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Planktonic algae are useful as indicators of water quality because their composition and distribution reflects environmental condition in lakes. Therefore, understanding their dynamics can aid certain water quality management goals. Lake Diefenbaker is a large mesotrophic reservoir in the Canadian Prairies. Approximately 98 % of its inflow is from the South Saskatchewan River. The composition and ecology of the phytoplankton community has not been reported comprehensively since the 1980s. This is a potential problem for a reservoir with multiple end users. Therefore, I collected epilimnetic whole water samples along its length from June to October in 2011 and in 2012. I examined the phytoplankton community and related their distribution to environmental factors. A total of 72 phytoplankton genera were observed with the chlorophytes having the highest number of genera (33). The increased nutrient load and non-algal turbidity associated with high inflow from the South Saskatchewan River may be related to the dominance of the cryptophytes and bacillariophytes (together constituting ~89 % of the total phytoplankton biomass). The cryptophytes were abundant during periods of high flow rates and thermal stratification whereas the bacillariophytes were abundant during cool, isothermal conditions. Lake Diefenbaker is characterized by numerous embayments. Some of these embayments are exposed to human activities including development (housing, golf courses, marinas) and livestock operations (e.g., cattle watering). These localized activities could increase the frequency or size of algal blooms that will adversely affect the water quality. Therefore, I compared the phytoplankton community composition from eight exposed embayments, four unexposed embayments and six main channel sites. Phytoplankton community compositions were not significantly different in exposed, unexposed embayments and main channel sites (P > 0.05). High flows may have overridden localized influence from embayments. Hence, similar environmental conditions were present in the embayments and main channel. Blooms of cyanobacteria are of concern because of the potential of some genera to produce cyanotoxins. I examined cyanobacteria in Lake Diefenbaker. Cyanobacterial biomass was low in Lake Diefenbaker (< 5 %). However, I observed some potential toxin and bloom-forming genera that may threaten the water quality under different environmental conditions in the future.

As the importance of natural gas as a resource increases, the importance of volumetric dry gas reservoirs with mobile water as the dominant gas reservoir types will also increase. This research developed an efficient, user-friendly simulation program specifically designed to model two-phase flow of gas and water in these reservoirs. Since fluid compression and viscous forces are the dominant parameters that control fluid movement in a dry gas reservoir, we used the Implicit Pressure and Explicit Saturation (IMPES) formulation of flow equations in which neither gravity nor capillary pressure terms are pertinent. Therefore, the IMPES approach showed greater stability for all cases considered in this work. The developed simulator is a Visual Basic Application (VBA) code for which the users can obsereve the results in a pertinent Microsoft Excel file. This program allows users to study the depletion behavior of volumetric dry gas reservoirs with mobile water as efficiently and accurately as is now possible in more expensive commercially available reservoir simulators. The program was validated by comparing the results with a well-recognized commercial reservoir simulator (CMG). The results of a battery of tests of this simulator matched very well with results of the commercial reservoir simulator for all tested schemes including different simulation plans; reservoir, grid and fluid data; and well configurations. The observed applicability of the program suggests when dealing with volumetric dry gas reservoirs with mobile water there is no need to employ more expensive commercial reservoir simulators, as the program can reliably be used for any simulation scheme of this case. Furthermore, the program can later be applied in a more robust reservoir simulator as the part that handles dry gas cases.

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Sedimentation rates for many Texas reservoirs may be skewed by overstated estimates of design capacity and assumptions perpetuated through subsequent volumetric surveys. Multi-frequency reservoir surveys offer the means by which we may improve existing reservoir data and validate historic sedimentation rate estimates. To demonstrate application of this technology and value of its data derivatives, a multi-year, multi-frequency acoustic survey of Granger Lake, located in Williamson County, Texas was undertaken. Objectives of the study were to use hydro-acoustic survey techniques to verify assumptions of original reservoir capacity, examine the general accuracy of previously derived sedimentation rate, and document conservation implementation effectiveness. The intended benefit of these pre and post-watershed conservation implementation project surveys was to provide a temporal snapshot of sediment flux. Specifically, these data would be used as a tool to quantitatively estimate project success or non-success in annual sediment delivery reduction to the reservoir. During the course of the Granger Lake Watershed Implementation project, Granger Lake lost on average 343 acre feet of water storage annually to watershed sediment contribution. Sediment profiling results indicate pre-impoundment design estimates were overstated, thus skewing subsequent sediment deliver estimates. Since the mid-1990's, an accelerating sedimentation trend is apparent. Conservation implementation is not plainly responsible for the decrease in sediment delivery, and in fact may be undetectable for the foreseeable future. The study illustrates the value of examining previously established reservoir sedimentation estimates and assumptions of reservoir life based on design capacity estimates and routine volumetric surveys. Insights from this research highlight the importance of validating historic reservoir survey data and significance regarding its use in quantifying historic and future conservation effects, or other reservoir sustaining strategies.

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Drawdown is the lowering of the water level, and can refer to the groundwater, or the level of a river. In this thesis it will generally refer to a river going from a high flow condition to a lower flow condition. The rate of drawdown is expressed as either the change in flow per unit time, or the change in stage per unit time. The later is of most importance in terms of bank stability. (For complete abstract open document)