Utilizing the analytical solution of the steady state sharp interface saltwater intrusion model in coastal aquifers, a multi-objective optimization formulation of pumping rates and well locations in a coastal aquifer is formulated to solve problems in water management practice. The proposed optimization problem uses progressive genetic algorithm technique and the method developed is applied to the previous work of Cheng et al. [2000]. Through this analysis, several other applications are provided to demonstrate the use of the model in practical applications. This work is the first to optimize pumping rates as well as well locations simultaneously in coastal aquifer management. Known the limitation of the analytical solution, the work is expanded to cover the physics of saltwater intrusion in a more realistic way. This is variable density flow in a variably saturated porous medium. In this method, mixing between two fluids such as saltwater and freshwater can be described and the porous medium is also expanded to cover saturated and unsaturated zones together. One of the objectives is to develop a three dimensional physical model, verify the model, and apply to various applications in coastal aquifers. The developed model, TechFlow, is used to investigate instability issues associated with the numerical solution of the Elder problem in the perspective that includes physical instability issues associated with density differences used in numerical solutions, sensitivity of the solution to idealization irregularity, and the importance of accurate estimation of the velocity field and its association to the grid density levels that is necessary to solve the problem accurately. Saltwater intrusion hydrodynamics in a beach under the influence of tidal effects is also investigated using TechFlow. Based on the results of TechFlow with the use of various boundary conditions for the transport equation, the saltwater intrusion hydrodynamics in a beach under the influence of tidal effects shows unique dynamics. These solutions are primarily affected by density differences, tidal effects on a mild slope, variably saturated porous medium and finite domain solution condition. TechFlow is also used to investigate saltwater upconing beneath pumping wells both two- and three-dimensional applications.

Saltwater intrusion due to global change is expected to have a detrimental effect on the biogeochemistry of tidal freshwater wetlands. Of particular concern is that fact that salinization can alter the role of these ecosystems in the global carbon cycling by causing shifts in microbial metabolism that alter greenhouse gas emissions and increase carbon mineralization rates. However, our understanding of how wetland microbial community dynamics will respond to saltwater intrusion is limited. To address this knowledge gap and increase our understanding of how microbial communities in tidal freshwater wetlands change over time (1, 3, 12, and 49 weeks) under elevated salinity conditions, an in situ soil transplant was conducted. Throughout the 49 weeks of saltwater exposure, salinity had no effect on soil quality (organic matter content and C:N ratio). In contrast, the concentration of porewater ion species (SO4-2, NO3-, and NH4+) considerably increased. The activity of hydrolytic enzymes, (ß-1,4-glucosidase and 1,4-ß-cellobiohydrolase) gradually decreased with prolonged exposure to saline conditions; by the final sampling event (49 weeks), activity was reduced by ~70% in comparison to the freshwater controls. Short term exposure to salinity (3 and 12 weeks) had a greater effect on phenol oxidase, decreasing activity by 10-20%. Saltwater exposure had an immediate (1 week) effect on potential rates of carbon mineralization; overall, carbon dioxide production doubled and methane production decreased by ~20-fold. These changes in gas production were correlated to increased salinity and to changes in the abundance of methanogens and sulfate reducing bacteria, suggesting a shift in the terminal step in organic matter degradation from methanogenesis to sulfate reduction. Principal component analysis revealed distinct changes in soil environmental conditions and carbon metabolism within weeks, but the response of the microbial community was slower (months to a year). Taken together, results from this study indicate that the response of tidal freshwater wetlands to salinization is driven by complex interactions of microbial related processes and environmental changes that are dependent on the duration of exposure. Assessing the impact of environmental perturbation on ecosystem function may be better achieved by complementary analysis of both microbial community structure and function.

Saltwater intrusion alters the natural salinity and phosphorus (P) gradients in the oligotrophic, freshwater wetlands located near coastlines of the Caribbean Basin with important consequences to the structure and function of key ecosystem components, including plants, soil microbes, and periphyton. Periphyton communities, particularly diatoms, are extremely sensitive to water quality changes and can serve as excellent bioindicators; however, little is known about their use in detecting novel rates of saltwater intrusion into coastal, freshwater wetlands. I examined the individual and combined effects of elevated salinity and P on periphyton functional processes and diatom composition by conducting transect surveys along salinity and P gradients in the southern Everglades, as well as through mesocosm studies in which salinity and P were experimental manipulated. I demonstrated that conductivity (a proxy for salinity) and P gradients drive spatial patterns in diatom assemblage structure in the southern Everglades and that these assemblages have relatively low conductivity (2 mS cm-1) and total P thresholds (82 µg g-1). These findings were supported by the experimental work which showed that monthly pulses of elevated salinity only ~1 ppt above ambient was sufficient to cause significant shifts in periphytic diatom assemblages along with reduced periphyton productivity, total carbon, and nutrient content. The addition of P to freshwater and salt-treated periphyton significantly elevated mat total P, underscoring the P-uptake efficiency of periphyton. Surprisingly, addition of P to freshwater periphyton did not elicit significant functional or compositional responses, although chlorophyll-aconcentrations and accumulation rates tended to be higher with P. Similar chlorophyll-atrends were observed for salt-treated mats with added P, but these mats also exhibited significantly higher gross primary productivity and net ecosystem productivity compared to all other treatments and a diatom assemblage distinct from any other treatment. This research provides new and valuable information regarding periphyton dynamics in response to changing water sources that will allow us to extend the use of periphyton, and their diatom assemblages, as tools for environmental assessments related to saltwater intrusion in the southern Everglades and other karstic, freshwater wetlands.

