Browsing by Author "Hodder, Kyle"

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Open Access
Analysis of Lakewater Isotopes in the Northern Great Plains: Insights From Long-Term Monitoring and Spatial Surveys
(Faculty of Graduate Studies and Research, University of Regina, 2018-10) Haig, Heather Ann; Leavitt, Peter; Wissel, Bjoern; Simpson, Gavin; Hodder, Kyle; Weger, Harold; Stadnyk, Tricia
General circulation models predict that the precipitation deficit of the Northern Great Plains (NGP) will become more pronounced in the future, and that human adaptation to future climate change will require a greater understanding prairie hydrology in order to maintain freshwater ecosystems. One method for disentangling hydrological complexities is to use stable isotopes of hydrogen and oxygen in water to measure the hydrological properties of lakes, including their water balance. In this thesis, I present a long-term (2003-2016), bi-weekly record of water isotopes during summer to assess the differences between instrumental and isotopic measures of hydrology, and determine the variability in lakewater isotopes at the sub-annual and interannual scales. Insights from this long-term record were then applied to a spatial survey of over 100 lakes to quantify the spatial diversity of hydrologic parameters in lakes of the Canadian NGP and investigate the relationship between catchment characteristics and water balance of individual basins. Overall, lake-specific ratios of evaporation to inflow (E/I, %) from direct measurements (mean (μ) = 15.0%, standard deviation (σ) = 20.7) agreed well with isotopic estimates using headwater basin models (μ = 15.3, σ =7.8). Isotope-instrument agreement was improved (μ =12.6 vs. 6.2%) when basin-specific isotope models that considered local connectivity to upstream water bodies were used in calculations. In my assessment of isotope variability, seasonal variation in water isotope values routinely exceeded that at annual scales and demonstrated rapid changes in water sources within a single season, particularly in systems with water residence times <1 year. Inter-annual variability was regulated mainly by large hydrological events that caused isotopic source waters to become more similar across the Qu’Appelle River watershed. A spatial survey of 100+ prairie lakes revealed that isotopic values of inflow to basins was more similar to that of rainfall (δI, μ = -13.5‰, σ = 2.0) than to snow, and further showed that the flow regimes of most lakes (71%) were categorized as open despite the scarcity of channelized surface inflows. Mean water yield 100.8 mm yr-1 (σ= 181.0) and runoff coefficients 22.1% (σ= 45.9) were elevated relative to average conditions in the region, suggesting that lakes were an important feature capturing water on the prairie landscape. Together, these three studies provided a comprehensive assessment of the hydrological status of lakes in the Canadian NGP, and can be used to inform future research and management projects.
Open Access
Assessment of the influence of Nonstationary Climate on Extreme Hydrology of Southwestern Canada
(Faculty of Graduate Studies and Research, University of Regina, 2020-01) Gurrapu, Sunil; Sauchyn, David; Hodder, Kyle; St. Jacques, Jeannine-Marie; Wu, Peng; Hardenbicker, Ulrike; Dery, Stephen Jacques
The demand for water supplies across southwestern Canada has increased substantially over the past century with growing population and economic activities. At the same time, the region’s resilience to the impacts of hydrological extremes, floods and droughts is challenged by the increasing frequency of these extreme events. In addition, increased winter temperatures over the past century have led to declines in winter snowpack and caused earlier snowmelt, leading in some years to a substantial shortage of water during late summer and fall seasons. This calls for a better understanding of the flood and drought characteristics in addition to the information on water availability for effective water management and to design infrastructure resilient to such extreme conditions. The objective of this thesis is to examine the spatial and temporal variability of available water in the naturally flowing watersheds of southwestern Canada and evaluate various regional hydroclimatic and large-scale climatic indices in representing the regional hydrology and hydrological extremes. To do so, I first examined the empirical relationships between historically observed streamflow in 24 naturally flowing watersheds across southwestern Canada and the associated watershed’s hydroclimate, represented by the watershed averaged Standardised Precipitation Evapotranspiration Index (SPEI). The hydroclimate of all the selected watersheds is assumed to be represented by the second version of the NRCAN gridded climate dataset. These empirical relationships indicate that the water availability can be represented by the watershed averaged SPEI. I then developed SPEI-based principle component regression (PCR) equations and found them to be very efficient in representing the