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USGS2006

A computer program for estimating instream travel times and concentrations of a potential contaminant in the Yellowstone River, Montana

The Yellowstone River is very important in a variety of ways to the residents of southeastern Montana; however, it is especially vulnerable to spilled contaminants. In 2004, the U.S. Geological Survey, in cooperation with Montana Department of Environmental Quality, initiated a study to develop a computer program to rapidly estimate instream travel times and concentrations of a potential contaminant in the Yellowstone River using regression equations developed in 1999 by the U.S. Geological Survey. The purpose of this report is to describe these equations and their limitations, describe the development of a computer program to apply the equations to the Yellowstone River, and provide detailed instructions on how to use the program. This program is available online at [http://pubs.water.usgs.gov/sir2006-5057/includes/ytot.xls]. The regression equations provide estimates of instream travel times and concentrations in rivers where little or no contaminant-transport data are available. Equations were developed and presented for the most probable flow velocity and the maximum probable flow velocity. These velocity estimates can then be used to calculate instream travel times and concentrations of a potential contaminant. The computer program was developed so estimation equations for instream travel times and concentrations can be solved quickly for sites along the Yellowstone River between Corwin Springs and Sidney, Montana. The basic types of data needed to run the program are spill data, streamflow data, and data for locations of interest along the Yellowstone River. Data output from the program includes spill location, river mileage at specified locations, instantaneous discharge, mean-annual discharge, drainage area, and channel slope. Travel times and concentrations are provided for estimates of the most probable velocity of the peak concentration and the maximum probable velocity of the peak concentration. Verification of estimates of instream travel times and concentrations for the Yellowstone River requires information about the flow velocity throughout the 520 mi of river in the study area. Dye-tracer studies would provide the best data about flow velocities and would provide the best verification of instream travel times and concentrations estimated from this computer program; however, data from such studies does not currently (2006) exist and new studies would be expensive and time-consuming. An alternative approach used in this study for verification of instream travel times is based on the use of flood-wave velocities determined from recorded streamflow hydrographs at selected mainstem streamflow-gaging stations along the Yellowstone River. The ratios of flood-wave velocity to the most probable velocity for the base flow estimated from the computer program are within the accepted range of 2.5 to 4.0 and indicate that flow velocities estimated from the computer program are reasonable for the Yellowstone River. The ratios of flood-wave velocity to the maximum probable velocity are within a range of 1.9 to 2.8 and indicate that the maximum probable flow velocities estimated from the computer program, which corresponds to the shortest travel times and maximum probable concentrations, are conservative and reasonable for the Yellowstone River.

Scientific Investigations Report↗

USGS2006

Surface-water quality in rivers and drainage basins discharging to the southern part of Hood Canal, Mason and Kitsap Counties, Washington, 2004

Concentrations of nutrients, major ions, organic carbon, suspended sediment, and the nitrogen isotope ratio of nitrate (delta15N) were collected at surface-water sites in rivers and drainage basins discharging to the southern part of Hood Canal, Mason and Kitsap Counties, Washington. Base-flow samples were collected from sites on the Union, Tahuya, and Skokomish Rivers from June to August 2004. Concentrations of nutrients at all sites were low. Ammonia and orthophosphate were less than the detection limit for most samples, and nitrate plus nitrite concentrations ranged from less than the detection limit of 0.06 to 0.49 milligram per liter (mg/L). Nitrate plus nitrite concentrations were near the detection limit of 0.06 mg/L in the North Fork, South Fork, and mainstem of the Skokomish River. The concentration of nitrate plus nitrite in the Tahuya River system above Lake Tahuya was 0.17 mg/L, but decreased to 0.1 mg/L or less downstream of Lake Tahuya. Overall, the Union River contained the highest nitrate plus nitrite concentrations of the three large river systems, ranging from 0.12 to 0.28 mg/L. delta15N generally was within the range that encompasses most sources, providing little information on nitrate sources. Most nitrogen was in the dissolved inorganic form. Dissolved inorganic nitrogen in Lake Tahuya was converted into particulate and dissolved organic nitrogen. Dissolved organic carbon concentrations generally were less than 1 mg/L in the Tahuya and Skokomish Rivers and averaged 1.3 mg/L in the Union River. Dissolved organic carbon concentrations of 2.6 to 2.7 mg/L at sites just downstream of Lake Tahuya were highest for the three large river systems, and decreased to concentrations less than 1 mg/L, which was similar to concentrations in the Skokomish River. Total nitrogen concentrations near 0.5 mg/L were measured at two sites: Unnamed Creek at Purdy-Cutoff Road (site S2b) and downstream of Lake Devereaux (site SP5). Concentrations of nitrate plus nitrite were highest at site S2b (0.49 mg/L), and dissolved organic carbon concentrations (3.3 mg/L) were highest at the outlet of Lake Devereaux. However, the overall impact of these sites on the nutrient loading to Hood Canal probably is negligible because of the low streamflow and small loads. Springtime samples were collected from the Union River, Tahuya River, Mission Creek, and three smaller drainage basins in March 2004. Samples were collected during spring rain events to determine if increased runoff contributes larger amounts of sediment and nutrients from the land into the surface water. There was little difference in nutrient concentrations between samples collected in the spring and base-flow samples collected in the summer. This is likely due to the fact that the springtime samples were collected during a rain event and not necessarily during a peak in the hydrograph.

Scientific Investigations Report↗

USGS2006

Concentrations, fluxes, and yields of nitrogen, phosphorus, and suspended sediment in the Illinois River basin, 1996-2000

Concentrations, spatial and temporal variations, and fluxes of nitrogen, phosphorus, and suspended sediment were determined for 16 streams in the Illinois River Basin, Illinois from October 1996 through September 2000. Water samples were collected through the National Water-Quality Assessment's Lower Illinois River Basin (LIRB) and Upper Illinois River Basin (UIRB) Study Units on a monthly to weekly frequency from watersheds representing predominantly agricultural and urban land, as well as areas of mixed land-use. Streams in agricultural watersheds had high concentrations and fluxes of nitrate nitrogen, whereas streams in predominantly urban watersheds had high concentrations (above background levels) of ammonia nitrogen, organic nitrogen, and phosphorus. Median concentrations of nitrate nitrogen and total phosphorus were similar at the two Illinois River sampling stations (Illinois River at Ottawa, Ill. and Illinois River at Valley City, Ill.) that represented the downstream points of the UIRB and LIRB Study Units, respectively, and integrated multiple land-use areas. Concentrations of nitrogen were typically highest in the spring and lowest in the fall in agricultural watersheds, but highest in the winter in urban watersheds. Phosphorus concentrations in urban watersheds were highest in the fall and winter, but there was minimal seasonal variation in phosphorus concentrations in agricultural watersheds. Concentrations of nitrate and total nitrogen were affected primarily by non-point sources and hydrologic factors such as streamflow, storm intensity, watershed configuration, and soil permeability, whereas concentrations of phosphorus were affected largely by point-source contributions that typically have little seasonal variation. Seasonal variation in hydrologic conditions was an important factor for seasonal variation in nutrient concentration. Fluxes and yields of nitrogen and phosphorus forms varied substantially throughout the Illinois River Basin, and yields of specific nutrient forms were determined primarily by upstream land uses. Yields of nitrate nitrogen were highest in predominantly agricultural watersheds, whereas yields of phosphorus and ammonia nitrogen were highest in urban watersheds with wastewater effluent contributions. Yields of both total nitrogen and total phosphorus were similar at the two Illinois River stations representing the integrated UIRB and LIRB Study Units. Concentrations of suspended sediment ranged from 1 to 3,110 milligrams per liter (mg/L), with median concentrations generally higher in the UIRB. Suspended-sediment concentrations were highest and most variable in the LaMoine River Basin. The median concentration of suspended sediment in the Illinois River at Valley City, Ill. (155 mg/L) was twice as high as that at Ottawa, Ill. (80 mg/L). Fluxes of suspended sediment generally corresponded to watershed size and yields from agricultural watersheds were larger than yields from urban watersheds. The flux in the Illinois River at Valley City, Ill. (4,880,000 tons per year) was approximately four times the flux in the Illinois River at Ottawa, Ill. (1,060,000 tons per year).

