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USGS1976

Land subsidence and aquifer-system compaction in the San Jacinto Valley, Riverside County, California - A progress report

Widespread subsidence continues in the San Jacinto structural trough as water levels continue to decline. Subsidence is due principally to the compaction of water-bearing deposits as effective stresses are increased by artesian-head decline. Other possible contributory causes of subsidence are (1) local or regional tectonic adjustments and graben downfaulting, (2) natural compaction of deep water-bearing deposits below the bottom of well casings, and (3) continuing compaction of surficial deposits due to causes other than artesian-head decline. A careful analysis of 4 yr of correlative records of waterlevel, extensometer, and land-surface changes suggests three types of vertical ground movement occurring at the 4S/1W-21N2 recorder site near the San Jacinto reservoir site. The reservoir was drained in October 1973. Listed in descending order of magnitude these are (1) an elastic undulation of the land surface of about 0.06 ft (0.02 m) per year in close response to the roughly 50 ft (15 m) of seasonal water-level fluctuations, (2) a long-term permanent compaction of the deposits in the 0-1,237-ft (0-377-m) zone of about 0.04 ft (0.01 m) per year, and (3) a deep settlement of deposits below the 1,237-ft (377-m) extensometer anchor of 0.01-0.02 ft (0.003-0.006 m) per year, probably caused by continuing downfaulting in the graben trough. The specific compaction of the aquifer system at this site from 1970 to 1974 was about 1.3x 10 -2 (units of compaction per unit of increase in applied stress). The specific, expansion during this period decreased progressively from 1.29x 10 -3 (units of expansion per unit of stress decrease) in 1970-71 to 0.95x10 -3 in 1973-74, suggesting that excess pore pressures in the slow-draining aquitards were not completely dissipated each year.

California↗

USGS2015

Regional and temporal differences in nitrate trends discerned from long-term water quality monitoring data

Riverine nitrate (NO 3 ) is a well-documented driver of eutrophication and hypoxia in coastal areas. The development of the elevated river NO 3 concentration is linked to anthropogenic inputs from municipal, agricultural, and atmospheric sources. The intensity of these sources has varied regionally, through time, and in response to multiple causes such as economic drivers and policy responses. This study uses long-term water quality, land use, and other ancillary data to further describe the evolution of river NO 3 concentrations at 22 monitoring stations in the United States (U.S.). The stations were selected for long-term data availability and to represent a range of climate and land-use conditions. We examined NO 3 at the monitoring stations, using a flow-weighting scheme meant to account for interannual flow variability allowing greater focus on river chemical conditions. River NO 3 concentration increased strongly during 1945-1980 at most of the stations and have remained elevated, but stopped increasing during 1981-2008. NO 3 increased to a greater extent at monitoring stations in the Midwest U.S. and less so at those in the Eastern and Western U.S. We discuss 20th Century agricultural development in the U.S. and demonstrate that regional differences in NO 3 concentration patterns were strongly related to an agricultural index developed using principal components analysis. This unique century-scale dataset adds to our understanding of long-term NO 3 patterns in the U.S.

Journal of the American Water Resources Associatio↗

USGS2017

Seawater-flooding events and impact on freshwater lenses of low-lying islands: Controlling factors, basic management and mitigation

An unprecedented set of hydrologic observations was collected after the Dec 2008 seawater-flooding event on Roi-Namur, Kwajalein Atoll, Republic of the Marshall Islands. By two days after the seawater flooding that occurred at the beginning of dry season, the observed salinity of water withdrawn by the island’s main skimming well increased to 100% seawater concentration, but by ten days later already decreased to only 10–20% of seawater fraction. However, the damaging impact on the potability of the groundwater supply (when pumped water had concentrations above 1% seawater fraction) lasted 22 months longer. The data collected make possible analyses of the hydrologic factors that control recovery and management of the groundwater-supply quality on Roi-Namur and on similar low-lying islands. With the observed data as a guide, three-dimensional numerical-model simulation analyses reveal how recovery is controlled by the island’s hydrology. These also allow evaluation of the efficacy of basic water-quality management/mitigation alternatives and elucidate how groundwater withdrawal and timing of the seawater-flooding event affect the length of recovery. Simulations show that, as might be expected, by adding surplus captured rainwater as artificial recharge, the freshwater-lens recovery period (after which potable groundwater may again be produced) can be shortened, with groundwater salinity remaining lower even during the dry season, a period during which no artificial recharge is applied. Simulations also show that the recovery period is not lengthened appreciably by groundwater withdrawals during recovery. Simulations further show that had the flooding event occurred at the start of the wet season, the recovery period would have been about 25% (5.5 months) shorter than actually occurred during the monitored flood that occurred at the dry-season start. Finally, analyses show that artificial recharge improves freshwater-lens water quality, making possible longer use of groundwater as a water supply throughout each year, even when no seawater flooding has occurred.

