Browsing by Subject "Water resources"

In this work, we offer readers the ability to numerically simulate flow through a sudden expansion themselves. We choose to study the sudden expansion due to its prevalence in engineered and natural water distribution networks (i.e., pipes and rivers, respectively). The simulation is written in the Wolfram Language, also known as Mathematica. The symbolic nature of this programming language enables readers to implement physical theory directly, resulting in a highly readable numerical flow solver; a stark contrast with commonplace commercial flow solvers, which operate like “black box” technologies, and low-level programming languages, which require an advanced level of syntax knowledge and programming proficiency. Upon completion of this laboratory exercise, users should be able to: (i) describe the main principles underpinning the numerical simulation of non-linear models, (ii) apply numerical models to investigate the accuracy of simplified analytical models, (iii) demonstrate a beginner-level understanding of Mathematica and, more broadly, symbolic coding environments, (ii) and most generally, (iv) understand the proper context for physical and numerical experimentation. The novelty of this work is attributed to the fact that no such simulation tool is detailed and provided in the literature for readers to utilize and alter at their discretion.

This work was developed and undertaken in collaboration with my co-authors, Dr. Anil Ganti (A.G.), and Dr. Zbigniew Kabala (Z.J.K), my master’s advisor. Author contributions are as follows: conceptualization, Z.J.K.; methodology, A.H.F, A.G. and Z.J.K.; software, A.H.F and A.G.; validation, A.H.F, A.G. and Z.J.K.; formal analysis, A.H.F; investigation, A.H.F, A.G. and Z.J.K.; resources, Z.J.K; data curation, A.H.F, A.G. and Z.J.K.; writing—original draft preparation, A.H.F and Z.J.K.; writing—review and editing, A.H.F, A.G. and Z.J.K.; visualization, A.H.F.; supervision, Z.J.K.; project administration, A.H.F and Z.J.K.

Partial funding for this project has been received from Duke University Undergraduate Program Enhancement Fund (UPEF) grant 399-000226.

Fossil fuels continue to be a major component of the energy economies in North America, accounting for 60% of electricity generation in the U.S. Recent incidences (i.e. spills) and limited regulation of the fossil fuel industry has generated public concern about the risks fossil fuel development pose to water resources. Previous studies have identified negative impacts on water quality associated with the storage and disposal of coal combustion residuals, oil sands process-affected water, and oil and gas wastewater, as well as leaking of methane to groundwater in areas of hydraulic fracturing. In addition, contamination of water resources from natural (geogenic) sources has also been observed in many of the areas associated with fossil fuel development. Since naturally occurring saline water is common in some regions associated with fossil fuel explorations, delineating the effects of anthropogenic contamination sources is a major challenge for evaluating the impact of fossil fuel development on water quality.

This thesis investigates the geochemical and isotopic characteristics of wastewater from coal combustion residual storage ponds, unconventional oil and gas exploration, and oil sands mining, in an attempt to evaluate the use of geochemical and isotopic tracers to identify fossil fuel-associated wastewaters in the environment. This includes the investigation of (1) halogen (Br, I) and ammonium contents of oil and gas wastewater (OGW);(2) the lithium isotope ratios in OGW and coal combustion residuals; and (3) the inorganic geochemistry and boron, strontium and lithium isotope ratios of oil sands processed-affected water (OSPW). In three case studies, these geochemical and isotopic tools were integrated into comprehensive geochemical frameworks that investigated the (1) leaking of coal ash ponds to surface and groundwater in the southeastern United Sates; (2) geochemistry of groundwater in an area of shale gas development in West Virginia through time and space; and (3) evaluation of the sources of molybdenum in contaminated groundwater in southeastern

Wisconsin and possible links to coal ash surface disposal. These investigations illustrate a range of situations in which isotopic fingerprinting provided a unique geochemical tool that can successfully identify fossil fuel-related wastewater in the environment. These studies have also demonstrated the environmental impact upon releasing of fossil fuels wastewater to the environment. The case studies support the use of geochemical and isotope tools as robust methods to not only identify contamination of water resources by fossil fuel-related activities, but also to distinguish wastewater contamination from naturally occurring contamination in areas of fossil fuel development. These studies highlight the benefit of using a suite of geochemical tools when investigating water quality impacts.

Periods of drought and low streamflow can have profound impacts on both human and natural systems. People depend on a reliable source of water for numerous reasons including potable water supply and to produce economic value through agriculture or energy production. Aquatic ecosystems depend on water in addition to the economic benefits they provide to society through ecosystem services. Given that periods of low streamflow may become more extreme and frequent in the future, it is important to study the factors that control water availability during these times. In the absence of precipitation the slower hydrological response of groundwater systems will play an amplified role in water supply. Understanding the variability of the fraction of streamflow contribution from baseflow or groundwater during periods of drought provides insight into what future water availability may look like and how it can best be managed. The Mills River Basin in North Carolina is chosen as a case-study to test this understanding. First, obtaining a physically meaningful estimation of baseflow from USGS streamflow data via computerized hydrograph analysis techniques is carried out. Then applying a method of time series analysis including wavelet analysis can highlight signals of non-stationarity and evaluate the changes in variance required to better understand the natural variability of baseflow and low flows. In addition to natural variability, human influence must be taken into account in order to accurately assess how the combined system reacts to periods of low flow. Defining a combined demand that consists of both natural and human demand allows us to be more rigorous in assessing the level of sustainable use of a shared resource, in this case water. The analysis of baseflow variability can differ based on regional location and local hydrogeology, but it was found that baseflow varies from multiyear scales such as those associated with ENSO (3.5, 7 years) up to multi decadal time scales, but with most of the contributing variance coming from decadal or multiyear scales. It was also found that the behavior of baseflow and subsequently water availability depends a great deal on overall precipitation, the tracks of hurricanes or tropical storms and associated climate indices, as well as physiography and hydrogeology. Evaluating and utilizing the Duke Combined Hydrology Model (DCHM), reasonably accurate estimates of streamflow during periods of low flow were obtained in part due to the model’s ability to capture subsurface processes. Being able to accurately simulate streamflow levels and subsurface interactions during periods of drought can be very valuable to water suppliers, decision makers, and ultimately impact citizens. Knowledge of future droughts and periods of low flow in addition to tracking customer demand will allow for better management practices on the part of water suppliers such as knowing when they should withdraw more water during a surplus so that the level of stress on the system is minimized when there is not ample water supply.