• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 389
  • 15
  • 15
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 701
  • 701
  • 701
  • 372
  • 189
  • 162
  • 148
  • 115
  • 102
  • 101
  • 93
  • 87
  • 80
  • 78
  • 68
  • 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.
61

The power politics of water struggles| Local resource management in the West Bank

Mughal, Urooj 30 August 2013 (has links)
<p> This thesis examines the significance of a micro-level approach to the Israeli-Palestinian water conflict. By rethinking scale of analysis and examining local insecurities, Palestinian experiences reveal how water conflict plays out in latent and discursive ways. In a step-by-step method, I detail the processes and outcomes of the water struggle in the West Bank. First, I show how technical challenges ((i) poor water supply, (ii) antiquated water infrastructure, (iii) failed institutions) are shaped by political imperatives. Second, I show how Palestinians have responded to local water sector challenges: (iv) nonpayment to the Palestinian Water Authority for their water supply, (v) increasing rural to urban migration by Palestinian farmers. As a result, Palestinian society is stuck in cycles of crisis that make the conditions increasingly ungovernable. While Palestinians are stuck in a mode of ungovernability, their position in the peace process with Israel is undermined.</p>
62

Decision support for Wisconsin's manure spreaders| Development of a real-time Runoff Risk Advisory Forecast

Goering, Dustin C. 01 November 2013 (has links)
<p> The Runoff Risk Advisory Forecast (RRAF) provides Wisconsin's farmers with an innovative decision support tool which communicates the threat of undesirable conditions for manure and nutrient spreading for up to 10 days in advance. The RRAF is a pioneering example of applying the National Weather Service's hydrologic forecasting abilities towards the Nation's water quality challenges. Relying on the North Central River Forecast Center's (NCRFC) operational Snow17 and Sacramento Soil Moisture Accounting Models, runoff risk is predicted for 216 modeled watersheds in Wisconsin. The RRAF is the first-of-its-kind real-time forecast tool to incorporate 5-days of future precipitation as well as 10-days of forecast temperatures to generate runoff risk guidance. The forecast product is updated three times daily and hosted on the Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP) website. Developed with inter-agency collaboration, the RRAF model was validated against both edge-of-field observed runoff as well as small USGS gauged basin response. This analysis indicated promising results with a Bias Score of 0.93 and a False Alarm Ratio (FAR) of only 0.34 after applying a threshold method. Although the threshold process did dampen the Probability of Detection (POD) from 0.71 to 0.53, it was found that the magnitude of the events categorized as hits was 10-times larger than those classified as misses. The encouraging results from this first generation tool are aiding State of Wisconsin officials in increasing awareness of risky runoff conditions to help minimize contaminated agriculture runoff from entering the State's water bodies.</p>
63

Modification and Characterization of Ordered Mesoporous Carbons for Resorcinol Removal

Ren, Hanlong 30 April 2015 (has links)
<p> Ordered mesoporous carbon (OMC) materials have attracted great interests from NASA due to their remarkable properties, such as high specific surface area, regular and tunable pore size. These features show great potential for being used in the water recovery system (WRS) in the International Space Station (ISS) as potential adsorbents. Various methods have been explored on the OMC preparation and modification to achieve better adsorption results. In this research, acrylic acid was used as a carbon precursor to synthesize OMC using a common silica mesoporous template (SBA-15). The influence of silica template amount was tested by using different ratios of SBA-15 to acrylic acid. The modification processes were conducted by immersing methods using four different aqueous solutions: 30% ammonium hydroxide, 0.1% sodium hydroxide, 1 mol/L aluminum chloride, and 0.02 g/mL urea solution. BET-SSA, FT-IR, TEM, TGA, and XRD were used to characterize the structures of OMCs and modified OMCs. It demonstrated that all the products had well-ordered hexagonal structure. The modifying procedures had eroded the surface of the OMC, but the highly ordered structures had been preserved based on the TEM and XRD results. FT-IR analysis indicated that the functional groups were introduced to the surface of the modified OMCs, which affected the adsorption capacity significantly. Resorcinol, a typical total organic carbon (TOC) model compound, was selected to evaluate the adsorption behavior of the OMCs and modified OMCs. Adsorption study illustrates that OMC produced by 3:1 ratio of SBA-15 to acrylic acid showed a higher adsorption capacity than that of OMCs produced with other ratios. The ammonium hydroxide modified OMC had the highest adsorption capacity of 40.6 mg/g for resorcinol removal, compared with that of the other three modified OMCs.</p>
64

Quantifying the Impacts of Initial Condition and Model Uncertainty on Hydrological Forecasts