Journal of Hydrology↗

USGS2018

What environmental conditions reduce predation vulnerability for juvenile Colorado River native fishes?

The incompatibility of native Colorado River fishes and nonnative warm-water sport fishes is well documented with predation by nonnative species causing rapid declines and even extirpation of native species in most locations. In a few rare instances native fishes are able to survive and recruit despite the presence of nonnative warm water predators, indicating that specific environmental conditions may help reduce predation vulnerability. We experimented with turbidity, artificial blue water colorant, woody debris, rocks, and aquatic vegetation in a laboratory setting to determine if any of these types of cover could reduce predation vulnerability and confer survival advantages for juvenile bonytail Gila elegans, (mean = 70 mm TL), roundtail chub Gila robusta, (mean = 35 mm TL), humpback chub Gila cypha, (mean = 67 mm TL), and razorback sucker Xyrauchen texanus (mean = 74 mm TL). Juvenile native fishes were exposed to predation by adult largemouth bass Micropterus salmoides, smallmouth bass Micropterus dolomieu, green sunfish Lepomis cyanellus, flathead catfish Pylodictis olivaris, and black bullhead catfish Ameiurus melas, in overnight trials. Turbidity above 500 NTU reduced predation vulnerability by up to 50%, for the sight-feeding predators, but increased predation vulnerability to non-sight feeding predators such as flathead catfish and bullhead catfish. Turbidity was the only treatment which appeared to significantly alter predation mortality of native prey. These results may help to explain recent patterns of wild juvenile razorback sucker recruitment at the inflow of the San Juan River into Lake Powell and the inflow of the Colorado River into Lake Mead. These are both areas of high turbidity where flathead catfish are not currently present but other nonnative sportfish are relatively abundant.

Journal of Fish and Wildlife Management↗

USGS2018

Spatial variability of sediment transport processes over intratidal and subtidal timescales within a fringing coral reef system

Sediment produced on fringing coral reefs that is transported along the bed or in suspension affects ecological reef communities as well as the morphological development of the reef, lagoon, and adjacent shoreline. This study quantified the physical process contribution and relative importance of sea‐swell waves, infragravity waves, and mean currents to the spatial and temporal variability of sediment in suspension. Estimates of bed shear stresses demonstrate that sea‐swell waves are the key driver of the suspended sediment concentration (SSC) variability spatially (reef flat, lagoon, and channels) but cannot fully describe the SSC variability alone. The comparatively small but statistically significant contribution to the bed shear stress by infragravity waves and currents, along with the spatial availability of sediment of a suitable size and volume, is also important. Although intratidal variability in SSC occurs in the different reef zones, the majority of the variability occurs over longer slowly varying (subtidal) timescales, which is related to the arrival of large swell waves at a reef location. The predominant flow pathway, which can transport suspended sediment, consists of cross‐reef flow across the reef flat that diverges in the lagoon and returns offshore through channels. This pathway is primarily due to subtidal variations in wave‐driven flows but can also be driven alongshore by wind stresses when the incident waves are small. Higher frequency (intratidal) current variability also occurs due to both tidal flows and variations in the water depth that influence wave transmission across the reef and wave‐driven currents.

