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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

A Comparative Study of Resilience of the Water Commons in the Upper and Middle Rio Grande Basins of New Mexico

Deichmann, Jens W. 23 January 2014 (has links)
<p> This dissertation is a study of two water management systems and their respective potential for adaptive change. It compares the principles of traditional common-pool resource communities with the policies and practices of contemporary acequias and the Middle Rio Grande Conservancy District. A review of the biophysical environment and relevant water laws and institutions provides a historical and environmental perspective on how the two distinct systems evolved into their current forms. The respective systems' capacities to continue to function in their basic forms in the face of climate change are evaluated through the conceptual lenses of resilience theory and the adaptive change cycle. The severe and extended drought that New Mexico is experiencing is causing a sharpened focus on how to limit water use. Shortage sharing is a traditional practice in common-pool resource cultures, as are other measures to manage a limited and vital resource, including monitoring, sanctions, exclusion of free-riders, equity of use, and reliance on democratic institutions to ensure collective decisions. These principles and practices are present to varying degrees in both systems and provide solid bases upon which to innovate and adapt to new conditions. The challenge will be to mobilize the will to change sufficiently to adapt while honoring the cultural values represented in each system; in other words, to build resilience into the systems. Opportunities to do so are explored and evaluated for their potential positive effects and possible downsides</p>
102

The Champlain Sea/Lake Champlain Transition Recorded In The Northeast Arm Of Lake Champlain, USA-Canada

Belrose, Ashliegh Theresa 01 January 2015 (has links)
Sediment accumulated on a lakebed archives information about past climate and changes in the regional environment. Previous studies (Burgess, 2007; Koff, 2011; Palmer, 2012) in the Northeast Arm of Lake Champlain, specifically Missisquoi Bay and Saint Albans Bay, showed a period (~9,400 - 8,600 yBP) of elevated organic matter deposition in both bays, indicating a productive event that pre-dated any possible anthropogenic influence. However, the record was abruptly cut off and any documentation representing the span of time leading up to this event was not found. The elevated organic matter levels were explained as being the result of a warm, dry environment that reduced lake level and promoted productivity within the bay. A new goal was formulated to lengthen the Holocene record for Missisquoi Bay (MSB) and Saint Albans Bay (SAB) in order to compare paleorecords and capture the span of time leading up to this highly productive event, possibly related to the Champlain Sea/Lake Champlain Transition (~10,000 yBP). One sediment core was taken from each bay as close to the original coordinates as the sediment cores obtained in previous studies (Koff, 2011; Palmer, 2012). The sediment cores were processed in the lab and sediment samples were tested for water content (WC), %C, %N, C:N, and diatom content. Each bay's sediment record consisted of a distinct marker representing lowest water level, separating a Champlain Sea unit at the bottom and an overlying Lake Champlain unit. A warming climate coupled with low lake level during this time may be the cause of the increase of productivity (%C) associated with the markers in both bays. Between ~8,600 - 9,400 yBP, a distinct marker represented evidence of a wetland in Saint Albans Bay before the onset of Lake Champlain. Diatom content in the wetland sediments indicated a generally shallow oligotrophic and alkaline body of water that shifted back and forth from brackish to freshwater. The record shows the wetland was eventually drowned as water level continued to rise, slowly transitioning into the Lake Champlain unit. Proxy results showed that internal processes within the lake continued to change in response to climatic and environmental drivers until present day conditions were reached. At ~9,400 yBP in Missisquoi Bay, there is an erosional unconformity between the Champlain Sea and Lake Champlain units, which corresponds to the low water levels also inferred from the SAB record during that time. After this unconformity, %C results show production within MSB fluctuated, similar to SAB, in response to changing climate and water levels until the present-day conditions of Lake Champlain were established. In sum, MSB and SAB each contain evidence of an ancient shoreline marker in different forms. Both markers indicate that lowest water levels occurred ~9,400 yBP and that lake level has risen ~7 - 8.5 meters since that time. The rise in lake level is associated with the transition into Lake Champlain. This Champlain Sea/Lake Champlain Transition lasted from ~9,400 yBP until ~8,600 yBP. Therefore, the oldest Lake sediment in the Northeast Arm of Lake Champlain is only 8,600 yBP.
103

Modelling recreational angling demand in Sweden based on region-specific inclusive values

