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USGS2010

Habitat suitability and conservation of the giant gartersnake (Thamnophis gigas) in the Sacramento Valley of California

Resource managers often have little information regarding the habitat requirements and distribution of rare species. Factor analysis-based habitat suitability models describe the ecological niche of a species and identify locations where these conditions occur on the landscape using existing occurrence data.We used factor analyses to assess the suitability of habitats for Thamnophis gigas (Giant Gartersnake), a rare, threatened species endemic to the Central Valley of California, USA, and to map the locations of habitat suitable for T. gigas in the Sacramento Valley. Factor analyses indicated that the niche of T. gigas is composed of sites near rice agriculture with low stream densities. Sites with high canal densities and near wetlands also appeared suitable, but results for these variables were sensitive to potential sampling bias. In the Sacramento Valley, suitable habitats occur primarily in the central portion of the valley floor. Based upon the results of the factor analyses, recovery planning for T. gigas will require an on-the-ground assessment of the current distribution and abundance of T. gigas, maintaining the few remaining natural wetlands and the practice of rice agriculture in the Sacramento Valley, and studying the effects of agricultural practices and land use changes on populations of T. gigas.

California↗

USGS2024

Advancing at-risk species recovery planning in an era of rapid ecological change with a transparent, flexible, and expert-engaged approach

In the face of unprecedented ecological changes, the conservation community needs strategies to recover species at risk of extinction. On the Island of Maui, we collaborated with species experts and managers to assist with climate-resilient recovery planning for 36 at-risk native plant species by identifying priority areas for the management of recovery populations. To do this, we developed a tailored spatial conservation prioritization (SCP) approach distinguished by its emphasis on transparency, flexibility, and expert (TFE) engagement. Our TFE SCP approach consisted of 2 iterative steps: first, the generation of multiple candidate conservation footprints (i.e., prioritization solutions) with a flexible greedy algorithm that reflects conservation practitioners’ priorities and, second, the selection of an optimal conservation footprint based on the consideration of trade-offs in expert-agreed criteria among footprints. This process maximized buy-in by involving conservation practitioners and experts throughout, from setting goals to reviewing optimization data, defining optimization rules, and designating planning units meaningful to practitioners. We minimized the conservation footprint area necessary to meet recovery goals while incorporating species-specific measures of habitat suitability and climate resilience and retaining species-specific information for guiding recovery efforts. Our approach reduced the overall necessary conservation area by 36%, compared with selecting optimal recovery habitats for each species separately, and still identified high-quality habitat for individual species. Compared with prioritizr (an existing SCP tool), our approach identified a conservation area of equal size but with higher quality habitat. By integrating the strengths of existing techniques in a flexible and transparent design, our approach can address natural resource management constraints and provide outputs suitable for local recovery planning, consequently enhancing engagement and buy-in from conservation practitioners and experts. It demonstrates a step forward in making conservation planning more responsive to real-world complexities and helps reduce barriers to implementation for local conservation practitioners.

Hawaii↗

USGS2018

Increased scientific rigor will improve reliability of research and effectiveness of management

Rigorous science that produces reliable knowledge is critical to wildlife management because it increases accurate understanding of the natural world and informs management decisions effectively. Application of a rigorous scientific method based on hypothesis testing minimizes unreliable knowledge produced by research. To evaluate the prevalence of scientific rigor in wildlife research, we examined 24 issues of the Journal of Wildlife Management from August 2013 through July 2016. We found 43.9% of studies did not state or imply a priori hypotheses, which are necessary to produce reliable knowledge. We posit that this is due, at least in part, to a lack of common understanding of what rigorous science entails, how it produces more reliable knowledge than other forms of interpreting observations, and how research should be designed to maximize inferential strength and usefulness of application. Current primary literature does not provide succinct explanations of the logic behind a rigorous scientific method or readily applicable guidance for employing it, particularly in wildlife biology; we therefore synthesized an overview of the history, philosophy, and logic that define scientific rigor for biological studies. A rigorous scientific method includes 1) generating a research question from theory and prior observations, 2) developing hypotheses (i.e., plausible biological answers to the question), 3) formulating predictions (i.e., facts that must be true if the hypothesis is true), 4) designing and implementing research to collect data potentially consistent with predictions, 5) evaluating whether predictions are consistent with collected data, and 6) drawing inferences based on the evaluation. Explicitly testing a priori hypotheses reduces overall uncertainty by reducing the number of plausible biological explanations to only those that are logically well supported. Such research also draws inferences that are robust to idiosyncratic observations and unavoidable human biases. Offering only post hoc interpretations of statistical patterns (i.e., a posteriori hypotheses) adds to uncertainty because it increases the number of plausible biological explanations without determining which have the greatest support. Further, post hoc interpretations are strongly subject to human biases. Testing hypotheses maximizes the credibility of research findings, makes the strongest contributions to theory and management, and improves reproducibility of research. Management decisions based on rigorous research are most likely to result in effective conservation of wildlife resources.

Journal of Wildlife Management↗

USGS2005

Water withdrawals for irrigation, municipal, mining, thermoelectric-power, and drainage uses in Arizona outside of active management areas, 1991-2000

Economic development in Arizona is largely influenced by access to adequate water supplies owing to the State's predominantly semiarid to arid climate. Water demand is met by pumping ground water from aquifers or by conveying surface water through a system of reservoirs and canals. Water-withdrawal data provide important information on how water demand affects the State's water resources. Information on water withdrawals also can help planners and managers assess the effectiveness of water-management policies, regulations, and conservation activities. This report includes water-withdrawal data for irrigation, municipal, mining, thermoelectric-power, and drainage uses for 1991-2000, and describes the methods used to collect, compile, and estimate the data. Data are reported for the Arizona Department of Water Resources ground-water basins outside of Active Management Areas. Because of the climate, ground water and surface water are used to irrigate nearly all agricultural fields in Arizona. Irrigation accounted for the largest use of water in the study area during 1991-2000. The amount of water withdrawn for irrigation varies greatly from year to year for some of the basins, primarily because of differences in the consumptive water requirement for different crops and because of changes in irrigated acreage. The population of Arizona increased about 35 percent from 1991 to 2000-from about 3.79 million in 1991 to about 5.13 million in 2000. Correspondingly, water withdrawal for municipal use increased steadily in most of the basins during 1991-2000. Ground-water withdrawals for mining did not show any consistent trends during 1991-2000. Increases and decreases in withdrawals for mining were most likely due to variations in mineral production. Mineral prices and competition from mining in other States and foreign countries probably result in annual increases or decreases in mineral production in Arizona. Between 1991 and 2000, ground-water withdrawals for thermoelectric-power generation generally increased owing to an increase in production of electricity. Ground-water withdrawals for drainage of agricultural lands in the Lower Gila and Yuma Basins varied irregularly from year to year. Annual total water withdrawals are not presented in this report because for some years irrigation values for some of the basins are reported as "less than 1,000 acre-feet," and municipal and mining values for some of the basins are reported as "less than 300 acre-feet."

Arizona↗

USGS2021

Estimating trends of common raven populations in North America, 1966—2018

Over the last half century, common raven ( Corvus corax; raven) populations have increased in abundance across much of North America. Ravens are generalist predators known to depredate the eggs and young of several sensitive species. Quantifying raven population increases at multiple spatial scales across North America will help wildlife resource managers identify areas where population increases present the greatest risk to species conservation. We used a hierarchical Bayesian modeling approach to analyze trends of standardized raven counts from 1966 to 2018 using Breeding Bird Survey data within each Level I and II ecoregion of the United States and Canada. We also compared raven abundance within and outside the distributions of 9 sensitive or endangered species. Although we found substantial evidence that raven populations have increased across North America, populations varied in growth rates and relative abundances among regions. We found 73% of Level I (11/15) and II (25/34) ecoregions demonstrated positive annual population growth rates ranging from 0.2–9.4%. We found higher raven abundance inside versus outside the distributions of 7 of the 9 sensitive species included in our analysis. Gunnison sage-grouse ( Centrocercus minimus ) had the highest discrepancy, with 293% more ravens within compared to outside of their range, followed by greater sandhill crane ( Antigone canadensis tabida ; 280%), and greater sage-grouse ( C. urophasianus ; 204%). Only 2 species, least tern ( Sternula antillarum ) and piping plover ( Charadrius melodus ), indicated lower raven abundance within relative to outside their distributions. Our findings will help wildlife resource managers identify regional trends in abundance of ravens and anticipate which sensitive species are at greatest risk from elevated raven populations. Future research directed at identifying the underlying regional drivers of these trends could help elucidate the most appropriate and responsive management actions and, thereby, guide the development of raven population management plans to mitigate impacts to sensitive species.

