Geology topics

Research about Idaho

Source-linked reports with geographic coverage including Idaho.

At least 451 records · Page 25Linked to original sources

USGS2005

Instream flow characterization of upper Salmon River basin streams, central Idaho, 2004

Anadromous fish populations in the Columbia River Basin have plummeted in the last 100 years. This severe decline led to Federal listing of Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss) stocks as endangered or threatened under the Endangered Species Act (ESA) in the 1990s. Historically, the upper Salmon River Basin (upstream of the confluence with the Pahsimeroi River) in Idaho provided migration corridors and significant habitat for these ESA-listed species, in addition to the ESA-listed bull trout (Salvelinus confluentus). Human development has modified the original streamflow conditions in many streams in the upper Salmon River Basin. Summer streamflow modifications resulting from irrigation practices, have directly affected quantity and quality of fish habitat and also have affected migration and (or) access to suitable spawning and rearing habitat for these fish. As a result of these ESA listings and Action 149 of the Federal Columbia River Power System Biological Opinion of 2000, the Bureau of Reclamation was tasked to conduct streamflow characterization studies in the upper Salmon River Basin to clearly define habitat requirements for effective species management and habitat restoration. These studies include collection of habitat and streamflow information for the Physical Habitat Simulation System model, a widely applied method to determine relations between habitat and discharge requirements for various fish species and life stages. Model results can be used by resource managers to guide habitat restoration efforts by evaluating potential fish habitat and passage improvements by increasing streamflow. In 2004, instream flow characterization studies were completed on Salmon River and Beaver, Pole, Champion, Iron, Thompson, and Squaw Creeks. Continuous streamflow data were recorded upstream of all diversions on Salmon River and Pole, Iron, Thompson, and Squaw Creeks. In addition, natural summer streamflows were estimated for each study site using regional regression equations. This report describes Physical Habitat Simulation System modeling results for bull trout, Chinook salmon, and steelhead trout during summer streamflows. Habitat/discharge relations were summarized for adult and spawning life stages at each study site. Adult fish passage and discharge relations were evaluated at specific transects identified as a potential low-streamflow passage barrier at each study site. Continuous summer water temperature data for selected study sites were summarized and compared with Idaho Water Quality Standards and various water temperature requirements of targeted fish species. Continuous summer water temperature data recorded in 2003 and streamflow relations were evaluated for Fourth of July Creek using the Stream Segment Temperature model that simulates mean and maximum daily water temperatures with changes in streamflow. Results of these habitat studies can be used to prioritize and direct cost-effective actions to improve fish habitat for ESA-listed anadromous and native fish species in the basin. These actions may include acquiring water during critical low-flow periods by leasing or modifying irrigation delivery systems to minimize out-of-stream diversions.

Idaho↗

USGS2005

An assessment of Idaho's wildlife management areas for the protection of wildlife

Since 1940, Idaho Department of Fish and Game has developed a network of 31 Wildlife Management Areas (WMAs) across the state. This program has been focused mostly on conservation of game species and their habitats. We assessed the contribution of Idaho's WMAs to conservation of all Idaho's wildlife and other aspects of ecological diversity. Predicted occurrences of species' breeding habitats and other data were used to evaluate the representation of wildlife habitat and other ecological conditions. We found 33 of 39 natural land cover types were mapped as occurring in WMAs. WMAs occurred in 10 of 15 of Bailey's ecoregion sections, absent only from two sections that occupy greater than 1% of Idaho. Percent area of WMAs by elevation followed a pattern similar to percent area of Idaho; however, mean elevation for WMAs was lower than for the state and other protected areas in Idaho. We predicted breeding habitat for 98.4% of Idaho's wildlife and all federal and state listed threatened, endangered, or candidate terrestrial vertebrates to occur in at least one WMA. We predicted habitat for 39 species to occur on five or fewer WMAs, and predicted no habitat on WMAs for five species. We found that a system of WMAs established mainly to protect game species potentially conserves many other aspects of Idaho's ecological diversity, may provide habitat for more than 98% of Idaho's wildlife, and complements other protected areas in the state.

