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At least 1,045 records · Page 58Linked to original sources
USGS2023

Evaluating the institutional and ecological effects of invasive species prevention policy: A case study from the U.S. Fish and Wildlife Service

Wildlife and natural resource institutions play key roles in invasive species monitoring and management. Paradoxically, the extensive fieldwork undertaken by these institutions and their partners may result in the inadvertent movement and spread of invasive species within and between sensitive ecosystems. In this work, we consider the potential effects of internal guidelines and policies designed to prevent the spread of invasive species by the field activities of management institutions and their partners. Such policies could be high-leverage tools for invasive species prevention, however, as large, complex organizations seek to implement policies to limit the spread of invasive species, it may be challenging to accommodate the wide diversity of potential invasion pathways and mitigation efforts facilitated via the programs, activities, and ecosystems they manage. Prevention policies may also be met with resistance due to the costs of implementation unless concrete benefits can be demonstrated. Assessing and communicating the effects of prevention policies could motivate improved implementation and adherence by institutional units and partners and could help inform adaptive policy changes. However, assessing the effectiveness of invasive species prevention presents a unique set of challenges, including incomplete data on invasive species distribution and pathways, that make it difficult to measure the effects of prevention efforts. In this work, we present a conceptual framework for evaluating institutional policies for invasive species prevention. We describe a flexible, multifaceted approach that considers policy implementation and adherence as well as ecological outcomes. We discuss potential application of this framework using a policy recently implemented by the Pacific Region of the U.S. Fish and Wildlife Service to prevent the introduction and spread of invasive species by service personnel and partners during field activities as a case study.

Management of Biological Invasions↗
USGS2025

A comprehensive freshwater mussel database for the Duck River Drainage, Tennessee

We have developed a comprehensive database for freshwater mussels for the Duck River drainage in Tennessee, including its largest tributary, the Buffalo River. This database is intended to serve as an expandable template that could be applied statewide. The Duck River is one of the most biologically diverse rivers in the world, with historically over 70 mussel species, and it has been selected as a priority watershed by multiple management and conservation entities. The database for this system compiles over 7,000 mussel records, spanning 200 years, from multiple Federal, State, academic, and private entities, representing 77 native species. The database is spatially explicit and includes temporal and methodological data for each record, and notes of negative survey data were made when possible. The database can facilitate the creation of distribution maps for each species and temporal maps of species richness to show watershed-wide trends. This project addresses the present lack of a centralized mussel database in Tennessee for a critical system. It will be available to facilitate species status assessments, inform conservation planning, and serve as a model for similar databases for other Tennessee watersheds.

Tennessee↗
USGS2015

Linking degradation status with ecosystem vulnerability to environmental change

Environmental change can cause regime shifts in ecosystems, potentially threatening ecosystem services. It is unclear if the degradation status of ecosystems correlates with their vulnerability to environmental change, and thus the risk of future regime shifts. We assessed resilience in acidified (degraded) and circumneutral (undegraded) lakes with long-term data (1988–2012), using time series modeling. We identified temporal frequencies in invertebrate assemblages, which identifies groups of species whose population dynamics vary at particular temporal scales. We also assessed species with stochastic dynamics, those whose population dynamics vary irregularly and unpredictably over time. We determined the distribution of functional feeding groups of invertebrates within and across the temporal scales identified, and in those species with stochastic dynamics, and assessed attributes hypothesized to contribute to resilience. Three patterns of temporal dynamics, consistent across study lakes, were identified in the invertebrates. The first pattern was one of monotonic change associated with changing abiotic lake conditions. The second and third patterns appeared unrelated to the environmental changes we monitored. Acidified and the circumneutral lakes shared similar levels and patterns of functional richness, evenness, diversity, and redundancy for species within and across the observed temporal scales and for stochastic species groups. These similar resilience characteristics suggest that both lake types did not differ in vulnerability to the environmental changes observed here. Although both lake types appeared equally vulnerable in this study, our approach demonstrates how assessing systemic vulnerability by quantifying ecological resilience can help address uncertainty in predicting ecosystem responses to environmental change across ecosystems.