DeChant, Caleb Matthew 04 September 2014 (has links)
<p> Forecasts of hydrological information are vital for many of society's functions. Availability of water is a requirement for any civilization, and this necessitates quantitative estimates of water for effective resource management. The research in this dissertation will focus on the forecasting of hydrological quantities, with emphasis on times of anomalously low water availability, commonly referred to as droughts. Of particular focus is the quantification of uncertainty in hydrological forecasts, and the factors that affect that uncertainty. With this focus, Bayesian methods, including ensemble data assimilation and multi-model combinations, are utilized to develop a probabilistic forecasting system. This system is applied to the upper Colorado River Basin for water supply and drought forecast analysis. </p><p> This dissertation examines further advancements related to the identification of drought intensity. Due to the reliance of drought forecasting on measures of the magnitude of a drought event, it is imperative that these measures be highly accurate. In order to quantify drought intensity, hydrologists typically use statistical indices, which place observed hydrological deficiencies within the context of historical climate. Although such indices are a convenient framework for understanding the intensity of a drought event, they have obstacles related to non-stationary climate, and non-uniformly distributed input variables. This dissertation discusses these shortcomings, demonstrates some errors that conventional indices may lead to, and then proposes a movement towards physically-based indices to overcome these issues. </p><p> A final advancement in this dissertation is an examination of the sensitivity of hydrological forecasts to initial conditions. Although this has been performed in many recent studies, the experiment here takes a more detailed approach. Rather than determining the lead time at which meteorological forcing becomes dominant with respect to initial conditions, this study quantifies the lead time at which the forecast becomes entirely insensitive to initial conditions, and estimating the rate at which the forecast loses sensitivity to initial conditions. A primary goal with this study is to examine the recovery of drought, which is related to the loss of sensitivity to below average initial moisture conditions over time. Through this analysis, it is found that forecasts are sensitive to initial conditions at greater lead times than previously thought, which has repercussions for development of forecast systems.</p>
65

Stage III N-saturated forested watershed rapidly responds to declining atmospheric N deposition

Sabo, Robert D. 10 September 2014 (has links)
<p> This study used a mass balance approach by characterizing the input, output, and sink rates of N in order to assess a declared "stage III N-saturated forest" response to decreased atmospheric N deposition in western Maryland. Relying on the conceptual model of kinetic N-saturation to holistically link stream, vegetative, soil, and atmospheric compartments and the use of a novel stable isotopic technique, the study demonstrated dynamic soil NO<sub>3</sub>-N pools, unprocessed atmospheric NO<sub>3</sub>-N in base flow, and significant reductions in NO<sub>3</sub>-N yield in response to decreased atmospheric N deposition. A lumped conceptual model, incorporating a dormant season NO<sub>3</sub>-N flush, was proposed that explains forest response to decreased deposition and sheds light on the hydrologic processes that govern the storage/release of NO<sub>3</sub>-N among years. It is proposed that this flushing mechanism prevents forests from attaining higher stages of N-saturation and predicts forests will be responsive to further reductions in N deposition. </p>
66

Spatial Translation and Scaling Up of LID Practices in Deer Creek Watershed in East Missouri

Di Vittorio, Damien 07 November 2014 (has links)
<p> This study investigated two important aspects of hydrologic effects of low impact development (LID) practices at the watershed scale by (1) examining the potential benefits of scaling up of LID design, and (2) evaluating downstream effects of LID design and its spatial translation within a watershed. The Personal Computer Storm Water Management Model (PCSWMM) was used to model runoff reduction with the implementation of LID practices in Deer Creek watershed (DCW), Missouri. The model was calibrated from 2003 to 2007 (R<sup>2</sup> = 0.58 and NSE = 0.57), and validated from 2008 to 2012 (R<sup>2</sup> = 0.64 and NSE = 0.65) for daily direct runoff. Runoff simulated for the study period, 2003 to 2012 (NSE = 0.61; R<sup>2</sup> = 0.63), was used as the baseline for comparison to LID scenarios. Using 1958 areal imagery to assign land cover, a predevelopment scenario was constructed and simulated to assess LID scenarios' ability to restore predevelopment hydrologic conditions. The baseline and all LID scenarios were simulated using 2006 National Land Cover Dataset.</p><p> The watershed was divided in 117 subcatchments, which were clustered in six groups of approximately equal areas and two scaling concepts consisting of incremental scaling and spatial scaling were modelled. Incremental scaling was investigated using three LID practices (rain barrel, porous pavement, and rain garden). Each LID practice was simulated at four implementation levels (25%, 50%, 75%, and 100%) in all subcatchments for the study period (2003 to 2012). Results showed an increased runoff reduction, ranging from 3% to 31%, with increased implementation level. Spatial scaling was investigated by increasing the spatial extent of LID practices using the subcatchment groups and all three LID practices (combined) implemented at 50% level. Results indicated that as the spatial extent of LID practices increased the runoff reduction at the outlet also increased, ranging from 3% to 19%. Spatial variability of LID implementation was examined by normalizing LID treated area to impervious area for each subcatchment group. The normalized LID implementation levels for each group revealed a reduction in runoff at the outlet of the watershed, ranging from 0.6% to 3.7%. This study showed that over a long-term period LID practices could restore pre-development hydrologic conditions. The optimal location for LID practice implementation within the study area was found to be near the outlet; however, these results cannot be generalized for all watersheds. </p>
67

Vulnerability of groundwater to perchloroethylene contamination from dry cleaners in the Niles Cone Groundwater Basin, southern Alameda County, California