Idaho↗

USGS2004

Phosphorus amendment reduces bioavailability of lead to mallards ingesting contaminated sediments

Lead poisoning of waterfowl has been reported for decades in the Coeur d'Alene River Basin in Idaho as a result of the ingestion of lead-contaminated sediments. We conducted a study to determine whether the addition of phosphoric acid to sediments would reduce the bioavailability of lead to mallards ( Anas platyrhynchos ). When sediments were amended with 1% phosphorus under laboratory conditions, and diets containing 12% amended sediment were fed to mallards, reductions in tissue lead were 43% in blood, 41% in liver, and 59% in kidney with sediment containing about 4,520 μg/g lead on a dry-weight basis and 41, 30, and 57% with sediment containing about 6,990 μg/g lead. When sediments were treated with phosphorus and left to age for about 5 months in the field, reductions in lead were 56% in blood, 54% in liver, and 66% in kidney at one site with about 5,390 μg/g lead and 64, 57, and 77% at a second site with about 6,990 μg/g lead. In the field, the inability to mix the phosphoric acid uniformly and deeply enough into the sediment may have resulted in more than 1% phosphorus being added to the sediment. Although both lab and field amendments of phosphorus substantially reduced the bioavailability of lead, lead concentrations in the tissues of mallards fed the amended sediments were still above those believed to be harmful to waterfowl. Based on earlier studies of sediment toxicity to waterfowl in the Coeur d'Alene River Basin, combined with the results of our amendment study, the addition of phosphoric acid as we used it might only significantly benefit waterfowl where sediments or soils contain less than 1,000-2,000 μg/g lead.

Idaho↗

USGS2004

Effects of lead-contaminated sediment and nutrition on mallard duckling brain growth and biochemistry

Day-old mallard (Anas platyryhnchos) ducklings received either a clean sediment (24%) supplemented control diet, Coeur d'Alene River Basin, Idaho (CDARB) sediment (3449 ug/g lead) supplemented diets at 12% or 24%, or a positive control diet (24% clean sediment with equivalent lead acetate to the 24% CDARB diet) for 6 weeks. The 12% CDARB diet resulted in a geometric mean concentration of 396 ppb (WW) brain lead with decreased brain protein and ATP concentrations but increased oxidized glutathione (GSSG) relative to the control diet. The 24% CDARB diet resulted in a concentration of 485 ppb brain lead with lower brain weight and ATP concentration than controls but higher concentrations of reduced glutathione (GSH) and calcium. Lead acetate accumulated twice as well as CDARB derived lead and resulted in histopathological lesions of the brain. With a combination of a suboptimal diet and 24% CDARB, brain lead concentration was higher (594 ppb) than with 24% CDARB in the standard diet, histopathological lesions became apparent and GSH was higher than suboptimal diet controls.

Idaho↗

USGS2004

Effects of lead-contaminated sediment and nutrition on mallard duckling brain growth and biochemistry

Day-old mallard ( Anas platyryhnchos ) ducklings received either a clean sediment (24%) supplemented control diet, Coeur d'Alene River Basin, Idaho (CDARB) sediment ( 3449 μg/g lead ) supplemented diets at 12% or 24%, or a positive control diet (24% clean sediment with equivalent lead acetate to the 24% CDARB diet) for 6 weeks. The 12% CDARB diet resulted in a geometric mean concentration of 396 ppb (WW) brain lead with decreased brain protein and ATP concentrations but increased oxidized glutathione (GSSG) relative to the control diet. The 24% CDARB diet resulted in a concentration of 485 ppb brain lead with lower brain weight and ATP concentration than controls but higher concentrations of reduced glutathione (GSH) and calcium. Lead acetate accumulated twice as well as CDARB derived lead and resulted in histopathological lesions of the brain. With a combination of a suboptimal diet and 24% CDARB, brain lead concentration was higher (594 ppb) than with 24% CDARB in the standard diet, histopathological lesions became apparent and GSH was higher than suboptimal diet controls.