Oecologia↗
USGS1976

Erosional landform map of the Redwood Creek drainage basin, Humboldt County, California, 1947-74

Landslides and actively eroding stream channels disrupt roads, damage valuable timberland, and increase stream sediment loads in northwestern California. This 1:62,500 photointerpretative map shows the distribution of ten common types of fluvial and mass-movement erosional landforms in the drainage basin of Redwood Creek in 1947 and 1974. The mapped landforms include slides, slumps, large compound earthflows, debris avalanches, unstable streambanks and adjacent hillslopes, small mass-movement features, questionable or inactive landslides, deeply incised amphitheater shaped drainage basins, small actively eroding water courses, and actively eroding main channel stream banks. The map legend describes these landforms and the techniques used in preparing the map. The amount and diversity of erosional activity increased greatly between 1947 and 1974. This increased activity apparently reflects major floods in 1953, 1955, 1964, and 1972, as well as the start of large scale, tractor-yarded clearcut timber harvest in the basin. (Woodard-USGS)

California↗
USGS2023

Method for identification of reservoir regulation within U.S. Geological Survey streamgage basins in the Central United States using a decadal dam impact metric

Researchers routinely study streamflow data to understand the effects of natural climate variability and anthropogenic climate change, and to develop methods for estimating streamflow at ungaged locations. These studies require streamflow data that are not modified or largely altered by other anthropogenic activities, such as reservoirs or diversions. This report discusses a method for identifying basins with reservoir regulation using a decadal impact metric that characterizes the degree of regulation of a given river reach. The method is applied to U.S. Geological Survey streamgage basins from eight States in the Central United States. Using this metric, 140 streamgages with known regulation effects (annual peak streamflow values qualified with a code 6) were evaluated for their impact metric values in decades with annual peak streamflow values qualified with code 6. Based on the distribution of median impact metric values at these regulated basins, a threshold value of 0.1 was identified as the value that when exceeded was the most characteristic of the regulated streamgage basins in the study area. Streamgage basins from nine States with peak streamflow values that were not qualified with code 6 were evaluated for impact metric values equal to or greater than the established threshold. About 13 percent of streamgages (136 of 1,017) had an impact metric equal to or greater than the identified regulated threshold at some point in their periods of record. The method discussed in this report, which has limitations owing to characteristics of the data underlying the dam impact metric, provides a regionally consistent approach to identifying regulated U.S. Geological Survey streamgage basins.

Iowa, Illinois, Michigan, Missouri, Montana, North↗
USGS2025

Freshwater and diadromous Fishes of Puerto Rico

Freshwater and Diadromous Fishes of Puerto Rico describes the diversity of fishes in Puerto Rico’s freshwater environments and provides information on the history of research, management and conservation, and culture of fish and fisheries in Puerto Rico. This book’s catalog of fishes guides the reader in the identification of more than 50 native and nonnative species of fish from 22 families that occur in Puerto Rico’s freshwater lagoons, rivers, streams, and reservoirs. Each species account includes a map of known occurrences, and a description of each species’ morphological characteristics, biology, and distribution. Freshwater and Diadromous Fishes of Puerto Rico is the result of decades of scientific research; however, it is intended to be accessible and useful to readers with a variety of backgrounds, including scientists, students, and outdoor enthusiasts such as recreational anglers and freshwater snorkelers. Conservation and management are underlying themes of Freshwater and Diadromous Fishes of Puerto Rico . Though the main goal of this book is to be a resource for the identification of Puerto Rico’s freshwater fishes, and on their biology and ecology, it is also intended to increase awareness of threats to these fishes and their value to people and ecosystems.

Puerto Rico↗
USGS2012

Spawning and nursery habitats of neotropical fish species in the tributaries of a regulated river

This chapter provides information on ontogenetic patterns of neotropical fish species distribution in tributaries (Verde, Pardo, Anhanduí, and Aguapeí rivers) of the Porto Primavera Reservoir, in the heavily dammed Paraná River, Brazil, identifying key spawning and nursery habitats. Samplings were conducted monthly in the main channel of rivers and in marginal lagoons from October through March during three consecutive spawning seasons in 2007-2010. Most species spawn in December especially in Verde River. Main river channels are spawning habitats and marginal lagoons are nursery areas for most fish, mainly for migratory species. The tributaries have high diversity of larvae species: a total of 56 taxa representing 21 families, dominated by Characidae. Sedentary species without parental care are more abundant (45.7%), and many long-distance migratory fish species are present (17.4%). Migrators included Prochilodus lineatus , Rhaphiodon vulpinus , Hemisorubim platyrhynchos , Pimelodus maculatus , Pseudoplatystoma corruscans , Sorubim lima , two threatened migratory species: Salminus brasiliensis and Zungaro jahu , and one endangered migratory species: Brycon orbignyanus . Most of these migratory species are vital to commercial and recreational fishing, and their stocks have decreased drastically in the last decades, attributed to habitat alteration, especially impoundments. The fish ladder at Porto Primavera Dam appears to be playing an important role in re-establishing longitudinal connectivity among critical habitats, allowing ascent to migratory fish species, and thus access to upstream reaches and tributaries. Establishment of Permanent Conservation Units in tributaries can help preserve habitats identified as essential spawning and nursery areas, and can be key to the maintenance and conservation of the fish species in the Paraná River basin.

