Geology topics
Research about Idaho
Source-linked reports with geographic coverage including Idaho.
Field evaluation of lead effects on Canada geese and mallards in the Coeur d'Alene River Basin, Idaho
Hatch year (HY) mallards ( Anas platyrhynchos ) in the Coeur d'Alene (CDA) River Basin had higher concentrations of lead in their blood than HY Western Canada geese ( Branta canadensis moffitti ) (geometric means 0.98 versus 0.28 μg/g, wet weight). The pattern for adults of both species was similar, although geometric means (1.77 versus 0.41 μg/g) were higher than in HY birds. HY mallards captured in the CDA River Basin in 1987 contained significantly lower lead concentrations in their blood than in 1994–95 (0.36 versus 0.98 μg/g); however, some very young mallards were sampled in 1987, and concentrations in adults were not significantly different in 1987, 1994, or 1995 (1.52, 2.07, 1.55 μg/g, respectively). Both species in the CDA River Basin in 1994–95 showed significantly reduced red blood cell delta-aminolevulinic acid dehydratase (ALAD) activity compared to the reference areas: Canada geese (HY −65.4 to −86.0%, adults −82.3%), and mallards (HY −90.7 to −95.5%, adults −94.1%). Canada goose goslings were divided into size classes, and the two smaller classes from the CDA River Basin had significantly elevated free erythrocyte protoporphyrin (protoporphyrin) levels compared to the reference area (15.2× and 6.9×). HY and adult mallards both had significantly elevated protoporphyrin (5.9× and 7.5×). Recognizing that interspecific differences exist in response and sensitivity to lead, it appears (at least for hemoglobin and hematocrit) that Canada geese were more sensitive to lead than mallards, i.e ., adverse hematologic effects occur at lower blood lead concentrations. Only Canada geese from the CDA River Basin, in spite of lower blood lead concentrations, had significantly reduced mean hemoglobin and hematocrit values. No euthanized Canada geese (all HYs) from CDA River Basin were classified as clinically lead poisoned, but 38 Canada geese found dead in the CDA River Basin during a concurrent study succumbed to lead poisoning between 1992 and 1997. Only 6 (15.8%) of these 38 contained ingested lead shot, which contrasts greatly with the 75–94% incidence of ingested lead shot when mortality was due to lead shot ingestion. Lead from other contaminated sources ( i.e ., sediments and vegetation) in the CDA River Basin was strongly implicated in most Canada goose deaths. Based on the 31 live mallards and Canada geese collected in the CDA River Basin, which were representative of the live populations blood sampled only, the prevalence of subclinical and clinical lead poisoning (as determined by liver lead concentrations, excluding birds with ingested lead shot) was higher in mallards: subclinical (4 of 8, 50% HYs and 6 of 11, 55% adults); clinical (0% HYs and 4 of 11, 36% adults), with less data available for Canada geese (only 1 of 9, 11% HYs marginally subclinical). The clinically lead-poisoned mallards had extremely high concentrations of lead in blood (2.69–8.82 μg/g) and liver (6.39–17.89 μg/g). Eight mallards found dead in the CDA River Basin during a concurrent study were diagnosed as lead poisoned, and only one (12.5%) contained ingested lead shot, which again strongly implicates other lead sources. The finding of dead lead poisoned Canada geese together with the high percentage of live mallards classified as subclinically or clinically lead poisoned, in combination with the low incidence of ingested lead shot causes us concern for both of these species, which live in association with lead-contaminated sediment in the CDA River Basin.
Developmental toxicity of lead-contaminated sediment to mallard ducklings
Sediment ingestion has been identified as an important exposure route for toxicants in waterfowl. The toxicity of lead-contaminated sediment from the Coeur d'Alene River Basin (CDARB) in Idaho was examined on posthatching development of mallard ( Anas platyrhynchos ) ducklings for 6 weeks. Day-old ducklings received either untreated control diet, clean sediment (24%) supplemented control diet, CDARB sediment (3,449 μg/g lead) supplemented diets at 12% or 24%, or a positive control diet containing lead acetate equivalent to that found in 24% CDARB. The 12% CDARB diet resulted in a geometric mean blood lead concentration of 1.41 ppm (WW) with over 90% depression of red blood cell ALAD activity and over threefold elevation of free erythrocyte protoporphyrin concentration. The 24% CDARB diet resulted in blood lead of 2.56 ppm with over sixfold elevation of protoporphyrin and lower brain weight. In this group the liver lead concentration was 7.92 ppm (WW), and there was a 40% increase in hepatic reduced glutathione concentration. The kidney lead concentration in this group was 7.97 ppm, and acid-fast inclusion bodies were present in the kidneys of four of nine ducklings. The lead acetate positive control group was more adversely affected in most respects than the 24% CDARB group. With a less optimal diet (mixture of two thirds corn and one third standard diet), CDARB sediment was more toxic; blood lead levels were higher, body growth and liver biochemistry (TBARS) were more affected, and prevalence of acid-fast inclusion bodies increased. Lead from CDARB sediment accumulated more readily in duckling blood and liver than reported in goslings, but at given concentrations was generally less toxic to ducklings. Many of these effects are similar to ones reported in wild mallards and geese within the CDARB.