Scientific Investigations Report↗

USGS2006

Water-quality characteristics, including sodium-adsorption ratios, for four sites in the Powder River drainage basin, Wyoming and Montana, water years 2001-2004

The U.S. Geological Survey, in cooperation with the Wyoming Department of Environmental Quality, monitors streams throughout the Powder River structural basin in Wyoming and parts of Montana for potential effects of coalbed natural gas development. Specific conductance and sodium-adsorption ratios may be larger in coalbed waters than in stream waters that may receive the discharge waters. Therefore, continuous water-quality instruments for specific conductance were installed and discrete water-quality samples were collected to characterize water quality during water years 2001-2004 at four sites in the Powder River drainage basin: Powder River at Sussex, Wyoming; Crazy Woman Creek near Arvada, Wyoming; Clear Creek near Arvada, Wyoming; and Powder River at Moorhead, Montana. During water years 2001-2004, the median specific conductance of 2,270 microsiemens per centimeter at 25 degrees Celsius (?S/cm) in discrete samples from the Powder River at Sussex, Wyoming, was larger than the median specific conductance of 1,930 ?S/cm in discrete samples collected downstream from the Powder River at Moorhead, Montana. The median specific conductance was smallest in discrete samples from Clear Creek (1,180 ?S/cm), which has a dilution effect on the specific conductance for the Powder River at Moorhead, Montana. The daily mean specific conductance from continuous water-quality instruments during the irrigation season showed the same spatial pattern as specific conductance values for the discrete samples. Dissolved sodium, sodium-adsorption ratios, and dissolved solids generally showed the same spatial pattern as specific conductance. The largest median sodium concentration (274 milligrams per liter) and the largest range of sodium-adsorption ratios (3.7 to 21) were measured in discrete samples from the Powder River at Sussex, Wyoming. Median concentrations of sodium and sodium-adsorption ratios were substantially smaller in Crazy Woman Creek and Clear Creek, which tend to decrease sodium concentrations and sodium-adsorption ratios at the Powder River at Moorhead, Montana. Dissolved-solids concentrations in discrete samples were closely correlated with specific conductance values; Pearson's correlation coefficients were 0.98 or greater for all four sites. Regression equations for discrete values of specific conductance and sodium-adsorption ratios were statistically significant (p-values <0.001) at all four sites. The strongest relation (R2=0.92) was at the Powder River at Sussex, Wyoming. Relations on Crazy Woman Creek (R2=0.91) and Clear Creek (R2=0.83) also were strong. The relation between specific conductance and sodium-adsorption ratios was weakest (R2=0.65) at the Powder River at Moorhead, Montana; however, the relation was still significant. These data indicate that values of specific conductance are useful for estimating sodium-adsorption ratios. A regression model called LOADEST was used to estimate dissolved-solids loads for the four sites. The average daily mean dissolved-solids loads varied among the sites during water year 2004. The largest average daily mean dissolved-solids load was calculated for the Powder River at Moorhead, Montana. Although the smallest concentrations of dissolved solids were in samples from Clear Creek, the smallest average daily mean dissolved-solids load was calculated for Crazy Woman Creek. The largest loads occurred during spring runoff, and the smallest loads occurred in late summer, when streamflows typically were smallest. Dissolved-solids loads may be smaller than average during water years 2001-2004 because of smaller than average streamflow as a result of drought conditions.

Scientific Investigations Report↗

USGS2006

Hydrologic Characteristics of a Managed Wetland and a Natural Riverine Wetland along the Kankakee River in Northwestern Indiana

Characteristics of ground-water/surface-water interactions were identified at a managed wetland (Hog Marsh) and a natural riverine wetland (LaSalle) located on the north and south sides, respectively, of the Kankakee River in northwestern Indiana. Hog Marsh covers about 390 hectares of the Grand Kankakee Marsh County Park. LaSalle covers about 100 hectares of the LaSalle State Fish and Wildlife Area, and is about 20 kilometers downstream of Hog Marsh. Hydrologic characteristics of the two wetlands were investigated using data from 1997 to 1999 for 22 wells adjacent to the Kankakee River in northwestern Indiana. Surface-water levels at the managed wetland were controlled by a system of channels, levees, and managed flooding. Surface-water levels at the natural riverine wetland were not controlled. Ground-water levels in the unconfined surficial aquifer beneath the two wetlands were analyzed by assessing water-level fluctuations. Fifteen wells at Hog Marsh and seven wells at LaSalle were monitored. The interquartile range in ground-water levels away from the river at Hog Marsh fluctuated less (from 0.4 to 0.7 meters) than all ground-water levels in the same aquifer beneath LaSalle (from 0.9 to 1.0 meters). The difference in the range of water-level fluctuation probably is attributable to the managed flooding of Hog Marsh units, which tends to maintain somewhat uniform water levels in that wetland. Ground-water-flow directions along a vertical section through the unconfined surficial aquifer at the managed wetland were more variable than those at the natural riverine wetland. During winter and spring, when flow in the Kankakee River is high, flow is from the Kankakee River into the adjacent surficial aquifer and towards a 2-meter-wide Brown Ditch on the north side of Hog Marsh. Water levels in Brown Ditch remain lower than those in the Kankakee River during this period. From June to December, when flow in the Kankakee River is moderate to low, a flow divide developed near the center of the managed wetland. Ground-water flow south of the divide is to the Kankakee River; north of the divide, it is toward Brown Ditch. Slight ground-water mounding near the center of the managed wetland is accentuated by water-management practices that intentionally flood that area. Ground-water flow in the surficial aquifer at the natural riverine wetland was not impeded by ditches or managed flooding, and a simple flow-through system from areas south of the Kankakee River to the river was observed. A ground-water flow model was constructed along a representative cross section through the surficial aquifer at the managed wetland and calibrated using data collected at the site. A no-flow boundary was used beneath the Kankakee River, and head-dependent boundaries were used along the north end of the model and at the base of the model. The model simulations indicated that artificial controls on the managed-wetland hydrology create sites of recharge to and discharge from the surficial aquifer that are absent at the natural riverine wetland. The steady-state flow simulation represented flow conditions following a 4-month period of no changes in hydrologic stresses. The simulation results indicated that flow paths originating from flooded areas near the center of the managed wetland are sources of aquifer recharge during the managed-flooding period. Brown Ditch captured almost all of the ground water north of the managed wetland. The simulated water budget along a well transect indicated that 88 percent of inflow to the surficial aquifer beneath the managed wetland was from a distribution channel and from flooding in the management units. These modeling results identify differences in flow patterns between the managed and natural riverine wetlands in addition to those identified by the water-level data. Results of transient simulations indicated that surface water from the Kankakee River penetrated only about 2 to 3 meters into the surficial aquif