Jurek, Anne C. 11 November 2014 (has links)
<p> Releases of perchloroethylene (PCE) from dry cleaners pose a threat to groundwater quality. An assessment was performed of the Niles Cone Groundwater Basin to determine its vulnerability to PCE contamination from both historic and more recently operating dry cleaners. Sensitivity assessments of the Basin's two subbasins were performed using a modification of the DRASTIC Index Method, whereby the hydrogeological variables of depth to water, aquifer media, vadose zone media, and soil drainage classification were represented by a range of sensitivity categories and ratings assigned to each range. A source assessment was performed by identifying the locations of historic and presently operating dry-cleaning plants and assigning a threat ranking to each based on the approximate years in which the four generations of dry-cleaning machinery were introduced. Using ArcGIS, the sensitivity assessments and the source assessment were mapped, and the source assessment was superimposed over the sensitivity maps to create vulnerability maps of the two subbasins. The most sensitive area of the Below Hayward Fault subbasin in the forebay area near the Hayward Fault is due to a higher proportion of coarse-grained aquifer and vadose zone media and a thinner to absent aquitard due to deposition from the Alameda Creek. The existence of dry cleaners of higher threat makes this an area that is vulnerable to PCE contamination.</p>
68

Quantifying the restorable water volume of Sierran meadows

Emmons, Jason Daniel 31 May 2014 (has links)
<p> The Sierra Nevada is estimated to provide over 66% of California's water supply, which is largely derived from snowmelt. Global climate warming is expected to result in a decrease in snow pack and an increase in melting rate, making the attenuation of snowmelt by any means, an important ecosystem service for ensuring water availability. Montane meadows are dispersed throughout the mountain range providing wildlife habitat, water filtration, and water storage. Despite the important role of meadows in the Sierra Nevada, the majority are degraded from stream incision, which increases volume outflows and reduces overbank flooding, thus reducing infiltration and potential water storage. Restoration of meadow stream channels would therefore improve hydrological functioning, including increased water storage. The potential water holding capacity of restored meadows has yet to be quantified, thus this research seeks to address this knowledge gap by estimating the restorable water volume due to stream incision. More than 17,000 meadows were analyzed by categorizing their erosion potential using channel slope and soil texture, ultimately resulting in six general erodibility types. Field measurements of over 100 meadows, stratified by latitude, elevation, and geologic substrate, were then taken and analyzed for each erodibility type to determine average depth of incision. Restorable water volume was then quantified as a function of water holding capacity of the soil, meadow area and incised depth. Total restorable water volume across meadows in the Sierra Nevada was found to be 120 x 10<sup>6</sup>m<sup>3</sup>, or approximately 97,000 acre-feet. Using 95% confidence intervals for incised depth, the upper and lower bounds of the total restorable water volume were found to be 107 x 10<sup>6</sup>m<sup> 3</sup> &ndash; 140 x 10<sup>6</sup>m<sup>3</sup>. Though this estimate of restorable water volume is small in regards to the storage capacity of typical California reservoirs, restoration of Sierra Nevada meadows remains an important objective. Storage of water in meadows benefits California wildlife, potentially attenuates floods, and elevates base flows, which can ease effects to the spring snowmelt recession from the expected decline in Sierran snowpack with atmospheric warming.</p>
69

Water Quality and Quantity in Intermittent and Continuous Piped Water Supplies in Hubli-Dharwad, India

Kumpel, Emily 31 May 2014 (has links)
<p> In at least 45 low- and middle-income countries, piped water systems deliver water for limited durations. Few data are available of the impact of intermittent water supply (IWS) on the water quality and quantity delivered to households. This thesis examines the impact of intermittently supplied piped water on the quality and quantity of water delivered to residential taps in Hubli-Dharwad, India, when compared to continuous piped water supply. A framework for understanding the pathways through which IWS can impact water quality is first developed. The extent to which contamination occurs in Hubli-Dharwad is quantified by comparing microbial water quality throughout the distribution system in an intermittent system and a continuous system in the same city. The mechanisms affecting water quality in the IWS network in Hubli-Dharwad are identified by measuring changes in water quality over time using continuous measurements from pressure and physico-chemical sensors paired with grab samples tested for indicator bacteria. In the final chapter, a new method of measuring household water consumption in an IWS when supply durations are limited and few metered data are available is developed. This thesis showed that the intermittent supply was frequently subject to contamination in the distribution system and that households with intermittent supply consumed limited quantities of water. While these results demonstrated that converting to a continuous water supply can improve water quality when compared to intermittent supply, this conversion may not be possible in the near future for resource-constrained towns and cities. This thesis contributes to knowledge of the mechanisms causing contamination and constricting water access in IWS systems, which can help improve systems to ensure that people with piped water receive water that is reliable, safe, and sufficient.</p>
70

Determining the relative influence of mental pollutants in Newport and Laguna beach seawater on the Giant Kelp (Macrocystis pyrifera) populations of Crystal Cove State Park by analysis of sieve sap metals

Burnett, Danielle Lee 29 April 2014 (has links)
<p> The abstract is not available from PDF copy and paste.</p>

Page generated in 0.1364 seconds