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Earth and Environmental Sciences

Permanent URI for this collectionhttps://uwspace.uwaterloo.ca/handle/10012/9943

This is the collection for the University of Waterloo's Department of Earth and Environmental Sciences.

Research outputs are organized by type (eg. Master Thesis, Article, Conference Paper).

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Browsing Earth and Environmental Sciences by Author "Brookfield, Andrea"

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Now showing 1 - 4 of 4
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    Assessing Sensitivity of Subsurface Mine-Dewatering Activities to Climate Change
    (University of Waterloo, 2023-09-01) Calvert, Adam; Brookfield, Andrea
    Underground mining activities require constant removal of groundwater from their void spaces to maintain dry and safely accessible excavations for ore extraction in a process known as dewatering. The nature and degree of dewatering activities is heavily dependent on the amount of groundwater that can reach the mined areas and, conversely, dewatering of mines has a significant effect on the regional groundwater flow in their vicinity. Furthermore, groundwater supply to mining areas may be linked to climatic conditions, connected surface water bodies and the geologic structures that link the surface and subsurface. Typically, fully saturated groundwater models are used in industry to simulate site conditions and to plan mine dewatering infrastructure. These models often take historical climate averages into account when determining recharge to groundwater from the surface, and they do not typically account for feedback between groundwater and surface water systems. While this has been sufficiently accurate in the past, it is expected that the progression of climate change will yield future estimates of groundwater recharge that differ significantly from historical averages. These changes may be captured more accurately with fully coupled methods of simulating groundwater and surface water simultaneously in areas with large surface water bodies overlying aquifers, or in locations where geologic structures provide significant preferential pathways between the surface and subsurface. Here, we explored the changes in predicted dewatering rates for a real mining property in Central Quebec when considering a typical, industry standard fully saturated groundwater model with historically averaged recharge and a fully integrated groundwater/surface water iii model that incorporates results from future climate scenarios. The two models were constructed, parameterized, and calibrated for a site in Central Quebec. Simulations of underground mine dewatering were run with both models, and the predicted dewatering rates from each model were compared. Simulation results demonstrated that the fully integrated groundwater/surface water model with future climate yielded an estimated rate of dewatering that was approximately 2% higher than that predicted by the fully saturated groundwater model with historical climate averages.
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    Guiding future research to support water management decisions in the Canadian Prairies using an integrated hydrologic model
    (University of Waterloo, 2024-08-22) Wilson, Hilary; Brookfield, Andrea; Andre, Unger; Stotler, Randy; Ferguson, Greg
    Groundwater is the main source of water for most people in the Canadian Prairies. As the Canadian Prairies are prone to droughts, the need for additional water supplies is expected to increase as more changes to the climate in this region occur. With climate change, an increase in temperature and precipitation are anticipated. While an increase in precipitation should lead to an increase in infiltration of precipitation into the groundwater systems, this is not necessarily the case. As the temperature increases, it is expected that the already high rate of evapotranspiration will increase, limiting the chance for water to infiltrate the subsurface. This leads to the need for water management plans, which requires an understanding of the hydrologic flow system in the area. Hydrologic models are commonly used to help support water management decisions; however, they are often not developed until after most of the data collection and interpretation is completed. The utility of a preliminary hydrologic model to guide data collection efforts is not often employed, despite the opportunity for significant insight into key processes and data gaps. The goal of this research is to develop a preliminary integrated hydrologic model of an aquifer in the Canadian Prairies to identify research and data gaps that limit the creation of water management plans. The model, created using HydroGeoSphere, is based on the Dalmeny aquifer in Saskatchewan. A base model representing steady state historic conditions was developed, and then three climate change scenarios were simulated and compared to the results of this base model. These climate change scenarios were chosen based on their prevalent use by the Government of Canada using Representative Concentration Pathways. The three climate change scenarios are representative of (1) a significant reduction in global emissions of greenhouse gases, (2) there is no change to the current projected increase in global greenhouse gas emissions, and (3) a significant increase in global greenhouse gas emissions. The results of the base model indicate that groundwater flow is driven by topography, and yet updated, high-resolution topographical data is not readily available, indicating a data gap. The results of the climate scenarios