Indiana↗

USGS2007

Base flow (1966-2005) and streamflow gain and loss (2006) of the Brazos River, McLennan County to Fort Bend County, Texas

During 2006–07, the U.S. Geological Survey (USGS), in cooperation with the Texas Water Development Board, did a study to quantify historical (water years 1966–2005) base flow and streamflow gains and losses from two streamflow-measuring surveys (March and August 2006) in the Brazos River from McLennan County to Fort Bend County, Texas. The Brazos River is hydraulically connected to the Brazos River alluvium aquifer, which in turn is hydraulically connected to several underlying aquifers, the outcrops of which occur in laterally adjacent layers generally parallel to the coast (major aquifers, Carrizo-Wilcox and Gulf Coast, and minor aquifers, Queen City, Sparta, and Yegua-Jackson). Hydrograph separation was done using the USGS computer program Hydrograph Separation and Analysis with historical streamflow from 10 USGS gaging stations, three on the Brazos River and seven on selected tributaries to the Brazos River. Streamflow data for computation of gains and losses were collected in March 2006 from 36 sites on the Brazos River and 19 sites on 19 tributaries to the Brazos River; and in August 2006 from 28 sites on the Brazos River and 16 sites on tributaries. Hydrograph separation and associated analyses indicate an appreciable increase in base flow as a percentage of streamflow in the reach of the Brazos River that crosses the outcrops of the Carrizo-Wilcox, Queen City, Sparta, and Yegua-Jackson aquifers compared to that in the adjacent upstream reach (on average from about 43 percent to about 60 percent). No increase in base flow as a percentage of streamflow in the reach of the Brazos River crossing the Gulf Coast aquifer compared to that in the adjacent upstream reach was indicated. Streamflow gains and losses computed for March 2006 for 35 reaches defined by pairs of sites on the Brazos River indicated that five reaches were verifiably gaining streamflow (computed gain exceeded potential flow measurement error) and none were verifiably losing streamflow. Four of the five gaining reaches are in the outcrop areas of the Carrizo-Wilcox and Yegua-Jackson aquifers. The results of the synoptic gain and loss surveys are consistent with the results of the base-flow analysis of historical streamflow. Appreciable increases in streamflow, apparently the result of increases in base flow, occur in the reach of the Brazos River that crosses the outcrops of the Carrizo-Wilcox, Queen City, Sparta, and Yegua-Jackson aquifers.

Texas↗

USGS2009

Hydrologic Conditions that Influence Streamflow Losses in a Karst Region of the Upper Peace River, Polk County, Florida

The upper Peace River from Bartow to Fort Meade, Florida, is described as a groundwater recharge area, reflecting a reversal from historical groundwater discharge patterns that existed prior to the 1950s. The upper Peace River channel and floodplain are characterized by extensive karst development, with numerous fractures, crevasses, and sinks that have been eroded in the near-surface and underlying carbonate bedrock. With the reversal in groundwater head gradients, river water is lost to the underlying groundwater system through these karst features. An investigation was conducted to evaluate the hydrologic conditions that influence streamflow losses in the karst region of the upper Peace River. The upper Peace River is located in a basin that has been altered substantially by phosphate mining and increases in groundwater use. These alterations have changed groundwater flow patterns and caused streamflow declines through time. Hydrologic factors that have had the greatest influence on streamflow declines in the upper Peace River include the lowering of the potentiometric surfaces of the intermediate aquifer system and Upper Floridan aquifer beneath the riverbed elevation due to below-average rainfall (droughts), increases in groundwater use, and the presence of numerous karst features in the low-water channel and floodplain that enhance the loss of streamflow. Seepage runs conducted along the upper Peace River, from Bartow to Fort Meade, indicate that the greatest streamflow losses occurred along an approximate 2-mile section of the river beginning about 1 mile south of the Peace River at Bartow gaging station. Along the low-water and floodplain channel of this 2-mile section, there are about 10 prominent karst features that influence streamflow losses. Losses from the individual karst features ranged from 0.22 to 16 cubic feet per second based on measurements made between 2002 and 2007. The largest measured flow loss for all the karst features was about 50 cubic feet per second, or about 32 million gallons per day, on June 28, 2002. Streamflow losses varied throughout the year, and were related to seasonal fluctuations in groundwater levels. When groundwater levels were at their lowest level at the end of the dry season (May and June), there was an increased potential for streamflow losses. During this study, the largest streamflow losses occurred at the beginning of the summer rainy season when discharge in the river increased and large volumes of water were needed to replenish unfilled cavities and void spaces in the underlying aquifers. The underlying geology along the upper Peace River and floodplain is highly karstified, and aids in the movement and amount of streamflow that is lost to the groundwater system in this region. Numerous karst features and fractured carbonates and cavernous zones observed in geologic cores and geophysical logs indicate an active, well-connected, groundwater flow system. Aquifer and dye tests conducted along the upper Peace River indicate the presence of cavernous and highly transmissive layers within the floodplain area that can store and transport large volumes of water in underground cavities. A discharge measurement made during this study indicates that the cavernous system associated with Dover Sink can accept over 10 million gallons per day (16 cubic feet per second) of streamflow before the localized aquifer storage volume is replenished and the level of the sink is stabilized.

Scientific Investigations Report↗

USGS2010

Assessment of ecological conditions and potential effects of water produced from coalbed natural gas development on biological communities in streams of the Powder River structural basin, Wyoming and Montana, 2005-08

Ongoing development of coalbed natural gas in the Powder River structural basin in Wyoming and Montana led to formation of an interagency task group to address concerns about the effects of the resulting production water on biological communities in streams of the area. The interagency task group developed a monitoring plan and conducted sampling of macroinvertebrate, algal, and fish communities at 47 sites during 2005-08 to document current ecological conditions and determine existing and potential effects of water produced from coalbed natural gas development on biological communities. Macroinvertebrate, algal, and fish community composition varied between drainage basins, among sites within drainage basins, and by year. Macroinvertebrate communities of the main-stem Tongue River were characterized by higher taxa richness and higher abundance of Ephemeroptera, for example, compared to macroinvertebrate communities in plains tributaries of the Tongue River and the main-stem Powder River. Fish communities of the Tongue River were characterized by higher taxa richness and abundance of introduced species compared to the Powder River where native species were dominant. Macroinvertebrate community metric values from sites in the middle reach of the main-stem Powder River, from below Willow Creek to below Crazy Woman Creek, differed from metric values in the upper and lower reaches of the Powder River. Metrics indicative of communitywide differences included measures of taxa richness, relative abundance, feeding mode, and tolerance. Some of the variation in the macroinvertebrate communities could be explained by variation in environmental variables, including physical (turbidity, embeddedness, bed substrate size, and streamflow) and chemical (alkalinity and specific conductance) variables. Of these environmental variables, alkalinity was the best indicator of coalbed natural gas development because of the sodiumbicarbonate signature of the production water. Algal samples from the main-stem Powder River generally confirmed the pattern observed in the macroinvertebrate communities. Algal communities at sites in the middle reach of the Powder River commonly were characterized by dominance by a single taxon and by low biovolume of algae compared to other sites. In contrast to the macroinvertebrate and algal communities, species richness of fish communities was highest in the middle reach of the Powder River. Although a few significant differences in fish metrics were determined along the main-stem Powder River, the differences did not correspond to the pattern observed for the macroinvertebrate and algae communities. Differences in biological communities were noted between years, potentially due to the effects of drought. Macroinvertebrate community metrics, such as Diptera taxa richness, were significantly different in the severe drought year of 2006 from metric values in 2005 and 2007-08. Waterquality data collected during the study indicated that, with few exceptions, water-quality constituents generally did not exceed State or Federal acute and chronic criteria for the protection of aquatic life.