Upper Paraná River↗
USGS2015

Genomics and introgression: Discovery and mapping of thousands of species-diagnostic SNPs using RAD sequencing

Invasive hybridization and introgression pose a serious threat to the persistence of many native species. Understanding the effects of hybridization on native populations (e.g., fitness consequences) requires numerous species-diagnostic loci distributed genome-wide. Here we used RAD sequencing to discover thousands of single-nucleotide polymorphisms (SNPs) that are diagnostic between rainbow trout (RBT, Oncorhynchus mykiss ), the world’s most widely introduced fish, and native westslope cutthroat trout (WCT, O. clarkii lewisi ) in the northern Rocky Mountains, USA. We advanced previous work that identified 4,914 species-diagnostic loci by using longer sequence reads (100 bp vs . 60 bp) and a larger set of individuals ( n = 84). We sequenced RAD libraries for individuals from diverse sampling sources, including native populations of WCT and hatchery broodstocks of WCT and RBT. We also took advantage of a newly released reference genome assembly for RBT to align our RAD loci. In total, we discovered 16,788 putatively diagnostic SNPs, 10,267 of which we mapped to anchored chromosome locations on the RBT genome. A small portion of previously discovered putative diagnostic loci (325 of 4,914) were no longer diagnostic (i.e., fixed between species) based on our wider survey of non-hybridized RBT and WCT individuals. Our study suggests that RAD loci mapped to a draft genome assembly could provide the marker density required to identify genes and chromosomal regions influencing selection in admixed populations of conservation concern and evolutionary interest.

Montana↗
USGS2025

Status and trends of the Lake Huron prey fish community, 1976-2024

The U. S. Geological Survey-Great Lakes Science Center has monitored annual changes in the offshore (depth > 9m) prey fish community of Lake Huron since 1973. Monitoring of prey fish populations in Lake Huron is based on a bottom trawl survey that targets demersal species (i.e., those predominantly or intermittently associated with the lake bottom) and an acoustic-midwater trawl survey that targets pelagic species and life stages. Prey fish abundance and species composition in 2024 was generally consistent with trends observed over the past decade. Bloater ( Coregonus hoyi ) remains the most abundant and widespread prey species, although its abundance is starting to decline owing to changes in demographic factors that are interacting to suppress reproduction. Rainbow Smelt ( Osmerus mordax ) remain widely distributed across Lake Huron but their dynamics vary by basin. Rainbow Smelt populations currently are larger in Georgian Bay and the North Channel than in the main basin where they have produced eight weak year classes over the past decade including in 2024. Populations of Alewife ( Alosa pseudoharengus ) continue to be comprised of low numbers of age-0 individuals, and sculpin communities consist primarily of Deepwater Sculpin ( Myoxocephalus thompsonii ) due to the reduced abundance and distribution of Slimy Sculpin ( Cottus cognatus ). In contrast, biomass of the invasive Round Goby ( Neogobius melanostomus ) in 2024 was the highest observed in the bottom trawl time series and was over four times greater than in 2023. Overall status of main basin prey fish community was rated as ‘fair.’ Stable dynamics of main basin Bloater populations and evidence of continued recovery by Cisco ( Coregonus artedi ) in the North Channel were interpreted as positive community trends, whereas growth and expansion of Round Goby populations and low species diversity of pelagic prey fish communities are inconsistent with fish community objectives. Use of complementary surveys (bottom trawl, acoustics) remains useful for evaluating prey fish status in Lake Huron, where prey fish community dynamics vary by basin and prey fish responses to changing environmental conditions depend on species and/or habitat.