variability in historically observed monthly and annual streamflow. These equations are simpler to build than calibrating a numerical hydrological model S. Gurrapu, 2020 P a g e | iii and can be applied over large areas and many sub-basins with minimal data requirements to estimate streamflow. I then analysed the annual peak flows in 119 naturally flowing watersheds and 8 regulated watersheds, but with naturalized streamflow datasets, across southwestern Canada to examine the impact of the Pacific Decadal Oscillation (PDO) on annual flood risk. Using Spearman’s rank correlation ρ and permutation tests on quantile-quantile plots, I found that higher magnitude floods are more likely during the negative phase of the PDO than during the positive phase. In addition, the flood frequency analysis (FFA) stratified according to PDO phase suggests that higher magnitude floods may also occur more frequently during the negative PDO phase than during the positive phase. These results question the validity of the stationarity assumption made in FFA and suggest that the knowledge of large-scale climate state should be considered prior to the design and construction of key infrastructure. The results indicate that the stationarity assumption is not tenable in the watersheds of southwestern Canada. To demonstrate the invalidity of the stationarity assumption, I evaluated the variability in drought characteristics, i.e. severity, duration and frequency as applied to the City of Calgary, as a case study. The drought characteristics are defined by the historic (100 years of observed) and prehistoric (900 years of stochastically generated from tree-ring reconstructions of annual streamflow) weekly streamflow datasets. The results indicate that the severity and duration of hydrological drought with the same frequency is substantially larger and longer in the prehistoric period than that observed over the historical period. The results also indicate that varying lengths of data used in determining characteristics of extreme events produce varying results, which indicate that the stationarity assumption could be deceptive. Overall, the results demonstrate the implications of the non-stationary climate. in the analysis of hydrological extremes.
Open Access
Cartographic visualization of Saskatchewan’s population using dasymetric mapping.
(Faculty of Graduate Studies and Research, University of Regina, 2012-07) Krahnen, Anne; Siemer, Julia; Widdis, Randy; Piwowar, Joseph; Hodder, Kyle; Wheate, Roger
Maps of population density are commonly displayed using the choropleth method. Although choropleth maps are popular in mapping population density, strictly speaking, they are often incorrect due to non-conforming boundaries of populated places and administrative areas. This thesis looks at the dasymetric concept as an alternative to the choropleth map and investigates how it can be applied to display Saskatchewan’s population. Using ancillary data, the dasymetric method can redistribute statistical population data exclusively to areas identified as populated. As a basis for the research, 12 existing dasymetric methods were reviewed and evaluated for their applicability to Saskatchewan. Based on this evaluation, three methods (Binary Method, Intelligent Dasymetric Method and the Chinese Population Distribution Model) were selected and applied to a test area (Saskatchewan’s Census Division 6). It was assumed that the test area’s geographical attributes were representative for the province. The ancillary dataset used for the dasymetric mapping was chosen based on the results of regression analysis. Different file formats (raster and vector) were considered when producing the dasymetric maps. It was observed that, due to the regular sizes of raster cells, dasymetric maps using raster data are generally more accurate than dasymetric maps using vector data. In the mapping process, 88 dasymetric maps were produced for the test area. All maps were evaluated subjectively (visually), as well as quantitatively by calculating the variations from population densities of Dissemination Blocks (the most accurate population data available for this project) using the Mean Absolute Error. In both analyses, the binary method using raster data was determined to be the method producing the most accurate maps for the test area. Based on the results, three dasymetric maps were produced for the Province of Saskatchewan. The binary method using raster data was applied at three different resolutions (250m, 1,125m and 2,500 m). The resulting maps were therefore optimized for three different scales (1:5,000; 1:2,250,000 and 1:5,000,000). Keywords: Cartography; GIS; Population Maps; Dasymetric Concept; Binary Method; Intelligent Dasymetric Method; Chinese Population Distribution Model; Mean Absolute Error; Saskatchewan
Open Access
Community service-learning in the Faculty of Arts: an evaluation of the Arts CARES 2009 program final report
(2009-10-19T17:50:50Z) Hansen, Yolanda; Hodder, Kyle
This is the final report of the CRU's evaluation of the Arts CARES 2009 program.
