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At least 1,207 records · Page 67Linked to original sources
USGS2002

Kilometer-scale rapid transport of naphthalene sulfonate tracer in the unsaturated zone at the Idaho National Engineering and Environmental Laboratory

To investigate possible long-range flow paths through the interbedded basalts and sediments of a 200-m-thick unsaturated zone, we applied a chemical tracer to seasonally filled infiltration ponds on the Snake River Plain in Idaho. This site is near the Subsurface Disposal Area for radioactive and other hazardous waste at the Idaho National Engineering and Environmental Laboratory. Within 4 mo, we detected tracer in one of 13 sampled aquifer wells, and in eight of 11 sampled perched-water wells as far as 1.3 km away. These detections show that (i) low-permeability layers in the unsaturated zone divert some flow horizontally, but do not prevent rapid transport to the aquifer; (ii) horizontal convective transport rates within the unsaturated zone may exceed 14 m d −1 , perhaps through essentially saturated basalt fractures, tension cracks, lava tubes, or rubble zones; and (iii) some perched water beneath the Subsurface Disposal Area derives from episodic surface water more than 1 km away. Such rapid and far-reaching flow may be common throughout the Snake River Plain, and possibly occurs in other locations that have a geologically complex unsaturated zone and comparable sources of infiltrating water.

Idaho↗
USGS2007

Research activities at U.S. Government agencies in subsurface reactive transport modeling

The fate of contaminants in the environment is controlled by both chemical reactions and transport phenomena in the subsurface. Our ability to understand the significance of these processes over time requires an accurate conceptual model that incorporates the various mechanisms of coupled chemical and physical processes. Adsorption, desorption, ion exchange, precipitation, dissolution, growth, solid solution, redox, microbial activity, and other processes are often incorporated into reactive transport models for the prediction of contaminant fate and transport. U.S. federal agencies use such models to evaluate contaminant transport and provide guidance to decision makers and regulators for treatment issues. We provide summaries of selected research projects and programs to demonstrate the level of activity in various applications and to present examples of recent advances in subsurface reactive transport modeling.

Vadose Zone Journal↗
USGS2010

Response to Germann's "Comment on 'theory for source-responsive and free-surface film modeling of unsaturated flow'"

Germann's (2010) comment helpfully presents supporting evidence that I have missed, notes items that need clarification or correction, and stimulates discussion of what is needed for improved theory of unsaturated flow. Several points from this comment relate not only to specific features of the content of my paper (Nimmo, 2010), but also to the broader question of what methodology is appropriate for developing an applied earth science. Accordingly, before addressing specific points that Germann identified, I present here some considerations of purpose and background relevant to evaluation of the unsaturated flow model of Nimmo (2010).

Vadose Zone Journal↗
USGS2012

Response to "Comments on 'Theory for source-responsive and free-surface film modeling of unsaturated flow'"

I am grateful to Masciopinto (2012) for raising several issues from my study (Nimmo, 2010) that deserve elaboration or clarification. In this reply, I address these in what I judge to be the order of importance, the main ones being (i) the discrepancy of scales between the two domains that treat preferential and diffuse unsaturated flow, and (ii) the properties that must be evaluated to characterize the medium.

Vadose Zone Journal↗
USGS2016

Quantitative framework for preferential flow initiation and partitioning

A model for preferential flow in macropores is based on the short-range spatial distribution of soil matrix infiltrability. It uses elementary areas at two different scales. One is the traditional representative elementary area (REA), which includes a sufficient heterogeneity to typify larger areas, as for measuring field-scale infiltrability. The other, called an elementary matrix area (EMA), is smaller, but large enough to represent the local infiltrability of soil matrix material, between macropores. When water is applied to the land surface, each EMA absorbs water up to the rate of its matrix infiltrability. Excess water flows into a macropore, becoming preferential flow. The land surface then can be represented by a mesoscale (EMA-scale) distribution of matrix infiltrabilities. Total preferential flow at a given depth is the sum of contributions from all EMAs. Applying the model, one case study with multi-year field measurements of both preferential and diffuse fluxes at a specific depth was used to obtain parameter values by inverse calculation. The results quantify the preferential–diffuse partition of flow from individual storms that differed in rainfall amount, intensity, antecedent soil water, and other factors. Another case study provided measured values of matrix infiltrability to estimate parameter values for comparison and illustrative predictions. These examples give a self-consistent picture from the combination of parameter values, directions of sensitivities, and magnitudes of differences caused by different variables. One major practical use of this model is to calculate the dependence of preferential flow on climate-related factors, such as varying soil wetness and rainfall intensity.

