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USGS2019

Formation pressure and fluid flow measurements in marine gas hydrate reservoirs, NGHP-02 expedition, offshore India

Open Hole Modular Dynamic Testing (MDT) measurements were conducted in a gas hydrate-bearing sand-rich reservoir offshore India during the National Gas Hydrate Program 02 (NGHP-02) Expedition. The primary goal of this test was to obtain effective reservoir petrophysical properties in the presence of gas hydrates. The test plan included a series of pre-hydrate dissociation flow and build-up (shut-in) tests, and an attempt to dissociate gas hydrate in a sand-rich reservoir by depressurization to collect formation fluid samples and to further characterize in situ gas hydrate stability conditions. Schlumberger’s wireline MDT tool was used in a dual-packer configuration to isolate the formation being tested. This paper presents the results of the open hole MDT measurements that were conducted in Hole NGHP-02-23-C in Krishna-Godavari Basin at a water depth of 2553.5 m. The MDT dual packer test was conducted in 27 cm (10.63 in) diameter open hole section of the borehole within a 1-m interval isolated between two inflatable packers with the midpoint of the test interval at 2853.0 meter below rig floor (mbrf) (271.0 meter below sea floor (mbsf)). This was the first gas hydrate MDT test ever conducted in ultradeep water to characterize a gas hydrate reservoir system. Pre-hydrate dissociation testing was performed with a drawdown period (depressurization) of 20 minutes followed by a build-up (shut-in) of 20 minutes. The measured formation pressure was 4090.7 psia and the formation fluid (i.e., water) mobility was calculated at 1.98 mD/cP. During the second dissociation phase of the same test a maximum pressure drawdown of 840 psia was achieved; however, falling short of the 1120 psia drawdown required for dissociation. During the dissociation test the flow line pressure stabilized at a flowing pressure of 3250 psia which can be attributed to the relatively high mobility of the free water phase in the hydrate-bearing reservoir. Good quality formation pressure and near well bore mobility data was acquired that yielded a “high confidence” reservoir effective radial permeability-thickness product of 0.2 mD.m (or a horizontal effective permeability of 0.1 mD assuming a reservoir thicknees of 1.8 m) using pressure transient analysis (radial flow regime was achieved) despite unstable borehole conditions and complex operations in these shallow unconsolidated sedimentary sections.

Journal of Marine and Petroleum Geology↗

USGS2011

Adaptive finite volume methods with well-balanced Riemann solvers for modeling floods in rugged terrain: Application to the Malpasset dam-break flood (France, 1959)

The simulation of advancing flood waves over rugged topography, by solving the shallow-water equations with well-balanced high-resolution finite volume methods and block-structured dynamic adaptive mesh refinement (AMR), is described and validated in this paper. The efficiency of block-structured AMR makes large-scale problems tractable, and allows the use of accurate and stable methods developed for solving general hyperbolic problems on quadrilateral grids. Features indicative of flooding in rugged terrain, such as advancing wet-dry fronts and non-stationary steady states due to balanced source terms from variable topography, present unique challenges and require modifications such as special Riemann solvers. A well-balanced Riemann solver for inundation and general (non-stationary) flow over topography is tested in this context. The difficulties of modeling floods in rugged terrain, and the rationale for and efficacy of using AMR and well-balanced methods, are presented. The algorithms are validated by simulating the Malpasset dam-break flood (France, 1959), which has served as a benchmark problem previously. Historical field data, laboratory model data and other numerical simulation results (computed on static fitted meshes) are shown for comparison. The methods are implemented in GEOCLAW, a subset of the open-source CLAWPACK software. All the software is freely available at. Published in 2010 by John Wiley & Sons, Ltd.