indicate an overall decrease in hydraulic head in the aquifer due to increased estimated evapotranspiration. Evapotranspiration in this region is complex, as annual potential evapotranspiration is greater than precipitation, and so higher temporal resolution evapotranspiration data is necessary to capture infiltration. The direction of flow in some portions of the aquifer also change, leading to one of the boundaries, which is along the South Saskatchewan River, to change from a gaining river in the base scenario, to a losing river in the climate change scenarios. The uncertainty along the river boundaries, particularly related to their connectedness to the aquifer and their temporal and spatial variability, are key data gaps that should be addressed. In summary, this work shows that the preliminary integrated hydrologic model results indicate that , in order to support a more accurate simulation to support water management, additional data is necessary to improve: 1) the resolution of the topographical information of the study site, 2) the available methods of estimating temporally appropriate evapotranspiration and, 3) the understanding of groundwater-surface water interactions along the rivers, particularly South Saskatchewan River. With these alterations, a more robust water management plan can be developed, that will protect the availability of groundwater in the study area. By developing a preliminary model with limited information, improvements to the model development of the study area can be pursued.
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    Integrated hydrologic model calibration under non-stationary climates
    (University of Waterloo, 2024-01-17) Song, Mohan; Brookfield, Andrea
    With global climate change, quantifying water availability for management under non-stationary conditions is, and will continue to be, a major challenge. When hydrologic models are calibrated to historic climatic conditions, they may lack the ability to simulate future extreme climates. This research quantified changes in model calibration under non-stationary climate conditions using the Harold L. Disney Training Center (HLDTC) site in Kentucky, USA for demonstration. An integrated hydrologic model of the site was developed using HydroGeoSphere (HGS) and was calibrated using PEST. Hydraulic conductivity (K), specific storage (Ss), and surface friction coefficient parameters were calibrated under four different climate scenarios based on two moderately-extreme precipitation events during the observation period: a. the entire observation record, including the two moderately-extreme precipitation events (base scenario), b. the entire observation record minus the short duration event (April 2017), c. the entire observation record minus the long duration event (February 2018), and d. the observation record without either event. The results demonstrate that the inclusion of observations from extreme precipitation events impact the calibration of the hydrologic model. The variations in K and Ss were the highest between scenarios of all the calibration parameters tested, while the ridge surface friction, topsoil hydraulic conductivity, or clayey sand specific storage remain unchanged. K has the greatest decrease in lateral K (x and y direction) of the clayey sand layers in Scenario D, and greatest increase in lateral K of fractured rock formation in Scenario C. This indicates the importance of lateral flow in the fractured rock during the shorter duration precipitation event. Ss changed in the fractured rock formation in Scenario B, indicating the importance of storage in the fractured rock during the longer duration precipitation event. The model constructed by this study can better capture shorter duration moderately-extreme precipitation events, demonstrated by a better match between observed and simulated hydraulic heads in Scenario C. The results also suggest that not only the presence or absence of these events informs model calibration, but the timing and duration of these events influences the parameters it informs.
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    Quantifying the Effects of Water Management Decisions on Streambank Stability
    (University of Waterloo, 2022-09-30) Wei, Quan; Brookfield, Andrea
    Streams continuously change due to natural processes and human activities, significantly affecting streambank erosion and stability. These changes cause severe environmental issues, including sedimentation of reservoirs, contamination of streams, loss of productive land, and damage to infrastructure. Many factors affect streambank erosion and stability, including hydrological conditions of the stream and streambank environment, which are often controlled by environmental structures and water management decisions. Much is known about hydrology and water management, as well as hydrology and streambank stability. However, there is still little research that considers the connection between water management and streambank stability. The objective of this work is to quantify how water management decisions, particularly reservoir operations, affect streambank stability. A module was developed to estimate streambank stability using a factor of safety approach and uses results from an established integrated hydrologic model to characterize hydrologic conditions. This module is validated and then demonstrated using model results from the Lower Republican River Basin in Kansas, USA. Results applied at the LRRB indicated that several water management decisions may negatively affect streambank stability by changing pore water pressure, the weight of the streambank soil, and the status of erosion.