Dams have altered flow distributions in rivers everywhere, causing a host of changes in channel morphology and sediment dynamics. Although major changes in flow regime have occurred along Yegua Creek, Texas, since the closure of Somerville Dam in 1967, the issue of sediment transport has not been studied in detail. The extent to which sediment is moving through the system remains unclear. This study addresses the extent to which sediment is moving through and downstream of the dam. Analysis of sediment samples collected at 23 sites in the Yegua Creek channel system showed that coarse sand to silt-sized materials dominate the creek upstream of the dam, whereas finer silt and clay sediments characterize the downstream portions. Calculation of the trapping efficiency of the dam indicates that approximately 99.8% of materials from the upper watershed are trapped behind Somerville Dam. Investigations of sediment mobility further suggest that present flows are capable of mobilizing sediments downstream of the dam. Although a de-coupling between the upper and lower portions of the Yegua Creek watershed has likely occurred due to the high rate of sediment trapping, new sediment sources that include tributaries and alluvial storage likely play a larger role in providing materials for sediment transport downstream. Despite a reuction in peak flows, the channel morphology of Yegua Creek has apparently adjusted over the four decades since construction of Somerville Dam to achieve a new equilibrium characterized by sediment movement. These results are corroborated by analysis of aerial photographs. These findings augment our understanding of the many facets of the response of fluvial systems to the disturbance posed by dam construction. Because Yegua Creek is a major tributary to the Brazos River draining to the Texas coast, increased understanding of sediment dynamics within Yegua Creek provides critical insights into the efficacy of sediment delivery in a regional context, and ultimately to the Texas coastline. The findings of this study also provide useful information for managing stream ecosystems affected by impoundments.

Water resource management operations have significantly modified river flow regimes globally, prompting widespread lotic ecosystem responses. There is a growing need to better understand how increasingly prevalent hydrological alterations to riverine systems will affect biota dependent on specific elements of river flow regimes. This thesis examines macroinvertebrate community responses to river flow regimes modified by various water resource management operations across southwest England though four detailed investigations. The first study examines the influence of river impoundments and how macroinvertebrate communities differ between regulated and non-regulated sections of river. Findings from this investigation highlight that flow regulation alters the structure and function of faunal assemblages due to significant changes to the flow regime, rather than stream temperature modifications associated with the reservoirs. The second study focusses on groundwater dominated headwater streams transitioning from temporary (i.e. reaches periodically drying positioned furthest upstream) to perennial flow conditions which are subjected to variable groundwater abstraction intensities. The results indicate that macroinvertebrate communities respond significantly to the duration of antecedent flowing conditions and the spatial proximity of sampling sites to perennial sources; but faunal assemblages are not sensitive to groundwater abstraction. The third study examines how communities inhabiting different organic and mineralogical lotic habitats responded to multiple river flow properties (hydrological indices, anthropogenic flow alteration measures and hydraulic variables) in perennial, groundwater dominated systems. The findings highlight that faunal assemblages are most responsive to local hydraulic conditions measured at the point of sampling, rather than antecedent hydrological conditions. The influence of hydraulic properties on communities differs between lotic habitats, highlighting that mineralogical and organic characteristics of riverbeds strongly mediate how biota respond to flow. The final study presents the results of a long-term (1995-2016), region-wide (spanning Dorset, Hampshire and Wiltshire) examination of macroinvertebrate communities inhabiting groundwater dominated rivers and their responses to hydrological variability (including extreme low- and high-flow events) and anthropogenic flow alterations. The results indicate that indices characterising the proportion of discharge added to (through effluent water returns and low-flow alleviation strategies) or removed from the river (via groundwater abstraction) exert profound effects on faunal assemblages over long-term periods. These results provide empirical evidence that reductions in river discharges via groundwater abstraction of approximately 15% have no perceptible negative ecological effects on macroinvertebrate communities. The results from the four detailed investigations are used to develop conceptual models to illustrate how research undertaken within this thesis can be applied more widely. The findings and study designs presented within this thesis could inform surface and groundwater water resource management operations and underpin the development of environmental flow methodologies required to conserve riverine ecosystems globally.