Chemical and physical properties affecting strontium distribution coefficients of surficial-sediment samples at the Idaho National Engineering and Environmental Laboratory, Idaho
The U.S. Geological Survey and Idaho State University, in cooperation with the U.S. Department of Energy, conducted a study to determine strontium distribution coefficients (K d s) of surficial sediments at the Idaho National Engineering and Environmental Laboratory (INEEL). Batch experiments using synthesized aqueous solutions were used to determine K d s, which describe the distribution of a solute between the solution and solid phase, of 20 surficial-sediment samples from the INEEL. The K d s for the 20 surficial-sediment samples ranged from 36 to 275 ml/g. Many properties of both the synthesized aqueous solutions and sediments used in the experiments also were determined. Solution properties determined were initial and equilibrium concentrations of calcium, magnesium, and strontium, pH and specific conductance, and initial concentrations of potassium and sodium. Sediment properties determined were grain-size distribution, bulk mineralogy, whole-rock major-oxide and strontium and barium concentrations, and Brunauer-Emmett-Teller (BET) surface area. Solution and sediment properties were correlated with strontium K d s of the 20 surficial sediments using Pearson correlation coefficients. Solution properties with the strongest correlations with strontium K d s were equilibrium pH and equilibrium calcium concentration correlation coefficients, 0.6598 and –0.6518, respectively. Sediment properties with the strongest correlations with strontium K d s were manganese oxide (MnO), BET surface area, and the >4.75-mm-grain-size fraction correlation coefficients, 0.7054, 0.7022, and –0.6660, respectively. Effects of solution properties on strontium K d s were interpreted as being due to competition among similarly charged and sized cations in solution for strontium-sorption sites; effects of sediment properties on strontium K d s were interpreted as being surface-area related. Multivariate analyses of these solution and sediment properties resulted in r 2 values of 0.8071 when all five properties were used and 0.8043 when three properties, equilibrium pH, MnO, and BET surface area, were used.
Characteristic length scale of input data in distributed models: implications for modeling grain size
The appropriate spatial scale for a distributed energy balance model was investigated by: (a) determining the scale of variability associated with the remotely sensed and GIS-generated model input data; and (b) examining the effects of input data spatial aggregation on model response. The semi-variogram and the characteristic length calculated from the spatial autocorrelation were used to determine the scale of variability of the remotely sensed and GIS-generated model input data. The data were collected from two hillsides at Upper Sheep Creek, a sub-basin of the Reynolds Creek Experimental Watershed, in southwest Idaho. The data were analyzed in terms of the semivariance and the integral of the autocorrelation. The minimum characteristic length associated with the variability of the data used in the analysis was 15 m. Simulated and observed radiometric surface temperature fields at different spatial resolutions were compared. The correlation between agreement simulated and observed fields sharply declined after a 10×10 m 2 modeling grid size. A modeling grid size of about 10×10 m 2 was deemed to be the best compromise to achieve: (a) reduction of computation time and the size of the support data; and (b) a reproduction of the observed radiometric surface temperature.