International Journal for Numerical Methods in Flu↗

USGS2012

The influence of formation material properties on the response of water levels in wells to Earth tides and atmospheric loading

The water level in an open well can change in response to deformation of the surrounding material, either because of applied strains (tidal or tectonic) or surface loading by atmospheric pressure changes. Under conditions of no vertical fluid flow and negligible well bore storage (static-confined conditions), the sensitivities to these effects depend on the elastic properties and porosity which characterize the surrounding medium. For a poroelastic medium, high sensitivity to applied areal strains occurs for low porosity, while high sensitivity to atmospheric loading occurs for high porosity; both increase with decreasing compressibility of the solid matrix. These material properties also influence vertical fluid flow induced by areally extensive deformation and can be used to define two types of hydraulic diffusivity which govern pressure diffusion, one for applied strain and one for surface loading. The hydraulic diffusivity which governs pressure diffusion in response to surface loading is slightly smaller than that which governs fluid flow in response to applied strain. Given the static-confined response of a water well to atmospheric loading and Earth tides, the in situ drained matrix compressibility and porosity (and hence the one-dimensional specific storage) can be estimated. Analysis of the static-confined response of five wells to atmospheric loading and Earth tides gives generally reasonable estimates for material properties.

Journal of Geophysical Research Solid Earth↗

USGS2003

Ostracode-based reconstruction from 23,300 to about 20,250 cal yr BP of climate, and paleohydrology of a groundwater-fed pond near St. Louis, Missouri

The water chemistry of a groundwater-fed sinkhole-pond near St. Louis, Missouri, and its associated climate during the last glaciation are reconstructed by comparison with autecological data of modern ostracodes from about 5,500 sites in Canada. A 4.8-m succession of fossiliferous sediment yielded ostracode assemblages that collectively are generally found today in ponds in North America including the species Cyclocypris ampla, C. laevis, Cypridopsis vidua, Candona crogmaniana, C. distincta, and C. ohioensis. Fossils of Picea needles and the ostracode Cyclocypris sharpei imply that best analog sites for the succession are in central to south-central Canada. The pond formed 23,300 ?? 400 cal yr BP when a sinkhole became plugged by a clay bed about 1 m thick. By about 20,250 cal yr BP, the pond had desiccated and was buried by loess. The sediment accumulation rate was about 0.18 cm/yr, and each sample interval (6 cm) represents a time slice of ???33 years. Data from this record provides the first fairly high resolution proxy record of the glacial paleoclimate of the mid-latitude of North America. The analog data indicate the water in the hydrologically-open spring-fed pond was less than 1 m deep. The paleoclimatic reconstructions imply gradually drier conditions and uniform, cool temperatures. The shallow water depth indicates that the temperature reconstruction is robust with mean annual temperatures (MATs) that ranged between 0.8 and 3.9??C, and mean July temperatures that ranged from 16.8 and 18.1??C. Other estimated climatic parameters include mean annual precipitation (MAP; 430 to 840 mm/yr), and moisture balance (P-E; -111 to 298 mm/yr). Compared to values measured today at St. Louis, the MAP was about 400 mm less, MAT about 10??C cooler, and P-E, about the same. These values are consistent with other published reconstructions based on modern analog analysis of fossil beetles and pollen, and paleothermometry based on amino acid racemization. The total dissolved solids (TDS) progressively increased from about 87 to 431 mg/L. Changes in TDS reflect either the balance between the relative inputs of karst groundwater and overland flow, or changes in the duration of water-rock interaction associated with the groundwater. The postulated long-term 900 ?? 200 year cyclicity of growing-season moisture and temperature, attributed to El Nin??o-Southern Oscillation cycles, is not expressed in the reconstructed hydrologic or climatic data. This is attributed, in part, to the mediating effect on temperature by monothermic groundwater input to this flow-through system.