This study was carried out with the purpose to evaluate the short-term impact of a dam construction on the community of the immature Odonata through their analysis in lentic and lotic environments, before and after the impoundment of the reservoir. In the preimpoundment phase 17 stations were sampled, five in lentic environments (dams and ponds), and 12 in lotic environments (tributaries of the Rio Jacuí) between January and October 2000. In the post-impoundment sampling, five points inside the reservoir were studied (between May 2001 and October 2002) in lentic environments, and four points, in lotic environments (between November 2000 and May 2002). The lentic environments were sampled by using sieves, and the lotic ones, with a Surber sampler. Some abiotic factors measured were air and water temperatures, dissolved oxygen, pH, depth and, for lotic environments, the current velocity. The total number collected was 1298 specimens, attributed to eight families and 27 genera, of which 16 are new records for the State: Heteragrion, Oxystigma, Neuraeschna, Tibiogomphus, Phyllocycla, Desmogomphus, Cacoides, Archeogomphus, Anatya, Brechmorhoga, Libellula, Tramea, Cyanallagma, Forcepsioneura, Protoneura and Epipleoneura. The lentic habitat was better represented in abundance and richness in the pre-impoundment (681 individuals and 14 genera), with a drastic decrease in the post-impoundment (n = 41, S = 8), while the opposite occurs for lotic environments (n = 200 individuals and 14 genera versus 376 and 17, respectively). The lotic environments studied here showed greater richness than the lentic environments, presenting a greater heterogeneity of habitats, especially related to aquatic vegetation. For the lentic environments, the higher richness and abundance of odonatofauna were found in stable environments (ponds of greater depths and dimensions), with marginal and aquatic vegetation. In the post-impoundment phase, the fauna restoration occured mainly in points inside the reservoir where prevailed lotic conditions, as the mouth of the tributaries. For lotic environments, the sites of greatest abundance and richness were tributaries of the medium reaches (4th order), characterized by small size and shading of one of the margins by riparian vegetation. The points of 7th order, located in the Rio Jacuí (one of them downstream of the dam), showed the lowest values concerning the fauna, since these sites were strongly influenced by changes in water level of the U.H.E. Itaúba, located upstream. These results were enhanced after the impoundment of the reservoir of U.H.E Dona Francisca. Multivariate analysis showed that the effect of U.H.E. Dona Francisca construction on the immature stages of Odonata was not direct, interacting with the characteristics of each habitat, for both the abundance and the composition of the fauna. / Este estudo foi realizado com o objetivo de avaliar o impacto de curto prazo da construção de uma barragem sobre a comunidade de imaturos de Odonata através da sua análise em ambientes lênticos e lóticos, antes e após o enchimento do reservatório. Na fase de pré-enchimento foram amostradas 17 estações de coleta, sendo cinco em ambientes lênticos (açudes e charcos), e 12 em ambientes lóticos (tributários do Rio Jacuí), no período entre janeiro e outubro de 2000. Na fase de pós-enchimento as coletas em ambientes lênticos prosseguiram em cinco pontos no interior do reservatório (entre maio de 2001 e outubro de 2002), enquanto nos ambientes lóticos quatro pontos foram amostrados, no período compreendido entre novembro de 2000 e maio de 2002. Os ambientes lênticos foram amostrados usando-se peneiras, e os lóticos, amostrador de Surber. Alguns fatores ambientais foram coligidos: temperaturas do ar e da água, oxigênio dissolvido, pH, profundidade, e, para os ambientes lóticos, a velocidade da correnteza. Foram coletados 1298 espécimes, pertencentes a 27 gêneros distribuídos em oito famílias, dos quais 16 gêneros constituem novos registros para o Estado: Heteragrion, Oxystigma, Neuraeschna, Tibiogomphus, Phyllocycla, Desmogomphus, Cacoides, Archeogomphus, Anatya, Brechmorhoga, Libellula, Tramea, Cyanallagma, Forcepsioneura, Protoneura e Epipleoneura. O hábitat lêntico esteve mais bem representado em abundância e riqueza na fase de pré-enchimento (681 indivíduos e 14 gêneros) tendo uma drástica diminuição na fase de pós-enchimento (n = 41, S = 8), o contrário ocorrendo para os ambientes lóticos (n = 200 indivíduos e 14 gêneros versus 376 e 17, respectivamente). Os ambientes lóticos aqui estudados apresentaram maior riqueza que os ambientes lênticos devido à maior heterogeneidade de hábitats, principalmente em função da vegetação aquática. Para os ambientes lênticos as maiores riqueza e abundância da odonatofauna foram encontradas em ambientes mais estáveis (charcos de maiores profundidades e dimensões), com vegetação aquática e marginal. Na fase de pós-enchimento, a fauna restabeleceu-se principalmente em locais do reservatório onde prevalecem condições lóticas, como a desembocadura dos tributários. Para os ambientes lóticos, os locais de maiores abundância e riqueza foram tributários de trechos médios (4ª ordem), caracterizados pelo pequeno porte e com sombreamento em pelo menos uma das margens pela vegetação ribeirinha. Os pontos de 7ª ordem, localizados no Rio Jacuí (um deles à jusante do barramento), apresentaram os menores valores relacionados à fauna, uma vez que estes locais eram fortemente influenciados pelas variações no nível da água da U.H.E. Itaúba, localizada à montante, tendo estes resultados se intensificado quando da formação do reservatório da U.H.E. Dona Francisca. As análises multivariadas mostraram que o efeito da implantação da U.H.E. Dona Francisca sobre os estágios imaturos de Odonata não foi direto, interagindo com aspectos de cada hábitat, tanto para a abundância quanto para a composição da fauna.