Lake Huron↗
USGS2024

Simulation of groundwater flow in the Long Island, New York regional aquifer system for pumping and recharge conditions from 1900 to 2019

The U.S. Geological Survey has developed a transient, groundwater-flow model that simulates hydrologic conditions in the Long Island aquifer system as part of an ongoing (since 2016) multiyear, cooperative investigation with the New York State Department of Environmental Conservation. The goals of this investigation are to assist stakeholders and resource managers to evaluate the response of the hydrologic system to changes in future hydraulic stresses. Responses in the hydrologic system include changes in water levels in the hydrogeologic units; discharge to streams, coastal waters, and subsurface infrastructure; and the extent of saline groundwater in the aquifers. Hydraulic stresses include future water-supply management and changes in land use and infrastructure. The numerical model synthesizes a diverse set of physiographic, geologic, climatic, land-use, and historical population, water use, and infrastructure data to physically represent the Long Island aquifer system from land surface to bedrock and to simulate annual hydrologic conditions between 1900 and 2019. A three-dimensional hydrogeologic framework was developed from existing and recently collected borehole geologic and geophysical data collected as part of a companion drilling program. Water-transmitting properties of the principal aquifer sediments were defined in three dimensions from new and existing lithologic logs. The distribution of recharge from precipitation was estimated from landscape characteristics and climate data. Anthropogenic recharge from wastewater, leaky infrastructure, and storm runoff were estimated from population, infrastructure, and pumping data. Water-use data, including well locations, depths, and pumping rates, were obtained from historical sources and records and used to estimate pumping stresses continuously in time and space, at an annual average time scale. The data were incorporated into a three-dimensional numerical model using the U.S. Geological Survey finite difference modeling code MODFLOW 6; the model encompassed all of Long Island and surrounding surface waters and simulated historical hydrologic conditions from 1900 to 2019. The calibration process involved trial and error adjustments using prior knowledge to improve general fit to observations followed by an inverse calibration to update and optimize input parameters, using an iterative ensemble smoother algorithm implemented in PEST++ version 5.0. This resulted in a model that generally was in good agreement with observed, dynamically varying hydrologic conditions from 1900 to 2019. The calibrated model was used to develop two base-case models for scenario testing of future, hypothetical conditions where one represented average-annual conditions, and one represented average-seasonal conditions from 2010 to 2019. The model representing average-annual conditions was modified further to represent an alternate sea-level position of 6 feet above the North American Vertical Datum of 1988, and the model representing average-seasonal conditions was modified to represent the average seasonal effects of a 5-year drought imposed upon current hydrologic conditions. Recharge is the sole source of water to the aquifer system; groundwater discharges to coastal water and streams and is withdrawn by pumped wells. Model-estimated annual recharge ranged from about 11 inches in 1965 to 41 inches in 1983. On average, from 2010 to 2019, about 23 percent of water was pumped from wells, and about 47 and 27 percent discharged to coastal waters and streams, respectively; the remaining 4 percent was water that moved into storage in the aquifer matrix. Water levels on Long Island vary naturally during time in response to changes in recharge; the amount of variation is largest in the interior of the island, in areas with highest water table altitudes near groundwater divides and lowest near streams and the coastal waters. The total range of water table altitudes on Long Island between 1900 and 2019 ranged from near 0 to more than 70 feet in western parts of Long Island. The largest range in altitudes is in New York City and is associated with areas of large historical withdrawals between the 1920s and the late 1980s. Water table altitudes generally varied by less than 10 feet in eastern Suffolk County, where the aquifer is under more natural conditions. Saltwater intrusion is of great concern on Long Island, particularly in western Long Island where both the unconfined and confined parts of the aquifer system have been intruded in response to large-scale groundwater withdrawals; however, the volume of freshwater in the islandwide aquifer system only has changed by about 5 percent between 1900 and 2019. The decadal change in the freshwater volume was largest during the early and mid-20th century, corresponding to the largest historical pumping, but that volume change did not exceed 1 percent. The negligible change in freshwater volume suggests that saltwater intrusion as of 2019 was limited at an islandwide scale but continues to occur in local areas of Queens and Nassau Counties, adversely affecting current water supplies and limiting future water supplies for affected communities. The regional groundwater model developed for this investigation is a tool that can be used to help determine the viability of current and future water supplies at a regional scale and can be used to support development of additional models at finer scale to support more focused assessments of groundwater sustainability.