Idaho↗

USGS2004

Chapter 8 Petrogenesis and mineralogic residence of selected elements in the meade peak phosphatic shale member of the permian phosphoria formation, Southeast Idaho

The Meade Peak Phosphatic Shale Member of the Permian Phosphoria Formation hosts the ore mined by the phosphate industry of southeast Idaho. It also hosts environmentally sensitive elements (ESE) such as Se, As, Hg, Ni, Cd, Zn, and Cr. Primary chemistry, elemental distribution patterns, and mineralogy within the Meade Peak were modified by element migration and possibly the introduction of elements. Fluids moved within the Meade Peak throughout its history, although the passage of fluids was highly variable in space and time, resulting in small domains of different rock chemistry and different mineralogy. Timing of major events affecting the Meade Peak and mineral habit are used to differentiate among detrital, diagenetic, epigenetic, and supergene mineral assemblages. Cross-cutting relationships among minerals are too rare to provide much paragenetic infor- mation. Carbonate fluorapatite (CFA) occurs in several forms, but dominantly as pelloids, some of which may have formed in situ during diagenesis. The other volumetrically signifi- cant form of CFA is interstitial cement that formed during diagenesis. Beginning during diagenesis and continuing intermittently, multiple generations of carbonate (dolomite and calcite) formed overgrowths and texturally complex carbonate cements. Movement and precipitation of silica followed a similar pattern. The ammonium feldspar buddingtonite, which generally rims orthoclase, also formed during diagenesis. Bacteria apparently played a significant role during diagenesis as well as during supergene processes, resulting in extreme fractionation of S isotopes and the possible bacterially mediated formation of minerals such as glauconite and sphalerite. Catagenesis, apparently culminating in oil generation, was the last significant diagenetic change. Thrusting accompanied by fluid (oil and brine) migration began during catagenesis in the Late Jurassic or Cretaceous and continued into the early Eocene. Fluorite ± carbonate ± barite± bitumen veins formed as a result of brittle deformation and accompanying fluid movement. This fracturing event may have been associated with a period of extension and normal faulting (Neogene to Holocene). Passage of the Yellowstone hot spot to the north of the area during the Neogene is marked by silicic domes and basaltic flows. The enrichment of Hg in fracture coatings might be the result of deposition from warm fluids associated with the emplacement of the silicic domes or a generally elevated, regional thermal gradient associated with the volcanism. Many of the fracture systems are still open and continue to provide fluid pathways that are the primary depositional sites for a wide variety of supergene minerals (such as Se, efflorescent salts) and element associations (such as Hg, Cd-S, Fe-Cr-O) in which many of the ESE are concentrated. Native Se is the most commonly identified host of Se in the studied samples. The largest concentration of Se occurs in open-fracture systems that cross-cut waste rock and ore units. The age(s) of native Se formation is not known; how- ever, the latest period of Se mobility is the present. Direct measurement of efflorescent “salts” forming on new mine faces indicate that several ESE, including both Se and Zn, are concentrated on the faces soon after they are exposed. Zinc is present as hydrous sulfates, but the residence of Se in these “salts” is unknown.

Idaho↗

USGS2004

Chapter 14 Rex Chert member of the Permian Phosphoria Formation: Composition, with emphasis on elements of environmental concern