Western Australia↗

USGS2009

Assessment of water quality trends in the Minnesota River using non-parametric and parametric methods

Excessive loading of sediment and nutrients to rivers is a major problem in many parts of the United States. In this study, we tested the non-parametric Seasonal Kendall (SEAKEN) trend model and the parametric USGS Quality of Water trend program (QWTREND) to quantify trends in water quality of the Minnesota River at Fort Snelling from 1976 to 2003. Both methods indicated decreasing trends in flow-adjusted concentrations of total suspended solids (TSS), total phosphorus (TP), and orthophosphorus (OP) and a generally increasing trend in flow-adjusted nitrate plus nitrite-nitrogen (NO 3 -N) concentration. The SEAKEN results were strongly influenced by the length of the record as well as extreme years (dry or wet) earlier in the record. The QWTREND results, though influenced somewhat by the same factors, were more stable. The magnitudes of trends between the two methods were somewhat different and appeared to be associated with conceptual differences between the flow-adjustment processes used and with data processing methods. The decreasing trends in TSS, TP, and OP concentrations are likely related to conservation measures implemented in the basin. However, dilution effects from wet climate or additional tile drainage cannot be ruled out. The increasing trend in NO 3 -N concentrations was likely due to increased drainage in the basin. Since the Minnesota River is the main source of sediments to the Mississippi River, this study also addressed the rapid filling of Lake Pepin on the Mississippi River and found the likely cause to be increased flow due to recent wet climate in the region. Copyright ?? 2009 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

Journal of Environmental Quality↗

USGS2025

The Grouse & Grazing Project: Effects of cattle grazing on demographic traits of greater sage-grouse

Greater sage-grouse (Centrocercus urophasianus) were once widespread within sagebrush -grassland ecosystems of western North America, but populations have declined since the mid-1960s. Though sage-grouse were not listed as threatened or endangered under the Endangered Species Act (ESA), when examined in 2015, they remain a species of interest and concern. Roughly half of the sage-grouse’s remaining habitat is on federal land, most of it managed by the Bureau of Land Management (BLM) and the U.S. Forest Service (USFS). Livestock grazing is the most extensive land use within sage-grouse habitat and the effects of livestock grazing on sage-grouse are often debated. The extensive decade-long research project summarized in this report was initiated to provide rigorous experimental research to inform the debate regarding the relationship between livestock grazing and sage-grouse. In 2012, the Idaho Grouse & Grazing Project was started with several partners including the University of Idaho, BLM, Idaho Department of Fish and Game (IDFG), and other partners to evaluate the effects of cattle grazing on sage-grouse vital rates. Many additional supporters have provided resources to this research effort including the Public Lands Council, Idaho Cattle Association, Idaho Governor’s Office of Species Conservation, Western Association of Fish & Wildlife Agencies, U.S. Fish and Wildlife Service, USFS, and numerous grazing associations and ranchers in Idaho. This 10-year research project was a scientifically rigorous and replicated experiment, occurring across five study sites in Idaho. This document is intended to provide a summary of the findings of this unprecedented study. Annual reports are available on the project’s website: https://idahogrousegrazing.org and scientific papers are being prepared and submitted to journals. The project focused on the influence of spring cattle grazing on sage-grouse vital rates across five study sites in Idaho including 21 BLM grazing pastures. From 2014-2023, we captured 1,343 grouse, documented the fate of 1,285 nests, and tracked 399 broods. Vegetation was characterized at 4,777 plots and grazing utilization levels were recorded at >30,000 locations. Because insects are an important food source for sage-grouse hens and their chicks, insect biomass and diversity were also examined in this study. We collected arthropods in 12,151 pitfall samples and 6,217 sweep-net samples across 786 plots within our five study sites. At each study site, three or four grazing treatments were implemented after two years of pre-treatment field investigations. These controlled cattle grazing treatments included spring-grazing in even years, spring-grazing in odd years, spring-and-fall grazing in alternating years, and a no grazing (or rested) control. Once grazing treatments were implemented at a study site, we measured sage-grouse demographic traits for 4-8 years post-treatment. Stocking rate (grazing intensity) was assessed across pastures each year and was influenced by vegetation communities, topography, and water sources. Grazed pastures exhibited lower grass cover and height compared to the no grazing pastures, and the extent of this difference varied based on annual precipitation levels. Rested pastures maintained higher grass cover and grass height, but the differences in habitat structure did not consistently translate to differences in sage-grouse demographic traits. Apparent nesting success varied annually and by site, ranging from 24% to 44% over the study period. Like some other studies, results from this research show that successful (i.e., hatched) sage-grouse nests have taller grass heights than failed nests. The average grass height surrounding successful nests in grazed pastures was shorter than that surrounding successful nests in non-grazed (i.e., rested) pastures. It is well documented that grazing reduces grass height, and these observations have led to widely held assumptions that livestock grazing reduces grass height which negatively affects sage-grouse nesting habitat. At the pasture scale, this study has found that sage-grouse nesting success is no greater in pastures that were rested for 4-8 years than those currently or recently grazed. This study gives no indication that removing cattle from pastures affected nesting success. We found some evidence that nest density varied among the grazing treatments, but we did not see compelling evidence of increases in density of nesting hens following cessation of grazing in the no grazing treatments. Brood survival varied by site and year but showed no strong effect of grazing treatment. Climatic conditions, particularly drought in 2021, had a greater effect on brood survival than grazing metrics. We also found no differences in hen survival among the grazing treatments. Results of this study suggest that hens nesting in spring and fall grazed pastures had similar or even slightly higher brood survival than hens in the rested pastures or the spring grazed pastures. Arthropod biomass and species diversity varied among our study sites and the differences between grazed and rested pastures also varied among study sites. Average biomass and diversity of arthropods was higher in the spring grazed pastures on two of three sites examined but higher in the rested pastures on the other site examined. Some taxa of arthropods were more abundant in grazed pastures while other taxa were more abundant in rested pastures. For example, Carabidae (Ground Beetles) and Formicidae (Ants) had higher biomass in grazed pastures, while Tenebrionidae (Darkling Beetles) and Acrididae (Grasshoppers) had higher biomass in non-grazed pastures. Results indicate that grazing effects on arthropod biomass and arthropod diversity are study site-dependent, suggesting a need to better quantify the most important prey taxa for sage-grouse chicks and to better control for other factors that influence arthropod abundance. Based on results of this research, livestock grazing, when properly managed, does not appear to negatively impact sage-grouse nest survival or brood success. This study provides critical insights for land managers balancing livestock production with sage-grouse conservation, supporting adaptive grazing strategies that maintain both economic and ecological objectives.