Human-Wildlife Interactions↗

USGS2006

Fish assemblage responses to water withdrawals and water supply reservoirs in Piedmont streams

Understanding effects of flow alteration on stream biota is essential to developing ecologically sustainable water supply strategies. We evaluated effects of altering flows via surface water withdrawals and instream reservoirs on stream fish assemblages, and compared effects with other hypothesized drivers of species richness and assemblage composition. We sampled fishes during three years in 28 streams used for municipal water supply in the Piedmont region of Georgia, U.S.A. Study sites had permitted average withdrawal rates that ranged from < 0.05 to > 13 times the stream’s seven-day, ten-year recurrence low flow (7Q10), and were located directly downstream either from a water supply reservoir or from a withdrawal taken from an unimpounded stream. Ordination analysis of catch data showed a shift in assemblage composition at reservoir sites corresponding to dominance by habitat generalist species. Richness of fluvial specialists averaged about 3 fewer species downstream from reservoirs, and also declined as permitted withdrawal rate increased above about 0.5 to one 7Q10-equivalent of water. Reservoir presence and withdrawal rate, along with drainage area, accounted for 70% of the among-site variance in fluvial specialist richness and were better predictor variables than percent of the catchment in urban land use or average streambed sediment size. Increasing withdrawal rate also increased the odds that a site’s Index of Biotic Integrity score fell below a regulatory threshold indicating biological impairment. Estimates of reservoir and withdrawal effects on stream biota could be used in predictive landscape models to support adaptive water supply planning intended to meet societal needs while conserving biological resources.

Georgiq↗

USGS2022

Structured decision making to rank North American Wetland Conservation Act proposals within joint venture regions

The North American Wetlands Conservation Act (16 U.S.C. 4401-4412) provided funding and administration for wetland management and conservation projects. The North American Wetland Conservation Fund, enabled in 1989 with the Act, provides financial resources. Resource allocation decisions are based, in part, on regional experts, particularly migratory bird Joint Ventures (JVs) (i.e., partnerships for cooperative planning and coordinated management of the continent’s waterfowl populations and habitats). The JVs evaluate funding proposals submitted with their respective regions each year and make funding recommendations to decision makers. Proposal evaluation procedures differ among JVs, however, it could be helpful to consider a transparent, repeatable, and data-driven framework for prioritization within regions. We used structured decision making and linear additive value models for ranking proposals within JV regions. We used two JVs as case studies and constructed two different value models using JV-specific objectives and weights. The framework was developed through a collaborative process with JV staff and stakeholders. Models were written in Microsoft Excel. To test these models, we used six NAWCA proposals submitted to the Upper Mississippi / Great Lakes Joint Venture in 2016 and seven proposals submitted to the Gulf Coast Joint Venture in 2017. We compared proposal ranks assigned by the value model to ranks assigned by each JV’s management board. Ranks assigned by the value model differed from ranks assigned by the board for the Upper Mississippi / Great Lakes Joint Venture, but not for the Gulf Coast Joint Venture. However, ranks from the value model could change markedly with different objective weights and value functions. The weighted linear value model was beneficial for ranking NAWCA proposals because it allows JVs to treat the ranking as a multiple objective problem and tailor the ranking to their specific regional concerns. We believe a structured decision making approach could be adapted by JV staff to facilitate a systematic and transparent process for proposal ranking by their management boards.