Scientific Investigations Report↗

USGS2011

Monitoring to assess progress toward meeting the Assabet River, Massachusetts, phosphorus total maximum daily load - Aquatic macrophyte biomass and sediment-phosphorus flux

In 2004, the Total Maximum Daily Load (TMDL) for Total Phosphorus in the Assabet River, Massachusetts, was approved by the U.S. Environmental Protection Agency. The goal of the TMDL was to decrease the concentrations of the nutrient phosphorus to mitigate some of the instream ecological effects of eutrophication on the river; these effects were, for the most part, direct consequences of the excessive growth of aquatic macrophytes. The primary instrument effecting lower concentrations of phosphorus was to be strict control of phosphorus releases from four major wastewatertreatment plants in Westborough, Marlborough, Hudson, and Maynard, Massachusetts. The improvements to be achieved from implementing this control were lower concentrations of total and dissolved phosphorus in the river, a 50-percent reduction in aquatic-plant biomass, a 30-percent reduction in episodes of dissolved oxygen supersaturation, no low-flow dissolved oxygen concentrations less than 5.0 milligrams per liter, and a 90-percent reduction in sediment releases of phosphorus to the overlying water. In 2007, the U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection, initiated studies to evaluate conditions in the Assabet River prior to the upgrading of wastewater-treatment plants to remove more phosphorus from their effluents. The studies, completed in 2008, implemented a visual monitoring plan to evaluate the extent and biomass of the floating macrophyte Lemna minor (commonly known as lesser duckweed) in five impoundments and evaluated the potential for phosphorus flux from sediments in impounded and free-flowing reaches of the river. Hydrologically, the two study years 2007 and 2008 were quite different. In 2007, summer streamflows, although low, were higher than average, and in 2008, the flows were generally higher than in 2007. Visually, the effects of these streamflow differences on the distribution of Lemna were obvious. In 2007, large amounts of floating macrophytes accumulated behind bridge constrictions and dams; in 2008, high flows during the early part of the growing season carried floating macrophytes past bridges and over dams, minimizing accumulations. Samples of Lemna were collected and weighed to provide an estimate of Lemna biomass based on areal coverage during the summer growing seasons at eight sites in the five impoundments. Average estimated biomass during 2007 was approximately twice the 2008 biomass in each of the areas monitored. In 2007, in situ hyperspectral and high-resolution, multispectral data from the IKONOS satellite were obtained to evaluate the feasibility of using remote sensing to monitor the extent of aquatic plant growth in Assabet River impoundments. Three vegetation indices based on light reflectance were used to develop metrics with which the hyperspectral and satellite data were compared. The results of the comparisons confirmed that the high-resolution satellite imagery could differentiate among the common aquatic-plant associations found in the impoundments. The use of satellite imagery could counterbalance emphasis on the subjective judgment of a human observer, and airborne hyperspectral data can provide higher resolution imagery than multispectral satellite data. In 2007 and 2008, the potential for sediment flux of phosphorus was examined in free-flowing reaches of the river and in the two largest impoundments-Hudson and Ben Smith. These studies were undertaken to determine in situ flux rates prior to the implementation of the Assabet River Total Maximum Daily Load (TMDL) for phosphorus and to compare these rates with those used in the development and evaluation of the TMDL. Water samples collected from a chamber placed on the river bottom were analyzed for total phosphorus and orthophosphorus. Ambient dissolved oxygen concentrations and seasonal temperature differences appeared to affect the rates of sequestration and sediment release of phosphorus. When dissolved oxygen concentrations remained relatively high in the chambers and when the temperature was relatively low, the tendency was for phosphorus concentrations to decrease in the chambers, indicating sediment sequestration of phosphorus; when dissolved oxygen concentrations dropped to near zero and temperatures were warmest, phosphorus concentrations increased in the chambers, indicating phosphorus flux from the sediment. The rates of release and sequestration in the in situ studies were generally comparable with the rates determined in laboratory studies of Assabet River sediment cores for State and Federal agencies. Sediment-core and chamber studies produced substantial sediment fluxes to the water column only under extremely low-DO or anaerobic conditions rarely found in the Assabet River impoundments; thus, sediment is not likely to be a major phosphorus source, especially when compared to the wastewater effluent, which sustains higher ambient concentrations. The regulatory agencies now (2011) have substantial laboratory and field data with which to determine the required 90-percent reduction in phosphorus flux after the completion of upgrades to the wastewater-treatment plants that discharge to the Assabet River.

Massachusetts↗

USGS2013

Estimates of gains and losses from unmeasured sources and sinks for streamflow and dissolved-solids load in selected reaches of the Arkansas River, southeastern Colorado, 2009-2010

The Arkansas River is an important municipal water supply and is the primary supply for about 400,000 acres of irrigated land in southeastern Colorado. The suitability of this water for domestic, agricultural, and industrial use is affected by high salinity in parts of the Arkansas River. There is a need to quantify mass loading of dissolved solids (DS) in the Arkansas River. In 2009, the U.S. Geological Survey, in cooperation with the Arkansas River Basin Regional Resource Planning Group and the Colorado Water Conservation Board, began a study to estimate gains and losses from unmeasured sources and sinks for streamflow and DS load in selected reaches of the Arkansas River in southeastern Colorado. Two study reaches were selected for investigation—Canon City to just upstream from Pueblo Reservoir (UARB) and Avondale to Las Animas (LARB). The results from the water-budget analyses indicated that potential areas of unmeasured sources and sinks of streamflow were identifiable in the two study reaches. In the UARB, a substantial volume of water in the subreach from Ark at Canon City to the seasonal gaging station 5 miles downstream (Ark nr Canon City) was unaccounted for by the methodology used in this analysis. The daily gain from unmeasured sources in this subreach was estimated to be about 100 cubic feet per second (ft 3 /s) or about 20 ft 3 /s per river mile. Water-budget estimates for the remaining 18 miles of the UARB study reach indicated that gains or losses from unmeasured sources or sinks were within the measurement error as defined for this report. In the LARB, gains and losses from unmeasured sources and sinks were identified in some of the subreaches but the magnitude of the flux generally was small. Unmeasured sources ranging from less than 2 to 3 ft 3 /s per mile were identified in the river subreaches from Ark at Catlin Dam downstream to Ark at Swink. A streamflow loss was indicated along the subreach from Ark at Nepesta to Ark at Catlin Dam, particularly in 2010. The mechanism and spatial extent of this sink was not identified, and further investigation would be required to better quantify the loss. The results from the analyses of unmeasured sources of DS load indicated that potential source areas were identifiable in the study areas. It might be expected that unmeasured DS load flux would be identified along the same reaches where unmeasured streamflow flux was identified. To that extent, some of the observed results from the analysis of daily DS loading did mirror the streamflow results. In some subreaches of the Arkansas River, however, unmeasured sources and sinks of DS load did not appear to be directly associated with unmeasured sources and sinks of streamflow. In the UARB from Ark at Canon City to Ark nr Canon City, unmeasured gains in DS load were estimated to range from 11 to 22 tons per day per mile in 2009 and from about 8 to 13 tons per day per mile in 2010; streamflow from unmeasured sources was estimated to be about 20 ft 3 /s per mile along this same reach. Downstream from this short reach, DS load to the river from unmeasured sources was estimated to range from 5.4 to 7.6 tons per day per mile in 2010 for Ark nr Canon City to Ark at Portland and from 11 to 16 tons per day per mile in 2009 for Ark at Portland to Ark nr Portland. Unmeasured gains in streamflow were not identified in either of these subreaches. Several small tributaries with DS concentrations ranging from 3,000 mg/L to as high as 6,000 mg/L enter the river along these subreaches. These inputs may indicate a potential source of groundwater that could affect DS loading in the river. Further investigation would be needed to identify the unmeasured source or sources of DS load to determine the nature and extent of unmeasured inputs. In the LARB, gains in DS load from unmeasured sources were identified for the subreach from Ark nr Avondale to Ark at Nepesta, although no substantial amounts of streamflow from unmeasured sources were identified for this subreach. In 2009, the estimated gain in DS load from unmeasured sources for this subreach was 4.7 tons per day per mile. An increase in DS load from unmeasured sources also was identified along the subreach of the river from Ark at Catlin to Swink; the DS load from unmeasured sources was estimated to range from 10 to 28 tons per day per mile. The only loss of DS load was identified for the subreach from Nepesta to Catlin Dam in 2010. The mechanism and spatial extent of the losses were not identified, and further investigation would be required to better understand the results.