Journal of Paleolimnology↗

USGS2016

Dynamic reusable workflows for ocean science

Digital catalogs of ocean data have been available for decades, but advances in standardized services and software for catalog search and data access make it now possible to create catalog-driven workflows that automate — end-to-end — data search, analysis and visualization of data from multiple distributed sources. Further, these workflows may be shared, reused and adapted with ease. Here we describe a workflow developed within the US Integrated Ocean Observing System (IOOS) which automates the skill-assessment of water temperature forecasts from multiple ocean forecast models, allowing improved forecast products to be delivered for an open water swim event. A series of Jupyter Notebooks are used to capture and document the end-to-end workflow using a collection of Python tools that facilitate working with standardized catalog and data services. The workflow first searches a catalog of metadata using the Open Geospatial Consortium (OGC) Catalog Service for the Web (CSW), then accesses data service endpoints found in the metadata records using the OGC Sensor Observation Service (SOS) for in situ sensor data and OPeNDAP services for remotely-sensed and model data. Skill metrics are computed and time series comparisons of forecast model and observed data are displayed interactively, leveraging the capabilities of modern web browsers. The resulting workflow not only solves a challenging specific problem, but highlights the benefits of dynamic, reusable workflows in general. These workflows adapt as new data enters the data system, facilitate reproducible science, provide templates from which new scientific workflows can be developed, and encourage data providers to use standardized services. As applied to the ocean swim event, the workflow exposed problems with two of the ocean forecast products which led to improved regional forecasts once errors were corrected. While the example is specific, the approach is general, and we hope to see increased use of dynamic notebooks across the geoscience domains.

Journal of Marine Science and Engineering↗

USGS2014

Where the waters meet: sharing ideas and experiences between inland and marine realms to promote sustainable fisheries management

Although inland and marine environments, their fisheries, fishery managers, and the realm-specific management approaches are often different, there are a surprising number of similarities that frequently go unrecognized. We contend that there is much to be gained by greater cross-fertilization and exchange of ideas and strategies between realms and the people who manage them. The purpose of this paper is to provide examples of the potential or demonstrated benefits of working across aquatic boundaries for enhanced sustainable management of the world’s fisheries resources. Examples include the need to (1) engage in habitat management and protection as the foundation for fisheries, (2) rethink institutional arrangements and management for open-access fisheries systems, (3) establish “reference points” and harvest control rules, (4) engage in integrated management approaches, (5) reap conservation benefits from the link to fish as food, and (6) reframe conservation and management of fish to better engage the public and industry. Cross-fertilization and knowledge transfer between realms could be realized using environment-independent curricula and symposia, joint scientific advisory councils for management, integrated development projects, and cross-realm policy dialogue. Given the interdependence of marine and inland fisheries, promoting discussion between the realms has the potential to promote meaningful advances in managing global fisheries.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2016

Supporting diverse data providers in the open water data initiative: Communicating water data quality and fitness of use

Shared, trusted, timely data are essential elements for the cooperation needed to optimize economic, ecologic, and public safety concerns related to water. The Open Water Data Initiative (OWDI) will provide a fully scalable platform that can support a wide variety of data from many diverse providers. Many of these will be larger, well-established, and trusted agencies with a history of providing well-documented, standardized, and archive-ready products. However, some potential partners may be smaller, distributed, and relatively unknown or untested as data providers. The data these partners will provide are valuable and can be used to fill in many data gaps, but can also be variable in quality or supplied in nonstandardized formats. They may also reflect the smaller partners' variable budgets and missions, be intermittent, or of unknown provenance. A challenge for the OWDI will be to convey the quality and the contextual “fitness” of data from providers other than the most trusted brands. This article reviews past and current methods for documenting data quality. Three case studies are provided that describe processes and pathways for effective data-sharing and publication initiatives. They also illustrate how partners may work together to find a metadata reporting threshold that encourages participation while maintaining high data integrity. And lastly, potential governance is proposed that may assist smaller partners with short- and long-term participation in the OWDI.