Journal of Fish and Wildlife Management↗

USGS2015

Status assessment and conservation plan for the Grasshopper Sparrow ( Ammodramus savannarum )

The Grasshopper Sparrow (Ammodramus savannarum) breeds in grassland habitats throughout much of the U.S., southern and southeastern Canada, and northern Mexico. Additional subspecies are resident in Central America, northern South America, and the Caribbean. It winters primarily in the coastal states of the southeastern U.S., southern portions of the southwestern states, and in Mexico, Central America, and the Caribbean. The species prefers relatively open grassland with intermediate grass height and density and patchy bare ground; because it is widely distributed across different grassland types in North America, it selects different vegetation structure and species composition depending on what is available. In the winter, they use a broader range of grassland habitats including open grasslands, as well as weedy fields and grasslands with woody vegetation. Analyses show significant range-wide population declines from the late 1960s through the present, primarily caused by habitat loss, degradation, and fragmentation. Grasshopper Sparrow is still a relatively common and broadly distributed species, but because of significant population declines and stakeholder concerns, the species is considered of conservation concern nationally and at the state level for numerous states. Many factors, often related to different grassland management practices (e.g., grazing, burning, mowing, management of shrub encroachment, etc.) throughout the species’ range, have impacts on Grasshopper Sparrow distribution, abundance, and reproduction and may represent limiting factors or threats given steep declines in this species’ population. Because of the concerns for this species, Grasshopper Sparrow has been identified as a focal species by the U.S. Fish and Wildlife Service (USFWS) and this Status Assessment and Conservation Plan for Grasshopper Sparrow has been developed. Through literature searches and input from stakeholders across its range, this plan presents information about Grasshopper Sparrow population status, distribution, habitat needs, threats and limiting factors; synthesis of these resources has identified recommended action items addressing population status and trends, habitat conservation, management, research, inventory and monitoring, and education and outreach components that will facilitate Grasshopper Sparrow conservation across its full annual cycle.

Report↗

USGS2008

Low-flow characteristics and regionalization of low-flow characteristics for selected streams in Arkansas

Water use in Arkansas has increased dramatically in recent years. Since 1990, the use of water for all purposes except power generation has increased 53 percent (4,004 cubic feet per second in 1990 to 6,113 cubic feet per second in 2005). The biggest users are agriculture (90 percent), municipal water supply (4 percent) and industrial supply (2 percent). As the population of the State continues to grow, so does the demand for the State’s water resources. The low-flow characteristics of a stream ultimately affect its utilization by humans. Specific information on the low-flow characteristics of streams is essential to State water-management agencies such as the Arkansas Department of Environmental Quality, the Arkansas Natural Resources Commission, and the Arkansas Game and Fish Commission when dealing with problems related to irrigation, municipal and industrial water supplies, fish and wildlife conservation, and dilution of waste. Low-flow frequency data are of particular value to management agencies responsible for the development and management of the State’s water resources. This report contains the low-flow characteristics for 70 active continuous-streamflow record gaging stations, 59 inactive continuous-streamflow record stations, and 101 partial-record gaging stations. These characteristics are the annual 7-day, 10-year low flow and the annual 7-day, 2-year low flow, and the seasonal, bimonthly, and monthly 7-day, 10-year low flow for the 129 active and inactive continuous-streamflow record and 101 partial-record gaging stations. Low-flow characteristics were computed on the basis of streamflow data for the period of record through September 2005 for the continuous-streamflow record and partial-record streamflow gaging stations. The low-flow characteristics of these continuous- and partial-record streamflow gaging stations were utilized in a regional regression analysis to produce equations for estimating the annual, seasonal, bimonthly, and monthly (November through April) 7-day, 10-year low flows and the annual 7-day, 2-year low flow for ungaged streams in the western two-thirds of Arkansas.