Relation of waterfowl poisoning to sediment lead concentrations in the Coeur d'Alene River Basin
For many years, waterfowl have been poisoned by lead after ingesting contaminated sediment in the Coeur d'Alene River Basin, in Idaho. Results of studies on waterfowl experimentally fed this sediment were combined with results from field studies conducted in the Basin to relate sediment lead concentration to injury to waterfowl. The first step in the model estimated exposure as the relation of sediment lead concentration to blood lead concentration in mute swans ( Cygnus olor ), ingesting 22% sediment in a rice diet. That rate corresponded to the 90th percentile of sediment ingestion estimated from analyses of feces of tundra swans ( Olor columbianus ) in the Basin. Then, with additional laboratory studies on Canada geese ( Branta canadensis ) and mallards ( Anas platyrhynchos ) fed the sediment, we developed the general relation of blood lead to injury in waterfowl. Injury was quantified by blood lead concentrations, ALAD (δ-aminolevulinic acid dehydratase) activity, protoporphyrin concentrations, hemoglobin concentrations, hepatic lead concentrations, and the prevalence of renal nuclear inclusion bodies. Putting the exposure and injury relations together provided a powerful tool for assessing hazards to wildlife in the Basin. The no effect concentration of sediment lead was estimated as 24 mg/kg and the lowest effect level as 530 mg/kg. By combining our exposure equation with data on blood lead concentrations measured in moribund tundra swans in the Basin, we estimated that some mortality would occur at a sediment lead concentration as low as 1800 mg/kg.
Groundwater “fast paths” in the Snake River Plain aquifer: Radiogenic isotope ratios as natural groundwater tracers
Preferential flow paths are expected in many groundwater systems and must be located because they can greatly affect contaminant transport. The fundamental characteristics of radiogenic isotope ratios in chemically evolving waters make them highly effective as preferential flow path indicators. These ratios tend to be more easily interpreted than solute-concentration data because their response to water-rock interaction is less complex. We demonstrate this approach with groundwater 87 Sr/ 86 Sr ratios in the Snake River Plain aquifer within and near the Idaho National Engineering and Environmental Laboratory. These data reveal slow-flow zones as lower 87 Sr/ 86 Sr areas created by prolonged interaction with the host basalts and a relatively fast flowing zone as a high 87 Sr/ 86 Sr area.
Zooplanktivory and nutrient regeneration by invertebrate (Mysis relicta) and vertebrate (Oncorhynchus nerka) planktivores: Implications for trophic interactions in oligotrophic lakes
We investigated zooplanktivory and nutrient regeneration by the opossum shrimp Mysis relicta and kokanee Oncorhynchus nerka to assess the relative roles of these planktivores in oligotrophic food webs. Using bioenergetic models and clearance rate estimates, we quantified phosphorus (P) excretion rates and consumption of cladoceran prey by Mysis and kokanees in Lake Pend Oreille, Idaho, from 1995 to 1996. Consumption of cladoceran prey by Mysis was 186 kg·ha −1 ·year −1 , whereas consumption by kokanees was less than one quarter as much, at 45 kg·ha −1 ·year −1 . Similarly, Mysis excreted approximately 0.250 kg P·ha −1 ·year −1 during nighttime migrations into the upper water column, whereas P excretion by kokanees was less than one third as much, at approximately 0.070 kg P·ha −1 ·year −1 . On a volumetric basis, nocturnal excretion by Mysis ranged from 0.002 to 0.007 μg P·L −1 ·d −1 and accounted for less than 1% of the soluble reactive P typically measured in the upper water column of the lake. Hence, nutrient recycling by Mysis may be limited in the upper water column because of the nocturnal feeding habitats that constrain Mysis to deeper strata for much of the day. In spring and autumn months, low abundance of cladoceran prey coincided with high seasonal energy requirements of the Mysis population that were linked to timing of annual Mysis brood release and abundance of age-0 Mysis. Predation by Mysis accounted for 5–70% of daily cladoceran standing stock, supporting the notion that seasonal availability of cladocerans may be regulated by Mysis predation. In lakes where Mysis experience little predation mortality, they likely play a dominant role in food web interactions (e.g., trophic cascades) relative to planktivorous fishes. Biotic mechanisms, such as successful predator-avoidance behavior, omnivorous feeding habits, and seasonal variation in Mysis biomass, enhance the ability of Mysis to influence food web interactions from an intermediate trophic level.
Ghosts of habitats past: Contribution of landscape change to current habitats used by shrubland birds
Models of habitat associations for species often are developed with an implicit assumption that habitats are static, even though recent disturbance may have altered the landscape. We tested our hypothesis that trajectory and magnitude of habitat change influenced observed distribution and abundance of passerine birds breeding in shrubsteppe habitats of southwestern Idaho. Birds in this region live in dynamic landscapes undergoing predominantly large-scale, radical, and unidirectional habitat change because wildfires are converting shrublands into expanses of exotic annual grasslands. We used data from field surveys and satellite image analyses in a series of redundancy analyses to partition variances and to determine the relative contribution of habitat change and current landscapes. Although current habitats explained a greater proportion of total variation, changes in habitat and measures of habitat richness and texture also contributed to variation in abundance of Horned Larks ( Eremophila alpestris ), Brewer’s Sparrows ( Spizella breweri ), and Sage Sparrows ( Amphispiza belli ). Abundance of birds was insensitive to scale for nonspatial habitat variables. In contrast, spatial measures of habitat richness and texture in the landscape were significant only at large spatial scales. Abundance of Horned Larks, Western Meadowlarks ( Sturnella neglecta ), and Brewer’s Sparrows, but not Sage Thrashers ( Oreoscoptes montanus ) or Sage Sparrows, was positively correlated with changes toward stable habitats. Because dominant habitat changes were toward less stable conditions, regional declines of those birds in shrubsteppe habitats reflect current landscapes as well as the history, magnitude, and trajectory of habitat change.