Journal of the American Water Resources Associatio↗

USGS2009

Effects of open marsh water management on numbers of larval salt marsh mosquitoes

Open marsh water management (OMWM) is a commonly used approach to manage salt marsh mosquitoes than can obviate the need for pesticide application and at the same time, partially restore natural functions of grid-ditched marshes. OMWM includes a variety of hydrologic manipulations, often tailored to the specific conditions on individual marshes, so the overall effectiveness of this approach is difficult to assess. Here, we report the results of controlled field trials to assess the effects of two approaches to OMWM on larval mosquito production at National Wildlife Refuges (NWR). A traditional OMWM approach, using pond construction and radial ditches was used at Edwin B. Forsythe NWR in New Jersey, and a ditch-plugging approach was used at Parker River NWR in Massachusetts. Mosquito larvae were sampled from randomly placed stations on paired treatment and control marshes at each refuge. The proportion of sampling stations that were wet declined after OMWM at the Forsythe site, but not at the Parker River site. The proportion of samples with larvae present and mean larval densities, declined significantly at the treatment sites on both refuges relative to the control marshes. Percentage of control for the 2 yr posttreatment, compared with the 2 yr pretreatment, was >90% at both treatment sites.

New Jersey;Massachusetts↗

USGS2018

U.S. Geological Survey science for the Wyoming Landscape Conservation Initiative—2016 annual report

This is the ninth annual report highlighting U.S. Geological Survey (USGS) science and decision-support activities conducted for the Wyoming Landscape Conservation Initiative (WLCI). The activities address specific management needs identified by WLCI partner agencies. In fiscal year (FY) 2016, there were 26 active USGS WLCI science-based projects. Of these 26 projects, one project was new for FY2016, and three were completed by the end of the fiscal year (though final products were still in preparation or review). USGS WLCI projects were grouped under five categories: (1) Baseline Synthesis, (2) Long-Term Monitoring, (3) Effectiveness Monitoring, (4) Mechanistic Studies of Wildlife, and (5) Data and Information Management. Each of these topic areas is designed to address WLCI management needs: identifying key drivers of change, identifying the condition and distribution of key wildlife species and habitats and of species’ habitat requirements, development of an integrated inventory and monitoring strategy, use of emerging technologies and development and testing of innovative methods for maximizing the efficiency and efficacy of monitoring efforts, evaluating the effectiveness of habitat treatment projects, evaluating the responses of wildlife to development, and developing a data clearinghouse and information management framework to support and provide access to results of most USGS WLCI projects. In FY2016, we assisted with updating the WLCI Conservation Action Plan and associated databases as part of the Comprehensive Assessment, and we also assisted with the Bureau of Land Management 2015 WLCI annual report. By the end of FY2016, we completed or had nearly completed assessments of WLCI energy and mineral resources and had submitted a manuscript on modeled effects of oil and gas development on wildlife to a peer-reviewed journal. We also initiated a study on the effects of wind energy on wildlife in the WLCI region. A USGS circular on WLCI long-term monitoring was in review at the end of the fiscal year, and seven projects monitoring water and vegetation (including changes in sagebrush cover and patterns of sagebrush mortality) continued through the year. USGS scientists continued many projects in FY2016 that evaluate the effectiveness of habitat conservation actions (including sagebrush, cheatgrass, and aspen habitat treatments) and provide tools in support of mechanistic studies of wildlife. In FY2016, USGS scientists, along with university and State partners, continued work on five focal wildlife species/communities (pygmy rabbits [ Brachylagus idahoensis ], greater sage grouse , mule deer, sagebrush songbirds, and native fish). In FY2016, the USGS Information Management Team presented information to WLCI scientists on how USGS tools and resources can be used to fulfill the requirements of new USGS policies regarding data release, data management, and data visualization.

Wyoming↗

USGS2022

How lions move at night when they hunt?

Movement patterns of lions ( Panthera leo ) reveal how they hunt large herbivores in heterogeneous landscapes such as the Kruger National Park in South Africa. Large herbivores are distributed differently on the landscape and therefore have different vulnerabilities as prey for lions. For instance, blue wildebeest ( Connochaetes taurinus ) occupy small grazing lawns at night but are difficult for lions to capture because open areas lack cover for stalking. African buffalo ( Syncerus caffer ) aggregate in large herds but are less available because these herds only intermittently enter the home ranges of individual lion prides. Unlike large herds of wildebeest and buffalo, plains zebra ( Equus quagga ) move widely in small herds while browsing greater kudus ( Tragelaphus strepsiceros ) and giraffes ( Giraffa camelopardalis giraffa ) generally occur in lower densities. We used spatial data derived from GPS collars to investigate several hypotheses regarding the movements of three lion prides in response to their prey. We found that lions were most active and moved longer distances during nighttime than during daytime. Lions remained within their core home ranges on 87% of nights and wandered to the outlying areas of the home ranges every second night. Lions visited grazing lawns, that is, area of short grass, where wildebeest herds resided every second night, and moved toward the direction of buffalo herds within 2 km of vicinity. Lions spent more time near riverbanks that provided dense woody cover at night than expected but concentrated only weakly near sites with surface water where herbivores drank in the dry season. Our study contributes to understanding how lions vary their movements in response to the spatial and temporal heterogeneity in the relative availability and vulnerability of multiple prey species.

Kruger National Park↗

USGS2004

Gas evolution in eruptive conduits: Combining insights from high temperature and pressure decompression experiments with steady-state flow modeling

In this paper we examine the consequences of bubble nucleation mechanism on eruptive degassing of rhyolite magma. We use the results of published high temperature and pressure decompression experiments as input to a modified version of CONFLOW, the numerical model of Mastin and Ghiorso [(2000) U.S.G.S. Open-File Rep. 00-209, 53 pp.] and Mastin [(2002) Geochem. Geophys. Geosyst. 3, 10.1029/2001GC000192] for steady, two-phase flow in vertical conduits. Synthesis of the available experimental data shows that heterogeneous nucleation is triggered at ΔP <5–20 MPa in water-saturated rhyolite and leads to equilibrium degassing through a discrete nucleation event. Typically 10 5 –10 7 bubbles/cm 3 are produced which evolve Gaussian bubble size distributions. Homogeneous nucleation requires ΔP >120–150 MPa, and leads to disequilibrium degassing at extreme H 2 O supersaturation. In this latter case, nucleation is an ongoing process controlled by changing supersaturation conditions. Exponential bubble size distributions are often produced with number densities of 10 6 –10 9 bubbles/cm 3 . Our numerical analysis adopts an end-member approach that specifically compares equilibrium degassing with delayed, disequilibrium degassing characteristic of homogeneously-nucleating systems. The disequilibrium simulations show that delaying nucleation until ΔP =150 MPa restricts degassing to within ∼1500 m of the surface. Fragmentation occurs at similar porosity in both the disequilibrium and equilibrium modes (∼80 vol%), but at the distinct depths of ∼500 m and ∼2300 m, respectively. The vesiculation delay leads to higher pressures at equivalent depths in the conduit, and the mass flux and exit pressure are each higher by a factor of ∼2.0. Residual water contents in the melt reaching the vent are between 0.5 and 1.0 wt%, roughly twice that of the equilibrium model.

Journal of Volcanology and Geothermal Research↗

USGS2003

Demographic and growth responses of a guerrilla and a phalanx perennial grass in competitive mixtures