Idaho↗

USGS2024

Cold blood in warming waters: Effects of air temperature, precipitation, and groundwater on Gulf Sturgeon thermal habitats in a changing climate

Objective In a changing climate, the effects of air temperature, precipitation, and groundwater on water temperature and thermal habitat suitability for Gulf Sturgeon Acipenser desotoi , listed as threatened under the U.S. Endangered Species Act, are not well understood. Hence, we incorporated these factors into thermal habitat models to forecast how Gulf Sturgeon may be affected by wide‐ranging climate change scenarios in 2024–2074. Methods Using data from the Choctawhatchee River, Florida, we developed precipitation‐ and groundwater‐corrected air–water temperature models, compared their accuracy with that of conventional air–water temperature models used in fisheries management, and projected future Gulf Sturgeon thermal habitat suitability for normal physiological functioning and fieldwork (i.e., population sampling and telemetry surgeries) in summer (May–August) under 16 climate change scenarios. Result Precipitation‐ and groundwater‐corrected models were more accurate than conventional air–water temperature models (mean improvement in adjusted R 2 = +0.45; range = +0.09 to +0.75). Water temperature was projected to warm at widely variable rates across climate change scenarios encompassing different air temperature, precipitation, and groundwater regimes. Importantly, Gulf Sturgeon summer aggregation areas were cooler and influenced more by precipitation and groundwater and less by air temperature than were non‐aggregation areas. If precipitation and groundwater—as drivers of cooling—become warm in a changing climate, summer aggregation areas were projected to exhibit thermal habitat degradation equivalent to or greater than that of non‐aggregation areas. Conclusion Our results add hydrological context to the premise that aggregation areas provide cool water and energetic savings for Gulf Sturgeon during summer, underscoring the importance of protecting these habitats through groundwater conservation, water quality monitoring, and riparian/watershed habitat management. Our findings indicate that identifying thermally appropriate times for fieldwork activities will be increasingly important and time‐restricted as climate change intensifies. However, our research provides managers with a portfolio of water temperature models and an accurate, cost‐effective, management‐relevant approach to forecasting thermal habitat conditions for Gulf Sturgeon and other species in a changing climate.

Alabama, Florida↗

USGS2023

Low-complexity floodplain inundation model performs well for ecological and management applications in a large river ecosystem

Flooding is a dominant physical process that drives the form and function of river-floodplain ecosystems. Efficiently characterizing flooding dynamics can be challenging, especially over geographically broad areas or at spatial and temporal scales relevant for ecosystem management activities. Here, we empirically evaluated a low-complexity geospatial model of floodplain inundation in six study segments of the Upper Mississippi River System (UMRS) by pairing spatially extensive, temporally limited and spatially limited, temporally extensive sampling designs. We found little evidence of systematic bias in model performance although discrepancies between model predictions and empirical data did occur locally. Assessments of model predictions revealed low segment-wide discrepancies of wetted extent under contrasting flow conditions and agreement for inundation event detection and duration. Model performance for predicting event frequency and duration was similar among sites expected to exhibit contrasting patterns of hydrologic connectivity with the main channel. Our results suggest that low-complexity models can efficiently characterize a critical physical process across geographically broad, complex river-floodplain ecosystems. Such tools have the potential for advancing scientific understanding of landscape-scale ecological patterns and for prioritizing management actions in large, complex river-floodplain ecosystems like the UMRS.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗

USGS2021

Lagged wetland CH4 flux response in a historically wet year

While a stimulating effect of plant primary productivity on soil carbon dioxide (CO 2 ) emissions has been well documented, links between gross primary productivity (GPP) and wetland methane (CH 4 ) emissions are less well investigated. Determination of the influence of primary productivity on wetland CH 4 emissions (FCH 4 ) is complicated by confounding influences of water table level and temperature on CH 4 production, which also vary seasonally. Here, we evaluate the link between preceding GPP and subsequent FCH 4 at two fens in Wisconsin using eddy covariance flux towers, Lost Creek (US-Los) and Allequash Creek (US-ALQ). Both wetlands are mosaics of forested and shrub wetlands, with US-Los being larger in scale and having a more open canopy. Co-located sites with multi-year observations of flux, hydrology, and meteorology provide an opportunity to measure and compare lag effects on FCH 4 without interference due to differing climate. Daily average FCH 4 from US-Los reached a maximum of 47.7 ηmol CH 4 m −2 s −1 during the study period, while US-ALQ was more than double at 117.9 ηmol CH 4 m −2 s −1 . The lagged influence of GPP on temperature-normalized FCH 4 ( T air -FCH 4 ) was weaker and more delayed in a year with anomalously high precipitation than a following drier year at both sites. FCH 4 at US-ALQ was lower coincident with higher stream discharge in the wet year (2019), potentially due to soil gas flushing during high precipitation events and lower water temperatures. Better understanding of the lagged influence of GPP on FCH 4 due to this study has implications for climate modeling and more accurate carbon budgeting.

Journal of Geophysical Research: Biogeosciences↗

USGS2019

Stormwater-quality performance of line permeable pavement systems

Three permeable pavements were evaluated for their ability to improve the quality of stormwater runoff over a 22-month period in Madison, Wisconsin. Using a lined system with no internal water storage, permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA) were able to significantly remove sediment and sediment-bound pollutant loads from runoff originating from an asphalt parking lot five times larger than the receiving permeable pavement area. Reductions in total suspended solids were similar for all three surfaces at approximately 60 percent. Clogging occurred after approximately one year, primarily due to winter sand application that led to high sediment load in spring runoff. Winter road salt application resulted in high chloride load that was initially attenuated in all three permeable pavements but later released during subsequent spring runoff events. Total phosphorus load was reduced by nearly 20 percent for PICP and PA, and 43 percent for PC. These values were likely tempered by the export of dissolved phosphorus observed in PICP and PA, but not PC. Average removal efficiencies for metals were 40, 42, and 49 percent in PA, PICP, and PC, respectively. A median pH of 10.2 in PC effluent could explain elevated removal efficiency of phosphorus and select metals in PC over PICP and PA (median = 7.5 and 7.8, respectfully) through enhanced precipitation. Elevated pH values in PC may also have led to higher removal efficiencies for select metals than PICP or PA. The environmental benefits as well as potential unintended consequences of stormwater practices like permeable pavement that utilize infiltration as a form of treatment warrant consideration in management of urban runoff.

Wisconsin↗

USGS2004

Late Pleistocene to Holocene environmental changes as recorded in the sulfur geochemistry of coastal plain sediments, southwestern Taiwan

A core, drilled at San-liao-wan in the southwestern coastal plain of Taiwan, has been analyzed for total sulfur contents, isotopic values, as well as ratios of pyritic sulfur to organic carbon. Our results demonstrate a close relationship between late Pleistocene sea-level change and the proxies generated in this study. The inorganic sulfur contents indicate that at our study site, the Holocene transgression started at ???11 ka and remained under seawater for thousands of years until the late Holocene, corresponding to a depth of 20 m in the study core. The uppermost 20 m of core shows relatively high total organic carbon (TOC) and ??34S of inorganic sulfur, suggesting a transitional environment such as muddy lagoon or marsh, before the site turned into a modern coastal plain. In the lower part of the core, at depths of 110-145 m (corresponding ages of ???12-30 ka), low sulfur contents are recorded, probably indicating fluvial sediments deposited during the oceanic isotope stage (OIS) 2, a sea-level lowstand. The lower part of the core, roughly within OIS 3, records at least two transgressions, although the transgressional signals may be somewhat obscured by subsequent weathering. The reworked origin of organic matter reported in previous studies is confirmed by our organic sulfur data; however, the marine organic source was periodically dominant. The modern high sulfate concentrations in pore water have no correlation to the other sulfur species in the sediments, probably indicating that the sulfate migrated into the site subsequent to early diagenesis. ?? 2003 Elsevier Ltd. All rights reserved.

Journal of Asian Earth Sciences↗

USGS2008

Light-toned salty soils and co-existing Si-rich species discovered by the Mars Exploration Rover Spirit in Columbia Hills

Light-toned soils were exposed, through serendipitous excavations by Spirit Rover wheels, at eight locations in the Columbia Hills. Their occurrences were grouped into four types on the basis of geomorphic settings. At three major exposures, the light-toned soils are hydrous and sulfate-rich. The spatial distributions of distinct types of salty soils vary substantially: with centimeter-scaled heterogeneities at Paso Robles, Dead Sea, Shredded, and Champagne-Penny, a well-mixed nature for light-toned soils occurring near and at the summit of Husband Hill, and relatively homogeneous distributions in the two layers at the Tyrone site. Aeolian, fumarolic, and hydrothermal fluid processes are suggested to be responsible for the deposition, transportation, and accumulation of these light-toned soils. In addition, a change in Pancam spectra of Tyrone yellowish soils was observed after being exposed to current Martian surface conditions for 175 sols. This change is interpreted to be caused by the dehydration of ferric sulfates on the basis of laboratory simulations and suggests a relative humidity gradient beneath the surface. Si-rich nodules and soils were observed near the major exposures of S-rich soils. They possess a characteristic feature in Pancam visible near-infrared (Vis-NIR) spectra that may be diagnostic of hydrated species, and this spectral feature can be used to search for additional Si-rich species. The exposures of hydrated salty soils within various geomorphic settings imply the potential existence of hydrous minerals in similar settings over a much wider area. Hydrous sulfates represent one of the candidates that may contribute the high level of water equivalent hydrogen in equatorial regions detected by the Neutron Spectrometer on Mars Odyssey.

Journal of Geophysical Research↗

USGS2007

Evidence of lake whitefish spawning in the Detroit River: Implications for habitat and population recovery

