability of live passage from one compartment to the next t time units after having entered the compartment can be viewed as the product of the probability of having survived to time t, the probability of transiting the compartment in t time units, and the probability of a successful transition between compartments at time t. From this basic premise, a general passage model is developed. Focusing on survival through Columbia and Snake River reservoirs (as opposed to dam-related mortality), a specific model which uses a Poisson death process and a gamma distribution to describe transmit time is presente. Analytical solutions to the single-compartment system are derived with extensions to the multi-compartment system. Empirical data from the Columbia River is used to demonstrate the utility of the model as well as to highlight problems that exist in fitting the model using existing data. Graphical techniques are presented for using the model to assess the effectiveness of management actions that are designed to improve the reservoir survival of smolts.