Arkansas↗

USGS2019

Assessment of site-specific agricultural Best Management Practices in the Upper East River watershed, Wisconsin, using a field-scale SWAT model

The Great Lakes “Priority Watershed” effort targeted the Upper East River watershed, a 116.5 km2 tributary watershed to Green Bay in Wisconsin, to reduce sediment and nutrients entering Green Bay. A Soil and Water Assessment Tool (SWAT) model was created to determine the effectiveness of Best Management Practices (BMPs) derived from the U.S. Department of Agriculture-Natural Resources Conservation Service National Conservation Planning (NCP) Database. The model was calibrated at the monthly timestep for flow, sediment, dissolved reactive phosphorus (DRP), total phosphorus (TP), and total nitrogen (TN). Field- and watershed-scale sediment and nutrient reductions were calculated due to the implementation of 74 BMP combinations on dairy and cash grain rotations. Modeling results indicated that when multiple BMPs are placed on a field, especially those that included filter strips and grassed waterways, generally reduced sediment and nutrient loads more than a single BMP implementation. The most effective in-field practice at reducing DRP and TP on dairy fields was a combination of 5 different BMPs: cover crops, crop rotation, nutrient management plan, reduced tillage, and a filter strip. Conservation cover was the most effective practice at reducing sediment and nutrient yields. Sediment and nutrient loads decreased at the watershed scale as the quantity and coverage of BMPs increased. When all contracted NCP BMPs were simulated at the watershed scale, sediment loads were reduced 2%, while TP, DRP, TN and nitrate loads were reduced 20%, 9%, 24%, and 17%, respectively. Modeling scenarios indicated that as the number and area of BMPs were increased, sediment and nutrient load reductions were also increased.

Wisconsin↗

USGS2018

Cooperative Fish and Wildlife Research Units Program—2017 year in review

The Cooperative Fish and Wildlife Research Units Program was involved in a number of notable events during 2017, many concerning our personnel. Dr. Barry Grand left his position as Leader of the Alabama Cooperative Fish and Wildlife Research Unit to become the Cooperative Units Program Supervisor for the South, replacing Dr. Kevin Whalen who took over as Supervisor for the West. We welcomed Dr. Sarah Converse who left the Patuxent Wildlife Research Center to become Leader of the Washington Cooperative Fish and Wildlife Research Unit. Dr. Amanda Rosenberger joined the Tennessee Cooperative Fishery Research Unit as Assistant Leader, transferring from the Missouri Cooperative Unit. Dr. Scott Carleton left his position as Assistant Unit Leader in New Mexico to become Chief of the Region 2 Migratory Bird Program of the U.S. Fish and Wildlife Service. We said farewell to many colleagues who retired. Their departure is bittersweet as we wish them health, happiness, and wellness in retirement. We will miss their companionship and the extraordinary contributions they have made to the Cooperative Fish and Wildlife Research Units Program and conservation. The Cooperative Fish and Wildlife Research Units Program has a record high number of vacant scientist positions due to a combination of retirements and base funding short-falls. These issues are affecting our ability to meet cooperator needs. Yet, we remain highly productive. For example, this year we released a report ( https://doi.org/10.3133/cir1427 ) containing abstracts of nearly 600 of our research projects, covering thematic areas ranging from advanced technologies to wildlife diseases. We provided highly competent, trained scientists and natural resource managers for our cooperators’ workforce. We delivered technical training and guidance to professional practitioners. We provided critical information to cooperators for decisions on species status assessments and management of species of greatest conservation need. This year we had an active presence at major national meetings, including the North American Wildlife and Natural Resources Conference where we co-sponsored a workshop on continuing education as a means to bridge the gap between science and management. During the coming year, with support from the U.S. Geological Survey and our cooperators, we intend to reduce the number of vacancies in the program. It will take time and active support of our cooperators to get back to full strength, but I am committed to this goal and encouraged by the resolve of our partners. We look forward to an even more productive year in 2018!