The advantages of guerrilla and phalanx growth for the guerrilla Elymus lanceolatus ssp. lanceolatus and phalanx E. l. ssp. wawawaiensis were evaluated over 2 years in two taxon mixtures with a range of densities of each subspecies and under two levels of watering. Ramet numbers and biomass of the guerrilla subspecies were higher than those of the phalanx grass in the first year but in the second year declined greatly, while the phalanx grass showed no change in biomass and an increase in ramet numbers. High neighbour densities affected the phalanx subspecies more strongly than the guerrilla subspecies in the first year, but in the second year there were few differences between subspecies. Biomass of the guerrilla grass remained greater than that of the phalanx grass but ramet numbers were similar in the second year. For both subspecies in both years, probability of flowering decreased at higher neighbour densities, indicating adaptation for competitive ability. In the first year, biomass was more strongly reduced by densities than flowering was, but in the second year, when crowding was apparently greater, flowering was more severely affected. Genet survival was high and similar for both subspecies. The presumed advantage of guerrilla subspecies in exploiting open space was supported. The guerrilla grass exploited resources more quickly in the first year by faster growth and greater ramet production, but its biomass, ramet numbers and rhizome growth, and thus its advantage, were reduced in the second year. The phalanx subspecies had slower growth, produced more ramets in later years, and delayed flowering until later years. Although less able to exploit open resources, it appeared adapted to more stressful conditions, and may be able to exploit temporal resource pulses more effectively.

Journal of Ecology↗

USGS2019

Wave-current interaction between Hurricane Matthew wave fields and the Gulf Stream

Hurricanes interact with the Gulf Stream in the South Atlantic Bight (SAB) through a wide variety of processes, which are crucial to understand for prediction of open-ocean and coastal hazards during storms. However, it remains unclear how waves are modified by large-scale ocean currents under storm conditions, when waves are aligned with the storm-driven circulation and tightly coupled to the overlying wind field. Hurricane Matthew (2016) impacted the US southeast coast, causing extensive coastal change due to large waves and elevated water levels. The hurricane traveled on the continental shelf parallel to the SAB coastline, with the right side of the hurricane directly over the Gulf Stream. Using the Coupled Ocean Atmosphere Wave Sediment Transport Modeling System, we investigate wave-current interaction between Hurricane Matthew and the Gulf Stream. The model simulates ocean currents and waves over a grid encompassing the US east coast, with varied coupling of the hydrodynamic and wave components to isolate the effect of the currents on the waves, and the effect of the Gulf Stream relative to storm-driven circulation. The Gulf Stream modifies the direction of the storm-driven currents beneath the right side of the hurricane. Waves transitioned from following currents that result in wave lengthening, through negative current gradients that result in wave steepening and dissipation. Wave-current interaction over the Gulf Stream modified maximum coastal total water levels, and changed incident wave directions at the coast by up to 20°, with strong implications for the morphodynamic response and stability of the coast to the hurricane.

East Coast, Gulf Coast↗

USGS2000

Estimating formation properties from early-time oscillatory water levels in a pumped well

Hydrologists often attempt to estimate formation properties from aquifer tests for which only the hydraulic responses in a pumped well are available. Borehole storage, turbulent head losses, and borehole skin, however, can mask the hydraulic behavior of the formation inferred from the water level in the pumped well. Also, in highly permeable formations or in formations at significant depth below land surface, where there is a long column of water in the well casing, oscillatory water levels may arise during the onset of pumping to further mask formation responses in the pumped well. Usually borehole phenomena are confined to the early stages of pumping or recovery, and late-time hydraulic data can be used to estimate formation properties. In many instances, however, early-time hydraulic data provide valuable information about the formation, especially if there are interferences in the late-time data. A mathematical model and its Laplace transform solution that account for inertial influences and turbulent head losses during pumping is developed for the coupled response between the pumped borehole and the formation. The formation is assumed to be homogeneous, isotropic, of infinite areal extent, and uniform thickness, with leakage from an overlying aquifer, and the screened or open interval of the pumped well is assumed to fully penetrate the pumped aquifer. Other mathematical models of aquifer flow can also be coupled with the equations describing turbulent head losses and the inertial effects on the water column in the pumped well. The mathematical model developed in this paper is sufficiently general to consider both underdamped conditions for which oscillations arise, and overdamped conditions for which there are no oscillations. Through numerical inversion of the Laplace transform solution, type curves from the mathematical model are developed to estimate formation properties through comparison with the measured hydraulic response in the pumped well. The mathematical model is applied to estimate formation properties from a singlewell test conducted near Waialua, Oahu, Hawaii. At this site, both the drawdown and recovery showed oscillatory water levels in the pumped well, and a step-drawdown test showed that approximately 86% of the drawdown is attributed to turbulent head losses. Analyses at this site using late-time drawdown data were confounded by the noise present in the measured water levels due primarily to nearby irrigation wells and ocean tides. By analyzing the early-time oscillatory recovery data at the Waialua site, upper and lower bounds were placed on the transmissivity, T, storage coefficient, S, and the leakance of the confining unit, K′/B′. The upper and lower bounds on T differ by a factor of 2. Upper and lower bounds on S and K′/B′ are much larger, because drawdown stabilized relatively quickly after the onset of pumping.