Sensitivity of species habitat-relationship model performance to factors of scale
Researchers have come to different conclusions about the usefulness of habitat-relationship models for predicting species presence or absence. This difference frequently stems from a failure to recognize the effects of spatial scales at which the models are applied. We examined the effects of model complexity, spatial data resolution, and scale of application on the performance of bird habitat relationship (BHR) models on the Craig Mountain Wildlife Management Area and on the Idaho portion of the U.S. Forest Service's Northern Region. We constructed and tested BHR models for 60 bird species detected on the study areas. The models varied by three levels of complexity (amount of habitat information) and three spatial data resolutions (0.09 ha, 4 ha, 10 ha). We tested these models at two levels of analysis: the site level (a homogeneous area <0.5 ha) and cover-type level (an aggregation of many similar sites of a similar land-cover type), using correspondence between model predictions and species detections to calculate kappa coefficients of agreement. Model performance initially increased as models became more complex until a point was reached where omission errors increased at a rate greater than the rate at which commission errors were decreasing. Heterogeneity of the study areas appeared to influence the effect of model complexity. Changes in model complexity resulted in a greater decrease in commission error than increase in omission error. The effect of Spatial data resolution on the performance of BHR models was influenced by the variability of the study area. BHR models performed better at cover-type levels of analysis than at the site level for both study areas. Correct-presence estimates (1 - minus percentage omission error) decreased slightly as number of species detections increased on each study area. Correct-absence estimates (1 - percentage commission error) increased as number of species detections increased on each study area. This suggests that a large number of detections may be necessary to achieve reliable estimates of model accuracy.
Nitrate concentrations in ground water in the Henrys Fork Basin, eastern Idaho
In 1998 and 1999, the U.S. Geological Survey (USGS) completed comprehensive studies of nitrate concentrations in ground water in the Henrys Fork Basin in eastern Idaho (fig. 1A). These studies were done in cooperation with the following agencies or groups: Idaho Division of Environmental Quality (DEQ), District 7 Health Department, Idaho Department of Water Resources (IDWR), Idaho Department of Agriculture (IDAG), Bureau of Reclamation, Henrys Fork Foundation, Fremont County, and Madison County. This Fact Sheet presents selected results of these investigations.
A study of porewater in water saturated sediments of levee banks and marshes in the lower Coeur d'Alene River valley, Idaho: Sampling, analytical methods, and results
This report contains information about the composition of interstitial porewater and solids from water saturated, metal contaminated levee banks at the river's edge and marshes in the lower Coeur d'Alene River valley. Data include pH, alkalinity, and concentrations of sulfate and metals (arsenic [As], cadmium [Cd], copper [Cu], iron [Fe], mercury [Hg], manganese [Mn], lead [Pb], antimony [Sb], and zinc [Zn]) in porewater and sulfur (S), carbon (C), and metal contents of associated solids. The results indicate that the pH of the porewater in all of the sediments is less than the pH of the Coeur d'Alene River. Dissolved concentrations of Mn and Fe are elevated in all of the porewater and levels of sulfate in porewater are below detection limits in almost all marsh sediments and in levee banks at the 2 sites furthest downstream. These observations suggest that levee bank and marsh sediments are suboxic or anoxic below the surface. Concentrations of dissolved Cd are greater in the Coeur d'Alene River than in porewater, while concentrations of As are greater in the porewater relative to the Coeur d'Alene River. Some concentrations of Cu, Pb, Sb, and Zn in porewater are lower, while others are higher, than dissolved concentrations in the Coeur d'Alene River. In addition, leaching experiments (i.e., Standard Elutriate Tests [SET]) were done in the laboratory to evaluate potential water quality impacts resulting from the addition of oxygen and water to these sediments. The intent of the experiments was to simulate how metal concentrations in water may be affected during dredging of contaminated sediments in the lower Coeur d'Alene River valley. The results indicate that there are releases of protons, sulfate, As, Mn, Pb, Sb, and Zn from the majority of levee bank and marsh sediments during leaching by Coeur d'Alene River water. At a water to sediment ratio of 4 to 1, most values of pH and dissolved concentrations of Cd, Fe, Pb, and Zn in the leaching solutions exceed the freshwater aquatic life standards for water of a hardness of 100 mg CaCOa/L. This work was funded by the U.S. EPA and was done to support their Remedial Investigation/Feasibility Study of the Coeur d'Alene and Spokane River basins.