Open Access
Community service-learning in the Faculty of Arts: an evaluation of the Arts CARES 2009 program summary report
(2009-10-19T17:50:39Z) Hansen, Yolanda; Hodder, Kyle
This report presents the summary findings of the evaluation of Arts CARES 2009, an intensive community service-learning program in the Faculty of Arts.
Open Access
Comparison of isotopic mass balance and instrumental techniques as estimates of basin hydrology in seven connected lakes over 12 years
(Elsevier, 2019-11-22) Haig, Heather A.; Hayes, Nicole M.; Simpson, Gavin L.; Yi, Y.; Wissel, Bjoern; Hodder, Kyle; Leavitt, Peter R
Mass-balance models using stable isotopes of hydrogen and oxygen provide useful estimates of the water balance of lakes, particularly in the absence of instrumental data. However, isotopic mass balances are rarely compared directly to measured water fluxes. Here we compared instrumental and isotope-based determinations of water fluxes in seven connected lakes over 12 years to quantify how agreement between the two approaches is affected by lake type and its position in the landscape. Overall, lake-specific ratios of evaporation to inflow (E/I) from instrumental measurements (median, x̃ = 0.06, median absolute deviation, MAD = 0.06) agreed well with isotopic estimates using headwater models (x̃ = 0.14, MAD = 0.08), with the exception of one lake with limited channelized inflow of surface waters (x̃ instrumental = 0.51 vs. x̃ headwater = 0.24). Isotope-instrument agreement improved (x̃ = 0.09 vs. x̃ = 0.03) when basin-specific (‘best-fit’) isotope models also considered local con- nectivity to upstream water bodies. Comparison among years revealed that mean isotopic E/I values were lowest in 2011 (mean, μ = 0.06, standard deviation, σ = 0.09) during a 1-in-140 year spring flood, and highest during a relatively arid year, 2003 (μ = 0.22, σ = 0.19), while interannual variability in E/I generally increased with distance downstream along the mainstem of the watershed. Similar patterns of agreement between methods were recorded for water-residence time. Isotope models also documented the expected low water yield from lake catchments (μ = 36.2 mm yr−1 , σ = 62.3) suggesting that isotope models based on late-summer samples integrate annual inputs from various sources that are difficult to measure with conventional methods. Overall, the strong positive agreement between methods confirms that water isotopes can provide substantial insights into landscape patterns of lake hydrology, even in ungauged systems.
Open Access
Dynamics of River-Sediment Delivery and Turbidity Current Flow Observed in Lillooet Lake, British Columbia
(Faculty of Graduate Studies and Research, University of Regina, 2019-04) MacDonald, Duncan Shayne; Hodder, Kyle; Hardenbicker, Ulrike; Velez-Caicedo, Maria; Marker, Michael
A study linking sediment-discharge dynamics and lake-bottom properties to plunging river flow was undertaken at Lillooet Lake, British Columbia. This study was initiated to understand the dynamics of turbidity currents that plunge off the front of the Lillooet-Green River delta and how those factors have an influence on turbidity current development. Understanding how turbidity currents behave is important to understanding the sedimentary budget and hydrology of lakes and reservoirs. To achieve the objectives of understanding how sediment-discharge dynamics and lake-bottom properties influence the development of turbidity currents in Lillooet Lake, field monitoring was undertaken for 10 days in July 2015. Field monitoring consisted of monitoring river stage (discharge), river temperature, and suspended sediment concentration as well as monitoring lake currents using an aDcp and a moored lake-temperature array. Water profiles were taken along the front of the delta. Changes to the subaqueous delta were monitored using single-beam sonar and the surface of the delta was monitored using an Unmanned Aerial Vehicle. During this study, record-low discharge and lake levels were encountered which had a detrimental effect on monitoring flow properties. The resultant analysis provided several key observations based on the data collected during this study, given these conditions. (1) The fluvial sediment-discharge relationship had negative hysteresis, possibly due to the decoupled nature of the sources of sediment and meltwater in Lillooet-Green River. (2) The lower boundary of turbidity current showed pulsating velocity through time, thought to be the result of shearing at the boundary between the current and ambient lake water. (3) A benthic trough was observed in front of the plunge line lobe that is believed to be a path for preferential flow as well as an eroded surface from turbidity currents originating from Lillooet-Green River delta. The findings indicate that even at low-flows the sediment laden water plunging off the Lillooet-Green River delta can produce interflows and underflows described as turbidity currents. Plunging water appears to be more dynamic than has previously been shown which is illustrated by the gradient of water velocity and changes to the delta slopes of Lillooet-Green River delta.