Vadose Zone Journal↗
USGS2023

The use of historical data and global climate models to assess historical and future surface water and groundwater availability in the Trinity River Basin in Texas

This paper describes the results of a study that was done by the USGS to assess recent (2017) water availability, forecast long-term trends in water availability, assess changes in water availability, and forecast future water availability in the Trinity River Basin in Texas. The Trinity River Basin surface water model and Trinity River alluvium aquifer (TRAA) groundwater model were created to evaluate future conditions under different global climate models (GCM). The results of this study show minimal overall changes in water availability for both surface water and groundwater. Trend analyses using historical data (1900–2017) indicated an increase of annual precipitation on the watersheds that drain into the reservoirs in Regional Water Planning Group C. However, the Trinity River Basin surface water model GCM ensemble mean annual precipitation indicates a downward trend, resulting in a downward trend in surface runoff. Additionally, the GCM ensemble mean for the Trinity River Basin surface water model and the TRAA groundwater model both indicate a downward trend in recharge while the TRAA model GCM ensemble mean indicates an upward trend in the amount of groundwater leaving the aquifer to rivers and streams resulting in an upward trend of cumulative storage change.

Texas↗
USGS2018

Dietary bioprocessed soybean meal does not affect the growth of exercised juvenile rainbow trout (Oncorhynchus mykiss)

Context : This 88-day experiment evaluated the rearing performance of juvenile rainbow trout ( Oncorhynchus mykiss ) fed one of three isonitrogenous and isocaloric diets and reared at velocities of either 2.3 or 18.7 cm s -1 . Objective : Evaluate the effects of diet and exercise during rainbow trout rearing. Design : Fishmeal was the primary protein source for one diet, with bioprocessed soybean meal (BSM) replacing either 60 or 85% of the fishmeal in the other two diets. Setting : This study was performed at Cleghorn Springs State Fish Hatchery in Rapid City, South Dakota, USA. Results : At the end of the experiment there were no significant differences among the dietary treatments in gain, percent gain, specific growth rate (SGR), or percent mortality. However, fish fed the fishmeal-based diet ate significantly more, experienced a significantly higher feed conversion ratio (FCR), and had a significantly higher hepatosomatic index than the fish fed the 85% BSM diet. Intestinal histology was not affected by the inclusion of BSM. Fish reared at 2.3 cm/s -1 had significantly lower FCRs, gain, percent gain, and SGR than the fish reared at 18.7 cm/ s -1 . There was a significant interaction in food consumed between diet and velocity, but no other significant interactions between the dietary and exercise treatments were observed. Conclusion : Based on these results, BSM can replace at least 85% of the fishmeal in juvenile rainbow trout, even if the fish are exercised.

South Dakota↗
USGS1961

Chemotherapy of hexamitiasis in fish

Heramita salmonis , the causative agent of hexamitiasis in salmonoid fishes, is endemic in most trout and salmon hatcheries throughout North America. The etiologic agent, a protozoan flagellate, ostensibly causes cellular damage in the caecal mucosa of afflicted fishes. It is also believed that heavy infections may interfere with normal growth by direct competition with the host for available nutrients in the intestinal tract. While the role of this supposed pathogen is relatively unclear, its presence in test fishes at this laboratory has caused considerable concern during the conduct of controlled nutritional studies. Although McNeil et al (1941) showed that the incidence of Hexamita infections is widespread, hexamitiasis appears to be commercially important only in turkeys (Almquist and Johnson, 1951) and fish (Davis, 1953). Very little has been reported on the protozoacidal effects of various drugs on the Hexamita infections in fish (Fish and McKernan, 1940; Smith and Quistorff, 1940; and Nelson, 1941). The most widely used chemotherapeutic agents are p-carbamidobenzene arsonic acid (carbarsone) and mild mercurous chloride (calomel). Initial attempts at this laboratory to control the parasite in infected fish populations using these two drugs at the recommended concentrations demonstrated that the former was erratic in effectiveness and the latter was toxic and produced loss in fish weight. The present study, therefore, was undertaken to find more effective therapeutic agents which would be palatable, non-toxic, and still effectively eradicate the protozoan from fish.

Journal of Parasitology↗
USGS1970

Correction of bias in belt transect studies of immotile objects

Unless a correction is made, population estimates derived from a sample of belt transects will be biased if a fraction of, the individuals on the sample transects are not counted. An approach, useful for correcting this bias when sampling immotile populations using transects of a fixed width, is presented. The method assumes that a searcher's ability to find objects near the center of the transect is nearly perfect. The method utilizes a mathematical equation, estimated from the data, to represent the searcher's inability to find all objects at increasing distances from the center of the transect. An example of the analysis of data, formation of the equation, and application is presented using waterfowl nesting data collected in Colorado.

Colorado↗
USGS1974

Population dynamics of molting pintail drakes banded in south-central Saskatchewan

A total of 18,820 adult male pintails ( Anas acuta ) were trapped, banded, and released on Pel and Kutawagan marshes in south-central Saskatchewan in July 1955-58. Two hundred and fortyeight of these banded birds were recaptured on the same marshes during subsequent trapping operations, and 1,440 were recovered (shot or found dead) during legal hunting seasons, 1955-70. The size of the adult drake pintail population associated with Pel and Kutawagan marshes was estimated to have been approximately 313,600 in July 1956 and 232,800 in July 1957. Estimates of annual survival varied from approximately 60 percent to 85 percent with an average of 73 percent. Between July 1956 and July 1957, approximately 71,100 birds joined the population segment associated with Pel and Kutawagan marshes and 25,400 birds left the population segment for other areas. Indices to harvest pressure were low, varying from 2.26 in 1958 to 3.54 in 1956. Estimates of harvest rates varied from 5.6 percent to 8.8 percent, and kill rates varied from approximately 7.0 to 11.0 percent. The index to harvest pressure was highest in 1956, while survival during the 1956-57 period was the lowest, suggesting the possibility of an inverse relationship between harvest rate and total survival.

