Discussion of "Flume tests on hydrocarbon reaeration tracer gases"
No abstract available.
Journal of Environmental Engineering↗
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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.
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Closure to “Standard penetration test-based probabilistic and deterministic assessment of seismic soil liquefaction potential” by K. Onder Cetin, Raymond B. Seed, Armen Der Kiureghian, Kohji Tokimatsu, Leslie F. Harder Jr., Robert E. Kayen, and Robert E. S. Moss
No abstract available.
Journal of Geotechnical and Geoenvironmental Engin↗
WTAQ - A computer program for aquifer-test analysis of confined and unconfined aquifers
Computer program WTAQ was developed to implement a Laplace-transform analytical solution for axial-symmetric flow to a partially penetrating, finite-diameter well in a homogeneous and anisotropic unconfined (water-table) aquifer. The solution accounts for wellbore storage and skin effects at the pumped well, delayed response at an observation well, and delayed or instantaneous drainage from the unsaturated zone. For the particular case of zero drainage from the unsaturated zone, the solution simplifies to that of axial-symmetric flow in a confined aquifer. WTAQ calculates theoretical time-drawdown curves for the pumped well and observation wells and piezometers. The theoretical curves are used with measured time-drawdown data to estimate hydraulic parameters of confined or unconfined aquifers by graphical type-curve methods or by automatic parameter-estimation methods. Parameters that can be estimated are horizontal and vertical hydraulic conductivity, specific storage, and specific yield. A sample application illustrates use of WTAQ for estimating hydraulic parameters of a hypothetical, unconfined aquifer by type-curve methods. Copyright ASCE 2004.
Conference Paper↗
Testing a high-resolution satellite interpretation technique for crop area monitoring in developing countries
District-level crop area (CA) is a highly uncertain term in food production equations, which are used to allocate food aid and implement appropriate food security initiatives. Remote sensing studies typically overestimate CA and production, as subsistence plots are exaggerated at coarser resolution, which leads to overoptimistic food reports. In this study, medium-resolution (MR) Landsat 7 Enhanced Thematic Mapper Plus (ETM+) images were manually classified for Niger and corrected using CA estimates derived from high-resolution (HR) sample image, topographic and socioeconomic data. A logistic model with smoothing splines was used to compute the block-average (0.1°) probability of an area being cropped. Livelihood zones and elevation explained 75% of the deviance in CA, while MR did not add explanatory power. The model overestimates CA when compared to the national inventory, possibly because of temporal changes in intercropping and the exclusion of some staple crops in the national inventory.
International Journal of Remote Sensing↗
Re-analysis of a banding study to test the effects of an experimental increase in bag limits of mourning doves
In 1966-1971, eastern US states with hunting seasons on mourning doves (Zenaida macroura) participated in a study designed to estimate the effects of bag limit increases on population survival rates. More than 400 000 adult and juvenile birds were banded and released during this period, and subsequent harvest and return of bands, together with total harvest estimates from mail and telephone surveys of hunters, provided the database for analysis. The original analysis used an ANOVA framework, and resulted in inferences of no effect of bag limit increase on population parameters (Hayne 1975). We used a logistic regression analysis to infer that the bag limit increase did not cause a biologically significant increase in harvest rate and thus the experiment could not provide any insight into the relationship between harvest and annual survival rates. Harvest rate estimates of breeding populations from geographical subregions were used as covariates in a Program MARK analysis and revealed an association between annual survival and harvest rates, although this relationship is potentially confounded by a latitudinal gradient in survival rates of dove populations. We discuss methodological problems encountered in the analysis of these data, and provide recommendations for future studies of the relationship between harvest and annual survival rates of mourning dove populations.