No description available.

In 2011, Texas experienced the worst drought in recorded history. This has escalated concerns regarding environmental flows needed to sustain freshwater and estuarine systems as human needs are addressed during drought periods. In this thesis, I analyze fish assemblages and water quality variables in order to observe the effects of drought in the lower Neches River below the saltwater barrier located upstream from Beaumont, Texas. Fish and water quality samples were taken during drought conditions during fall 2011 and summer 2012, after a season of rain. During fall 2011, sites surveyed above the barrier had lower salinity but similarly low dissolved oxygen (DO) levels compared with sites surveyed below the barrier. Salinity levels during fall 2011 were relatively high (reaching up to 15 ppt), whereas salinity during summer 2012 never rose above 1.5 ppt. For gillnet samples obtained during fall 2011, fish species richness was higher in December following a series of rain events than during drought conditions in October and November. Although fish species richness was similar between fall 2011 and summer 2012, species composition varied greatly. For seine samples obtained during summer 2012, species richness was higher during May and July (when the barrier was open) than during June and August (when the barrier was closed). Species richness was lowest for sites in closest proximity to a paper mill effluent discharge pipe located below the barrier. Also, species richness was higher at sites above the barrier than at sites below the barrier regardless of whether or not the barrier was closed. Multivariate statistical analyses of gillnet samples revealed a large amount of compositional overlap among fish assemblages, regardless of time period and location; however, analyses of seine samples revealed that fish assemblages above the barrier were different than those from samples obtained below the barrier and that fish assemblages varied based on time period. Results indicate that, during periods of low flow, water quality deteriorates in the Lower Neches River below the saltwater barrier. During these periods of environmental degradation, fish assemblages have reduced diversity and sensitive freshwater species decline in abundance, with some absent from survey samples.

Thesis (Ph. D.)--University of Massachusetts Amherst, 2002. / "September 2002." Includes bibliographical references (p. 199-207). Also available online in PDF format via the NOAA Coastal Services Center home page.

Thesis (M. Phil.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 115-120).

Thesis (doctoral)--Frei Universität Berlin, 2005. / "September 2005"--P. [2] of cover. Added thesis t.p. Includes bibliographical references (p. 93-99). Also available via the World Wide Web.

For this dissertation I studied phosphorus (P) sorption dynamics in the shallow groundwater of the southern Everglades. In particular, I examined how the ambient water type governs soluble reactive P (SRP) availability through adsorption/desorption reactions with the aquifer matrix. Chapter 2 investigated how P sorption dynamics of the mangrove root zone sediment are affected by high bicarbonate brackish groundwater compared to both fresh groundwater and saltwater. The results from chapter 2 show that the sediment exhibited exceptionally low sorption efficiency in the high bicarbonate brackish water, which would allow ambient water SRP concentration to be maintained at a higher level. Chapter 3 is a detailed analysis of how P sorption dynamics in two bedrock samples are affected by incremental increases in saltwater content in a freshwater-saltwater transition zone. The results of chapter 3 indicate that a sorption edge occurs at 3 mM Cl- concentration. In water exceeding this Cl- concentration, SRP would be expected to desorb from the bedrock due to a sharp decrease in sorption efficiency between the freshwater saltwater. These results suggest that SRP is active in the ion exchange front of saltwater intrusion, with a rapid increase in SRP availability expected at the leading edge of saltwater intrusion. A landward incursion of 3 mM Cl- concentration water would be expected to raise ambient SRP concentration along the affected aquifer zone, in turn increasing SRP availability in the ecosystem where the transitional waters discharge to the surface. Chapter 4 investigates the kinetics SRP release accompanying saltwater intrusion using a column of carbonate aquifer solids and alternating inflow between fresh groundwater and saltwater. The results show an immediate and high magnitude increase in SRP concentration when saltwater flows into the column. The combined results of this dissertation show that, in the southern Everglades and possibly other carbonate coastlines as well, water type strongly controls P sorption behavior of the sediment and bedrock, and may have a direct influence on the local ecology through increased P availability. A fundamental understanding of the abiotic exchange mechanisms between SRP and the aquifer solids can aid in the successful management and protection of this unique and important ecosystem.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22421号 / 工博第4682号 / 新制||工||1731(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 大津 宏康, 教授 三村 衛, 准教授 PIPATPONGSA Thirapong / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM