Geology topics

Cassandra D. Smith

Publications and source records attributed to Cassandra D. Smith.

12 recordsLinked to original sources

USGS2025

Beaver dams and their effects on urban streams in the Tualatin River Basin, northwestern Oregon

Introduction In response to growing interest in beaver-assisted restoration in the Tualatin River Basin of northwestern Oregon, the U.S. Geological Survey (USGS), in partnership with Clean Water Services, collected data from 2016–17 and completed a series of studies to: (1) inventory known locations of beaver dams and activity in the Tualatin River Basin, (2) estimate the number of beaver dams in the Tualatin River Basin as of 2017 and the potential number of beaver dams that could be supported with riparian vegetation improvements, and (3) assess the effects of beaver dams and ponds on storm hydrology, hydraulics, and floodplain inundation, suspended-sediment transport and deposition, and water quality along two urban stream reaches (Fanno Creek at Greenway Park and Bronson Creek between Kaiser and Saltzman Roads). This fact sheet summarizes the results of these studies and implications for beaver-assisted restoration in the Tualatin River Basin.

Oregon↗

USGS2025

Stream network capacity to support beaver dams in the Tualatin River Basin, northwestern Oregon

Significant Findings Beaver dams can help streams connect to their floodplains. These floodplain connections can expand the range of available aquatic habitats and aid in the restoration of stream and floodplain function and processes. American beavers ( Castor canadensis ) occupy a wide variety of aquatic habitats; however, their ability to build dams, the agent of stream and floodplain change, is constrained in large part by three physical variables—local vegetation, topography, and hydrology. These three physical variables are combined in the Beaver Restoration Assessment Tool (BRAT), a geographic information system-based utility that uses a Fuzzy Inference System (FIS) to estimate the capacity of each reach within a stream network to support beaver dams. In this study, version 1.0 of BRAT was adapted and applied to the entire perennial stream network of Tualatin River Basin in northwestern Oregon. Beaver-dam locations in the Tualatin River Basin were compiled to (1) define the distribution of dams in the basin during 2013–16 and (2) provide necessary data for calibrating and validating BRAT predictions. BRAT was calibrated to the current known distribution of dams, as compiled in the inventory. The input FIS equations of the original BRAT model were adjusted to account for local topographic conditions; specifically, the low gradient of many streams in the basin, although subsequent updates to BRAT may obviate the need for these changes. Results from this modified BRAT model reasonably simulated the dam inventory. Results show that beavers can currently build the greatest density of dams, defined as number of dams per kilometer of stream, in the higher-gradient forested streams of the basin, whereas they can build the fewest number of dams per kilometer in urban streams along the lower-gradient valley floor. Estimated dam density was generally 5-15 dams per kilometer (km) for forested streams and 2-4 dams/km for urban streams. Improving riparian vegetation along urban streams may allow beavers to build on average four additional dams per kilometer compared to current conditions. Results from this study may help inform local stream and stormwater management by (1) identifying stream reaches with the most potential to support beaver dams, (2) determining the likely factors limiting potential for dam building, and (3) identifying potential areas where dam building may affect human infrastructure.

Oregon↗

USGS2025

Effects of beaver dams and ponds on the transport and deposition of suspended sediment in urban streams of the Tualatin River Basin, northwestern Oregon

Significant Findings This study investigated the effects of natural beaver dams and ponds on sediment transport and deposition in two urban beaver-affected reaches in the Tualatin River Basin, northwestern Oregon. Data were collected during 2016–17 from Fanno Creek at Greenway Park (between SW Hall Boulevard and SW Pearson Court) and Bronson Creek (between NW Laidlaw Road and NW Kaiser Road); each study reach contained multiple beaver dams. Continuous turbidity, discrete suspended-sediment samples, and streamflow measurements were collected during storms and baseflow periods to calculate suspended-sediment loads (SSLs) and to compare differences in SSLs upstream and downstream from the two beaver-affected reaches. Turbidity was measured continuously upstream, within, and downstream from these reaches to evaluate seasonal and longitudinal turbidity patterns and fluctuations. The volume and mass of sediment deposited in a large pond along the Fanno Creek study reach were also estimated. Study results include: Instantaneous SSLs at the upstream reach boundaries often were greater at Bronson Creek compared to Fanno Creek during storm events. These differences were likely caused by the greater mean basin slope upstream from the Bronson Creek reach and its proximity to the headwaters in the Tualatin Mountains. In contrast, the frequency of sediment transport events was greater at the upstream boundary of the Fanno Creek study reach than at the upstream boundary of the Bronson Creek study reach, likely because Fanno Creek has a larger upstream contributing area and more frequent streamflow runoff events typical of urban streams. During water year 2017, approximately 140 metric tons (t) of sediment (11 percent of the total incoming load) were deposited in the Fanno Creek study reach, and 1,420 t of sediment (89 percent of the total incoming load) were deposited in the Bronson Creek study reach. Longitudinal reductions in turbidity were observed in both study reaches but varied among the two reaches. Turbidity reductions along the Fanno Creek study reach were associated with sediment deposition and storage in the south pond, a large floodplain pond formed by a beaver dam. Turbidity decreased gradually along the Bronson Creek study reach, indicating that sediment was deposited between the upstream and downstream boundaries. Differences in decreases in SSLs and turbidity among the two study reaches were attributed to reach characteristics, such as beaver dam characteristics, stream-floodplain hydraulic connections, and the type and density of the vegetation. The eastern part of the south pond in the Fanno Creek study reach trapped approximately 1,100 cubic meters of sediment (estimated 250 t) from 2012 to 2016 (the period between when beaver dams were first built in the reach and when topographic surveys were collected for this study). This amount is equivalent to about one seventh of the mean annual SSL moving through Fanno Creek as estimated by a previous study at the downstream U.S. Geological Survey streamgage at Fanno Creek at Durham Road (14206950). Beaver dams and ponds in urban streams can reduce SSLs and trap sediment. Consideration of reach-specific factors influencing the effects of beaver dams on sediment transport could help create realistic expectations for restoration programs about this potential benefit associated with beaver activity.

Oregon↗

USGS2025

Effects of beaver dams and ponds on water quality in urban streams of the Tualatin River Basin, northwestern Oregon

Significant Findings American beavers ( Castor canadensis ) are native to the Pacific Northwest, and their populations have increased in many locations after being nearly removed by historical trapping. Beaver dams have well-documented effects on water quality in forested streams, but their effects on water quality in urban streams have not been well characterized. The study documented the water-quality effects of beaver dams and beaver activity in selected urban streams of the Tualatin River Basin in northwestern Oregon. Variations in water quality upstream, downstream, and within ponded areas behind beaver dams were quantified with continuous measurements of water temperature, specific conductance, dissolved oxygen, and pH from May 2016 to November 2017 in two intensively monitored reaches of urban streams (Fanno and Bronson Creeks). Five other urban stream reaches were monitored upstream and downstream from beaver ponds using water-temperature sensors to document water-temperature changes in additional beaver-affected reaches. Spatial water-quality variations within a beaver pond along Fanno Creek were characterized in more detail on four hot summer afternoons with numerous measurements of temperature and dissolved oxygen. Results from the study were used to document and derive insights from measured patterns in the water-quality data, such as the following: Shallow and unshaded ponds created by beaver dams (such as at Fanno Creek) capture more solar radiation than channelized and shaded stream reaches, resulting in substantially warmer water temperatures during summer. A large beaver pond along Fanno Creek had variable water depths and riparian shade, resulting in a wide range of water-temperature and dissolved-oxygen conditions. Some conditions measured during summer were stressful for sensitive aquatic species, with temperatures higher than 18 degrees Celsius (°C) and (or) dissolved-oxygen concentrations less than 2 milligrams per liter (mg/L). Although water flowing out of beaver-affected reaches was warmer than water entering the reaches, water tended to cool downstream when streams returned to a more-shaded, confined channel (such as at Fanno Creek) or received subsurface inputs and exchange (such as at Bronson Creek). The magnitude of water-temperature increases in beaver ponds depended on site characteristics, such as the surface area and depth of the ponds, the extent of riparian shade, and the potential for subsurface exchange. Beaver dams caused Fanno Creek to overflow its banks, resulting in a wide and shallow floodplain pond that had little riparian shade in most places. In contrast, Bronson Creek remained in its stream channel behind the beaver dams, was often deeper and more shaded, and had more subsurface water exchange than the Fanno Creek reach. Despite the longer reach length, these differences caused the Bronson Creek reach to warm less than the Fanno Creek reach. Beaver dams trapped sediment and organic matter, and ponding increased the time available for organic matter to decompose in the trapped sediments, thus consuming dissolved oxygen. The construction of a beaver dam in the monitored reach of Bronson Creek during the study caused an increase in oxygen demands and a rapid decrease in dissolved-oxygen concentrations. Dissolved-oxygen concentrations in monitored study reaches were affected by primary production (algal photosynthesis) and respiration, and hypoxic (low to zero dissolved oxygen) conditions were measured in the two intensively monitored reaches for multiple weeks during summer. Two single-station stream metabolism models were used to calculate net ecosystem production in the two intensively monitored urban stream reaches. Results indicated that the reaches were heterotrophic, with respiration demands consuming more oxygen than what was produced through photosynthesis. Beaver ponds at all sites had a measurable effect on water quality, causing wider ranges in temperature and dissolved-oxygen conditions than would have occurred without ponding. That wider range (both spatially and temporally) might support a variety of aquatic organisms, but also is likely to increase the frequency of water-quality standard violations in those beaver-affected reaches. Any water-quality effects or standard violations associated with beaver dams and ponds, however, may be localized or transitory along the stream network. Restored stream reaches can attract beavers. Considering the potential for beaver colonization when designing habitat restoration plans will require evaluation of the potential water-quality changes associated with beaver dams and ponds alongside other desired physical changes.

Oregon↗

USGS2025

Managing water for birds—A tool for the Malheur National Wildlife Refuge, southeastern Oregon

The “Water for Birds Tool” is a spreadsheet-based tool (using Microsoft Excel) designed to help resource managers assess the spatial extent and types of bird habitats in the Malheur National Wildlife Refuge, southeastern Oregon. The tool quantifies the areas of open water, partial water, and water depths on a monthly timescale during the irrigation season (April–July) from 2021 to 2024. This tool combines previously published datasets and models but also incorporates new measurements collected by partners. Results show that the relation between the amount of bird habitat and the extent (partial and open water) of Malheur Lake varies by bird guild. The Donner und Blitzen River supplied all or most of the surface water inflow to Malheur Lake during the analysis years, emphasizing the importance of informed management of the river. Additional gaging of inflows and diversions and better estimates of recharge and irrigated areas can help refine estimates of water use on the refuge.

Oregon↗

USGS2023

Integrated science strategy for assessing and monitoring water availability and migratory birds for terminal lakes across the Great Basin, United States

Executive Summary In 2022, the U.S. Geological Survey (USGS) established the Saline Lake Ecosystems Integrated Water Availability Assessment (IWAAs) to monitor and assess the hydrology of terminal lakes in the Great Basin and the migratory birds and other wildlife dependent on those habitats. Scientists from across the USGS (with specialties in water quantity, water quality, limnology, avian biology, data science, landscape ecology, and science communication) formed the Saline Lake Ecosystems IWAAs Team. The team has developed this regional strategic science plan to guide data collection and assessment activities at terminal lakes in the Great Basin. The U.S. Congress requested the USGS to establish the Saline Lake Ecosystems IWAAs in response to historically low water levels at terminal lakes and associated wetlands across the Great Basin. Not all Great Basin terminal lakes have high salinity; however, all terminal lakes occur in endorheic, closed, basins with no surface-water outflow. Low lake levels across the Great Basin are the result of increased water use for agriculture and municipalities, drought conditions, and a warming climate. Great Basin terminal lake water extents have decreased by as much as 90 percent over the last 150 years, and terminal lake wetlands have decreased in area by as much as 47 percent since 1984. Lake elevations and wetland areas are primarily supported by freshwater inputs from snowmelt feeding upgradient rivers, streams, and springs. These freshwater inputs have been severely reduced because of continued and increased surface-water diversions and surface-water capture through groundwater pumping for agriculture, mining, and public supply as well as unprecedented drought conditions and warming temperatures related to climate change. Water quality, specifically salinity, is highly variable for terminal lakes of the Great Basin, and this variability is a result of the balance between freshwater inflow and evaporation. Variability of salinity at each of the terminal lakes can be affected by lake morphology, hydrogeologic features of the basin, annual variability in weather patterns, and changes in upgradient water use. Hypersaline terminal lakes provide abundant food resources such as brine shrimp and brine flies that support nesting and migrating birds. The density and composition of invertebrates are closely tied to lake salinity. Increased salinity can exceed the tolerance of invertebrates, severely limiting their biomass. In contrast, decreased salinity can lead to altered invertebrate community composition, reducing the abundance of optimal avian prey resources. Great Basin terminal lake ecosystems, including open-water and adjacent aquatic and terrestrial environments, provide resources necessary to sustain many animal populations throughout the year. Although a variety of taxa use terminal lakes, these ecosystems are of acute importance for the millions of migratory waterbirds (for example, shorebirds, wading birds, and waterfowl) dependent on the network of terminal lakes and their associated wetlands. Migratory birds transiting the Pacific and Central Flyways use Great Basin terminal lake ecosystems throughout the year to feed, nest, and transit between wintering and breeding ranges. As such, successful conservation of birds and their habitats requires coordinated management of water and habitats across the Great Basin network of terminal lakes and wetlands. The linkages between water availability and ecosystem vulnerability of terminal lakes in the Great Basin are not well understood. The vulnerability of terminal lakes is related to the factors driving change and adaptive capacity of the lake ecosystem. Saline lake ecosystems are vulnerable when changes in water quantity affect ecosystem function. Water quantity affects salinity, which affects food webs and habitat; these linkages can be investigated with water-quality and food web monitoring. Water quantity also affects inundated habitat, which can be quantified through remote sensing. It is necessary to quantify hydroclimatic and water use controls on water availability to terminal lakes to assess the response of the ecosystems. Remotely sensed data can provide a broad-scale and long-term synoptic view of terminal lake hydrologic characteristics, but ground observations are required to interpret changes in water quality and ecological functions. Some terminal lake basins have ongoing monitoring and modeling efforts within the Great Basin (for example, Great Salt Lake, Carson River Basin), yet most monitoring locations are hydrologically upgradient and too far away from lake inflows to provide an accurate assessment of hydrological trends for the lake ecosystems. Other terminal lakes have no long-term hydrological monitoring in their respective watersheds (for example, Lake Abert). Ecological data collection in the Great Basin is also insufficient to understand how many birds exist on the landscape, how birds use the mosaic of terminal-lake habitats as an interconnected system, and how Great Basin terminal lakes are linked to the larger continental system of the Pacific and Central Flyways. Across agencies and organizations, tracking bird movement, abundance, and diversity is inconsistent, with some lakes having once- or twice-a-year bird survey efforts and a few locations having more intensive ecological data-gathering efforts (for example, Great Salt Lake, Lake Abert). Bridging hydrological and ecological information gaps will improve understanding of the trends in water supply and water quality, habitat availability and usage, and impacts on vulnerable waterbird species, all of which would be used by managers in coordinated conservation of this unique network of terminal-lake habitats. The terminal lakes of the Great Basin are part of the Basin and Range physiographic province that extends from the Colorado Plateau on the east to the Sierra Nevada on the west, and from the Snake River Plain on the north to the Garlock fault and the Mojave block on the south. The Great Basin is larger than 650,000 square kilometers and encompasses most of the State of Nevada but also extends to western Utah, eastern California, southeastern Idaho, southwestern Wyoming, and southeastern Oregon. The climate is arid to semiarid with a hydrologic regime that is snowmelt dominated, providing as much as 75 percent of total annual runoff for the region. Terminal lakes of the Great Basin occupy the lowest areas of closed (endorheic) drainage basins, such that lake levels and water quality respond rapidly to surface-water inflow. Terminal lakes provide local and regional economic value to the States in the Great Basin, including mineral extraction, aquaculture, public works, and recreational uses. As an example, assessments of Great Salt Lake’s ecological health and economic impact find hemispheric importance for the former and regional importance for the latter. Great Salt Lake creates about 7,000 jobs and $2 billion of economic output per year, most of which would be lost with further declines in lake level. The objectives of this Science Strategy are threefold: (1) to identify how changing water availability affects the quality, diversity, and abundance of habitats supporting continental waterbird populations; (2) to highlight the scientific monitoring and assessment needs of Great Basin terminal lakes; and (3) to support coordinated management and conservation actions to benefit those ecosystems, migratory birds, and other wildlife. There are long-term hydrological, ecological, and societal challenges associated with terminal lakes ecosystems in the Great Basin. This Science Strategy benefits partners by providing a conceptual model, nested at different spatial extents, that identifies key scientific information needs to inform coordinated implementation of management and conservation plans within and among hydrologic basins to address these complex challenges.

California, Idaho, Nevada, Oregon, Utah, Wyoming↗

USGS2023

Implications of water, sediment, and nutrient budgets for the restoration of a shallow, turbid lake in semiarid southeastern Oregon

Malheur Lake is the largest lake in the endorheic Harney Basin in southeastern Oregon. Since the 1990s, Malheur Lake—which averages depths of about 1 meter—has been in a degraded, turbid state lacking submergent and emergent vegetation. The goals of this study were to identify the major sources of sediment and nutrients to Malheur Lake to determine the importance of managing nutrients for lake restoration. Discrete water samples were analyzed for nutrient (total phosphorus, total nitrogen, orthophosphate, nitrate+nitrite, and ammonia) and suspended-sediment concentrations, and additional parameters including chlorophyll- a and phytoplankton biomass were measured in lake samples. Lake area fluctuated from a minimum of 3,300 hectares (ha) to a maximum of 11,300 ha in water years 2019 and 2020. In water year 2019, inflow from the tributaries created a 1,400-hectare area in the lake with low turbidity that persisted for multiple months. Land-use practices and water diversions along the tributaries affected the hydrographs and nutrient and suspended-sediment concentrations reaching the lake. As lake area increased, storage of sediment-associated constituents in the water column increased in excess of external loads because of resuspension. In 2019, 69 percent of the increase in suspended-sediment storage in the water column was attributed to internal resuspension and 31 percent was from external loading. Sediment was deposited as lake area decreased, and water-column storage decreased even as positive external loading continued. The internal resuspension, deposition, and external loading of suspended sediment likely is decreasing topographic heterogeneity in the lake. Concentrations of total phosphorus and orthophosphate are substantially higher than in the 1980s, and the lake is eutrophic. Phytoplankton in the lake was light limited in 2019–20, and restoration actions that prioritize vegetation establishment would reduce bioavailable nutrients for phytoplankton while increasing light in the water column.

Oregon↗

USGS2022

Light attenuation and erosion characteristics of fine sediments in a highly turbid, shallow, Great Basin Lake—Malheur Lake, Oregon, 2017–18

Malheur Lake is a large, shallow, turbid lake in southeastern Oregon that fluctuates widely in surface area in response to yearly precipitation and climatic cycles. High suspended-sediment concentrations (SSCs) likely are negatively affecting the survival of aquatic plants by reducing the intensity of solar radiation reaching the plants, thus inhibiting photosynthesis. This study was designed to determine the types of suspended material, the erodibility of the lakebed, the attenuation of photosynthetically active radiation (PAR) through the water column, and the effects of wind and precipitation on SSC. Two sites in the lake were monitored for approximately 5 months during the summer growing season each year (2017–19). At these sites, turbidity, chlorophyll a fluorescence (a surrogate for concentration), and underwater PAR measurements were collected continuously, and discrete samples were collected every 2 weeks and analyzed for SSC, loss on ignition, and chlorophyll a concentration. Underwater PAR profile measurements were collected during site visits, and a nearby meteorological station recorded terrestrial PAR and wind speeds. About 18 percent of suspended material in the water was organic and mostly detrital. Nearly 100 percent of all suspended material was fine material (less than 63 micrometers), and more than 90 percent of the surficial lakebed material was fine material. The high concentrations of fine material in the water column can be expected to strongly attenuate light. SSC was significantly higher at both sites in 2018 compared to 2017 and 2019; the interannual differences were mostly due to the lower amount of precipitation in 2018, which resulted in shallower lake depths. Three years of SSC values multiplied by water depth showed a seasonal pattern: concentrations were often highest in early spring, lowest in summer, and intermediate in autumn. Episodic wind events with speeds of 5–10 meters per second caused rapid increases in turbidity above background that lasted for a few days. However, a baseline SSC value multiplied by water depth (estimated to be 0.11 kilograms per square meter) was present between wind events and even under ice, suggesting a persistent suspension of very fine, highly erodible material. Terrestrial and underwater PAR measurements were used to develop a relation between PAR attenuation and turbidity that can be used in modeling restoration scenarios. Calculated bottom shear stress caused by wind-generated waves ranged from 0 to 0.4 pascals (Pa). Erosion experiments indicated variability in the bottom sediments from the two lake sites, but much of the lakebed is highly erodible at a threshold of 0.05 to 0.1 Pa. Restoration actions may target the persistent turbidity (for example, the use of flocculation) or transient turbidity (for example, construction of wave-reduction barriers), with a goal of attaining approximately 36 micromoles photons per square meter per second of PAR at the lakebed to promote emergence of sago pondweed and other desirable plants. Currently, that threshold often is reached from 4 to 34 centimeters (cm) below the water surface in 1 meter water depth, depending on wind conditions, but halving persistent turbidity would increase the upper end of the range to 55 cm. Additional studies regarding the effects of (1) sediment drying on resuspension and (2) nutrient inputs and internal cycling on phytoplankton populations would help determine the most appropriate restoration strategies.

Oregon↗

USGS2020

Temperature and water-quality diversity and the effects of surface-water connection in off-channel features of the Willamette River, Oregon, 2015–16

Water-quality conditions (including temperature) in the Willamette River and many of its adjacent off-channel features, such as alcoves and side channels, were monitored between river miles 67 (near Salem, Oregon) and 168 (near Eugene, Oregon) during the summers of 2015 and 2016. One or more parameters (water temperature, dissolved oxygen, pH, specific conductance, and [or] water depth) were continuously measured at sites in the main channel (9 sites in 2015; 5 sites in 2016) and select off-channel features (20 features in 2015; 22 features in 2016). This study was initiated in reaction to the unusually warm, dry weather and resulting low streamflows that occurred in the Pacific Northwest in 2015 and the need for flow managers to understand the effects of streamflow on water-quality conditions in off-channel features of the Willamette River. Field monitoring was focused on documenting water-quality conditions during low summer streamflows and during fluctuations in streamflow, including when side channels became alcoves and reconnected to become side channels again. Water in the main channel of the Willamette River upstream from river mile 50 near Newberg typically is well mixed during summer, with warm water temperatures (greater than 18 degrees Celsius) and high dissolved-oxygen concentrations (often greater than 7.7 milligrams per liter). During low summer flows, a diverse suite of off-channel features exists adjacent to the main channel of the Willamette River. Despite temporal and spatial variability within individual features, comparison of continuous water-temperature data between the main channel and off-channel features indicated that some off-channel features were consistently cooler than the main channel, some were consistently warmer than the main channel, and others frequently fluctuated between warmer or cooler than the main channel. Site-specific characteristics including upstream connection, depth, and presence or absence of aquatic or riparian vegetation were factors that seemed to affect the water quality of a feature. Results from this study showed a relation between the geomorphology, hydrology, ecology, and water quality of an off-channel feature. Data confirmed that many features that can be classified as cold-water refuges based on water-temperature standards also contained low concentrations of dissolved oxygen that may not be suitable for sensitive fish species. A simplified site classification scheme is proposed that links water-quality conditions in measured off-channel features with site-specific characteristics and summer streamflows. The site classification scheme was extended to create a theoretical process matrix that relates measured water-quality conditions to a list of the processes and site-specific characteristics that could create those conditions.

Oregon↗

USGS2020

Evaluation of restoration alternatives using water-budget tools for the Wapato Lake National Wildlife Refuge, northwestern Oregon

The lakebed in Wapato Lake National Wildlife Refuge (NWR) in northwestern Oregon was farmed for decades prior to the establishment of the refuge in 2013. Planning for restoration of these lands required extensive data collection and construction of a water budget and tools to design and evaluate potential restoration strategies. The U.S. Geological Survey (USGS) and U.S. Fish and Wildlife Service worked together to monitor streamflow and water levels in and around Wapato Lake NWR, apply the USGS Shoreline Management Tool (SMT), then construct and apply a water-budget-based Water Management Scenario Tool (WMST). The SMT was used to determine the spatial availability of different water depths (as potential habitat for different species) as a function of water level and other factors, based on topographic data. The WMST uses a water-budget approach to predict daily water levels, inflows, outflows, and areas of specific categories of water depth in the refuge over the course of a water year in response to a range of hydrologic and meteorological conditions and potential water-management strategies. In this study, two hypothetical water-management strategies were simulated to predict their effect on water levels and areas with specific water depths as an indicator of potential habitat. In the first scenario, several tributaries that had been diverted around the lakebed since the 1930s were reconnected to the lake, and an outflow weir was used to control lake level and to create a lake and seasonal wetlands of specific depths. In the second scenario, an outflow weir was combined with pumps to help meet target lake levels. Results showed that reconnecting the largest three tributaries to Wapato Lake would provide sufficient water to create a range of aquatic conditions in most years. For a median water year, rainfall and tributary flows in these scenarios provided 99 percent of total inputs to the lake, whereas pumping, weir outflows, and open-water evaporation accounted for 95–97 percent of losses. Management of lake levels could be accomplished with a variable-elevation outflow weir or a combination of a weir and pumps. The lake would take longer to fill to a higher seasonal target level during a dry year. Without an outflow weir or other means of allowing water to flow out of the lake, the largest of two existing pumps would need to be used during late spring or early summer to attain a lower seasonal target water level in summer. High-water conditions downstream of Wapato Lake may prevent the use of a simple outflow weir, as historical downstream water levels in winter and spring sometimes were higher than the target water levels used in these scenarios. Water-budget-based methods applied in this study have proven to be valuable for the design and evaluation of potential restoration strategies at Wapato Lake NWR.

Wapato Lake National Wildlife Refuge↗

USGS2018

Temporal and spatial monitoring of cyanobacterial blooms at Willow Creek Reservoir, North-Central Oregon

The U.S. Geological Survey (USGS) and U.S. Army Corps of Engineers (USACE) investigated the spatial and temporal dynamics of cyanobacterial (blue-green algal) blooms in Willow Creek Reservoir in north-central Oregon in 2015–16. A combination of cameras and water-quality monitoring equipment was used to assess the frequency and duration of blooms and their effects on water quality. A surveillance camera captured color images every 15 minutes during daylight hours of the northwestern corner of Willow Creek Reservoir, where surface blooms tend to accumulate due to the prevailing summer winds. In 2015, a water-quality instrument was deployed in the northwestern corner of the reservoir to continuously measure water temperature, pH, dissolved oxygen, specific conductance, turbidity, total chlorophyll, and the blue-green algae pigment phycocyanin. In 2016, a water-quality instrument was used to collect measurements along transects throughout the reservoir to create spatial maps of water quality. The spatially integrated mapping process was repeated on three different days under varying algal conditions. Also in 2016, a telemetry connection was established allowing resource managers to view the reservoir images in near-real time. Results from 2015 indicate that surface accumulations of cyanobacteria can form and dissipate within minutes in the reservoir, and that blooms can cause substantial changes to water quality. A persistent cyanobacterial bloom in August and September 2015 resulted in pH values of 9.5 standard units, 220 percent oxygen saturation, and pronounced increases in turbidity and total chlorophyll. The stationary water-quality instrument collected data during periods with and without blooms, increasing our understanding of the effects of blooms on water quality and revealing potential restoration benchmarks for the freshwater reservoir. The spatially integrated mapping data showed the variation in water quality across the reservoir that occurs during blooms and baseline conditions and indicated regions of the reservoir to focus restoration efforts. Additional spatial data collection can be timed to collect daily extremes. The camera deployment in 2016 demonstrated that telemetering images from remote sites is possible and provides valuable and timely information. Monitoring with a surveillance camera is inexpensive and supplies data regarding surface-bloom presence or absence. The use of a camera can help target site visits to periods when blooms are observed, which may increase the accuracy of beginning and ending dates for water body closures. Monitoring cyanobacterial blooms in Willow Creek Reservoir with multiple devices provided a more comprehensive dataset than any one monitoring method. The camera images showed when a surface bloom initiated and dissipated while the water-quality instrument revealed the magnitude, or potential severity, of the effects on water quality.

Oregon↗

USGS2018

Klamath River Basin water-quality data

The Klamath River Basin stretches from the mountains and inland basins of south-central Oregon and northern California to the Pacific Ocean, spanning multiple climatic regions and encompassing a variety of ecosystems. Water quantity and water quality are important topics in the basin, because water is a critical resource for farming and municipal use, power generation, and for the support of wildlife, aquatic ecosystems, and endangered species. Upper Klamath Lake is the largest freshwater lake in Oregon (112 square miles) and is known for its seasonal algal blooms. The Klamath River has dams for hydropower and the upper basin requires irrigation water to support agriculture and grazing. Multiple species of endangered fish inhabit the rivers and lakes, and the marshes are key stops on the Pacific flyway for migrating birds. For these and other reasons, the water resources in this basin have been studied and monitored to support their management distribution.

California, Oregon↗