Journal of Applied Statistics↗
Field-based evaluations of horizontal flat-plate fish screens, II: Testing of a unique off-stream channel device - The Farmers Screen
Screens are installed at water diversion sites to reduce entrainment of fish. Recently, the Farmers Irrigation District (Oregon) developed a unique flat-plate screen (the “Farmers Screen”) that operates passively and may offer reduced installation and operating costs. To evaluate the effectiveness of this screen on fish, we conducted two separate field experiments. First, juvenile coho salmon Oncorhynchus kisutch were released over a working version of this screen under a range of inflows (0.02–0.42 m 3 /s) and diversion flows (0.02–0.34 m 3 /s) at different water depths. Mean approach velocities ranged from 0 to 5 cm/s and sweeping velocities ranged from 36 to 178 cm/s. Water depths over the screen surface ranged from 1 to 25 cm and were directly related to inflow. Passage of fish over the screen under these conditions did not severely injure them or cause delayed mortality, and no fish were observed becoming impinged on the screen surface. Second, juvenile coho salmon and steelhead O. mykiss were released at the upstream end of a 34-m flume and allowed to volitionally move downstream and pass over a 3.5-m section of the Farmers Screen to determine whether fish would refuse to pass over the screen after encountering its leading edge. For coho salmon, 75–95% of the fish passed over the screen within 5 min and 82–98% passed within 20 min, depending on hydraulic conditions. For steelhead, 47–90% of the fish passed over the screen within 5 min and 79–95% passed within 20 min. Our results indicate that when operated within its design criteria, the Farmers Screen provides safe and efficient downstream passage of juvenile salmonids under a variety of hydraulic conditions.
North American Journal of Fisheries Management↗
Design and testing of a mesocosm-scale habitat for culturing the endangered Devils Hole Pupfish
aptive propagation of desert spring fishes, whether for conservation or research, is often difficult, given the unique and often challenging environments these fish utilize in nature. High temperatures, low dissolved oxygen, minimal water flow, and highly variable lighting are some conditions a researcher might need to recreate to simulate their natural environments. Here we describe a mesocosm-scale habitat created to maintain hybrid Devils Hole × Ash Meadows Amargosa Pupfish ( Cyprinodon diabolis × C. nevadensis mionectes ) under conditions similar to those found in Devils Hole, Nevada. This 13,000-L system utilized flow control and natural processes to maintain these conditions rather than utilizing complex and expensive automation. We designed a rotating solar collector to control natural sunlight, a biological reactor to consume oxygen while buffering water quality, and a reverse-daylight photosynthesis sump system to stabilize nighttime pH and swings in dissolved oxygen levels. This system successfully controlled many desired parameters and helped inform development of a larger, more permanent desert fish conservation facility at the U.S. Fish and Wildlife Service’s Ash Meadows National Wildlife Refuge, Nevada. For others who need to raise fish from unique habitats, many components of the scalable and modular design of this system can be adapted at reasonable cost.
North American Journal of Aquaculture↗
Habitat selection responses of parents to offspring predation risk: An experimental test
The ability of nest predation to influence habitat settlement decisions in birds is widely debated, despite its importance in limiting fitness. Here, we experimentally manipulated nest predation risk across a landscape and asked the question, do migratory birds assess and respond to variation in nest predation risk when choosing breeding habitats? We examined habitat preference by quantifying the density and settlement date of eight species of migratory passerines breeding in areas with and without intact nest predator communities. We found consistently more individuals nesting in areas with reduced nest predation than in areas with intact predator assemblages, although predation risk had no influence on settlement or breeding phenology. Additionally, those individuals occupying safer nesting habitats exhibited increased singing activity. These findings support a causal relationship between habitat choice and nest predation risk and suggest the importance of nest predation risk in shaping avian community structure and breeding activity. ?? 2006 by The University of Chicago. All rights reserved.
American Naturalist↗
Contrasts between channels and backwaters in a large, floodplain river: Testing our understanding of nutrient cycling, phytoplankton abundance, and suspended solids dynamics
In floodplain rivers, variability in hydraulic connectivity interacts with biogeochemistry to determine the distribution of suspended and dissolved substances. Nutrient, chlorophyll a , and suspended solids data spanning longitudinal (5 study reaches across 1300 river km), lateral (main channel and backwaters), and temporal (1994–2011) gradients in the Upper Mississippi River (UMR) were used to examine the extent to which observed differences between the main channel and backwaters were consistent with expectations based on current understanding of biogeochemical processes in large rivers. For N and P, the results largely conformed to expectations. N concentrations were greater in the main channel than in the backwaters in 82 to 96% of the observations across river reaches. Maximum TP concentrations generally occurred in backwaters during summer, when backwater TP often exceeded that of the main channel. Flux of P from sediments may be a substantial source of water-column P in UMR backwaters in summer. The data for suspended solids and chlorophyll a suggest that some refinements are needed of our understanding of ecosystem processes in large rivers. During low-discharge conditions, concentrations of inorganic suspended solids often were greater in backwaters than in the main channel, suggesting the importance of sediment resuspension. Chlorophyll a concentrations were usually greater in backwaters than in the main channel, but exceptions indicate that phytoplankton abundance in the main channel of the UMR can sometimes be greater than is typically expected for large rivers.