Analytical data for reconnaissance geochemical samples from mine dumps, stream sediments and waters at the Thompson Creek Tungsten Mine, Custer County, Idaho
The Thompson Creek mine is an inactive and abandoned tungsten mine located along Thompson Creek about 10.5 miles (17 km) northwest of Clayton, Idaho (see location map in file LOCATION.PDF). The mine consisted initially of open pit mining of outcrops and later of underground workings accessed by a single adit. The mine was worked through 1955 and waste piles presently reside in the flood plain above the east bank of Thompson Creek. A view of the collapsed adit is provided in the TIFF (Tagged-Image File Format) file ADIT.TIF (all photographs taken on 08/13/99). A south-facing view of the mine waste dumps is provided in the TIFF file SOUTH.TIF and a north-facing view is provided in NORTH.TIF.
Hydrologic and meteorological data for an unsaturated-zone study area near the Radioactive Waste Management Complex, Idaho National Engineering and Environmental Laboratory, Idaho, 1997 to 1999
The Radioactive Waste Management Complex (RWMC) Subsurface Disposal Area (SDA) at the Idaho National Engineering and Environmental Laboratory (INEEL) has been used for burial of radioactive waste since 1952. In 1985, the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, began a multi-phase study of the geohydrology of the RWMC to provide a basis for estimating the extent of and the potential for migration of radionuclides in the unsaturated zone beneath the waste trenches and pits. This is the final phase in a study to provide hydrologic and meteorological data collected at a designated test trench area established by the U.S. Geological Survey in 1985 adjacent to the northern boundary of the RWMC SDA. Soil-moisture content measurements were collected approximately monthly during the 1997-99 period from 13 neutron-probe access holes with a neutron moisture gage. A meteorological station inside the test trench area provides data for the determination of evapotranspiration rates. This station measures soil surface temperature, net radiation, air temperature, relative humidity, windspeed, wind direction, soil heat flux, and precipitation, and also calculates vapor pressure. Meteorological data for the test trench area are available for 1997 and part of 1998. The meteorological and soil-moisture data are contained in files on a compact disk included with this report. The data are presented in simple American Standard Code for Information Interchange (ASCII) format with tab-delimited fields.
Concentrations and loads of cadmium, lead, and zinc measured near the peak of the 1999 snowmelt-runoff hydrographs for 42 water-quality stations, Coeur d'Alene River basin, Idaho
The Remedial Investigation/Feasibility Study conducted by the U.S. Environmental Protection Agency within the Spokane River Basin of northern Idaho and eastern Washington included extensive data-collection activities to determine the nature and extent of trace-element contamination within the basin. The U.S. Geological Survey designed and implemented synoptic sampling of the 1999 snowmelt-runoff event at 42 water- quality stations during the 1999 water year. The distribution of the 42 stations was as follows: North Fork Coeur d’Alene River and tributaries, 4 stations; South Fork Coeur d’Alene River, 13 stations; Canyon, Ninemile, and Pine Creeks, 4 stations each; other tributaries to South Fork Coeur d’Alene River, 10 stations; and main stem Coeur d’Alene River, 3 stations. The objective was to synoptically collect discharge and water-quality data in order to significantly improve the estimation of trace-element loads from multiple contributing source areas during the snowmelt-runoff event. Discharge and water-quality data were collected near the peak discharge during late May 1999. Each station was sampled for whole-water recoverable and dissolved concentrations and loads of cadmium, lead, and zinc. Three general concentration levels of cadmium, lead, and zinc were noted among the 42 stations. Dissolved cadmium concentrations were less than 1 microgram per liter (μg/L) at 26 stations, exceeded 10 μg/L at 1 station, and ranged from 1 to 10 μg/L at the remaining 15 stations. Whole-water recoverable cadmium concentrations were less than 1 μg/L at 23 stations, exceeded 10 μg/L at 4 stations, and ranged from 1 to 10 μg/L at the remaining 15 stations. Dissolved lead concentrations were less than 1 μg/L at 22 stations, exceeded 10 μg/L at 7 stations, and ranged from 1 to 10 μg/L at the remaining 13 stations. Whole-water recoverable lead concentrations were less than 10 μg/L at 13 stations, exceeded 500 μg/L at 20 stations, and ranged from 10 to 500 μg/L at the remaining 9 stations. Dis- solved zinc concentrations were less than 10 μg/L at 14 stations, exceeded 