Historic reports imply that the lower Detroit River was once a prolific spawning area for lake whitefish ( Coregonus clupeaformis ) prior to the construction of the Livingstone shipping channel in 1911. Large numbers of lake whitefish migrated into the river in fall where they spawned on expansive limestone bedrock and gravel bars. Lake whitefish were harvested in the river during this time by commercial fisheries and for fish culture operations. The last reported landing of lake whitefish from the Detroit River was in 1925. Loss of suitable spawning habitat during the construction of the shipping channels as well as the effects of over-fishing, sea lamprey ( Petromyzon marinus ) predation, loss of riparian wetlands, and other perturbations to riverine habitat are associated with the disappearance of lake whitefish spawning runs. Because lake whitefish are recovering in Lake Erie with substantial spawning occurring in the western basin, we suspected they may once again be using the Detroit River to spawn. We sampled in the Detroit River for lake whitefish adults and eggs in late fall of 2005 and for lake whitefish eggs and fish larvae in 2006 to assess the extent of reproduction in the river. A spawning-ready male lake whitefish was collected in gillnets and several dozen viable lake whitefish eggs were collected with a pump in the Detroit River in November and December 2005. No lake whitefish eggs were found at lower river sites in March of 2006, but viable lake whitefish eggs were found at Belle Isle in the upper river in early April. Several hundred lake whitefish larvae were collected in the river during March through early May 2006. Peak larval densities (30 fish/1,000 m3 of water) were observed during the week of 3 April. Because high numbers of lake whitefish larvae were collected from mid- and downstream sample sites in the river, we believe that production of lake whitefish in the Detroit River may be a substantial contribution to the lake whitefish population in Lake Erie.

Michigan↗

USGS2001

Flow of variably fluidized granular masses across three-dimensional terrain 2. Numerical predictions and experimental tests

Numerical solutions of the equations describing flow of variably fluidized Coulomb mixtures predict key features of dry granular avalanches and water-saturated debris flows measured in physical experiments. These features include time-dependent speeds, depths, and widths of flows as well as the geometry of resulting deposits. Threedimensional (3-D) boundary surfaces strongly influence flow dynamics because transverse shearing and cross-stream momentum transport occur where topography obstructs or redirects motion. Consequent energy dissipation can cause local deceleration and deposition, even on steep slopes. Velocities of surge fronts and other discontinuities that develop as flows cross 3-D terrain are predicted accurately by using a Riemann solution algorithm. The algorithm employs a gravity wave speed that accounts for different intensities of lateral stress transfer in regions of extending and compressing flow and in regions with different degrees of fluidization. Field observations and experiments indicate that flows in which fluid plays a significant role typically have high-friction margins with weaker interiors partly fluidized by pore pressure. Interaction of the strong perimeter and weak interior produces relatively steep-sided, flat-topped deposits. To simulate these effects, we compute pore pressure distributions using an advection-diffusion model with enhanced diffusivity near flow margins. Although challenges remain in evaluating pore pressure distributions in diverse geophysical flows, Riemann solutions of the depthaveraged 3-D Coulomb mixture equations provide a powerful tool for interpreting and predicting flow behavior. They provide a means of modeling debris flows, rock avalanches, pyroclastic flows, and related phenomena without invoking and calibrating Theological parameters that have questionable physical significance.

Journal of Geophysical Research B: Solid Earth↗

USGS2012

Lake sturgeon population attributes and reproductive structure in the Namakan Reservoir, Minnesota and Ontario

Quantified were the age, growth, mortality and reproductive structure of lake sturgeon ( Acipenser fulvescens ) collected in the US and Canadian waters of the Namakan Reservoir. The hypotheses were tested that (i) age and growth of lake sturgeon in the Namakan Reservoir would differ by sex and reproductive stage of maturity, and (ii) that the relative strength of year-classes of lake sturgeon in the reservoir would be affected by environmental variables. To quantify age, growth and mortality of the population, existing data was used from a multi-agency database containing information on all lake sturgeon sampled in the reservoir from 2004 to 2009. Lake sturgeon were sampled in the Minnesota and Ontario waters of the Namakan Reservoir using multi-filament gillnets 1.8 m high and 30–100 m long and varying in mesh size from 178 to 356 mm stretch. Reproductive structure of the lake sturgeon was assessed only during spring 2008 and 2009 using plasma testosterone and estradiol-17β concentrations. Ages of lake sturgeon >75 cm ranged from 9 to 86 years (n = 533, mean = 36 years). A catch-curve analysis using the 1981–1953 year classes estimated total annual mortality of adults to be 4.8% and annual survival as 95.2%. Using logistic regression analysis, it was found that total annual precipitation was positively associated with lake sturgeon year-class strength in the Namakan Reservoir. A 10 cm increase in total annual precipitation was associated with at least a 39% increase in the odds of occurrence of a strong year class of lake sturgeon in the reservoir. Plasma steroid analysis revealed a sex ratio of 2.4 females: 1 male and, on average, 10% of female and 30% of male lake sturgeon were reproductively mature each year (i.e. potential spawners). Moreover, there was evidence based on re-captured male fish of both periodic and annual spawning, as well as the ability of males to rapidly undergo gonadal maturation prior to spawning. Knowledge of lake sturgeon reproductive structure and factors influencing recruitment success contribute to the widespread conservation efforts for this threatened species.