New York↗
USGS2019

The major coral reefs of Maui Nui, Hawai‘i—distribution, physical characteristics, oceanographic controls, and environmental threats

Coral reefs are widely recognized as critical to Hawaiʻi’s economy, food resources, and protection from damaging storm waves. Yet overfishing, land-based pollution, and climate change are threatening the health and sustainability of those reefs, and accordingly, both the Federal and State governments have called for protection and effective management. In 2000, the U.S. Coral Reef Task Force stated that 20 percent of coral reefs should be protected by 2010. In 2016, the Governor of Hawaiʻi committed to effective management of 30 percent of Hawaiian coastal habitats by 2030 to protect coral reefs. At present, the amount of coral protected in the main Hawaiian Islands is less than 1 percent. Most of the large, highly diverse coral reef tracts in the main Hawaiian Islands surround the four islands of Maui, Molokaʻi, Lānaʻi, and Kahoʻolawe, collectively known as Maui Nui. This report provides fundamental information on the location, extent, coral cover, threats, and connectivity of these major coral reef tracts in Maui Nui essential for identifying areas for management and protection. By combining high-resolution bathymetric data with available maps, publications, and satellite and underwater images, nine major coral reef tracts are identified in the coastal waters of Maui Nui. Three very large reef tracts lie along the south side of Molokaʻi, two on the east side of Lānaʻi, and four off Maui. The factors that make these Maui Nui coral reef tracts a major and important resource for Hawaiʻi include their vast size and high coral cover (nearly 16,000 acres of reef, most of which has more than 50 percent live coral cover); diversity of shape, size, and location; and separation between reefs while retaining connectivity via currents. The decline in the health of these coral reefs over the past several decades has been slow but persistent. Punctuation of the decline by large-scale disturbance events, such as the thermal bleaching that occurred in 2015, is accelerating the loss of viable reef areas by an order of magnitude. The economic, cultural, and recreational value of these coral reef tracts highlights the importance of their long-term survival to the local communities and all of Hawaiʻi. There is scientific consensus that increasing pressures from climate change, overfishing, and land-based pollution will virtually assure the continued, and perhaps accelerating, decline of Hawaiʻi’s coral reefs unless action is taken. Information presented in this report, coupled with the results of numerous scientific studies, provides scientific underpinning to help establish a network of large-scale, connected Marine Protected Areas to meet the Federal and State governments’ call for effective management and protection of coral reefs in Maui Nui.

Hawaii↗
USGS2010

Seasonal and Spatial Distribution of Freshwater Flow and Salinity in the Ten Thousand Islands Estuary, Florida, 2007-2009

The watershed of the Ten Thousand Islands (TTI) estuary has been substantially altered through the construction of canals and roads for the Southern Golden Gate Estates (SGGE), Barron River Canal, and U.S. 41 (Tamiami Trail). Two restoration projects designed to improve freshwater delivery to the estuary are the Picayune Strand Restoration Project, which includes the Southern Golden Gate Estates, and the Tamiami Trail Culverts Project; both are part of the Comprehensive Everglades Restoration Plan. To address hydrologic information needs critical for monitoring the effects of these restoration projects, the U.S. Geological Survey initiated a study in October 2006 to characterize freshwater outflows from the rivers, internal circulation and mixing within the estuary, and surface-water exchange between the estuary and Gulf of Mexico. The effort is conducted in cooperation with the South Florida Water Management District and complemented by monitoring performed by the Rookery Bay National Estuarine Research Reserve. Surface salinity was measured during moving boat surveys using a flow-through system that operated at planing speeds averaging 20 miles per hour. The data were logged every 10 seconds by a data recorder that simultaneously logged location information from a Global Positioning System. The major rivers, bays, and nearshore Gulf of Mexico region of the TTI area were surveyed in approximately 5 hours by two boats traversing about 200 total miles. Salinity and coordinate data were processed using inverse distance weighted interpolation to create salinity contour maps of the entire TTI region. Ten maps were created from salinity surveys performed between May 2007 and May 2009 and illustrate the dry season, transitional, and wet season salinity patterns of the estuarine rivers, inner bays, mangrove islands, and Gulf of Mexico boundary. The effects of anthropogenic activities are indicated by exceptionally low salinities associated with point discharge into the estuary from the Faka Union Canal and Barron River during the wet season. Low salinities in Faka Union Bay may cause reduced diversity and density of submerged aquatic vegetation, fish, and benthic organisms compared with neighboring Fakahatchee Bay. The Faka Union Canal System reduced the size of the watershed for the western TTI estuary, resulting in increased wet season salinities compared to those for the eastern TTI estuary, the watershed of which is composed of the relatively pristine Fakahatchee Strand Preserve State Park. Minimal river discharge and high evaporation caused hypersaline conditions to develop throughout the entire TTI region during the dry season. The 2007-2008 drought and passage of Tropical Storm Fay on August 18-19, 2008, demonstrated the effects of seasonal rainfall on salinity patterns, with substantially higher salinities observed during the 2007 wet season compared to those for the 2008 wet season. The salinity maps, coupled with data from the monitoring stations, provide baseline information of seasonal and spatial distribution of freshwater flow and salinity in the TTI estuary, and a means of monitoring the effects of restoration in improving freshwater delivery to the estuary.