Open Access
Effects of seasonal and interannual variability in water isotopes (δ2H, δ18O) on estimates of water balance in a chain of seven prairie lakes
(Elsevier, 2020-12-10) Haig, Heather A.; Hayes, Nicole M.; Simpson, Gavin L.; Yi, Y.; Wissel, Bjoern; Hodder, Kyle; Leavitt, Peter R
Stable isotopes of hydrogen (δ2H) and oxygen (δ18O) provide important quantitative measures of lake hydrology and water balance, particularly in lakes where monitoring of fluxes is incomplete. However, little is known of the relative effects of seasonal variation in water isotopes on estimates of lake hydrology, particularly over decadal scales. To address this gap, we measured water isotopes bi-weekly May-September during 2003–2016 in seven riverine lakes within the 52,000 km2 Qu’Appelle River drainage basin of the Canadian Prairies. Analyses revealed that within-year variation in δ18O values routinely exceeded that among years, reflecting rapid changes in water source, particularly in lakes with water residence times <1 year. Isotopic variation was greatest during spring following snowmelt, except in large deep lakes which exhibited limited differences among seasons or years. In contrast, large hydrological events (e.g., 1-in-140-year flood in 2011) homogenized isotopic values, even among riverine lakes separated by over 150 km, and exerted particularly strong legacy effects on large lakes. Overall, study lakes exhibited a strongly positive moisture balance (evaporation < inflow), despite regional precipitation deficits of 30 cm yr−1, with greater reliance on rainfall (vs. snow) and possibly evaporation in downstream lakes within more humid regions. We conclude that seasonal samples of water isotopes are required to characterize the hydrology of shallow lakes, or those with unknown reliance on snowmelt waters, as well as to better quantify lake susceptibility to climate variability.
Open Access
Investigation and Reconstructions of the Hydroclimatic Variability of the Souris River Basin
(Faculty of Graduate Studies and Research, University of Regina, 2012-02) Vanstone, Jessica Rae; Sauchyn, David; Piwowar, Joseph; Hodder, Kyle; Spence, Chris
growing dependence on surface water resources in the Prairie Provinces has resulted in an increasing vulnerability to hydrological drought. A serious risk from recent and projected climate warming in the Canadian Prairies is a shift in the amount and timing of streamflow. The Souris River Basin has, over the years, been plagued with problems associated with either inadequate water supplies and flooding, both of which affect the social and economic well being of the residents of the Souris River Basin. Managing for the greater range of hydrologic variability evident in proxy records versus gauged, hydrometric records can prepare water managers for adaptation to climate change. Fourteen (2 previously collected and 12 new) moisture sensitive tree-ring sites were chosen and 37 chronologies (annual, earlywood, and latewood) were developed and used to create robust multi-proxy reconstructions of annual water year (October – September) and summer (June – August) streamflow for four gauges within the Souris River Basin. Multiple linear regressions were able to account for ~54-76% and ~38-67% of the instrumental variance for water-year and summer flows, respectively, extending the historical record as far back as 1726, for a total of 280 years. Hydrological extremes were quantified and classified as abnormally wet years being in the 75th percentile, while discharge in the lowest 25th percentile were considered as drought years, with the most severe episodes indicated by flows in the lowest 10th percentile. Water year flows indicate that the most severe low flow events took place in the late 1810s, mid 1830s, 1860s, late 1890s to early 1900s, and again in the mid 1950s. Streamflow reconstructions for the Souris Basin capture the low flow events occurring during the late 1880s through the 1890s (the „Great Die-Up‟); as well as another event known as one of the most severe and long lasting reconstructed droughts from 1841 through 1865, the drought of the late 1790s through the early 1800s, and the occurrence of „El Año del Hambre‟ – the year of hunger, during the late 1780s , as well as during the 12 year period from the 1750s to early 1760s. Spectral analyses provide evidence that streamflow variability in the Souris River Basin is driven by a combination of interannual (~2-6 year), interdecadal (~7-11 year), and multidecadal (~20-30 year) ocean-atmosphere oscillations, such as indices of ENSO, solar sunspot cycles, and PDO, respectively. Correlation analyses, cross-wavelet transforms and wavelet transform coherence identify significant periods of high common power and coherence of high, interdecadal, and low frequency oscillation relationships of streamflow with ENSO, solar sunspot cycles, and PDO indices, respectively. When these sea-surface temperatures and atmospheric oscillations are coupled, and in-phase with each other, it may lead to more prolonged and possibly greater in magnitude extremes than when climate anomalies are out of phase, resulting in a relatively modest influence of streamflow variability.
Open Access
Irrigation Water Requirements under Climate Change and Drought Events in Saskatchewan,
(Faculty of Graduate Studies and Research, University of Regina, 2015-03) Kraemer, Evan Matthew; Hodder, Kyle; McMartin, Dena; St. Jacques, Jeannine-Marie; Ng, Kelvin Tsun Wai; Helgason, Warren
This research considers the effects of climate change projected by global climate models (GCMs) on irrigated agriculture and water supply in Saskatchewan using 27 different combinations of GCMs, special reports on emissions scenarios (SRES), and time periods (2020s, 2050s, 2080s). Future drought events are extracted from the scenarios using the Standardized Precipitation-Evapotranspiration Index (SPEI) to identify extremely dry conditions, and downscaled to create a daily time-series of temperature and precipitation. The CROPWAT agroclimatic model is used to calculate irrigation water requirements (IWR) under given conditions for two crops commonly grown in rotation, canola and dry beans. This process allows for analysis of current and future water demands for irrigated agriculture. Under future drought conditions, IWR changes are found to be from -10% to 20% relative to the 2001-02 drought event. The resulting water requirement from Lake Diefenbaker, including irrigation expansion to 200 000 ha, is up to 12% of annual supply volume for irrigation.
Open Access
Monitoring Water Quality of an Urban Waterfowl Sanctuary
(University of Regina Graduate Students' Association, 2011-04-02) Mertler, J.A.; Hodder, Kyle
The evaluation of physical parameters of water is crucial to determining the overall health of an aquatic eco-system. This study investigated the impact of a concentrated population of waterfowl on water quality in a controlled system of small, shallow, macrophyte-rich ponds situated in urban parkland in the city of Regina. The ponds are ideal for this assessment, as inflow and outflow are controlled, and proved useful in the assessment of potential human health risks associated with an urban waterfowl sanctuary. Water quality was assessed according to physical parameters, including pH, specific conductance (EC), temperature, and total dissolved solids (TDS). The measurement of these characteristics at the point of inflow was a direct indicator of water quality in the ponds’ main water source, a nearby urban lake. Extreme fluctuations in EC, basic-heavy pH, cool temperatures, and variable TDS levels indicated inflow of poor to variable quality. Outflow water quality was very different, and it appeared that waterfowl reduced pH, EC and TDS levels. The results have application in policy, planning, and programming decisions in urban parklands.