Colorado↗

USGS2013

Properties of basin-fill deposits, a 1971–2000 water budget, and surface-water-groundwater interactions in the upper Humboldt River basin, northeastern Nevada

This study was done in cooperation with Elko County, Nevada in response to concerns over growing demand for water within the county and increasing external demands that are occurring statewide. The upper Humboldt River basin encompasses 4,360 square miles in northeastern Nevada and includes the headwaters area of the Humboldt River. Nearly all of the mean annual flow of the Humboldt River originates in this area. Basin-fill deposits function as the principal aquifers in the upper Humboldt River basin. Over much of the basin lowlands, the upper 200 feet of basin fill consists of clay, silt, sand, and gravel deposited in a lake of middle to late Pliocene age. Fine-grained lacustrine sediments compose from 30 to more than 70 percent of the deposits. Mean values of transmissivity are less than 1,000 feet squared per day. Total inflow to the upper Humboldt River basin, about 3,330,000 acre-feet per year, is entirely from annual precipitation. Total outflow from the basin, about 3,330,000 acre-feet per year, occurs as evapotranspiration, streamflow, subsurface flow, and pumpage. The uncertainty of these values of inflow and outflow is estimated to be 25 percent. Baseflow of the Humboldt River is minimal upstream of the Elko Hills and in downstream reaches almost all baseflow comes from tributary inflow of the North Fork and South Fork Humboldt Rivers. However, the baseflow of these two tributaries comes from groundwater discharge to their respective channels in canyons incised in volcanic rocks along the North Fork and in carbonate rocks along the South Fork. Water levels in the shallow water-table aquifer along the Humboldt River flood plain fluctuate with changes in stage of the river. During high rising river stage in spring and early summer, streamflow enters the aquifer as bank storage. As stage begins to decline in early to mid-summer groundwater in bank storage begins discharging back into the river channel and this continues through late summer. In years of below average flow some reaches of the river are dry in late summer. Flood plain deposits are more permeable than adjacent and underlying fine-grained sediments of the Pliocene lake and the two aquifers are poorly connected.

Nevada↗

USGS2014

Suspended-sediment concentrations, loads, total suspended solids, turbidity, and particle-size fractions for selected rivers in Minnesota, 2007 through 2011

Sediment-laden rivers and streams pose substantial environmental and economic challenges. Excessive sediment transport in rivers causes problems for flood control, soil conservation, irrigation, aquatic health, and navigation, and transports harmful contaminants like organic chemicals and eutrophication-causing nutrients. In Minnesota, more than 5,800 miles of streams are identified as impaired by the Minnesota Pollution Control Agency (MPCA) due to elevated levels of suspended sediment. The U.S. Geological Survey, in cooperation with the MPCA, established a sediment monitoring network in 2007 and began systematic sampling of suspended-sediment concentrations (SSC), total suspended solids (TSS), and turbidity in rivers across Minnesota to improve the understanding of fluvial sediment transport relations. Suspended-sediment samples collected from 14 sites from 2007 through 2011 indicated that the Zumbro River at Kellogg in the driftless region of southeast Minnesota had the highest mean SSC of 226 milligrams per liter (mg/L) followed by the Minnesota River at Mankato with a mean SSC of 193 mg/L. During the 2011 spring runoff, the single highest SSC of 1,250 mg/L was measured at the Zumbro River. The lowest mean SSC of 21 mg/L was measured at Rice Creek in the northern Minneapolis- St. Paul metropolitan area. Total suspended solids (TSS) have been used as a measure of fluvial sediment by the MPCA since the early 1970s; however, TSS concentrations have been determined to underrepresent the amount of suspended sediment. Because of this, the MPCA was interested in quantifying the differences between SSC and TSS in different parts of the State. Comparisons between concurrently sampled SSC and TSS indicated significant differences at every site, with SSC on average two times larger than TSS concentrations. The largest percent difference between SSC and TSS was measured at the South Branch Buffalo River at Sabin, and the smallest difference was observed at the Des Moines River at Jackson. Regression analysis indicated that 7 out of 14 sites had poor or no relation between SSC and streamflow. Only two sites, the Knife River and the Wild Rice River at Twin Valley, had strong correlations between SSC and streamflow, with coefficient of determination (R 2 ) values of 0.82 and 0.80, respectively. In contrast, turbidity had moderate to strong relations with SSC at 10 of 14 sites and was superior to streamflow for estimating SSC at all sites. These results indicate that turbidity may be beneficial as a surrogate for SSC in many of Minnesota’s rivers. Suspended-sediment loads and annual basin yields indicated that the Minnesota River had the largest average annual sediment load of 1.8 million tons per year and the largest mean annual sediment basin yield of 120 tons of sediment per year per square mile. Annual TSS loads were considerably lower than suspended-sediment loads. Overall, the largest suspended-sediment and TSS loads were transported during spring snowmelt runoff, although loads during the fall and summer seasons occasionally exceeded spring runoff at some sites. This study provided data from which to characterize suspended sediment across Minnesota’s diverse geographical settings. The data analysis improves understanding of sediment transport relations, provides information for improving sediment budgets, and documents baseline data to aid in understanding the effects of future land use/land cover on water quality. Additionally, the data provides insight from which to evaluate the effectiveness and efficiency of best management practices at the watershed scale.