Journal of Hydrology↗

USGS2012

Using borehole flow logging to optimize hydraulic-test procedures in heterogeneous fractured aquifers

Hydraulic properties of heterogeneous fractured aquifers are difficult to characterize, and such characterization usually requires equipment-intensive and time-consuming applications of hydraulic testing in situ. Conventional coring and geophysical logging techniques provide useful and reliable information on the distribution of bedding planes, fractures and solution openings along boreholes, but it is often unclear how these locally permeable features are organized into larger-scale zones of hydraulic conductivity. New boreholes flow-logging equipment provides techniques designed to identify hydraulically active fractures intersecting boreholes, and to indicate how these fractures might be connected to larger-scale flow paths in the surrounding aquifer. Potential complications in interpreting flowmeter logs include: 1) Ambient hydraulic conditions that mask the detection of hydraulically active fractures; 2) Inability to maintain quasi-steady drawdowns during aquifer tests, which causes temporal variations in flow intensity to be confused with inflows during pumping; and 3) Effects of uncontrolled background variations in hydraulic head, which also complicate the interpretation of inflows during aquifer tests. Application of these techniques is illustrated by the analysis of cross-borehole flowmeter data from an array of four bedrock boreholes in granitic schist at the Mirror Lake, New Hampshire, research site. Only two days of field operations were required to unambiguously identify the few fractures or fracture zones that contribute most inflow to boreholes in the CO borehole array during pumping. Such information was critical in the interpretation of water-quality data. This information also permitted the setting of the available string of two packers in each borehole so as to return the aquifer as close to pre-drilling conditions as possible with the available equipment.

Hydrogeology Journal↗

USGS2020

A 450-year record of environmental change from Castle Lake, California (USA), inferred from diatoms and organic geochemistry

A 39-cm sediment core from Castle Lake, California (USA) spans the last ~ 450 years and was analyzed for diatoms and organic geochemistry (δ 15 N, δ 13 C, and C:N), with the goal of determining sensitivity to natural climate variation and twentieth century anthropogenic effects. Castle Lake is a subalpine, nitrogen-limited lake with ~ 5 months of annual ice cover. Human impacts include light recreational use, past fish stocking, and experimental use by the Castle Lake Research Station. The base of the core (below 32 cm; pre mid-1700s) represents the period of maximum ice cover. In contrast, the end of the Little Ice Age (mid 1700s–early 1800s) is dominated by cyclotelloids (mostly Discostella stelligera ), indicating significant open-water periods, a condition that persisted into the early 1900s. Cyclotelloids began to decline in the 1960s and were replaced by the Fragilaria tenera grp. (peak in 1970s), succeeded by Asterionella formosa (peak ~ 2010), and accompanied by a reduction in δ 15 N values and a decrease in C:N that may represent increased atmospheric nitrogen deposition. Another anthropogenic signal was discerned in the core and was interpreted to be the result of an ammonium nitrate fertilization experiment of the epilimnion that was conducted in 1980 and 1981. This signal was manifested in the core largely by a negative excursion in δ 15 N, possibly caused by fractionation during denitrification in surface sediment. A phytoplankton monitoring dataset collected by the Castle Lake Research Station from 1967 to 1984 corroborates the timing of increased araphid euplanktonic species in the 1970s, and increases in two benthic diatoms ( Staurosirella pinnata and Tabellaria fenestrata) , entrained in the phytoplankton tows during the experimentation years. Both ice cover and nitrogen addition appear to be strong drivers that affected the lake diatoms, although additional drivers, such as fish stocking and associated cascade effects need further exploration. These data will be helpful for interpreting longer core records from Castle Lake, should the opportunity arise, as well as cores from similar systems in the region.