The following is a thesis presented on the history, subsurface characterization and settlement analysis of the Conquista Tailings Impoundment located in Karnes City, TX. This research draws information from readily available sources at TCEQ in Austin, Texas. Documents included in this report date back to the mid-1980s and can be as recent as 2011. This thesis will focus on the eastern section of the Conquista Tailings Impoundment and will primarily observe and predict the settlement experienced in this portion of the site. The site has been analyzed using one-dimensional consolidation analysis, based on three (3) loading factors, and has been modeled using finite element analysis aided by the software PLAXIS. The research has justified the magnitude of settlement that has occurred in the area of concern and has provided just reasoning for the events. Further investigations into the subsurface conditions in the eastern portion of the Conquista Tailings Impoundment will be needed to confirm and refine the analysis presented. / text

Thesis (Ph. D.)--University of Wisconsin-Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

More than half the North American freshwater mussel species in the family Unionidae (unionids) are imperiled or extinct. Alteration of rivers is considered a major contributor to unionid population declines. Losses could occur through disruption of the reproductive cycle. Unionid reproduction requires attachment of larva (glochidia) to host fishes; therefore, changes in the host fish community could alter the reproductive potential in unionid communities. There have been few attempts to compare reproductive success before and after alteration. I examined the pattern of glochidia use on two common host fishes, Lepomis megalotis and Cyprinella venusta, before and after alteration of the Tombigbee River. While both host species declined in the river, the number of glochidia per infested fish and proportion of infested fish increased post-impoundment in L. megalotis but not C. venusta. My results demonstrate the importance of considering reproductive changes as a driver of unionid mussel declines in North America.

As ecologically sensitive organisms, freshwater mussels serve as environmental indicators in the rivers and lakes they inhabit. The South Fork of the Holston River has been impounded and channelized, which can result in habitat loss of riffle and shoal areas and negatively impact native species. The aim of this study is to analyze river conditions on a roughly 40 mile stretch of the S. Fork Holston River, encompassing the distance from Eastman Chemical Company in Kingsport to Boone Lake. Information has been gathered using mussel assemblages from two archaeological sites, 40SL34 and 40SL330, and two historic collecting events, SFHSkm25.1 and SFHSkm27.0. The computer program UNIO analyzes the ecological preferences of all input taxa to compile a list of river conditions, including flow velocity and substrate. Compiling the assemblages from all four sites has revealed an increase in unfavorable conditions for many species, leading to a loss in mussel diversity. What were once the most abundant species in the archaeological sites, Ptychobranchus subtentus and Fusconaia subrotanda, both prefer to live in riffle areas with fast current. Currently, P. subtentus is listed as endangered while F. subrotanda is listed as a special concern species. The most abundant species for both historic collecting events is Lampsilis fasciola, a species that is tolerant of conditions that are unfavorable for many species. The substrate of the S. Fork Holston River, a sandy-gravel, has remained the same, but evidence suggests that impoundment has resulted in the loss of fast-moving currents and riffle areas.

I assessed the potential for trophic competition between age-0 largemouth bass and juvenile bluegills by quantifying food resource use similarity in a Virginia recreational small impoundment and by experimentally stocking the species sympatrically and allopatrically in 1.0 m cages and monitoring mortality, growth, and resource use. Niche breadth of bluegills in the small impoundment was greater than that of largemouth bass for eight out of nine sampling dates during the summer and fall of 1997. Virtually every type of item consumed by largemouth bass also was consumed by bluegills. In spite of this, diet overlap between the species was low. Largemouth bass fed primarily on Calanoida, Ephemeroptera, and fish, while bluegills consumed Diptera and Cyclopoida. The fishery of the impoundment consisted of relatively high and moderate densities of slow- and average-growing largemouth bass and panfish, respectively. If the fishery was managed to provide a high density of small bluegill, largemouth bass and bluegill might compete considering the number of prey items shared. Manipulative cage experimentation, which consisted of stocking 5 largemouth bass alone, 10 bluegill alone, 5 largemouth bass and 10 bluegill, 5 largemouth bass and 30 bluegill, and 15 largemouth bass and 10 bluegill in cages, indicated that largemouth bass and bluegills can compete and that there exists a strong asymmetry in their competitive relationship. Bluegills had a much stronger impact on largemouth bass than the reverse. When stocked alone, largemouth bass grew significantly larger than when stocked with either 10 or 30 bluegills. There were no significant differences in bluegill growth rates except between bluegills stocked alone and bluegills stocked with 15 largemouth bass. The analysis of food resource use indicates that Copepoda and Diptera larvae may be the limiting resources catalyzing the competitive interaction. This research suggests that a competitive juvenile bottleneck could occur, depending largely on whether overwinter survival of largemouth bass is size related. Competition between largemouth bass and bluegills may explain why enhancement stocking of fingerling largemouth bass typically is not successful. Further research is needed on the appropriate timing and length at stocking of introductory largemouth bass stockings. Additionally, I recommend that resource partitioning and competition between largemouth bass and bluegills be explored in connection with studies concerning overwinter survival and angling opportunities in small impoundments. Competition between the species may impose an ecological constraint that restricts achievable options in certain systems. / Master of Science