Minnesota↗

USGS2014

Pesticide trends in major rivers of the United States, 1992-2010

This report is part of a series of pesticide trend assessments led by the National Water-Quality Assessment Program of the U.S. Geological Survey. This assessment focuses on major rivers of various sizes throughout the United States that have large watersheds with a range of land uses, changes in pesticide use, changes in management practices, and natural influences typical of the regions being drained. Trends were assessed at 59 sites for 40 pesticides and pesticide degradates during each of three overlapping periods: 1992–2001, 1997–2006, and 2001–10. In addition to trends in concentration, trends in agricultural-use intensity (agricultural use) were also assessed at 57 of the sites for 35 parent compounds with agricultural uses during the same three periods. The SEAWAVE-Q model was used to analyze trends in concentration, and parametric survival regression for interval-censored data was used to assess trends in agricultural use. All trends are provided in downloadable electronic files. A subset of 39 sites was chosen to represent non-nested, generally independent basins for a national analysis of pesticide and agricultural-use trends for the most prevalent pesticides (15 pesticides and 2 degradation products). Graphical and numerical results are presented to provide a national overview of concentration and use trends. As another perspective on understanding pesticide concentration trends in large rivers in relation to multiple tributary watersheds, this report also presents a detailed assessment of concentration and use trends for simazine, metolachlor, atrazine, deethylatrazine, and diazinon for a set of 17 nested sites in the Mississippi River Basin (including the Ohio and Missouri River Basins), for the second and third trend periods. Pesticides strongly dominated by agricultural use—cyanazine, metolachlor, atrazine, and alachlor—had widespread agreement between concentration trends and agricultural-use trends. Pesticides with substantial use in agricultural and urban applications—simazine, tebuthiuron, Dacthal, pendimethalin, chlorpyrifos, malathion, diazinon, fipronil, carbofuran, and carbaryl—had concentration trends that were mostly explained by a combination of agricultural-use trends and concentration trends in urban streams that were evaluated in a separate companion study. The importance of the urban stream trends for explaining concentration trends in major rivers indicates the significance of nonagricultural uses of some pesticides to concentrations in major rivers despite the much smaller area of urban land use compared to agriculture. Deethylatrazine, a degradate of atrazine, was the only pesticide compound assessed that had frequent occurrences during 1997–2006 and 2001–10 of concentration trends in the opposite direction of use trends (atrazine use). The nested analysis for the Mississippi River indicates that most trends observed in the largest rivers—multiple Mississippi River sites, the Ohio River, and the Missouri River—are consistent with streamflow contributions and concentration trends observed at tributary sites. Streamflow (incorporated into the trend model and shown in the nested basin analysis), trends in agricultural use of pesticides (quantified in this report), and urban use of pesticides (represented by concentration trends in a companion study of urban streams) are all important influences on pesticide concentrations in streams and rivers. Consideration of these influences is vital to understanding trends in pesticide concentrations.

Scientific Investigations Report↗

USGS2015

Evaluation of groundwater levels in the South Platte River alluvial aquifer, Colorado, 1953-2012, and design of initial well networks for monitoring groundwater levels

The South Platte River and underlying alluvial aquifer form an important hydrologic resource in northeastern Colorado that provides water to population centers along the Front Range and to agricultural communities across the rural plains. Water is regulated based on seniority of water rights and delivered using a network of administration structures that includes ditches, reservoirs, wells, impacted river sections, and engineered recharge areas. A recent addendum to Colorado water law enacted during 2002-2003 curtailed pumping from thousands of wells that lacked authorized augmentation plans. The restrictions in pumping were hypothesized to increase water storage in the aquifer, causing groundwater to rise near the land surface at some locations. The U.S. Geological Survey (USGS), in cooperation with the Colorado Water Conservation Board and the Colorado Water Institute, completed an assessment of 60 years (yr) of historical groundwater-level records collected from 1953 to 2012 from 1,669 wells. Relations of "high" groundwater levels, defined as depth to water from 0 to 10 feet (ft) below land surface, were compared to precipitation, river discharge, and 36 geographic and administrative attributes to identify natural and human controls in areas with shallow groundwater. Averaged per decade and over the entire aquifer, depths to groundwater varied between 24 and 32 ft over the 60-yr record. The shallowest average depth to water was identified during 1983-1992, which also recorded the highest levels of decadal precipitation. Average depth to water was greatest (32 ft) during 1953-1962 and intermediate (30 ft) in the recent decade (2003-2012) following curtailment of pumping. Between the decades 1993-2002 and 2003-2012, groundwater levels declined about 2 ft across the aquifer. In comparison, in areas where groundwater levels were within 20 ft of the land surface, observed groundwater levels rose about 0.6 ft, on average, during the same period, which demonstrated preferential rise in areas with shallow groundwater. Approximately 29 percent of water-level observations were identified as high groundwater in the South Platte River alluvial aquifer over the 60-yr record. High groundwater levels were found in 17 to 33 percent of wells examined by decade, with the largest percentages occurring over three decades from 1963 to 1992. The recent decade (2003-2012) exhibited an intermediate percentage (25 percent) of wells with high groundwater levels but also had the highest percentage (30 percent) of high groundwater observations, although results by observations were similar (26-29 percent) over three decades prior, from 1963 to 1992. Major sections of the aquifer from north of Sterling to Julesburg and areas near Greeley, La Salle, and Gilcrest were identified with the highest frequencies of high groundwater levels. Changes in groundwater levels were evaluated using Kendal line and least trimmed squares regression methods using a significance level of 0.01 and statistical power of 0.8. During 2003-2012, following curtailment of pumping, 88 percent of wells and 81 percent of subwatershed areas with significant trends in groundwater levels exhibited rising water levels. Over the complete 60-yr record, however, 66 percent of wells and 57 percent of subwatersheds with significant groundwater-level trends still showed declining water levels; rates of groundwater-level change were typically less than 0.125 ft/yr in areas near the South Platte River, with greater declines along the southern tributaries. In agreement, 58 percent of subwatersheds evaluated between 1963-1972 and 2003-2012 showed net declines in average decadal groundwater levels. More areas had groundwater decline in upgradient sections to the west and rise in downgradient sections to the east, implying a redistribution of water has occurred in some areas of the aquifer. Precipitation was identified as having the strongest statistically significant correlations to river discharge over annual and decadal periods (Pearson correlation coefficients of 0.5 and 0.8, respectively, and statistical significance defined by p-values less than 0.05). Correlation coefficients between river discharge and frequency of high groundwater levels were statistically significant at 0.4 annually and 0.6 over decadal periods, indicating that periods of high river flow were often coincident with high groundwater conditions. Over seasonal periods in five of the six decades examined, peak high groundwater levels occurred after spring runoff from July to September when administrative structures were most active. Between 1993-2002 and 2003-2012, groundwater levels rose while river discharge decreased, in part from greater reliance on surface water and curtailed pumping from wells without augmentation plans. Geographic attributes of elevation and proximity to streams and rivers showed moderate correlations to high groundwater levels in wells used for observing groundwater levels (correlation coefficients of 0.3 to 0.4). Local depressions and regional lows within the aquifer were identified as areas of potential shallow groundwater. Wells close to the river regularly indicated high groundwater levels, while those within depleted tributaries tended to have low frequencies of high groundwater levels. Some attributes of administrative structures were spatially correlated to high groundwater levels at moderate to high magnitudes (correlation coefficients of 0.3 to 0.7). The number of affected river reaches or recharge areas that surround a well where groundwater levels were observed and its distance from the nearest well field showed the strongest controls on high groundwater levels. Influences of administrative structures on groundwater levels were in some cases local over a mile or less but could extend to several miles, often manifesting as diffuse effects from multiple surrounding structures. A network of candidate monitoring wells was proposed to initiate a regional monitoring program. Consistent monitoring and analysis of groundwater levels will be needed for informed decisions to optimize beneficial use of water and to limit high groundwater levels in susceptible areas. Finalization of the network will require future field reconnaissance to assess local site conditions and discussions with State authorities.

Colorado↗

USGS2016

Surface-water quality and suspended-sediment quantity and quality within the Big River Basin, southeastern Missouri, 2011-13

Missouri was the leading producer of lead in the United States—as well as the world—for more than a century. One of the lead sources is known as the Old Lead Belt, located in southeast Missouri. The primary ore mineral in the region is galena, which can be found both in surface deposits and underground as deep as 200 feet. More than 8.5 million tons of lead were produced from the Old Lead Belt before operations ceased in 1972. Although active lead mining has ended, the effects of mining activities still remain in the form of large mine waste piles on the landscape typically near tributaries and the main stem of the Big River, which drains the Old Lead Belt. Six large mine waste piles encompassing more than 2,800 acres, exist within the Big River Basin. These six mine waste piles have been an available source of trace element-rich suspended sediments transported by natural erosional processes downstream into the Big River. A study was performed by the U.S. Geological Survey in cooperation with U.S. Environmental Protection Agency, Region 7, to calculate and characterize suspended-sediment quantity and quality within the Big River basin after reclamation of the mine waste piles ended in 2012. Streamflow and suspended sediments were quantified and sampled at two locations along a 68-mile reach of the Big River between Bonne Terre and Byrnes Mill, Missouri. The results will help regulatory agencies, such as the U.S. Environmental Protection Agency and U.S. Fish and Wildlife Service, determine impaired reaches and ecosystems for remedial and restoration efforts. Continuous stream stage, water temperature, and turbidity, and discrete suspended-sediment concentration data were collected at the two sites between October 2011 and September 2013. Suspended-sediment samples were collected during various hydrologic conditions to develop a regression model between discrete suspended-sediment concentration and continuous turbidity. Suspended sediments collected during stormflow events were analyzed for concentrations of trace elements such as barium, cadmium, lead, and zinc within two sediment size fractions. Event loads and annual loads of suspended sediment and select trace elements in suspended sediments also were calculated. Suspended-sediment loads computed by the regression model increased downstream from about 201,000 tons at the upstream site to about 355,000 tons at the downstream site during the study period. Stormflow-event-based (hereinafter referred to as “event-based”) suspended-sediment loads ranged from 180 to 32,000 tons at the upstream sampling site and 390 to 53,000 tons at the downstream site along the Big River. Although only seven stormflow events at the upstream site and six at the downstream site were sampled, the event-based suspended-sediment loads accounted for nearly 30 percent of the total suspended-sediment loads computed at both sites, indicating most of the suspended sediment transported through the Big River occurs during higher streamflows. Sediment quality guidelines, known as the threshold effect concentration and the probable effect concentration, used to assess toxicity of trace-element concentrations in sediments were compared to the cadmium, lead, and zinc concentrations in suspended sediment samples collected during stormflow events. All concentrations of cadmium, lead, and zinc in event-based suspended sediment samples exceeded the threshold and probable effect concentrations. Lead and zinc concentrations in the sediment size fraction less than 0.063 millimeters also exceeded the toxic effect threshold, above which sediment is considered to be heavily polluted causing adverse effects on sediment-dwelling organisms. Concentrations of cadmium and zinc in event-based suspended sediment samples were notably higher in samples from the upstream site than samples from the downstream site, indicating the sources of sediments enriched in these trace elements decrease in the downstream area of the watershed. The reduction in concentration of cadmium and zinc could be from dissolution of the constituents during transport or possibly a decrease in downstream source material. The lead concentration exceedance of the probable effects concentration as well as the threshold effects concentration indicates that lead-rich suspended sediments in the fraction less than 0.063 millimeters are readily available within the Big River Basin for transport. These sediments remain in the system from historical mining, and as the reclamation of mine waste piles in the upstream area of the watershed reduce additional sediment loadings, these fine sediments may be continually released as the river scours the streambed and erodes stream banks causing the lead-rich suspended sediment to remain in a state of equilibrium. Barium concentrations in suspended-sediments were nearly twice as high in stormflow event samples collected at the downstream site as compared to samples from the upstream site. The source of barium in the Big River could be from Mineral Fork and Mill Creek, which flow through the historical barite (barium sulfate, also known as tiff) mining district in Washington County, and discharge into the Big River between the two study sites. Total trace-element loads and yields in suspended sediments were computed from the sampled events for each year in the study. The total barium loads in suspended sediments were higher for sampled events collected at the downstream site than the upstream site during both study years. Cadmium and zinc loads in suspended sediments were lower at the downstream site than the upstream site, although the decrease in total load was not substantial during the study period. Lead loads in suspended sediments were lower at the downstream site during the first study year, with a slightly higher load downstream in the second year though the increase from upstream to downstream was small. Event-based yields were higher at the upstream site, indicating that readily available sediment sources are closer to the upstream site where more mining affected areas are located. The estimates determined during large precipitation events indicate that large sources of suspended sediments with large concentrations of trace elements are still available for transport within the Big River.

Missouri↗

USGS2016

Sediment loads and transport at constructed chutes along the Missouri River - Upper Hamburg Chute near Nebraska City, Nebraska, and Kansas Chute near Peru, Nebraska

The U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, monitored suspended sediment within constructed Missouri River chutes during March through October 2012. Chutes were constructed at selected river bends by the U.S. Army Corps of Engineers to help mitigate aquatic habitat lost through the creation and maintenance of the navigation channel on the Missouri River. The restoration and development of chutes is one method for creating shallow-water habitat within the Missouri River to meet requirements established by the amended 2000 Biological Opinion. Understanding geomorphic channel-evolution processes and sediment transport is important for the design of chutes, monitoring and maintenance of existing chutes, and characterizing the habitat that the chutes provide. This report describes the methods used to monitor suspended sediment at two Missouri River chutes and presents the results of the data analysis to help understand the suspended-sediment characteristics of each chute and the effect the chutes have on the Missouri River. Upper Hamburg chute, near Nebraska City, Nebraska, and Kansas chute, near Peru, Nebraska, were selected for monitoring. At each study site, monthly discrete samples were collected from April through October in the Missouri River main-channel transects upstream from the chute inlet, downstream from the chute outlet, at the outlet (downstream transect) of both chutes, and at the inlet (upstream transect) of Kansas chute. In addition, grab samples from all chute sampling locations were collected using autosamplers. Suspended-sediment concentration (SSC) and grain-size metrics were determined for all samples (discrete and grab). Continuous water-quality monitors recorded turbidity and water temperature at 15-minute intervals at the three chute sampling locations. Two acoustic Doppler velocimeters, one within each chute, measured water depth and current velocities continuously. The depth and velocity data were used to estimate streamflow within each chute. The sampling design was developed to understand the suspended-sediment differences within each chute and between the chute and the Missouri River main channel during discrete sampling. The sampling design also allowed for site-specific surrogate relations between SSC and turbidity to be developed, which could be used to compute real-time estimates of SSC and sediment loads within the chutes. Real-time estimates of SSC and sediment loads enable a better understanding of sediment transport within the chutes during times when physical samples are not collected, including periods of high flow. High flows during the summer of 2011 resulted in substantial alterations to both studied chutes; therefore, the U.S. Army Corps of Engineers repaired and modified both chutes during 2012. These unforeseen repairs and modifications within the chutes added uncertainty to the analysis because concentrations were altered by construction equipment and flow alteration. Daily suspended-sediment and suspended-silt loads were estimated based on surrogate relations with turbidity. A linear regression was used to estimate equal-width increment (EWI)-equivalent SSC from autosampler SSC before using the model-calibration dataset to determine the best-fit model for prediction of SSC from the turbidity and, in some cases, discharge. Correlation between suspended-sand concentration ( SSandC ) in EWI samples and concurrent samples collected by an autosampler was low; therefore, SSandC was excluded from development of surrogate relations because a large part of the calibration dataset was from autosamples. Instead, SSandC was estimated as SSC minus suspended-silt-clay concentration ( SSiltC ). At all sites, the best-fit models included the base-10 logarithm of concentration and turbidity, and at Kansas chute upstream, the base-10 logarithm of streamflow was also included in the best-fit models. These surrogate models were used to estimate continuous time series of SSC and SSiltC . Estimated concentrations of suspended sediment were used to estimate instantaneous and daily loads for total suspended sediment, suspended silt-clay, and suspended sand. Estimated daily suspended-sediment loads were not significantly different between upstream and downstream transects within the Kansas chute, and most individual daily loads within the chute were not significantly different between upstream and downstream transects when evaluated using overlap in daily 95-percent confidence intervals. The comparison of daily load values for upstream and downstream chute transects, as estimated from turbidity-based surrogate models for Kansas chute, documents the daily dynamic nature of sediment transport within the chute with a temporal resolution that is not practical with discrete suspended-sediment sampling alone. Comparisons of concentrations and loads from EWI samples collected from different transects within a study site resulted in few significant differences, but comparisons are limited by small sample sizes and large within-transect variability. When comparing the Missouri River upstream transect to the chute inlet transect, similar results were determined in 2012 as were determined in 2008—the chute inlet affected the amount of sediment entering the chute from the main channel. In addition, the Kansas chute is potentially affecting the sediment concentration within the Missouri River main channel, but small sample size and construction activities within the chute limit the ability to fully understand either the effect of the chute in 2012 or the effect of the chute on the main channel during a year without construction. Finally, some differences in SSC were detected between the Missouri River upstream transects and the chute downstream transects; however, the effect of the chutes on the Missouri River main-channel sediment transport was difficult to isolate because of construction activities and sampling variability.