Freshwater Science↗
Asynchronous hatching and food limitation: A test of Lack's hypothesis
Lack's (1954, 1968) hypothesis that asynchronous hatching of altricial birds is an adaptive response to unpredictable food shortages during the breeding season was examined in the highly granivorous Zebra Finch ( Poephila guttata ). I compared growth and survival of nestlings in asynchronous and artificially created synchronous broods reared under food-limited and food-abundant conditions in an aviary. I also examined the role of parental experience on survival and growth of nestlings. There was no differential mortality of Zebra Finch nestlings due to either asynchrony or food abundance. Young in abundant food treatments grew more rapidly, however, than those in food-restricted treatments. Heaviest Zebra Finch nestlings in a brood grew more quickly than their lightest siblings when food was limited, supporting Lack's hypothesis. Further, differential survival of light and heavy siblings occurred when food was abundant, suggesting that asynchronous hatching can be maladaptive under some ecological conditions. Nestlings reared by inexperienced parents suffered greater mortality and slower growth when food was abundant than nestlings raised by experienced parents. Prefledging mass was correlated with size at adulthood
The Auk↗
What hypothesis tests are not: a response to Colegrave and Ruxton
Explore the source record for details and available documents.
Behavioral Ecology↗
Now hiring! Empirically testing a three-step intervention to increase faculty gender diversity in STEM
Workforce homogeneity limits creativity, discovery, and job satisfaction; nonetheless, the vast majority of university faculty in science, technology, engineering, and mathematics (STEM) fields are men. We conducted a randomized and controlled three-step faculty search intervention based in self-determination theory aimed at increasing the number of women faculty in STEM at one US university where increasing diversity had historically proved elusive. Results show that the numbers of women candidates considered for and offered tenure-track positions were significantly higher in the intervention groups compared with those in controls. Searches in the intervention were 6.3 times more likely to make an offer to a woman candidate, and women who were made an offer were 5.8 times more likely to accept the offer from an intervention search. Although the focus was on increasing women faculty within STEM, the intervention can be adapted to other scientific and academic communities to advance diversity along any dimension.
BioScience↗
Initial river test of a monostatic RiverSonde streamflow measurement system
A field experiment was conducted on May 7-8, 2002 using a CODAR RiverSonde UHF radar system at Vernalis, California on the San Joaquin River. The monostatic radar configuration on one bank of the river, with the antennas looking both upriver and downriver, provided very high-quality data. Estimates of both along-river and cross-river surface current were generated using several models, including one based on normal-mode analysis. Along-river surface velocities ranged from about 0.6 m/s at the river banks to about 1.0 m/s near the middle of the river. Average cross-river surface velocities were 0.02 m/s or less.
California↗
Monitoring on-orbit stability of Terra MODIS and Landsat 7 ETM+ reflective solar bands using Railroad Valley Playa, Nevada (RVPN) test site
The Moderate Resolution Imaging Spectroradiometer (MODIS) Proto-Flight Model (PFM), launched on December 18, 1999, aboard NASA's Earth Observing System (EOS) Terra satellite has 20 reflective solar bands (RSB) with wavelengths ranging from 0.41 to 2.1 mum over a wide field of view (plusmn55deg). The Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) sensor was launched on April 15, 1999, and has six spectral bands located in the visible and shortwave infrared (SWIR) part of the electromagnetic spectrum (0.4 - 2.5 mum). The ETM+ belongs to the family of Thematic Mapper sensors flown on previous Landsat missions. In this study, over 75 cloud-free nadir near-simultaneous images over Railroad Valley Playa, Nevada (RVPN) were chosen covering entire missions of both sensors. RVPN (38.5degN and 115.7degW), located between the cities of Ely and Tonopah, Nevada, USA, is a high reflectance site with very high spatial, spectral, and temporal uniformity. It is referenced to the Worldwide Reference System-2 (WRS-2) with path 40 and row 33. Homogeneous regions of interest (ROI) were chosen and cross-calibration was performed using an image statistics approach to monitor the long-term stability of the two sensors.
Nevada↗
Testing the efficacy of industrial mitigation measures for caribou in the Arctic
1. Mitigation measures are commonly employed to reduce the negative effects of industrial development on wildlife but are not often evaluated for their efficacy. For example, oil fields in the Arctic typically incorporate design features intended to increase permeability for migratory, barren-ground caribou ( Rangifer tarandus) , even though there is limited empirical evidence of the effectiveness of some of these features. 2. Given expected increases in energy development in the North American Arctic, we examined whether two mitigation measures commonly used for migratory caribou, elevating pipelines and separating roads and pipelines, were effective at increasing the probability caribou would cross infrastructure. 3. We conducted our investigation on adult female caribou in the Central Arctic Herd of Alaska during summer, analyzing movement data from telemetry collars (2015-2020) in conjunction with spatial data on oil field infrastructure. To evaluate whether caribou would cross infrastructure as a function of the mitigation measures, we employed a generalized additive modeling framework capable of detecting non-linear and threshold responses. 4. We found that caribou were more likely to cross a pipeline when the nearest pipeline was elevated (≥1.9-m), a result that supports current mitigation recommendations. We also found that caribou were more likely to cross both a road and pipeline when they were directly adjacent to one another, as opposed to being spatially separated, a result that contradicts recommended mitigation strategies. 5. Synthesis and applications . As new energy projects are designed and implemented in environments around the globe, it is important to ensure that mitigation efforts for wildlife are scientifically validated for their efficacy. In the North American Arctic, such efforts will be critical for minimizing the impacts of expanding industrial development on migratory caribou and on the human communities that rely on them for subsistence.
Alaska↗
Testing hypotheses on distribution shifts and changes in phenology of imperfectly detectable species
With ongoing climate change, many species are expected to shift their spatial and temporal distributions. To document changes in species distribution and phenology, detection/non-detection data have proven very useful. Occupancy models provide a robust way to analyse such data, but inference is usually focused on species spatial distribution, not phenology. We present a multi-season extension of the staggered-entry occupancy model of Kendall et al . (2013, Ecology , 94, 610), which permits inference about the within-season patterns of species arrival and departure at sampling sites. The new model presented here allows investigation of species phenology and spatial distribution across years, as well as site extinction/colonization dynamics. We illustrate the model with two data sets on European migratory passerines and one data set on North American treefrogs. We show how to derive several additional phenological parameters, such as annual mean arrival and departure dates, from estimated arrival and departure probabilities. Given the extent of detection/non-detection data that are available, we believe that this modelling approach will prove very useful to further understand and predict species responses to climate change.
Methods in Ecology and Evolution↗
A test of critical thresholds and their indicators in a desertification-prone ecosystem: more resilience than we thought
Theoretical models predict that drylands can cross critical thresholds, but experimental manipulations to evaluate them are non-existent. We used a long-term (13-year) pulse-perturbation experiment featuring heavy grazing and shrub removal to determine if critical thresholds and their determinants can be demonstrated in Chihuahuan Desert grasslands. We asked if cover values or patch-size metrics could predict vegetation recovery, supporting their use as early-warning indicators. We found that season of grazing, but not the presence of competing shrubs, mediated the severity of grazing impacts on dominant grasses. Recovery occurred at the same rate irrespective of grazing history, suggesting that critical thresholds were not crossed, even at low cover levels. Grass cover, but not patch size metrics, predicted variation in recovery rates. Some transition-prone ecosystems are surprisingly resilient; management of grazing impacts and simple cover measurements can be used to avert undesired transitions and initiate restoration.
Ecology Letters↗