We present bulk chemical and mineralogical compositions, as well as petrographic and outcrop descriptions, of rocks collected from three measured outcrop sections of the Rex Chert Member of the Phosphoria Formation in southeast Idaho. The three measured sections were chosen from 10 outcrops of Rex Chert that were described in the field. The Rex Chert overlies the Meade Peak Phosphatic Shale Member of the Phosphoria Formation, the source of phosphate ore in the region. Rex Chert removed as overburden constitutes part of the material transferred to waste-rock piles during phosphate mining. It is also used to surface roads in the mining district. It has been proposed that the chert be used to cap and isolate waste piles, thereby inhibiting the leaching of potentially toxic elements into the environment. The rock samples studied here are from individual chert beds representative of each stratigraphic section sampled. The Cherty Shale Member of the Phosphoria Formation that overlies the Rex Chert in measured section 1 and the upper Meade Peak and the transition zone to the Rex Chert in section 7 were also described and sampled. The cherts are predominantly spiculite composed of granular and mosaic quartz, and sponge spicules, with various but minor amounts of other fossils and detrital grains. The Cherty Shale Member and transition rocks between the Meade Peak and Rex Chert are siliceous siltstones and argillaceous cherts with ghosts of sponge spicules and somewhat more detrital grains than the chert. The dominant mineral is quartz. Carbonate beds are rare in each section and are composed predominantly of calcite and dolomite in addition to quartz. Feldspar, mica, clay minerals, calcite, dolomite, and carbonate fluorapatite are minor to trace minerals in the chert. The concentration of SiO 2 in the chert averages 94.6 wt.%. Organic-carbon content is generally very low, but can be as much as 1.8% in Cherty Shale Member samples and as much as 3.3% in samples from the transition between the Meade Peak and Rex Chert. Likewise, phosphate (P 2 O 5 ) is generally low in the chert, but can be as much as 3.1% in individual chert beds. Selenium concentrations in Rex Chert and Cherty Shale Member samples vary from <0.2 to 138 ppm, with a mean concentration of 7.0 ppm. This mean Se content is heavily dependent on two values of 101 and 138 ppm for siliceous siltstone from the lower part of the Rex Chert, which contains rocks that are transitional in character between the Meade Peak and Rex Chert Members. Without those two samples, the mean Se concentration is < 1.0 ppm. Other elements of environmental interest, As, Cr, V, Zn, Hg, and Cd, generally occur in concentrations near or below that in average continental shale. Stratigraphic changes, equivalent to temporal changes in the depositional basin, in chemical composition of rocks are notable either as uniform changes through the sections or as distinct differences in the mean composition of rocks that comprise the upper and lower halves of the sections. Q-mode factors are interpreted to represent the following rock and mineral components: chert-silica component consisting of Si (±Ba); phosphorite-carbonate fluorapatite component composed of P, Ca, As, Y, V, Cr, Sr, and La (± Fe, Zn, Cu, Ni, Li, Se, Nd, Hg); shale component composed of Al, Na, Zr, K, Ba, Li, and organic C (± Ti, Mg, Se, Ni, Fe, Sr, V, Mn, Zn); carbonate component (dolomite, calcite, silicified carbonates) composed of carbonate C, Mg, Ca, and Si (±Mn); and, tentatively, organic matter-hosted elements (and/or sulfide-sulfate phases) composed of Cu (± organic C, Zn, Mn, Si, Ni, Hg, Li). Selenium shows a dominant association with organic matter and to lesser degrees associations with other shale components and carbonate fluorapatite. Consideration of larger numbers of factors in Q-mode analysis indicates that native Se (a factor containing Se (± Ba)) may also comprise a minor component of the Se complement. Comparison of our data with those from newly exposed outcrops in active phosphate mines indicates that weathering of typical Rex Chert outcrops likely plays an important role in removing environmentally sensitive elements.

Idaho↗

USGS2004

Selenium loading through the Blackfoot River watershed--linking sources to ecosystem