Data Series↗
USGS2016

Rangewide genetic analysis of Lesser Prairie-Chicken reveals population structure, range expansion, and possible introgression

The distribution of the Lesser Prairie-Chicken ( Tympanuchus pallidicinctus ) has been markedly reduced due to loss and fragmentation of habitat. Portions of the historical range, however, have been recolonized and even expanded due to planting of conservation reserve program (CRP) fields that provide favorable vegetation structure for Lesser Prairie-Chickens. The source population(s) feeding the range expansion is unknown, yet has resulted in overlap between Lesser and Greater Prairie-Chickens ( T. cupido ) increasing the potential for hybridization. Our objectives were to characterize connectivity and genetic diversity among populations, identify source population(s) of recent range expansion, and examine hybridization with the Greater Prairie-Chicken. We analyzed 640 samples from across the range using 13 microsatellites. We identified three to four populations corresponding largely to ecoregions. The Shinnery Oak Prairie and Sand Sagebrush Prairie represented genetically distinct populations ( F ST > 0.034 and F ST > 0.023 respectively). The Shortgrass/CRP Mosaic and Mixed Grass ecoregions appeared admixed ( F ST = 0.009). Genetic diversity was similar among ecoregions and N e ranged from 142 (95 % CI 99–236) for the Shortgrass/CRP Mosaic to 296 (95 % CI 233–396) in the Mixed Grass Prairie. No recent migration was detected among ecoregions, except asymmetric dispersal from both the Mixed Grass Prairie and to a lesser extent the Sand Sagebrush Prairie north into adjacent Shortgrass/CRP Mosaic ( m = 0.207, 95 % CI 0.116–0.298, m = 0.097, 95 % CI 0.010–0.183, respectively). Indices investigating potential hybridization in the Shortgrass/CRP Mosaic revealed that six of the 13 individuals with hybrid phenotypes were significantly admixed suggesting hybridization. Continued monitoring of diversity within and among ecoregions is warranted as are actions promoting genetic connectivity and range expansion.

Colorado, Kansas, New Mexico, Texas↗
USGS2025

Changes in streamflow seasonality associated with hydroclimatic variability in the north-central United States among three discrete temporal periods, 1946–2020

Study region North-central United States Study focus This study uses circular statistics to characterize the seasonal properties of annual maximum (AMS) and peaks-over-threshold (POT) streamflow time series for 841 and 623 selected U.S. Geological Survey (USGS) streamgages, respectively, without regulation or substantial diversion among common 75-, 50-, and 30-year trend periods through water year 2020 (the period from October 1, 2019, through September 30, 2020). A subset of AMS time series with detected change points (abrupt changes) in the median and (or) scale are analyzed on either side of the change point to evaluate changes in their circular statistics. New hydrologic insights for the region In the 50-year trend period, five regions share common mean flood timing in the AMS and POT partial duration series. Changes from asymmetric distributions to reflective symmetric distributions are detected particularly among the 50- and 30-year trend periods in the northernmost States of Minnesota, North Dakota, and Wisconsin. For the subset of streamgages with abrupt change points in the AMS, regional patterns of changes in seasonality are detected between the period of records before and after the change point. These findings can inform decisions related to the AMS used for flood frequency and potential mixed population analyses and flood control operations that may be affected by changes in when seasonal events occur, how long seasonal events last, and the long-term variability in the intensity and frequency of seasonal events.

