Despite decades of research, the water quality of many lakes is impaired by excess total phosphorus loading. Four studies were undertaken using watershed models to understand the temporal and spatial variability of diffuse urban and agricultural total phosphorus pollution to Hamilton Harbour, Ontario, Canada. In the first study, a novel Bayesian framework was introduced to apply Spatially Referenced Regressions on Watershed Attributes (SPARROW) to catchments with few long term load monitoring sites but many sporadic monitoring sites. The results included reasonable estimates of whole-basin total phosphorus load and recommendations to optimize future monitoring. In the second study, the static SPARROW model was extended to allow annual time series estimates of watershed loads and the attendant source-sink processes. Results suggest that total phosphorus loads and source areas vary significantly at annual timescales. Further, the total phosphorus export rate of agricultural areas was estimated to be nearly twice that of urban areas. The third study presents a novel Bayesian framework that postulates that the watershed response to precipitation occurs in distinct states, which in turn are characterized by different model parameterizations. This framework is applied to Soil-Water Assessment Tool (SWAT) models of an urban creek (Redhill Creek) and an agricultural creek (Grindstone Creek) near Hamilton. The results suggest that during the limnological growing season (May – September), urban areas are responsible for the bulk of overland flow in both Creeks: In Redhill Creek, between 90% and 98% of all surface runoff, and in Grindstone Creek, between 95% and 99% of all surface runoff. In the fourth chapter, suspended sediment is used as a surrogate for total phosphorus. Despite disagreements regarding sediment source apportionment between three model applications, Bayesian model averaging allows an unambiguous identification of urban land uses as the main source of suspended sediments during the growing season. Taken together, these results suggest that multiple models must be used to arrive at a comprehensive understanding of total phosphorus loading. Further, while urban land uses may not be the primary source of sediment (and total phosphorus) loading annually, their source strength is increased relative to agricultural land uses during the growing season.

Despite decades of research, the water quality of many lakes is impaired by excess total phosphorus loading. Four studies were undertaken using watershed models to understand the temporal and spatial variability of diffuse urban and agricultural total phosphorus pollution to Hamilton Harbour, Ontario, Canada. In the first study, a novel Bayesian framework was introduced to apply Spatially Referenced Regressions on Watershed Attributes (SPARROW) to catchments with few long term load monitoring sites but many sporadic monitoring sites. The results included reasonable estimates of whole-basin total phosphorus load and recommendations to optimize future monitoring. In the second study, the static SPARROW model was extended to allow annual time series estimates of watershed loads and the attendant source-sink processes. Results suggest that total phosphorus loads and source areas vary significantly at annual timescales. Further, the total phosphorus export rate of agricultural areas was estimated to be nearly twice that of urban areas. The third study presents a novel Bayesian framework that postulates that the watershed response to precipitation occurs in distinct states, which in turn are characterized by different model parameterizations. This framework is applied to Soil-Water Assessment Tool (SWAT) models of an urban creek (Redhill Creek) and an agricultural creek (Grindstone Creek) near Hamilton. The results suggest that during the limnological growing season (May – September), urban areas are responsible for the bulk of overland flow in both Creeks: In Redhill Creek, between 90% and 98% of all surface runoff, and in Grindstone Creek, between 95% and 99% of all surface runoff. In the fourth chapter, suspended sediment is used as a surrogate for total phosphorus. Despite disagreements regarding sediment source apportionment between three model applications, Bayesian model averaging allows an unambiguous identification of urban land uses as the main source of suspended sediments during the growing season. Taken together, these results suggest that multiple models must be used to arrive at a comprehensive understanding of total phosphorus loading. Further, while urban land uses may not be the primary source of sediment (and total phosphorus) loading annually, their source strength is increased relative to agricultural land uses during the growing season.