The upper Blackfoot River watershed in southeast Idaho receives drainage from 11 of 16 phosphate mines that have extracted ore from the Phosphoria Formation, three of which are presently active. Toxic effects from selenium (Se), including death of livestock and deformity in aquatic birds, were documented locally in areas where phosphatic shales are exposed ( Piper et al., 2000 ; Presser et al., Chapter 11). Current drainage conditions are leading to Se bioaccumulation at concentrations that pose a risk to fish in the Blackfoot River and its tributaries (Hamilton et al., Chapter 18). A gaging station on the Blackfoot River was re-activated in April 2001 to assess hydrologic conditions and concentration, load, and speciation for Se discharges on a watershed scale. The gaging-station data are considered to represent regional drainage conditions in the upper Blackfoot River water- shed because of its location near the outlet of the watershed and directly upstream of the Blackfoot Reservoir. Watershed discharges for 2001 and 2002 were below minimum hydrologic conditions for the gage as documented by the historical record. Drought emergencies were declared in the area in both 2001 and 2002. Unmonitored diversions for irrigation that routinely take place during the snowmelt season also affected conditions downstream. Annual cycles in Se concentration, load, and selenate (Se 6+ ) reached maxima in the spring during the period of maximum flow at the gaging station. Thirty-seven to 44% of annual flow occurred dur- ing the three-month high-flow season (April through June) in 2001 and 56% of annual flow occurred during that time period in 2002. Extrapolation from historical hydrographs for average and wet years and a limited data set of regional Se concentrations for 2001 and 2002 indicated potential for a 3.6- to 7.4-fold increase in Se loading because of increased seasonal flows in the Blackfoot River watershed. Supplementation data indicate that: (a) the difference between total Se and dissolved Se, as a measure of the contribution of particulate Se, was < 10% except at the peak of con- centration when total Se was 18% more than dissolved Se; (b) selenite (Se 4+ ) represented less than 10% of the dissolved species during all months of 2001; and (c) dissolved Se was approximately a 50:50 mixture of selenate and organic selenide (operationally defined Se 2- ) during summer 2001 (June through August). Ecological risk based on regional Se drainage occurred during both the high- and low-flow seasons. Seventy to 83% of the Se load occurred during the high-flow season. During early May of both years, dissolved-Se concentrations exceeded the criterion for the protection of aquatic life and the ecological threshold of 5 gL 1 Se at which sub- stantive risk occurs. During the majority of the three-month high-flow season, dissolved- Se concentrations exceeded the 2 gL 1 Se concern level for aquatic biota. The Se concentration in suspended material during high flow in 2002 was within the range of marginal risk to aquatic life (2-4 gg 1 Se, dry weight). Selenate was the major species during peak flows, with both selenate and organic selenide being major species during relatively low-flow periods in summer. A change in speciation to reduced Se may indicate elevated biotic productivity during summer months and could result in enhanced Se uptake in food webs. In addition to the magnitude of regional Se release in the Blackfoot River watershed, Se concentrations in individual source drains and waste-rock seeps, and those predicted by experimental column leaching of proposed mining overburden materials, also indicate that drainage options that currently meet existing demands for phosphate mining cause eco- logical risk thresholds to be exceeded. At times, the drinking-water Se standard (50 g L 1 Se) and the criterion for hazardous Se waste (1000 L -1 Se) ( US Department of the Interior, 1998 ; US Environmental Protection Agency, 1987 ) are also exceeded. For water-years 2001 and 2002, seasonal increased input of water in the mining area resulted in increased Se transport, suggesting a mechanism of contamination that involves a significant Se reservoir. Hence, recognition and monitoring of Se loading to the envi- ronment on a mass balance basis (i.e. inputs, fluxes and storage within environmental media, and outputs) are essential to evaluating how to control Se concentrations within environmentally protective ranges ( Presser and Piper, 1998 ). In areas where release of Se to aquatic systems is anticipated as a product of future expansion of phosphate mining, continuous monitoring of flow and development of seasonal Se loading patterns would help to model watersheds in terms of sources, flow periods, and environmental-Se con- centrations that most influence bioavailability. These data, in turn, could be linked to Se- bioaccumulation models specific to food webs and vulnerable species of the impacted areas to accurately project ecological effects. Gaging at this site on the Blackfoot River is planned to continue in order to establish a long-term (>10 year) record of hydrologic conditions.

Idaho↗

USGS2004

Habitat restoration across large areas: Assessing wildlife responses in the Clearwater basin, Idaho

Over the past century, fire suppression and prevention have altered disturbance regimes across the Pacific Northwest, resulting in a significant divergence of historical and current conditions in forested habitats. To address this continuing trend in habitat changes and begin restoring historical patterns of disturbance, the Clearwater Basin Elk Habitat Initiative (CEI) proposes relatively extensive management actions in the Clearwater basin of north-central Idaho. We attempted to evaluate potential effects of such management actions on selected wildlife species using extant data sets and suggest ways to improve such projects with respect to a multispecies and adaptive management approach. Although there is increased interest in ecosystem management over large areas, the increased scale of analysis and implementation require a substantial increase in the level of species information beyond what currently exists. We conclude that baseline information required for an effective multispecies land-management policy in the Clearwater basin does not exist for many terrestrial wildlife species. To implement a true multispecies or ecosystem approach, wildlife and land managers should cooperate to increase existing population data and modeling efforts for wildlife species in the basin and develop a sustainable monitoring program to evaluate habitat management changes and their influence on wildlife populations within the context of adaptive management theory. Management actions to restore disturbance patterns should attempt spatial and temporal scales that are biologically relevant to the population ecology of species being affected.