500 μg/L at 6 stations, and ranged from 10 to 500 μg/L at the remaining 22 stations. Whole-water recoverable zinc concentrations were less than 10 μg/L at 9 stations, exceeded 500 μg/L at 15 stations, and ranged from 10 to 500 μg/L at the remaining 18 stations. The accounting of tributary loads between two South Fork stations at O’Brien Gulch and Pinehurst revealed differences between dissolved and whole-water recoverable loads, as well as differences among the three trace elements. Tributary loads accounted for an average of 29 percent (range of 27 to 31.6 percent) of the differences in whole-water recoverable loads of the three trace elements between the O’Brien Gulch and Pinehurst stations. This result implies that the main stem of the South Fork Coeur d’Alene River is an important source of sediment-associated trace elements under elevated streamflows. In the case of dissolved loads of cadmium and zinc, the tributary loads accounted for about one-half (range of 47.3 to 55 percent) of the differences between the two South Fork stations. As with whole-water recoverable loads, this result indicates an important source of dissolved cadmium and zinc within the main stem. The picture is much different for dissolved lead loads: About 94 percent of the load difference between the O’Brien Gulch and Pinehurst stations was accounted for by loads from the 13 tributaries. The Coeur d’Alene River near Harrison transported 924 pounds of dissolved lead per day, of which 82.8 pounds came from the South Fork and 11.7 pounds from the North Fork. Only 10.2 percent of the load at Harrison was measured at the Pinehurst and Enaville stations; therefore, a substantial load of dissolved lead is being contributed downstream from the confluence of the North and South Forks.
Transport of suspended and bedload sediment at eight stations in the Coeur d'Alene River basin, Idaho
The Remedial Investigation/Feasibility Study conducted by the U.S. Environmental Protection Agency within the Spokane River Basin of northern Idaho and eastern Washington included extensive data-collection activities to determine the nature and extent of trace-element contamination within the basin. As part of the investigation, the U.S. Geological Survey designed and implemented a sampling program to assess sediment transport in the Coeur d’Alene River Basin. Suspended and bedload sediments were sampled at four stations at or near base flow and at eight stations during low, moderate, and high discharge conditions between February 1999 and April 2000. The concentrations and loads of suspended and bedload sediment at all stations were directly related to stream discharge. To quantify these relationships, a power function was used to develop sediment-transport curves at all stations. Although the transport curves for most of the stations indicate a good log-log relationship between stream discharge and suspended- and bedload-sediment discharge, there was a fair amount of scatter about the best-fit regression at most stations. For suspended-sediment discharge, the scatter can be primarily attributed to a hysteresis effect in the concentration of suspended sediment as stream discharge rises and falls. The effects of hysteresis on bedload-sediment discharge were difficult to assess because of a paucity of samples collected over the stream hydrograph. At most of the stations, and at the stream discharges sampled, the transport characteristics for fine- and sand-sized suspended sediment were similar. However, at the two main-stem Coeur d’Alene River stations, Rose Lake and Harrison, the suspended-sediment load was primarily composed of fine-grained sediment at stream discharges of less than 15,000 cubic feet per second. These two stations are characterized by relatively slow water velocities, which appear to be insufficient to transport sand-sized sediment at lower stream discharge. At most of the stations, and at the stream discharges sampled, the bedload was primarily composed of material greater than 2 millimeters in diameter, the break between sand and gravel. A predominance of sand-sized bedload was noted at only a few stations, and generally only during low stream discharge. The particle-size distribution of bedload sediment at most stations became proportionately coarser as stream discharge increased. During the peak of snowmelt runoff for water years 1999 and 2000, gravel-sized material between 2 and 64 millimeters in diameter comprised more than 70 percent of the bedload transport at most stations. However, at the station on the Coeur d’Alene River at Rose Lake, the bedload was predominantly composed of fine-grained material of less than 1 millimeter in diameter for all measured stream discharges. The slow water velocities at Rose Lake accounted for the predominance of fine-grained sediment transport.