Open Access
Potential mercury methylation Rates in Prairie Wetland Sediment
(Faculty of Graduate Studies and Research, University of Regina, 2013-07) Hoggarth, Cameron Grant John; Hall, Britt; Mitchell, Carl; Cameron, Andrew; Hodder, Kyle
Neurotoxic methylmercury (MeHg) biomagnifies in food webs and may harm human and wildlife health. Methylmercury is produced by the methylation of mercury (Hg), primarily by sulphate reducing bacteria and iron reducing bacteria in anaerobic sediments of aquatic systems. Anthropogenic emissions of Hg may circulate globally in the atmosphere and have increased deposition of Hg to aquatic systems remote from the sources of Hg emissions. Deposited Hg adds to the pool of Hg available for methylation. Wetlands in particular have been identified as sites of elevated MeHg production because of the anaerobic nature of wetland sediments. North America’s prairie pothole region contains millions of wetlands which provide waterfowl breeding habitat, carbon storage, and groundwater recharge. Surface water methylmercury concentrations in some prairie wetlands are elevated, suggesting the potential for substantial production of MeHg within these wetlands. In summer 2011 sediment cores from wetlands in Saskatchewan’s St. Denis National Wildlife Area were injected with 201Hg and incubated within wetlands to measure the rate of formation of Me201Hg from the injected isotope. In addition to measuring potential rates of MeHg production, concentrations of MeHg and total mercury (THg) in sediment, porewater, and surface water were also measured along other sediment and surface water parameters. Potential rates of MeHg production and sediment MeHg and THg concentrations were similar to those observed in other remote freshwater wetlands. Sediment porosity was negatively correlated with MeHg production. Concentrations of MeHg in wetland surface water were positively correlated with concentrations of sediment MeHg and calculated MeHg diffusive flux was from porewater to the surface water in the majority of studied wetlands. This is the first study to report potential Hg methylation rates in wetlands from the prairie pothole region.
Open Access
The Prevalence of Bacteria-Sediment Associations and Their Effect on Sediment Settling Velocities in Aquatic Environments of Agricultural Saskatchewan and Alpine British Columbia
(Faculty of Graduate Studies and Research, University of Regina, 2014-01) Barrett, David Clem; Hodder, Kyle; Hardenbicker, Ulrike; McMartin, Dena; deBoer, Dirk
Bacteria-sediment associations (BSA) are the natural interactions between bacteria and sediment particles that influence both bacterial survival rates and properties of sediment particles. A newly developed method for quantifying BSA was applied to an agricultural watershed in southeastern Saskatchewan and an alpine watershed in the southern Coast Mountains of British Columbia. Both watersheds exhibited spatial and temporal trends of BSA. Impacts corresponding to land use and anthropogenic activity are also present. Development of a novel method for determining BSA allowed for samples taken from remote areas to be assessed. Membranes with 8 μm pore diameter separated planktonic organisms from sediment-associated organisms. The use of acridine orange fluorochrome and a fluorescence microscope allowed for all organisms to be viewed. Samples from the Pipestone Creek watershed in southeast Saskatchewan confirmed the presence of BSA within in-field runoff, and in Pipestone Creek. The percentage of bacteria associated with sediment range from 2% at in-field locations to a maximum of 70% in Pipestone Creek with samples from the creek having significantly higher BSA values than those from in-field locations. Results from the Pipestone Creek watershed show that winter bale grazing (WBG) of cattle, when compared to fall manure spreading (FMS) and a control of no manure spreading, leads to a larger export of total bacteria during spring snowmelt. The application of WBG also leads to an increase in sediment export and a decrease in mean particle diameter. In the Lillooet River watershed, BSA were also noted to be present at all sample locations with the percentage of bacteria associated with sediment ranging from 1% - 40% depending on time of day and location within the watershed. Decreased BSA was measured at locations associated with planktonic bacteria influx via intensive agricultural runoff and wastewater treatment. Laboratory experiments using a laser backscatter device reveal an increase in sediment settling velocity associated with increased bacteria concentrations. Particle-size distributions of the sediment vary with an increase in some size classes and a decrease in others. The changes in particle sizes and settling velocities are consistent with the process of flocculation occurring within the 23-hour sample duration. The results from this study provide insight into the impacts of BSA in contrasting environments through the application of a novel BSA quantification method. Furthermore, the documentation of the impact of BSA on the settling velocity of sediments provides a more holistic understanding of varved sediments and therefore better informs process-inference, leading to more holistic paleoenvironmental reconstructions.