Mercury (Hg)-contaminated freshwater fisheries are a global toxicological concern. Previous research suggests that the slow release of Hg in runoff from upland soils may delay the recovery of Hg-contaminated aquatic systems. Four complementary studies were undertaken in a small boreal Shield headwater catchment as part of the Mercury Experiment to Assess Atmospheric Loading in Canada and the U.S. (METAALICUS) to assess the controls on the retention and release of historically-deposited Hg (ambient Hg) and newly-deposited (spike Hg) in the soil landscape. In the first study, hydrometric and GIS-based methods were used to quantify thresholds in terrestrial water storage and their relationship to observed rainfall-runoff response. It was found that event-scale hydrologic response displayed a threshold relationship with antecedent storage in the terminal depression and predictions of event runoff improved when storage excesses from upslope depressions were explicitly routed through the catchment. In the second study, it was shown that the dominant source of ambient Hg to the lake was likely derived from shallow soil-water flowing through the lower, well-humified organic soil horizon. Throughout the catchment, ambient Hg to soil organic carbon (SOC) ratios increased with depth and the experimentally-applied spike Hg was concentrated in the surface litter layer, suggesting that the vertical redistribution of Hg in the soil profile is a function of the rate of decomposition of SOC. In the third study, canopy type was found to be a good predictor of ambient Hg and spike Hg stocks in the lower organic horizon, while drainage conditions were not, suggesting that vertical fluxes of Hg dominate over lateral fluxes in topographically-complex landscapes. Lastly, it was shown that catchment discharge, antecedent depression storage and antecedent precipitation were the best predictors of dissolved organic carbon (DOC), ambient Hg and spike Hg concentrations in catchment runoff. A comparison of DOC, ambient Hg and spike Hg dynamics for two storm events showed that distinct shifts occurred in the concentration-discharge relationship as a result of differences in antecedent moisture conditions. Combined, the results of the four studies demonstrate the need to incorporate hydrological, biogeochemical and landscape controls into predictive models of terrestrial-aquatic Hg export.

Mercury (Hg)-contaminated freshwater fisheries are a global toxicological concern. Previous research suggests that the slow release of Hg in runoff from upland soils may delay the recovery of Hg-contaminated aquatic systems. Four complementary studies were undertaken in a small boreal Shield headwater catchment as part of the Mercury Experiment to Assess Atmospheric Loading in Canada and the U.S. (METAALICUS) to assess the controls on the retention and release of historically-deposited Hg (ambient Hg) and newly-deposited (spike Hg) in the soil landscape. In the first study, hydrometric and GIS-based methods were used to quantify thresholds in terrestrial water storage and their relationship to observed rainfall-runoff response. It was found that event-scale hydrologic response displayed a threshold relationship with antecedent storage in the terminal depression and predictions of event runoff improved when storage excesses from upslope depressions were explicitly routed through the catchment. In the second study, it was shown that the dominant source of ambient Hg to the lake was likely derived from shallow soil-water flowing through the lower, well-humified organic soil horizon. Throughout the catchment, ambient Hg to soil organic carbon (SOC) ratios increased with depth and the experimentally-applied spike Hg was concentrated in the surface litter layer, suggesting that the vertical redistribution of Hg in the soil profile is a function of the rate of decomposition of SOC. In the third study, canopy type was found to be a good predictor of ambient Hg and spike Hg stocks in the lower organic horizon, while drainage conditions were not, suggesting that vertical fluxes of Hg dominate over lateral fluxes in topographically-complex landscapes. Lastly, it was shown that catchment discharge, antecedent depression storage and antecedent precipitation were the best predictors of dissolved organic carbon (DOC), ambient Hg and spike Hg concentrations in catchment runoff. A comparison of DOC, ambient Hg and spike Hg dynamics for two storm events showed that distinct shifts occurred in the concentration-discharge relationship as a result of differences in antecedent moisture conditions. Combined, the results of the four studies demonstrate the need to incorporate hydrological, biogeochemical and landscape controls into predictive models of terrestrial-aquatic Hg export.

Hydrologic modeling and streamflow prediction of ungauged basins is an unsolved scientific problem as well as a policy-relevant science theme emerging as a major challenge to the hydrologic community. One way to address this problem is to improve hydrologic modeling capability through the use of spatial data and spatially distributed physically based models. This dissertation is composed of three papers focused on 1) the use of spatially distributed hydrologic models with spatially distributed precipitation inputs, 2) advanced multi-objective calibration techniques that estimate parameter uncertainty and use stream gauge and temperature data from multiple locations, and 3) an examination of the relationship between high-resolution soils data and streamflow recession for use in a priori parameter estimation in ungauged catchments. This research contributes to the broad quest to reduce uncertainty in predictions at ungauged basins by integrating developments of innovative modeling techniques with analyses that advance our understanding of natural systems.