Illinois, Iowa, Michigan, Minnesota, Missouri, Mon↗
USGS2014

Multilocus phylogeography and systematic revision of North American water shrews (genus: Sorex )

North American water shrews, which have traditionally included Sorex alaskanus , S. bendirii , and S. palustris , are widely distributed through Nearctic boreal forests and adapted for life in semiaquatic environments. Molecular mitochondrial signatures for these species have recorded an evolutionary history with variable levels of regional divergence, suggesting a strong role of Quaternary environmental change in speciation processes. We expanded molecular analyses, including more-comprehensive rangewide sampling of specimens representing North American water shrew taxa, except S. alaskanus , and sequencing of 4 independent loci from the nuclear and mitochondrial genomes. We investigated relative divergence of insular populations along the North Pacific Coast, and newly recognized diversity from southwestern montane locations, potentially representing refugial isolates. Congruent independent genealogies, lack of definitive evidence for contemporary gene flow, and high support from coalescent species trees indicated differentiation of 4 major geographic lineages over multiple glacial cycles of the late Quaternary, similar to a growing number of boreal taxa. Limited divergence of insular populations suggested colonization following the last glacial. Characterization of southwestern montane diversity will require further sampling but divergence over multiple loci is indicative of a relictual sky-island fauna. We have reviewed and revised North American water shrew taxonomy including the recognition of 3 species within what was previously known as S. palustris . The possibility of gene flow between most distantly related North American water shrew lineages coupled with unresolved early diversification of this group and other sibling species reflects a complex but potentially productive system for investigating speciation processes.

Journal of Mammalogy↗
USGS2011

Potential effects of groundwater pumping on water levels, phreatophytes, and spring discharges in Spring and Snake Valleys, White Pine County, Nevada, and adjacent areas in Nevada and Utah

Assessing hydrologic effects of developing groundwater supplies in Snake Valley required numerical, groundwater-flow models to estimate the timing and magnitude of capture from streams, springs, wetlands, and phreatophytes. Estimating general water-table decline also required groundwater simulation. The hydraulic conductivity of basin fill and transmissivity of basement-rock distributions in Spring and Snake Valleys were refined by calibrating a steady state, three-dimensional, MODFLOW model of the carbonate-rock province to predevelopment conditions. Hydraulic properties and boundary conditions were defined primarily from the Regional Aquifer-System Analysis (RASA) model except in Spring and Snake Valleys. This locally refined model was referred to as the Great Basin National Park calibration (GBNP-C) model. Groundwater discharges from phreatophyte areas and springs in Spring and Snake Valleys were simulated as specified discharges in the GBNP-C model. These discharges equaled mapped rates and measured discharges, respectively. Recharge, hydraulic conductivity, and transmissivity were distributed throughout Spring and Snake Valleys with pilot points and interpolated to model cells with kriging in geologically similar areas. Transmissivity of the basement rocks was estimated because thickness is correlated poorly with transmissivity. Transmissivity estimates were constrained by aquifer-test results in basin-fill and carbonate-rock aquifers. Recharge, hydraulic conductivity, and transmissivity distributions of the GBNP-C model were estimated by minimizing a weighted composite, sum-of-squares objective function that included measurement and Tikhonov regularization observations. Tikhonov regularization observations were equations that defined preferred relations between the pilot points. Measured water levels, water levels that were simulated with RASA, depth-to-water beneath distributed groundwater and spring discharges, land-surface altitudes, spring discharge at Fish Springs, and changes in discharge on selected creek reaches were measurement observations. The effects of uncertain distributed groundwater-discharge estimates in Spring and Snake Valleys on transmissivity estimates were bounded with alternative models. Annual distributed groundwater discharges from Spring and Snake Valleys in the alternative models totaled 151,000 and 227,000 acre-feet, respectively and represented 20 percent differences from the 187,000 acre-feet per year that discharges from the GBNP-C model. Transmissivity estimates in the basin fill between Baker and Big Springs changed less than 50 percent between the two alternative models. Potential effects of pumping from Snake Valley were estimated with the Great Basin National Park predictive (GBNP-P) model, which is a transient groundwater-flow model. The hydraulic conductivity of basin fill and transmissivity of basement rock were the GBNP-C model distributions. Specific yields were defined from aquifer tests. Captures of distributed groundwater and spring discharges were simulated in the GBNP-P model using a combination of well and drain packages in MODFLOW. Simulated groundwater captures could not exceed measured groundwater-discharge rates. Four groundwater-development scenarios were investigated where total annual withdrawals ranged from 10,000 to 50,000 acre-feet during a 200-year pumping period. Four additional scenarios also were simulated that added the effects of existing pumping in Snake Valley. Potential groundwater pumping locations were limited to nine proposed points of diversion. Results are presented as maps of groundwater capture and drawdown, time series of drawdowns and discharges from selected wells, and time series of discharge reductions from selected springs and control volumes. Simulated drawdown propagation was attenuated where groundwater discharge could be captured. General patterns of groundwater capture and water-table declines were similar for all scenarios. Simulated drawdowns greater than 1 ft propagated outside of Spring and Snake Valleys after 200 years of pumping in all scenarios.