Open Access
Regulation of carbon dioxide and methane in small agricultural reservoirs: optimizing potential for greenhouse gas uptake
(Copernicus Publications, 2019-11-08) Webb, Jackie; Leavitt, Peter R; Simpson, Gavin L.; Baulch, Helen M.; Haig, Heather A.; Hodder, Kyle; Finlay, Kerri
Small farm reservoirs are abundant in many agricultural regions across the globe and have the potential to be large contributing sources of carbon dioxide (CO2) and methane (CH4) to agricultural landscapes. Compared to natural ponds, these artificial waterbodies remain overlooked in both agricultural greenhouse gas (GHG) inventories and inland water global carbon (C) budgets. Improved understanding of the environmental controls of C emissions from farm reservoirs is required to address and manage their potential importance in agricultural GHG budgets. Here, we conducted a regional-scale survey (∼ 235 000 km2) to measure CO2 and CH4 surface concentrations and diffusive fluxes across 101 small farm reservoirs in Canada's largest agricultural area. A combination of abiotic, biotic, hydromorphologic, and landscape variables were modelled using generalized additive models (GAMs) to identify regulatory mechanisms. We found that CO2 concentration was estimated by a combination of internal metabolism and groundwater-derived alkalinity (66.5 % deviance explained), while multiple lines of evidence support a positive association between eutrophication and CH4 production (74.1 % deviance explained). Fluxes ranged from −21 to 466 and 0.14 to 92 mmol m−2 d−1 for CO2 and CH4, respectively, with CH4 contributing an average of 74 % of CO2-equivalent (CO2-e) emissions based on a 100-year radiative forcing. Approximately 8 % of farm reservoirs were found to be net CO2-e sinks. From our models, we show that the GHG impact of farm reservoirs can be greatly minimized with overall improvements in water quality and consideration to position and hydrology within the landscape.
Open Access
Seasonal Impacts and Regulation of Nitrogen Pollution in the Northern Great Plains Insights from Microcosm, Mesocosm, and Mensurative Scale Studies
(Faculty of Graduate Studies and Research, University of Regina, 2017-11) Swarbrick, Vanessa Jacqueline Anna-Maria; Leavitt, Peter; Yost, Christopher; Wissell, Bjoern; Hodder, Kyle; Jackson, Leland
The value of controlling nitrogen (N) and its impact on water quality are frequently contested, partly due to inconsistencies in the effects of N pollution depending on the form, amount, and seasonal conditions in which it is released to freshwater ecosystems. This thesis aims to shed light on some of those differential effects, and advance our understanding of the seasonal variation in the impacts and drivers of N pollution to prairie lentic and lotic environments. In my first chapter, I evaluate the seasonal and differential effects (i.e., suppression vs stimulation) of NH4 + on phytoplankton abundance, using 16 years of nutrient bioassay experiments, conducted bi-weekly during the open water season. Phytoplankton biomass was significantly affected by NH4 + amendment in 44.8% of the experiments, and generalized additive models (GAMs) demonstrated that the the seasonal patterns of phytoplankton response showed a marked rise in the occurrence of both spring suppression and summer stimulation over the study period. Binomial logit GAMs demonstrated that the likelihood of NH4 + suppression of phytoplankton growth increased with abundance of siliceous algae, cryptophytes, and unicellular cyanobacteria, when water temperatures and soluble reactive phosphorus (SRP) concentrations were low, while stimulation of phytoplankton growth was more likely when chlorophytes and non- N2-fixing cyanobacteria were abundant, and temperatures and SRP concentrations were high. In my second chapter, I present the results of a series of 22 factorial urea and phosphorus (P) fertilization experiments, conducted monthly from ice-off to ice-formation in 3000-L mesocosms. These mesocosm experiments were also run in tandem with NH4+ bioassays to compare the seasonal effects of urea pollution with those of NH4+. Results showed that addition of P alone had no significant impact on either phytoplankton abundance or community composition, but that urea, alone or concert with P, consistently increased abundance of cryptophytes, chlorophytes, and non-diazotrophic cyanobacteria in spring, and abundances of chlorophytes and non-diazotrophic cyanobacteria in the summer and early fall. Comparison of urea mesocosms with NH4 + bioassays demonstrated that urea lacked the inherent toxicity of NH4 + in cool waters. In my final chapter, I identify the temporal and spatial patterns in urea export along a 250-km lotic continuum in the NGP, using three years of data collected bi-weekly from May-September, and investigate the hydrologic, land use, and instream drivers of urea concentration. I found that urea concentrations were elevated compared to previously studied lentic systems in this region, and ranged from 5.2 – 792.1 μg N L-1. Significant differences in longitudinal patterns of urea concentration emerged over the course of the open water period (F(6, 290) = 8.183, p < 0.001), and were mediated by interactions between hydrology, land use inputs, and internal processing. Contrary to expectations, I detected no significant effect of wastewater effluent discharge on instream urea concentrations during low and moderate discharge rates. Instead, average porewater urea concentrations 􁈺􀝔̅ = 528.5 μg N L-1, SD = 229.8 μg N L-1) were over five times higher than instream concentrations, emphasizing the importance of hyporheic sources. Together, these three studies provide a comprehensive assessment of how the risk of N pollution to water quality in the NGP varies across the open water season, and informs a series of recommendations, provided in Chapter 5, for future water quality management.