Minnesota, Ontario↗

USGS2019

Subhourly mesoscale analysis of the 2011-2017 North American monsoon near its northwest boundary

The North American Monsoon (NAM) delivers precipitation to the southwestern USA during the warm-dry summer season. The seasonal extent of NAM precipitation is highly variable and is likely to change under future climate change. Our objective was to determine how large scale monsoonal patterns as well as local variables influence precipitation events near the NAM northwest boundary. Intra- and inter-annual changes in the northwest sector of the NAM were represented by subhourly weather data collected on the Sheep Range (2300 m asl), in the Mojave Desert of southern Nevada, during 2011-2017. Our study site is part of the Nevada Climate-ecohydrological Assessment Network (NevCAN), an automated observing system established in early 2011. Three seasons were classified using the subhourly weather data including: 1) cool season, 2) early warm season, 3) and late warm season, where the transition between early and late warm season was marked by the day when in situ dewpoint temperature first exceeded 9.4 ºC. Based on analysis of covariance (ANCOVA), dewpoint temperature had the greatest relationship with total hourly precipitation, followed by vapor pressure deficit, solar radiation, and air temperature. The only significant interaction term was between hour of the day and dewpoint temperature, highlighting the importance of dewpoint temperature for afternoon thunderstorms, which are typical of monsoonal precipitation. Besides in situ meteorological variables, we also analyzed NCEP/NCAR vertically integrated water vapor transport (IVT) and long-term 800-m PRISM precipitation time series. Regional composites were developed for IVT for the three seasons. Water vapor in the cool and early warm season originated mostly from the Pacific Ocean, while a transition in IVT to a NAM pattern occurred in the late warm season. Overall, this highly instrumented yet remote site was representative of NAM precipitation, despite noticeable variability in its timing and amount.

Nevada↗

USGS2020

Isotopic and geochemical assessment of the sensitivity of groundwater resources of Guam, Mariana Islands, to intra- and inter-annual variations in hydroclimate

Assessing the sensitivity of groundwater systems to hydroclimate variability is critical to sustainable management of the water resources of Guam, US territory. We assess spatial and temporal variability of isotopic and geochemical compositions of vadose and phreatic groundwater sampled from cave drip sites and production wells, respectively, to better understand the vulnerability of the freshwater lens on Guam to variability in hydroclimate. We independently evaluate the existing conceptual model of the Northern Guam Lens Aquifer that is largely based on physical, as opposed to geochemical, observations. Sampling was conducted from 2008 to 2015, over which rainfall gradually increased. Major ion geochemistry and Sr isotope values of groundwater show varying influence from soil, limestone bedrock, and seawater. Geochemical modeling that can explain spatial variability in groundwater Na+ and Mg2+ concentrations and Sr/Ca and 87Sr/86 Sr values indicates that groundwater compositions are dominantly controlled by mixing of freshwater with seawater and water-rock interaction. Differences between amount-weighted annual average precipitation δ18 O values and groundwater δ18 O values indicate a recharge bias toward the wet season, consistent with other tropical carbonate island aquifer settings. Intra- and inter-annual variations in Na+ concentrations and δ18 O values in groundwater reflect sensitivity of recharge to seasonal variations in rainfall amount and changes in annual rainfall amounts. Our results indicate the influence of multiple modes of recharge on groundwater compositions and spatial variability in the sensitivity of groundwater to seawater mixing. This sensitivity of the freshwater lens points to the vulnerability of groundwater resources to changes in recharge associated with climate, land-use change, and increases in population.

Journal of Hydrology↗