Circular↗

USGS1996

The Beaver Creek story

Beaver Creek watershed in West Tennessee includes about 95,000 acres of the Nation's most productive farmland and most highly erodible soils. In 1989 the U.S. Geological Survey, in cooperation with the Tennessee Department of Agriculture, began a study to evaluate the effect of agricultural activities on water quality in the watershed and for best management practices designed to reduce agricultural nonpoint-source pollution. Agrichemical monitoring included testing the soils, ground water, and streams at four farm sites ranging from 27 to 420 acres. Monitoring stations were operated downstream to gain a better understanding of the water chemistry as runoff moved from small ditches into larger streams to the outlet of the Beaver Creek watershed. Prior to the implementation of best management practices at one of the farm study sites, some storms produced an average suspended-sediment concentration of 70,000 milligrams per liter. After the implementation of BMP's, however, the average value never exceeded 7,000 milligrams per liter. No-till crop production was the most effective best management practice for conserving soil on the farm fields tested. A natural bottomland hardwood wetland and a constructed wetland were evaluated as instream resource-management systems. The wetlands improved water quality downstream by acting as a filter and removing a significant amount of nonpoint-source pollution from the agricultural runoff. The constructed wetland reduced the sediment, pesticide, and nutrient load by approximately 50 percent over a 4-month period. The results of the Beaver Creek watershed study have increased the understanding of the effects of agriculture on water resources. Study results also demonstrated that BMP's do protect and improve water quality.

Open-File Report↗

USGS2011

Envisioning the future of wildlife in a changing climate: Collaborative learning for adaptation planning

Natural resource managers are tasked with assessing the impacts of climate change on conservation targets and developing adaptation strategies to meet agency goals. The complex, transboundary nature of climate change demands the collaboration of scientists, managers, and stakeholders in this effort. To share, integrate, and apply knowledge from these diverse perspectives, we must engage in social learning. In 2009, we initiated a process to engage university researchers and agency scientists and managers in collaborative learning to assess the impacts of climate change on terrestrial fauna in the state of Wisconsin, USA. We constructed conceptual Bayesian networks to depict the influence of climate change, key biotic and abiotic factors, and existing stressors on the distribution and abundance of 3 species: greater prairie-chicken ( Tympanuchus cupido ), wood frog ( Lithobates sylvaticus ), and Karner blue butterfly ( Plebejus melissa samuelis ). For each species, we completed a 2-stage expert review that elicited dialogue on information gaps, management opportunities, and research priorities. From our experience, collaborative network modeling proved to be a powerful tool to develop a common vision of the potential impacts of climate change on conservation targets.

Wildlife Society Bulletin↗

USGS2009

Physical, Chemical, Ecological, and Age Data and Trench Logs from Surficial Deposits at Hatch Point, Southeastern Utah

This report presents data and describes the methodology for physical, chemical and ecological measurements of sediment, soil, and vegetation, as well as age determinations of surficial deposits at Hatch Point, Canyon Rims area, Colorado Plateau, southeastern Utah. The results presented in this report support a study that examines geomorphic and soil factors that may influence boundaries between shrubland and grassland ecosystems in the study area. Shrubland ecosystems dominated by sagebrush (Artemisia tridentata) and grassland ecosystems dominated by native perennial grasses (for example, Hilaria jamesii and Sporabolis sp.) are high-priority conservation targets for the Federal Bureau of Land Management (BLM) and other resource managers because of their diversity, productivity, and vital importance as wildlife habitat. These ecosystems have been recognized as imperiled on a regional scale since at least the mid-1990s due to habitat loss (type conversions), land-use practices, and invasive exotic plants. In the Intermountain West, the exotic annual cheatgrass (Bromus tectorum) is recognized as one of the most pervasive and serious threats to the health of native sagebrush and grassland ecosystems through effects on fire regimes and resource conditions experienced by native species.

Open-File Report↗

USGS2022

Potential effects of energy development on environmental resources of the Williston Basin in Montana, North Dakota, and South Dakota—Species of conservation concern