Scientific Investigations Report↗
USGS2004

Simulation of regional ground-water flow in the Upper Deschutes Basin, Oregon

This report describes a numerical model that simulates regional ground-water flow in the upper Deschutes Basin of central Oregon. Ground water and surface water are intimately connected in the upper Deschutes Basin and most of the flow of the Deschutes River is supplied by ground water. Because of this connection, ground-water pumping and reduction of artificial recharge by lining leaking irrigation canals can reduce the amount of ground water discharging to streams and, consequently, streamflow. The model described in this report is intended to help water-management agencies and the public evaluate how the regional ground-water system and streamflow will respond to ground-water pumping, canal lining, drought, and other stresses. Ground-water flow is simulated in the model by the finite-difference method using MODFLOW and MODFLOWP. The finite-difference grid consists of 8 layers, 127 rows, and 87 columns. All major streams and most principal tributaries in the upper Deschutes Basin are included. Ground-water recharge from precipitation was estimated using a daily water-balance approach. Artificial recharge from leaking irrigation canals and on-farm losses was estimated from diversion and delivery records, seepage studies, and crop data. Ground-water pumpage for irrigation and public water supplies, and evapotranspiration are also included in the model. The model was calibrated to mean annual (1993-95) steady-state conditions using parameter-estimation techniques employing nonlinear regression. Fourteen hydraulic-conductivity parameters and two vertical conductance parameters were determined using nonlinear regression. Final parameter values are all within expected ranges. The general shape and slope of the simulated water-table surface and overall hydraulic-head distribution match the geometry determined from field measurements. The fitted standard deviation for hydraulic head is about 76 feet. The general magnitude and distribution of ground-water discharge to streams is also well simulated throughout the model. Ground-water discharge to streams in the area of the confluence of the Deschutes, Crooked, and Metolius Rivers is closely matched. The model was also calibrated to transient conditions from 1978 to 1997 using traditional trial-and-error methods. Climatic cycles during this period provided an excellent regional hydrologic signal for calibration. Climate-driven water-level fluctuations are simulated with reasonable accuracy over most of the model area. The timing and magnitude of simulated water-level fluctuations caused by annual pulses of recharge from precipitation match those observed reasonably well, given the limitations of the time discretization in the model. Water-level fluctuations caused by annual canal leakage are simulated very well over most of the area where such fluctuations occur. The transient model also simulates the volumetric distribution and temporal variations in ground-water discharge reasonably well. The match between simulated and measured volume of and variations in ground-water discharge is, however, somewhat dependent on geographic scale. The rates of and variations in ground-water discharge are matched best at regional scales. Example simulations were made to demonstrate the utility of the model for evaluating the effects of ground-water pumping or canal lining. Pumping simulations show that pumped water comes largely from aquifer storage when pumping begins, but as the water table stabilizes, the pumping increasingly diminishes the discharge to streams and, hence, streamflow. The time it takes for pumping to affect streamflow varies spatially depending, in general, on the location of pumping relative to the discharge areas. Canal-lining simulations show similar effects.

Water-Resources Investigations Report↗
USGS1998

A comparison of small-mammal communities in a desert riparian floodplain

We compared small-mammal communities between inactive floodplain and actively flooded terraces of riparian habitat in the Verde Valley of central Arizona. We used species diversity, abundance, weight of adult males, number of juveniles, number of reproductively active individuals, longevity, residency status, and patterns of microhabitat use to compare the two communities. Although abundances of small mammals tended to be higher in the active floodplain, species diversity was greater in the inactive floodplain. Results were inconsistent with our initial prediction that actively flooded riparian habitat acts as a species source, whereas inactive floodplain acts as a sink or dispersal site for small mammals. Within each habitat type, we found evidence of significant microhabitat separation among the three most abundant small-mammal species (Peromyscus boylii, P. eremicus, and Neotoma albigula). Percent cover by annual and perennial grasses and shrubs, substrate, and frequency of shrubs, trees, and debris were significant determinants of small-mammal distribution within a habitat type. We found that the three most abundant species selected a nonrandom subset of available habitat. Nonrandom use of habitat and microhabitat separation were the two most important mechanisms structuring small-mammal communities in riparian habitat of central Arizona.

Journal of Mammalogy↗