Open Access
Stream Flow Simulation of a Canadian Prairie Watershed: Assessment of the Impact of Wetland Drainage and Climate Change on the Hydrology of the Pipestone Creek, Saskatchewan
(Faculty of Graduate Studies and Research, University of Regina, 2016-09) Perez-Valdivia, Cesar; McMartin, Dena; Jin, Yee-Chung; Sauchyn, David; Hodder, Kyle; Wu, Kangsheng; Kienzle, Stefan
Within the scope of Watershed Evaluation of Beneficial Management Practices project in Saskatchewan, the Soil Water Assessment Tool model has been calibrated and validated at daily and monthly time steps for a watershed within the Prairie Pothole region of North America. The model uses the concepts of the hydrological equivalent wetland, limited weather data, and the gross and effective drainage areas introduced in the 1950s to simulate flows at one streamflow gauge in a 2,242 km2 watershed. The Sequential Uncertainty Fitting algorithm version 2 was used to calibrate and validate the model at daily and monthly time steps for the period 1997-2005 and 2005-2009, respectively. The model performs well capturing the magnitude and timing of the peaks during spring runoff. Annual volumes during the calibration period are well represented by the model at monthly time steps, although the performance of the model decreases during the validation period (2002-2005) which is represented by lower statistics. The successful calibration and validation of the model make possible the assessment of the impact of wetland drainage and climate change on the hydrology of the Pipestone Creek Watershed. The impact of wetland drainage on hydrology is evaluated by creating three different drainage scenarios which account for a drainage of 15% (Scenario 1), 30% (Scenario 2), and 50% (Scenario 3) of the non-contributing area. Results of these simulations suggest that drainage increases spring peak flows by 50%, 79%, and 113% for scenarios 1, 2, and 3, respectively, while annual flow volumes are increased by 43%, 68%, and 98% in each scenario. Years wetter than normal present an increase of peak flows and annual flow volumes of less than the average of the simulated period. Alternatively, summer peak flows present the smaller increase in terms of percentage during the simulated period. In addition, five Global Circulation Models (GCMs) and three climate change scenarios are used to drive the calibrated model and assess the impacts of climate change for the period 2031-2060. Overall, the models agree, estimating an earlier spring runoff, higher spring flow volumes and soil water content. Actual evapotranspiration is expected to increase during spring and decrease during fall, while there is little anticipated change in summer actual evapotranspiration rates. The projections of streamflow and soil water content are more uncertain during the summer and fall seasons due to the wider range of change forecasted.
Open Access
Using a network of core samples to explore hydroclimatic proxy relationships within the sediments of an alpine, glacier-fed lake
(Copernicus Publications, 2015) Hodder, Kyle; Suchan, Jared
The attached file is the open access abstract from (Geophysical Research Abstracts, Vol. 17, EGU2015-7224, 2015, EGU General Assembly 2015, © Author(s) 2015. Published by Copernicus Publications. This is open access abstract is available under the Creative Commons Attribution 3.0 License (CC BY 3.0) license (https://creativecommons.org/licenses/by/3.0/). This abstract is available at https://meetingorganizer.copernicus.org/EGU2015/EGU2015-7224.pdf.