Idaho↗

USGS2004

Sexual differences in the post-breeding movements and habitats selected by Western toads (Bufo boreas) in southeastern Idaho

We used radio-telemetry to study the movements and habitat use of Western toads ( Bufo boreas ) in the Targhee National Forest in southeastern Idaho. Eighteen toads (10 male and 8 female) that bred in a seasonally flooded pond, were fitted with radio-transmitters, tracked, and their movements mapped and analyzed with global positioning and geographic information systems. We also analyzed their patterns of habitat selection at micro- and macro-scales by comparing sites used by toads with randomly selected sites. After breeding, two male and six female toads left the breeding pond and used terrestrial habitats extensively. Male and female toads showed different patterns of movement and habitat use, although all toads seemed to behave in ways that reduced loss of body water (e.g., such as traveling on nights of high humidity). Male toads traveled shorter distances from the pond than females (581 ± 98 m and 1105 ± 272 m, respectively). Female toads used terrestrial habitats extensively and were selective of cover types (e.g., shrub) that provided greater protection from dehydration. Female toads also preferred certain habitat edges and open forests over forests with closed canopies or clearcuts. Information from this study can assist land managers in establishing protective buffers and managing forests for the protection of toad populations.

Idaho↗

USGS2004

Radiochemical and Chemical Constituents in Water from Selected Wells and Springs from the Southern Boundary of the Idaho National Engineering and Environmental Laboratory to the Hagerman Area, Idaho, 2002

The U.S. Geological Survey, Idaho Department of Water Resources, and the State of Idaho INEEL Oversight Program, in cooperation with the U.S. Department of Energy, sampled water from 17 sites as part of the sixth round of a long-term project to monitor water quality of the eastern Snake River Plain aquifer from the southern boundary of the Idaho National Engineering and Environmental Laboratory to the Hagerman area. The samples were collected from eight irrigation wells, three domestic wells, one stock well, one dairy well, one commercial well, one observation well, and two springs and analyzed for selected radiochemical and chemical constituents. One quality-assurance sample, a sequential replicate, also was collected and analyzed. Many of the radionuclide and inorganic-constituent concentrations were greater than the reporting levels and most of the organic-constituent concentrations were less than the reporting levels. However, none of the reported radiochemical- or chemical-constituent concentrations exceeded the maximum contaminant levels for drinking water established by the U.S. Environmental Protection Agency. Statistical evaluation of the replicate sample pair indicated that, with 95 percent confidence, 132 of the 135 constituent concentrations of the replicate pair were equivalent.

Idaho↗

USGS2004

Instream flow characterization of upper Salmon River Basin streams, Central Idaho, 2003

Anadromous fish populations in the Columbia River Basin have plummeted in the last 100 years. This severe decline led to Federal listing of chinook salmon ( Oncorhynchus tshawytscha ) and steelhead trout ( Oncorhynchus mykiss ) stocks as endangered or threatened under the Endangered Species Act (ESA) in the 1990s. Historically, the upper Salmon River Basin (upstream from the confluence with the Pahsimeroi River) in Idaho provided migration corridors and significant habitat for these ESA-listed species, in addition to the federally listed bull trout ( Salvelinus confluentus ). Human development has modified the original streamflow conditions in many streams in the upper Salmon River Basin. Summer streamflow modifications, as a result of irrigation practices, have directly affected the quantity and quality of fish habitat and also have affected migration and (or) access to suitable spawning and rearing habitat for these fish. As a result of these ESA listings and Action 149 of the Federal Columbia River Power System Biological Opinion of 2000, the Bureau of Reclamation was tasked to conduct streamflow characterization studies in the upper Salmon River Basin to clearly define habitat requirements for effective species management and habitat restoration. These studies include the collection of habitat and streamflow information for the Physical Habitat Simulation (PHABSIM) model, a widely applied method to determine relations between habitat and discharge requirements for various fish species and life stages. Model results can be used by resource managers to guide habitat restoration efforts in the evaluation of potential fish habitat and passage improvements by increasing streamflow. Instream flow characterization studies were completed on Pole, Fourth of July, Elk, and Valley Creeks during 2003. Continuous streamflow data were collected upstream from all diversions on each stream. In addition, natural summer streamflows were estimated for each study site using regression equations. PHABSIM results are presented for bull trout, chinook salmon, and steelhead trout over a range of summer streamflows. Habitat/discharge relations are summarized for juvenile, adult, and spawning life stages at each study site. Adult fish passage and discharge relations are evaluated at specific transects identified as a potential low-streamflow passage barrier at each study site. Continuous summer water temperature data for selected study sites also are summarized and compared with Idaho Water Quality Standards and various temperature requirements of targeted fish species. Results of these habitat studies can be used to prioritize and direct cost-effective actions to improve fish habitat for ESA-listed anadromous and native fish species in the basin. These actions may include acquiring water during critical low-flow periods by leasing or modifying irrigation delivery systems to minimize out-of-stream diversions.