The ecosystems of the Williston Basin provide direct and indirect benefits to society. These benefits include carbon sequestration, flood control, nutrient rich soils for agricultural productivity, and habitat for wildlife. This chapter’s main focus is on the effects of energy development on species that occupy the ecosystems in the Williston Basin. We compiled a list of documented species of conservation concern that are of most interest to Federal regulators and resource managers. Species of concern were either listed as endangered or threatened under the Endangered Species Act or listed by States as species of concern in Natural Heritage Program checklists or State Wildlife Action Plans. All told, we determined that 357 species of concern likely occupy the Williston Basin. These species represented seven different taxonomic groups: plants (native and nonnative), terrestrial invertebrates, birds, mammals, reptiles and amphibians, and fish and mussels. We reviewed the existing scientific information pertaining to potential effects of energy development on these taxonomic groups. Currently, little is known about the abundance and distribution of many of these species. But some information exists that may be useful in predicting the potential effects of energy development on certain taxonomic groups. Most of this information has been developed through scientific research focused on effects to mammal and bird populations. Effects to other taxonomic groups seems to be understudied. In general, it seems that disturbances and modifications associated with development have the potential to negatively affect a wide range of species; however, many studies produce uncertain results because they are not designed to compare populations before and after energy development takes place. Most of these studies also do not monitor resources over multiple years and thus cannot detect population trends. Likewise, there are few examples of landscape-scale assessments of the cumulative effects of energy development that could be used for species or habitat management purposes. We suggest that more research needs to be completed to measure potential effects to a broad range of species in multiple taxonomic groups. This may require also developing some understanding about the basic ecology of many of the species covered in this report. In concert with this more basic research, we also suggest that more comprehensive assessments of potential negative cumulative effects across the Williston Basin should be developed in an effort to guide more strategic management of biological resources.

Montana, North Dakota, South Dakota↗

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↗

USGS2018

Variation in home range size and patterns in adult female American crocodiles Crocodylus acutus

The American crocodile Crocodylus acutus is a threatened species that uses relatively deep, open-water habitats with low salinity. Adult female American crocodiles nest on sandy coastal beaches, islands or human-made berms, assist in the hatching process, and can travel long distances to nesting habitat. We satellite-tracked 15 adult female American crocodiles in 2 hydrologically distinct areas in Everglades National Park, Florida, USA, to quantify the home range sizes, test for intraspecific differences in home range and core area size and structure, and identify important crocodile high-use areas. Overall home ranges (95% kernel density estimate; KDE) for adult female crocodiles in South Florida ranged from 30.0 to 141.9 km 2 (mean ± SD, 84.4 ± 32.3 km 2 ), and core areas (50% KDE) ranged from 4.7 to 27.4 km 2 (17.8 ± 7.3 km 2 ). We identified patterns in home range and core area overlap, seasonally shifting patterns in core area use, and the Fox Lake complex as an important crocodile high-use area. As the population of American crocodiles continues to grow and expand into new areas, it is important for conservation managers to understand individual crocodile habitat-use patterns and spatial resource requirements.

Florida↗

USGS2018

Calibration of a field-scale Soil and Water Assessment Tool (SWAT) model with field placement of best management practices in Alger Creek, Michigan

Subwatersheds within the Great Lakes “Priority Watersheds” were targeted by the Great Lakes Restoration Initiative (GLRI) to determine the effectiveness of the various best management practices (BMPs) from the U.S. Department of Agriculture-Natural Resources Conservation Service National Conservation Planning (NCP) Database. A Soil and Water Assessment Tool (SWAT) model is created for Alger Creek, a 50 km 2 tributary watershed to the Saginaw River in Michigan. Monthly calibration yielded very good Nash–Sutcliffe efficiency (NSE) ratings for flow, sediment, total phosphorus (TP), dissolved reactive phosphorus (DRP), and total nitrogen (TN) (0.90, 0.79, 0.87, 0.88, and 0.77, respectively), and satisfactory NSE rating for nitrate (0.51). Two-year validation results in at least satisfactory NSE ratings for flow, sediment, TP, DRP, and TN (0.83, 0.54, 0.73, 0.53, and 0.60, respectively), and unsatisfactory NSE rating for nitrate (0.28). The model estimates the effect of BMPs at the field and watershed scales. At the field-scale, the most effective single practice at reducing sediment, TP, and DRP is no-tillage followed by cover crops (CC); CC are the most effective single practice at reducing nitrate. The most effective BMP combinations include filter strips, which can have a sizable effect on reducing sediment and phosphorus loads. At the watershed scale, model results indicate current NCP BMPs result in minimal sediment and nutrient reductions (<10%).

Michigan↗