California↗

USGS1964

Sedimentology: general introduction and definitions : fluvial sediment and channel morphology

Sedimentology, the study of sedimentary rocks and the processes by which they are formed, includes and is related to a large number of phenomena. Sedimentology includes the five fundamental processes defined by the term sediaentation --weathering, erosion, transportation, deposition and diagenesis. Sedimentology shares with geomorphology the study of the surface features of the earth. Sedimentology also shares with hydrology the study of river.--channels. River channels are formed in part or in total as a result of flowing water and sediment transport, commonly called the "work of the rivers." This survey of published literature was made to aid in arriving at definitions which would be acceptable to, and representative of, a majority of professional personnel actively engaged in laboratory and field investigations related to the "work of the river." The definitions in this list are intended to explain the terms used in studies of fluvial sediment and channel morphology. No set of definitions can expect universal acceptance, however, i t is hoped that this compilation will be considered a summary and synthesis of present and past usage and that it will serve as a starting point for future usage. Multiple references are cited from textbooks, glossaries and dictionaries, scientific journals and u.s. Government publications. To obtain a mutual understanding and enhance precision, many of the proposed definitions are a composite of those selected from papers or reports covering research studies and field investigations. A draft of this glossary has been reviewed by a group of interested personnel. The results of this review have been carefully considered and the originally-suggested definitions have been revised accordingly, resulting in the present compilation. R. G. Wolff, with the help of Mrs. v. Blatcher, carried out the literature search and compilation of terms and the review results. Paul c. Benedict approved or composed the definitions as presented in this report.

Open-File Report↗

USGS2023

Population dynamics of the threatened Oregon spotted frog before and after drought mitigation

Amphibians are among the most sensitive taxa to climate change, and species inhabiting arid and semiarid landscapes at the extremes of their range are especially vulnerable to drought. The Jack Creek, Oregon, USA, population of Oregon spotted frogs ( Rana pretiosa ) faces unique challenges because it occupies the highest elevation site in the species' extant range and one that has been transformed by loss of American beavers ( Castor canadensis ), which historically maintained open water. We evaluated the effects of drought mitigation (addition of excavated ponds) on relationships between local and regional water availability, inactive legacy beaver dams, and Oregon spotted frog population dynamics in the Jack Creek system. We conducted egg mass surveys and capture-mark-recapture sampling at a treatment reach with excavated ponds and 3 reference reaches over 13 years; surveys spanned a period before and after pond excavation at the treatment and 1 primary comparison reference reach. We analyzed data using a combination of robust design capture-mark-recapture estimators and generalized linear mixed models to characterize population dynamics. Adult Oregon spotted frog survival was approximately 19.5% higher at the treatment reach than the primary reference reach during the study period. Annual survival was most strongly associated with late summer vegetation greenness, a proxy for water availability, and males had higher survival than females. Among the 4 study reaches, the treatment reach consistently had higher late summer vegetation greenness, and the hydrology functioned more independently of regional precipitation patterns relative to the reference reaches; however, these dynamics were not linked to pond excavation. Breeding was concentrated in 2 legacy beaver ponds that were deepened by excavation during the study compared to an unexcavated beaver pond, 2 excavated ponds without legacy beaver dams, and 9 reference ponds. These results point to the benefit of enhancing existing beaver structures and indicate that management actions aimed at maintaining surface water for breeding in spring and saturated soils and ponded water for adults in late summer would benefit this unique population of Oregon spotted frogs in the face of drought.

Oregon↗