Nebraska↗

USGS2019

Sediment storage and transport in the Nooksack River basin, northwestern Washington, 2006–15

The Nooksack River is a dynamic gravel-bedded river in northwestern Washington, draining off Mount Baker and the North Cascades into Puget Sound. Working in cooperation with the Whatcom County Flood Control Zone District, the U.S. Geological Survey studied topographic, hydrologic, and climatic data for the Nooksack River basin to document recent changes in sediment storage, long-term bed elevation trends, rates of sediment transport, and factors influencing surficial drainage in order to support ongoing river management. Differences in elevations between topographic and bathymetric surveys in 2005/06 and 2013/15 indicate the active channel aggraded about 1–2 feet locally near the cities of Ferndale and Everson but was primarily stable between them. The active channel upstream of Nugent’s Corner generally incised. Total incision upstream of Nugent’s Corner to Glacier Creek generated 2.3 ± 1.7 million cubic yards of sediment from 2005/06 to 2013 and likely represented a significant source of coarse sediment to the lower mainstem river over that time. Long-term records of local channel-bed elevation, derived from U.S. Geological Survey streamgage data, show bed-elevation changes of about 1–3 feet. The river bed at most streamgages exhibits long-term trends, with relatively consistent rates of change on the order of 1 foot per decade that persist years to decades. Lagged correlations in bed-elevation trends at all seven streamgages in the North Fork Nooksack and mainstem Nooksack suggest that decadal periods of persistent aggradation and incision originate in the North Fork and translate downstream. The channel-change signal propagates downstream 0.5–2.5 miles per year, with the rate of propagation scaling closely with channel slope. The pattern of incision and aggradation in the North Fork correlates with regional climate, where persistent incision follows extended cold and wet periods, and persistent aggradation follows extended warm and dry periods. Climate-driven variation in coarse-sediment delivery, primarily from the North Fork Nooksack, then appears to be a strong control on long-term vertical channel adjustments at sites downstream. The downstream-translating climate signal generated in the North Fork would account for recently observed aggradation at Everson and Ferndale but not the observed incision in unconfined reaches upstream of Nugent’s Corner from 2005–06 to 2013. This mismatch indicates that understanding how changes in sediment-supply influence those unconfined reaches remains a key uncertainty for predicting future channel change. Continuous turbidity monitoring integrated with suspended sediment and limited bedload sampling were used to calculate annual sediment loads at five sites in the basin. The sediment load in the lower river at Ferndale ranged from 0.78 to 1.17 million tons per year and averaged 0.97 million tons per year for WYs 2012–17. Suspended sediment made up 93 percent of the load, and bedload made up 7 percent. Most of the fine sediment load of the lower river is supplied from headwaters of the North, Middle, and South Fork Nooksack basins, with relatively little net increase in fine sediment loads in the lower mainstem basin. The three forks supply approximately equal proportions of the lower-river fine sediment load. However, the glacially sourced North and Middle Fork Nooksack basins carry a notably sandier suspended-sediment load than the South Fork Nooksack. A comparison of monthly streamflow and precipitation trends since 1981 indicate statistically significant increases in total spring precipitation and the number of spring days with measurable precipitation in much of the basin, as well as increases in mean spring river stage near Ferndale. Since no trends in mean spring discharge are observed, the trends in river stage are attributed primarily to observed changes in bed elevation. Changes in bed elevation and precipitation may then both have plausibly impacted field drainage in the lower river below Ferndale.

Washington↗

USGS2019

Streamflow gains and losses in New Fork and Green Rivers, upstream from Fontenelle Reservoir, Wyoming, October 2015

The Wyoming Landscape Conservation Initiative is a program created to implement a long-term, science-based program of assessing natural resources while facilitating responsible energy and other development and does studies in much of southwestern Wyoming, including all or parts of Lincoln, Sublette, Fremont, Sweetwater, and Carbon Counties. A synoptic study was completed by the U.S. Geological Survey as part of ongoing contributions to the Wyoming Landscape Conservation Initiative to better understand the streamflow dynamics in the New Fork and Green Rivers in an area with historical, current, and future energy development. Streamflow measurements were collected October 19–22, 2015, at 19 sites on the New Fork and Green Rivers in Wyoming to determine changes in streamflow and, where applicable, describe the inflow and outflow of groundwater. Streamflow in the New Fork River generally increased from 50 cubic feet per second (ft 3 /s) at the most upstream site near Pinedale, Wyoming, to 350 ft 3 /s at the mouth of the river. Streamflow in the Green River generally increased downstream from 250 ft 3 /s at the most upstream site at Warren Bridge to around 800 ft 3 /s at the most downstream site near La Barge, Wyo., upstream from Fontenelle Reservoir. Estimated streamflow gains and losses were calculated for five reaches on the New Fork River. Four of the five reaches on the New Fork River had a change greater than the associated measurement error and were gaining reaches; the reach with the largest gain was the most upstream reach. One reach, the most downstream reach, had a calculated change in streamflow less than the associated measurement error. Estimated streamflow gains and losses were calculated for four reaches on the Green River. One reach was determined to be a gaining reach, one was a losing reach, and two reaches had changes less than the associated measurement error. Comparing the annual streamflow hydrographs for three long-term streamgages likely showed the effects of applying irrigation water to the upstream areas of land draining to the Green and New Fork Rivers. Streamflows in the New Fork River near Big Piney and the Green River near La Barge, Wyo., are sustained later in the season compared to the upstream site of Green River at Warren Bridge, which has few diversions and minimal irrigation.

Wyoming↗