Master of Science / Department of Civil Engineering / David R. Steward / A one-dimensional model was developed to study the flow of groundwater in the sloping Ogallala Aquifer at a steady state during predevelopment condition. The sloping base was approximated using a stepping base model. GIS applications were applied during data collection and preparation, and later during interpretation of model results. Analytical and numerical methods were employed in the development of this model which was used to try to understand long-term water balance in the study region. The conservation of mass was achieved by balancing groundwater input, output, and storage; this led to understanding the interactions of groundwater and surface water in the predevelopment conditions. The study resulted in identification of where natural discharge from groundwater to surface water occurred, and the quantity of these flows was obtained. The Ogallala Aquifer is thick in the south western part of Kansas, this region had an average saturated thickness of 100m during predevelopment conditions. The model found that groundwater flowed at a discharge per width of approximately 17 m[superscript]2/d in this region. The aquifer thickness tends to gradually decrease from west to east and from south to north. The northern part had an average saturated thickness of 40m during predevelopment conditions; the model found that groundwater flowed at a discharge per width of approximately 3 m[superscript]2/d in this region. It was also found that groundwater leaves the Ogallala Aquifer on the eastern side with discharge per width between 0-3 m[superscript]2/d. The discharge from groundwater to surface water was summed over contributing areas to river basins. The discharge to streams necessary to satisfy long-term conservation of mass computed by the model showed that Cimarron River has total baseflow of about 5.5 m[superscript]3/s; this was found to be almost 100% of the total streamflow recorded during predevelopment conditions. The Arkansas River was found to have total baseflow of about 0.97 m[superscript]3/s, which is approximately 14.3% of the total streamflow recorded during predevelopment conditions. The Smoky Hill River was found to have total baseflow of about 1.7 m[superscript]3/s, which is approximately 73.9% of the total streamflow recorded during predevelopment conditions. The Solomon River was found to have total baseflow of about 0.95 m[superscript]3/s, which is approximately 41.1% of the total streamflow recorded during predevelopment conditions. The Saline River was found to have total baseflow of about 0.25 m[superscript]3/s, which is approximately 62.5% of the total streamflow recorded during predevelopment conditions. The Republican and Pawnee River was found to have total baseflow of about 0.38 m[superscript]3/s and 0.22 m[superscript]3/s, which is approximately 18.5% and 12.6% of the total streamflow in the predevelopment conditions respectively. The model was found to be always within -16 to +12 meters between observed values and the model results, with an average value of 0.15m and a root mean square error of 1.98m. Results from this study can be used to advance this study to the next level by making a transient model that could be used as a predictive tool for groundwater response to water use in the study region.

Master of Science / Department of Computing and Information Sciences / Mitchell L. Neilsen / The United States Department of Agriculture (USDA) is currently researching the effectiveness of various earth dam designs and their ability to prevent erosion. This report utilizes experimental results from the USDA experimental hydraulic engineering research unit to develop computational fluid dynamics models using OpenFOAM. Several variations of smooth and stepped dam models are created and analyzed with OpenFOAM on multiple cores using Message Passing Interface. In this report, seven dam designs are analyzed to extract flow velocities and pressures and animations. This data and OpenFOAM models are helpful for determining potential erosion conditions.

Doctor of Philosophy / Department of Geography / Melinda Daniels / Great Plains rivers are unique systems that vary from large, continental scale, to small intermittent streams with grain sizes that range from bedrock to cobbles to silt. These rivers have been subject to widespread hydrologic alteration both within the channel and the watershed, which has resulted in an alteration in their hydrologic and geomorphic regimes. Although there is an acknowledgement of this alteration, to date there has not been a synthesis of the hydrology of Great Plains rivers or of their longitudinal morphologies. Chapters in this dissertation provide, to my knowledge, the first comprehensive analyses of the hydrology and morphology of Great Plains rivers over a range of spatial and temporal scales. In the first study, I found that there was no uniform pattern of hydrologic alteration throughout the Great Plains, which is likely attributable to variable system-specific reservoir management objectives, land use changes, and climatic regimes over the large area the Great Plains encompass. Results of this study are the first to quantify the widespread hydrologic alteration of Great Plains rivers following impoundment. In the second study, I found an apparent decoupling between local moisture conditions and streamflow in intermittent prairie streams. Results of this study used statistical models to identify relationships between flow intermittence, mean annual flow, and flood flow characteristics with moisture to characterize flow in an intermittent prairie stream. In the final study, I found that the downstream trends in hydraulic geometry and substrate characteristics of the Ninnescah River were consistent with the expected trends proposed by hydraulic geometry and substrate theories. However, there were points that deviated from the expected trends, most notably where a substantially large tributary enters the Ninnescah River and as the Ninnescah River approaches the Arkansas River, and causal explanations for these deviations were explored. Results of this study are, to my knowledge, the first of its kind to assess the longitudinal hydraulic geometry and substrate characteristics of a large sand-bed river over a large spatial scale. To our knowledge, there have been no comparable studies exist that attempted to describe hydrologic and geomorphic characteristics of prairie streams.