Gustafsson, Johan January 2017 (has links)
This thesis endeavours to model a trip demand function for recreationalangling in Sweden, including the individual expected per-trip utility of regionalattributes. The analysis is conducted with the use of a Random Utility Model (RUM)for the estimation of ‘site-specific’ utility, and a negative binomial logit model fortrip demand. The site quality variable is stated as expected catch-rates (CR) definedin terms of three different specifications: sample mean CR, individually perfectlyforesighted CR, and an econometrically predicted individual CR. Results indicatethat the econometrically estimated individual catch-rate specification performs wellas an explanatory variable both when modelling discrete site choice and trip demand,while the sample mean and perfectly foresighted CR specifications provide withunintuitive and insignificant parameter values. The inclusive value of the regionchosen by the angler, estimated with the RUM, was subsequently found to be asignificant predicting variable for the number of recreational angling trips conductedby Swedish anglers.
104

Bacterial Response to Crude Oil Spillage in a Salt Marsh

Herwig, Russell Paul 01 January 1978 (has links)
No description available.
105

Recolonization of meiobenthos in oiled azoic subtidal muddy sands of the York River estuary, Virginia

Alongi, Daniel M. 01 January 1981 (has links)
No description available.
106

Use of Remote Sensing to Identify Essential Habitat for Aeschynomene virginica (L) BSP, a Threatened Tidal Freshwater Wetland Plant

Mountz, Elizabeth M. 01 January 2002 (has links)
No description available.
107

POTENTIAL FOR USE OF EFFLUENT WASTEWATER TREATED BY SOIL AQUIFER TREATMENT IN BANNING, CALIFORNIA

Vela, Arturo Castro 01 June 2015 (has links)
With the ever increasing demand for potable water due to the continued increase in population coupled with the threat of California’s current drought, water will remain a limited resource that must be managed responsibly. In order to strategically plan and manage water use in the most beneficial manner, water providers must take into account all sources of water, including recycled water and their applications. Recycled water as a source for supplementing high quality potable water is a sustainable strategy that will prove to be an essential tactic in any water management plan. The purpose of this project is to emphasize the importance of supplementing potable water in the City of Banning by discussing the characteristics of California’s current water drought; evaluating the City of Banning’s available water supplies and current water demand; discussing the Soil Aquifer Treatment process; summarizing California’s regulations related to recycled water; and discussing the quality of recycled water available at NP-1, an unequipped City owned water well, by examining water quality testing on water samples taken from NP-1. Analysis of water available at NP-1 showed that with additional disinfection, the water pumped from NP-1 could meet the recycled water requirements in order to be used on a local golf course. The local golf course is currently being irrigated with potable water, which would be supplemented with the recycled water from NP-1.
108

Factors influencing the distribution of brown trout (Salmo trutta) in a mountain stream: Implications for brown trout invasion success

Meredith, Christy 01 May 2012 (has links)
Brown trout (Salmo trutta), one of the world’s most successful introduced species, negatively impacts native aquatic communities through predation, competition, and ecosystemlevel effects. Thus, there is a need to understand factors controlling the distribution of exotic brown trout in river systems, in order to prioritize and develop conservation and management strategies. Within the context of invasion success, I investigated how the physical template of the Logan River influences the distribution of brown trout along a longitudinal gradient, and the potential for brown trout predation on the native mottled sculpin (Cottus bairdi). The Logan River, Utah USA, is a high-elevation, mountain river exhibiting a wide range of physical habitat characteristics along the altitudinal (or elevational) gradient. In chapter 1, I evaluated whether longitudinal trends in geomorphology contribute to higher potential mortality of brown trout fry at high elevations due to flood-caused streambed scour. High-elevation spawning gravels did not exhibit higher scour compared to low elevations, because brown trout locally chose low-scour areas for spawning. In chapter 2, I investigated the importance of gravel availability, versus other habitat factors, in controlling the spatial distribution of brown trout redd densities. Using a Bayesian hierarchical modeling approach, I demonstrated that anchor ice, distance from high-quality backwater habitat, and to a lesser-extent gravel availability, best explained redd densities. Finally, in chapter 3, I evaluated the potential predatory effects of exotic brown trout on native mottled sculpin (Cottus bairdi). High rates of sculpin consumption contrasted to previously documented low rates of predation by native Bonneville cutthroat (Oncorhynchus clarkii) and depended on abiotic factors controlling the distribution of both species. Collectively, my research suggests that both abiotic factors and source-population dynamics structure brown trout distributions on the Logan River, and ultimately the potential impacts of this invasive fish. Specifically, the distribution of anchor ice and distance from dam backwaters are important drivers of the brown trout distribution, which may extend to other systems. These drivers, including how they may be influenced by future climate change and habitat alteration, should be considered in management efforts to control brown trout expansion and to limit the predatory impacts of brown trout.
109