Idaho↗

USGS2004

Assessment of fish assemblages and minimum sampling effort required to determine botic integrity of large rivers in southern Idaho, 2002

A critical issue surrounding biomonitoring in large rivers (fifth- through seventh-order) is the minimum sampling-reach distance required to collect an adequate number of fish to represent the fish assemblage within a reach. Excessive sampling effort (excessive reach length) is costly in terms of work hours, reduces the number of sites that can be visited, can compromise field-crew safety, can be logistically unfeasible, and can cause unnecessary injury to captured fish. On the other hand, inadequate sampling effort can produce considerable variability in multiple samples collected at a site and may underrepresent the species or river condition present. During the summer of 2002, the U.S. Geological Survey, in cooperation with the Idaho Department of Environmental Quality, determined the minimum sampling effort required to characterize fish assemblages at 17 large-river sites in southern Idaho. The study was done as part of the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program. Electrofishing methods and multiple gear types were used to collect sample populations of fish in river reach lengths representing 40 and 100 times the wetted channel width. Minimum sampling effort was assessed by comparing the relation between reach length and the number of species collected, total individuals collected, and final Index of Biotic Integrity (IBI) scores. Thirty-two species of fish in the families Catostomidae, Centrarchidae, Cottidae, Cyprinidae, Ictaluridae, Percidae, and Salmonidae were collected. Of these, 12 alien species were collected, representing about 38 percent of all species collected during the study. Wetted channel width was determined to be sufficient for collecting an adequate number of fish to estimate species richness and evaluate biotic integrity. At most sites, about 250 fish were needed to effectively represent 95 percent of the species present. Fifty-three percent of the sites assessed, using an IBI developed specifically for large Idaho rivers, received scores of less than 50, indicating poor biotic integrity.

Idaho↗

USGS2003

Modeling precipitation and sorption of elements during mixing of river water and porewater in the Coeur d'Alene River basin

Reddish brown flocs form along the edge of the Coeur d'Alene River when porewater drains into river water during the annual lowering of water level in the basin. The precipitates are efficient scavengers of dissolved elements and have characteristics that may make metals associated with them bioavailable. This work characterizes the geochemistry of the porewater and models the formation and composition of the flocs. Porewater is slightly acidic, has suboxic to anoxic characteristics, tends to have higher alkalinity, and contains elevated concentrations of many constituents relative to river water. Laboratory mixing experiments involving porewater and river water were done to produce the precipitates. Thermodynamic predictions using PHREEQC indicate that predicted amounts of ferrihydrite and gibbsite agree with removal of Fe and Al. Predictions of element removal by adsorption onto ferrihydrite are consistent with observed removal using a combination of surface complexation constants for the generalized two-layer model (As and Se), alternative surface constants derived from experiments at high sorbate-to-sorbent ratios (Cd, Co, Cu, Ni, Pb, and Zn), and adjusted surface constants to fit experimental data (Cr, Mo, and Sb). This new set of surface complexation constants needs further testing in other contaminated systems.

Idaho↗

USGS2003

Mercury in soil near a long-term air emission source in southeastern Idaho

At the Idaho National Engineering and Environmental Laboratory in southeastern Idaho, a 500 °C fluidized bed calciner was intermittently operated for 37 years, with measured Hg emission rates of 9–11 g/h. Surface soil was sampled at 57 locations around the facility to determine the spatial distribution of Hg fallout and surface Hg variability, and to predict the total residual Hg mass in the soil from historical emissions. Measured soil concentrations were slightly higher ( p <0.05) within 5 km of the source but were overall very low (15–20 ng/g) compared to background Hg levels published for similar soils in the USA (50–70 ng/g). Concentrations decreased 4%/cm with depth and were found to be twice as high under shrubs and in depressions. Mass balance calculations accounted for only 2.5–20% of the estimated total Hg emitted over the 37-year calciner operating history. These results suggest that much of the Hg deposited from calciner operations may have been reduced in the soil and re-emitted as Hg(0) to the global atmospheric pool.