Recent studies have focused on dissolved organic matter (DOM) cycling throughout river corridors or in reservoirs, but few have explored DOM cycling in commonplace but understudied run-of-river (ROR) reservoir systems. Impoundments disrupt river flow patterns, as they increase hydraulic residence time and alter the flow of DOM downstream. During storms when the majority of DOM loading occurs, impoundments become less likely to hold DOM and will increase export of DOM downstream. In this study, we quantified DOM bioavailability and composition, carbon flux, and carbon dioxide (CO2) gas evasion in a ROR reservoir system at baseflow conditions and during a 1.5-year storm event. This study used a combination of high frequency spatial sensor data geotagged to GPS coordinates along the river to reservoir transition, and grab samples of surface water taken at two U.S. Geological Survey stream gauges and three additional sites. The landscape and shallow flow paths to ROR reservoir systems resulted in the export of both aromatic carbon and labile organic matter present within these waters, as water was mixed and exported downstream. Additionally, the reservoir was a net sink of DOC and BDOC flux, while also a source of DIC flux. Finally, CO2 evasion was magnified by high flow, with the reservoir changing from a sink to a source of CO2 to the atmosphere. ROR reservoirs may undergo "short-circuiting" during high flow, which alters DOM transformations and transport of carbon downstream. Our results provide critical insight on carbon dynamics in ROR reservoir systems and highlight the need to incorporate riverine DOM into carbon budgets, especially under variable flow conditions. / Master of Science / Recent studies have focused on dissolved organic matter (DOM) cycling through river corridors, as DOM provides energy to aquatic food webs and can be converted to carbon dioxide (CO₂) through microbial respiration. Few studies have explored DOM cycling in commonplace but understudied run-of-river (ROR) reservoir systems. ROR reservoirs are created by the implementation of a dam across a river channel and use the flow of the river to generate hydroelectric power. During storms, when the majority of DOM loading occurs, impoundments become less likely to hold DOM and will increase export of DOM downstream. In this study, we quantified DOM quality and composition, DOM transport, and carbon dioxide (CO₂) gas evasion in a ROR reservoir system at baseflow conditions and across a 1.5 year storm event. This study used a combination of high frequency spatial sensor data combined with GPS coordinates along the river to reservoir transition, and grab samples of surface water taken at two U.S. Geological Survey stream gauges and three additional sites. Results show that the landscape and shallow flow paths to ROR reservoir systems resulted in the export of both high and low quality carbon present within these waters, as water was mixed and exported downstream. Additionally, the reservoir was a net sink of DOM flux, retaining 40.7% of the total DOM loading for the storm event. Finally, CO₂ evasion was magnified by the storm event, with the reservoir changing from a sink to a source of CO₂ to the atmosphere. Our results provide critical insight on carbon dynamics in ROR reservoir systems and highlight the need to incorporate riverine DOM into carbon budgets, especially under variable flow conditions.

A new approach towards waste management in a mining environment is developed and applied. This dissertation specifically studies the storage and management of tailings in the platinum industry as well as the associated environmental impacts. The product is an alteration of conventional tailings storage methodologies, to a sustainable design strategy in order to minimise environmental impact and optimise social and natural conditions. Factors influencing Tailings Disposal Facility design is: geo-technical stability, public safety, economic considerations, visual impact, water, soil and air pollution, local social context and end land use goals. Each are discussed from an environmental and social impact point of view in order to arrive at a sustainable landform (Tailings Disposal Facility) design. / Dissertation (ML (Prof))--University of Pretoria, 2006. / Architecture / unrestricted