Watershed Management to control Pollution in the Ayuquila River, Jalisco, Mexico

Martinez Rivera, Luis Manuel 01 May 2004 (has links)
The Ayuquila River watershed is important to western Mexico because of its biodiversity, physiography, fisheries resources, and water production. However, human activities are continuingly affecting natural resources within the basin. Soil erosion, as result of land use change, agriculture in steep land, extensive grazing activities and forest fires; and water diversion and pollution of the Ayuquila River are two relevant issues that have affected the natural resources of this watershed. This river system plays an important role in wildlife conservation, containing 29 fish species, of which 12 are found inside the BRSM. The River also contains nine species of crustacean, one that is endemic to Jalisco State. The otter (Lontra longicaudis), a species threatened within the BRSM, is found in the Ayuquila- Armeria River watershed. This research focused on the reduction of river pollution and the reduction of negative impacts of water pollution delivered to those communities, some of the poorest in the state of Jalisco, that live downstream of the valley. This research was also designed as a way to increase the knowledge of soil erosion processes and water quantity and quality in tropical environments and to test and develop new tools that might facilitate parameter estimation and predictive capabilities within the Ayuquila River watershed. Research efforts in this dissertation had focused on the development of new scientific information about point and nonpoint-source pollution within the Ayuquila River based on three main research studies, the investigation into trail erosion, the production of an erosion sensitive map, and documenting and modeling water quantity and quality in the Ayuquila Watershed. Major concerns that this research seeks to contribute a solution, is to reduce negative impacts on public health, degradation in fisheries resources as source of local food supply, domestic water supplies for those communities, some of the poorest in the state of Jalisco, that live downstream the valley and that do not receive any benefit from the economic development of the Autlan- El Grullo Valley. Results from the commercial trail study, with sediment productions close to 100 ton/ha/yr, showed the importance of the application of conservation practices to reduce the potential erosion from commercial trails in my study area and potentially other tropical forests of Latin-American. The WEPP model used to predict soil erosion in the tropical mountain environments of Mexico was shown to be an adequate tool even with WEPP's limitations for tropical soil environments. WEPP effectively contributed to the estimation of sediment plume production on trails, detected vegetation type differences in runoff and soil erosion, predicted the amount of rainfall as runoff well, and adequately developed soil erosion sensitive maps. Water diversion and pollution within the Ayuquila River are important sources of disturbance in the ecological conditions of riparian ecosystems. These two impacts cause a potential break in the ecological continuity of the Ayuquila River. Water quantity and quality modeling will provide opportunities for discussion and analysis of alternatives to water management and possible impacts to the river.
110

Environmental Assessment of Streams: Linking Land Use, Instream Stressors, and Biological Indices to Infer Likely Causes of Ecological Impairment

Vander Laan, Jacob J. 01 May 2012 (has links)
To protect and restore the biological integrity of streams, we need to be able to both detect biological degradation and infer likely causes of impairment. Managers often use biological indices to measure biological condition and detect degradation. However, the ability to detect degradation can be limited by the performance of the indices we develop. Index performance varies widely, but the sources of this variation are often unclear. In addition, although bioassessments are useful tools for detecting biological degradation, they do not identify stressors associated with impairment. My thesis research had two general goals: 1) develop statistically and ecologically robust indices to measure biological condition in Nevada streams and 2) quantify relationships between land uses, stressors, and biological condition to infer likely causes of degradation. I developed two biological indices for Nevada streams, a multimetric index (MMI) and observed to expected (O/E) taxa ratios, and determined if index performance was related to site isolation and sample evenness. The Nevada O/E indices were relatively imprecise compared with those from other regions, which likely results from low assemblage predictability associated with spatial isolation of aquatic habitats in arid regions. In contrast, the Nevada MMI was more precise than most previously developed MMIs, likely the result of using models to reduce natural variation in index scores. Sample evenness was positively associated with both O/E and MMI scores. Adjustments of index scores for sample evenness increased index precision, but also altered relative differences in index values and therefore inferences of biological impairment at specific sites. I also quantified relationships between biological condition, instream stressors, and land uses and used a weight of evidence approach to infer likely causes of degradation. Land uses such as agriculture, urbanization, and mining were associated with the spatial distributions of instream stressors, and these stressors were associated with variation in biological condition. Total dissolved solids and metal contamination were the stressors most strongly associated with biological condition. By detecting biological degradation and identifying important stressors and their potential sources, the tools I developed should help managers target conservation and restoration efforts and improve their ability to protect freshwater resources.

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