Idaho↗

USGS2003

Mercury accumulation in snow on the Idaho National Engineering and Environmental Laboratory and surrounding region, southeast Idaho, USA

Snow was sampled and analyzed for total mercury (THg) on the Idaho National Engineering and Environmental Laboratory (INEEL) and surrounding region prior to the start-up of a large (9-11 g/h) gaseous mercury emission source. The objective was to determine the effects of the source on local and regional atmospheric deposition of mercury. Snow samples collected from 48 points on a polar grid near the source had THg concentrations that ranged from 4.71 to 27.26 ng/L; snow collected from regional background sites had THg concentrations that ranged from 0.89 to 16.61 ng/L. Grid samples had higher concentrations than the regional background sites, which was unexpected because the source was not operating yet. Emission of Hg from soils is a possible source of Hg in snow on the INEEL. Evidence from Hg profiles in snow and from unfiltered/filtered split samples supports this hypothesis. Ongoing work on the INEEL is investigating Hg fluxes from soils and snow.

Idaho↗

USGS2003

Importance of Sediment-Water Interactions in Coeur d'Alene Lake, Idaho, USA: Management Implications

A field study at Coeur d'Alene Lake, Idaho, USA, was conducted between October 1998 and August 2001 to examine the potential importance of sediment-water interactions on contaminant transport and to provide the first direct measurements of the benthic flux of dissolved solutes of environmental concern in this lake. Because of potential ecological effects, dissolved zinc and orthophosphate were the solutes of primary interest. Results from deployments of an in situ flux chamber indicated that benthic fluxes of dissolved Zn and orthophosphate were comparable in magnitude to riverine inputs. Tracer analyses and benthic-community metrics provided evidence that solute benthic flux were diffusion-controlled at the flux-chamber deployment sites. That is, effects of biomixing (or bioturbation) and ground-water interactions did not strongly influence benthic flux. Remediation efforts in the river might not produce desired water-quality effects in the lake because imposed shifts in concentration gradients near the sediment-water interface would generate a benthic feedback response. Therefore, development of water-quality models to justify remediation strategies requires consideration of contaminant flux between the water column and underlying sediment in basins that have been affected by long-term (decadal) anthropogenic activities.

Idaho↗

USGS2003

Calibration of remotely sensed, coarse resolution NDVI to CO2 fluxes in a sagebrush–steppe ecosystem

The net ecosystem exchange (NEE) of carbon flux can be partitioned into gross primary productivity (GPP) and respiration ( R ). The contribution of remote sensing and modeling holds the potential to predict these components and map them spatially and temporally. This has obvious utility to quantify carbon sink and source relationships and to identify improved land management strategies for optimizing carbon sequestration. The objective of our study was to evaluate prediction of 14-day average daytime CO 2 fluxes ( F day ) and nighttime CO 2 fluxes ( R n ) using remote sensing and other data. F day and R n were measured with a Bowen ratio–energy balance (BREB) technique in a sagebrush ( Artemisia spp.)–steppe ecosystem in northeast Idaho, USA, during 1996–1999. Micrometeorological variables aggregated across 14-day periods and time-integrated Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (iNDVI) were determined during four growing seasons (1996–1999) and used to predict F day and R n . We found that iNDVI was a strong predictor of F day ( R 2 =0.79, n =66, P <0.0001). Inclusion of evapotranspiration in the predictive equation led to improved predictions of F day ( R 2 =0.82, n =66, P <0.0001). Crossvalidation indicated that regression tree predictions of F day were prone to overfitting and that linear regression models were more robust. Multiple regression and regression tree models predicted R n quite well ( R 2 =0.75–0.77, n =66) with the regression tree model being slightly more robust in crossvalidation. Temporal mapping of F day and R n is possible with these techniques and would allow the assessment of NEE in sagebrush–steppe ecosystems. Simulations of periodic F day measurements, as might be provided by a mobile flux tower, indicated that such measurements could be used in combination with iNDVI to accurately predict F day . These periodic measurements could maximize the utility of expensive flux towers for evaluating various carbon management strategies, carbon certification, and validation and calibration of carbon flux models.

Idaho↗