south-central Saskatchewan↗
USGS1998

The effect of rearing methods on survival of reintroduced black-footed ferrets

We estimated minimum survival rates for 282 young-of-year, captive-reared, black-footed ferrets ( Mustela nigripes ) reintroduced into prairie dog ( Cynomys spp.) colonies in Wyoming, Montana, and South Dakota. We used night surveys with spotlights to locate ferrets about 1 month and 9 months postrelease. We modeled minimum survival rates using gender, year, site, and 4 rearing methods. Minimum survival rates were highest (30% for 1 month, 20% for 9 months) for ferrets reared from early ages in outdoor pens with simulated prairie dog habitat; survival was lowest for cage-reared ferrets released without pen experience (11% for 1 month, 2% for 9 months). Rearing method and year influenced 1-month survival in a comparison of 3 levels of pen experience (pen rearing as defined above, transfer of kits from zoos to pen facilities at age 60-90 days, transfer at age >90 days) during releases in 1994-95 in Montana. Higher survival was associated with intensive management of coyotes ( Canis latrans ) in 1995. Survival was not different (P > 0.05) between sites or sexes, regardless of model. We recommend routine use of outdoor pens for prerelease conditioning of black-footed ferret kits.

Colorado, Montana, South Dakota, Wyoming↗
USGS1998

Limits of retrospective power analysis

Power analysis after study completion has been suggested to interpret study results. We present 3 methods of estimating power and discuss their limitations. We use simulation studies to show that estimated power can be biased, extremely variable, and severely bounded. We endorse the practice of computing power to detect a biologically meaningful difference as a tool for study planning but suggest that calculation of confidence intervals on the parameter of interest is the appropriate way to gauge the strength and biological meaning of study results.

Journal of Wildlife Management↗
USGS1979

Robust estimation from line transect data

Line transect sampling often provides a practical way to approach estimation of wildlife population density (Seber 1973, Eberhardt 1978). Burnham and Anderson (1976) provided a general framework for the estimation of animal density from line transect data, and many specific analytical methods have been proposed in the literature. Numerous persons are researching methods of statistical analysis for line transect data; however, little consideration has been given to specifying criteria for "good" methods of line transect estimation. We present here some criteria which we believe line transect estimators should satisfy. We do not deal with the case where objects may move from their initial location before being detected.

Journal of Wildlife Management↗
USGS1994

Six years of change in Lake Nyos, Cameroon, yield clues to the past and cautions for the future

The catastrophic release of gas from Lake Nyos, Cameroon, in 1986 caused substantial but incomplete mixing of the stratified water column. The post-release evolution of water-column structure has been monitored through April 1992. Changes began immediately after the event as rainfall and inflow brought dilute fluid into the surface layer. Inflow and surface mixing have gradually deepened the chemocline. The Total Dissolved Solids (TDS) values in the upper 40 m of the water column have dropped from a few hundred mg/kg just after the release to <100 mg/kg. The chemocline is presently strongest at 50 m depth; 5 m below this, the TDS = 570 mg/kg. From 55 to 150 m depth is a gentle gradient in which TDS reaches 920 mg/kg. Little change in water-column chemistry has occurred in this depth interval since the release. Between 150 m depth and lake bottom at 210 m depth, a strong secondary chemocline has formed. Temperature, CO 2 concentration ([CO 2 ]), and TDS have all increased in the deepest layer in response to recharge by warm, mineralized water, reaching values of 25.0°C, 320 mmol/kg, and 1800 mg/kg, respectively, 1 m above lake bottom. Considering all these changes in part as a “recovery” process, it is possible to construct a model of the pre-release water column. The data indicate that the pre-release chemocline was at least 50 m deep. Above the chemocline was a dilute layer containing a seasonal thermocline; below the chemocline was probably a gradient zone(s) with correlated increases in TDS and [CO 2 ] and a secondary chemocline near lake bottom. Maximum values of TDS and [CO 2 ] calculated for pre-release bottom water are 2400 mg/kg and 430 mmol/kg, respectively, based on tritium data. From this pre-release structure, a model of the gas release is proposed that is consistent with available chemical and observational data. An important feature of the model is that disruption of the pre-existing stratification was much more extensive than previously proposed, and even the deepest water layers were involved in the event. This model is not intended to limit possible gas release mechanisms, and thus complete re-establishment of pre-1986 water-column conditions is not a prerequisite for a future release. Spontaneous instability could occur at lake bottom in <20 yr if dissolved gas pressures continue to increase in this zone by 0.5–1 bar/yr as they have for the last 6 yr.

Lake Nyos↗