Aquatic mercury (Hg) contamination caused by industrial Hg emissions, atmospheric transport and deposition to sensitive ecosystems is an ongoing concern in many parts of the world. Boreal ecosystems are particularly sensitive to Hg deposition, and large soil-Hg burdens in these regions may prolong recovery of Hg impacted surface waters for many decades. Four studies were undertaken to examine interactions between watershed characteristics, hydro-climatic variability and terrestrial-aquatic export of key chemical parameters linked to watershed Hg sensitivity. Two new quantitative techniques, hydrogeomorphic edge detection and characteristic morphology analysis, were developed to explicitly map and characterize the spatial distribution, geomorphic form and hydro-biogeochemical function of forested wetlands using airborne Light Detection and Ranging (LiDAR) surveys. The results demonstrate the critical contribution of forested wetlands and upland-wetland interactions to the production and mobilization of dissolved organic carbon (DOC) and methyl-mercury (MeHg) - respectively - to downstream surface waters. Results of strategic, event-based hydrochemical sampling also demonstrate the critical contribution of summer high-flow periods to terrestrial-aquatic MeHg export. Finally, an analysis of historical monitoring databases of streamflow volume, hydrochemistry and Hg concentrations in yearling perch in two contrasting headwater lake basins was conducted. The results indicate strong potential for short-term, hydrologically-driven shifts in terrestrial-aquatic coupling and watershed Hg sensitivity, but only for the wetland-dominated, humic lake that exhibited consistent, summertime hypolimnetic anoxia. These various findings suggest that accurate characterization of watershed structure can help researchers identify first-order limitations on whole-watershed methylation efficiency, particularly in relation to hydro-climatic drivers of terrestrial-aquatic coupling in Boreal headwater regions.

Aquatic mercury (Hg) contamination caused by industrial Hg emissions, atmospheric transport and deposition to sensitive ecosystems is an ongoing concern in many parts of the world. Boreal ecosystems are particularly sensitive to Hg deposition, and large soil-Hg burdens in these regions may prolong recovery of Hg impacted surface waters for many decades. Four studies were undertaken to examine interactions between watershed characteristics, hydro-climatic variability and terrestrial-aquatic export of key chemical parameters linked to watershed Hg sensitivity. Two new quantitative techniques, hydrogeomorphic edge detection and characteristic morphology analysis, were developed to explicitly map and characterize the spatial distribution, geomorphic form and hydro-biogeochemical function of forested wetlands using airborne Light Detection and Ranging (LiDAR) surveys. The results demonstrate the critical contribution of forested wetlands and upland-wetland interactions to the production and mobilization of dissolved organic carbon (DOC) and methyl-mercury (MeHg) - respectively - to downstream surface waters. Results of strategic, event-based hydrochemical sampling also demonstrate the critical contribution of summer high-flow periods to terrestrial-aquatic MeHg export. Finally, an analysis of historical monitoring databases of streamflow volume, hydrochemistry and Hg concentrations in yearling perch in two contrasting headwater lake basins was conducted. The results indicate strong potential for short-term, hydrologically-driven shifts in terrestrial-aquatic coupling and watershed Hg sensitivity, but only for the wetland-dominated, humic lake that exhibited consistent, summertime hypolimnetic anoxia. These various findings suggest that accurate characterization of watershed structure can help researchers identify first-order limitations on whole-watershed methylation efficiency, particularly in relation to hydro-climatic drivers of terrestrial-aquatic coupling in Boreal headwater regions.