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INTRODUCTION: Despite the advances in radiotherapy treatment delivery, target volume delineation remains one of the greatest sources of error in the radiotherapy delivery process, which can lead to poor tumour control probability and impact clinical outcome. Contouring assessments are performed to ensure high quality of target volume definition in clinical trials but this can be subjective and labour-intensive. This project addresses the hypothesis that computational segmentation techniques, with a given prior, can be used to develop an image-based tumour delineation process for contour assessments. This thesis focuses on the exploration of the segmentation techniques to develop an automated method for generating reference delineations in the setting of advanced lung cancer. The novelty of this project is in the use of the initial clinician outline as a prior for image segmentation. METHODS: Automated segmentation processes were developed for stage II and III non-small cell lung cancer using the IDEAL-CRT clinical trial dataset. Marker-controlled watershed segmentation, two active contour approaches (edge- and region-based) and graph-cut applied on superpixels were explored. k-nearest neighbour (k-NN) classification of tumour from normal tissues based on texture features was also investigated. RESULTS: 63 cases were used for development and training. Segmentation and classification performance were evaluated on an independent test set of 16 cases. Edge-based active contour segmentation achieved highest Dice similarity coefficient of 0.80 ± 0.06, followed by graphcut at 0.76 ± 0.06, watershed at 0.72 ± 0.08 and region-based active contour at 0.71 ± 0.07, with mean computational times of 192 ± 102 sec, 834 ± 438 sec, 21 ± 5 sec and 45 ± 18 sec per case respectively. Errors in accuracy of irregularly shaped lesions and segmentation leakages at the mediastinum were observed. In the distinction of tumour and non-tumour regions, misclassification errors of 14.5% and 15.5% were achieved using 16- and 8-pixel regions of interest (ROIs) respectively. Higher misclassification errors of 24.7% and 26.9% for 16- and 8-pixel ROIs were obtained in the analysis of the tumour boundary. CONCLUSIONS: Conventional image-based segmentation techniques with the application of priors are useful in automatic segmentation of tumours, although further developments are required to improve their performance. Texture classification can be useful in distinguishing tumour from non-tumour tissue, but the segmentation task at the tumour boundary is more difficult. Future work with deep-learning segmentation approaches need to be explored.

Community-based conservation projects have been promoted as a way of achieving both conservation and development goals. There is a growing literature surrounding the challenges of implementing such projects and achieving the outcomes sought, however questions remain including: To what extent do donors value community aspects of conservation projects? Does community conservation effectively build the capacity of participating communities? To what extent might interventions such as Payments for Ecosystem Services and promoting communication improve the ecological outcomes of such projects? In this thesis I attempt to answer these questions focusing on the case of community conservation conducted by Durrell Wildlife Conservation Trust in Madagascar. I use a combination of methods which rely on hypothetical scenarios (choice experiments and experimental games), and an evaluation of self-reported impacts measured using a Before-After-Control-Impact design. Firstly, I conducted a discrete choice experiment with visitors to Durrell's Jersey Zoo to explore the impact of highlighting community involvement in a conservation project (rather than species or habitat aspects) on likely donations. Respondents showed the highest willingness to pay for projects that have local community involvement in management. By simultaneously conducting a revealed preference study through an experimental campaign asking for real donations, I attempted to validate the choice experiment findings. With the level of donation we requested, most respondents made a donation so I was not able to demonstrate an effect of campaign type on real donations. Secondly, I conducted a household survey in Northern-central Madagascar across nine communities around a lake where a community conservation project was planned, and eight around an otherwise similar lake with no planned conservation project. I used this to develop indicators of community capacity and found that the levels and changes in indicators differed, showing a requirement for capacity to be considered in multidimensional space. In the following Chapter I used these measures of community capacity to evaluate the impact of capacity building activities carried out over the first two years of a community-based conservation project aimed at preparing the first lake for the reintroduction of the world's rarest duck. For this evaluation I used a before-after-control-impact approach allowing a robust estimation of impact. I found no evidence of impact in composite scores of capitals, though I found evidence of the impact of the intervention on some indicators of social capital. My analysis also revealed some evidence of elite capture of training and resources. Finally, I used an experimental game played with community members in both conservation and non-conservation sites to explore the hypothetical impact of potential interventions to improve ecosystem service provision by reducing pesticide use amongst farmers. I found that incentives in the form of subsidies increased co-operative behaviour and decreased the rate of non-cooperative behaviour. Enhancing communication did not increase the provision of ecosystem services across the game landscape, however it did increase cooperative behaviours between players. I argue that experimental games such as this have value beyond research and could be used as a tool for communities and conservation projects to explore the potential pros and cons of various interventions collaboratively. Together these chapters provide helpful evidence to improve the marketing, evaluation and future design of community-based conservation projects, in Madagascar and elsewhere, which will ultimately contribute to maximising benefits for both people and wildlife.

This project proposes a development plan framework for a Detroit project site which aims to address three main objectives. These objectives are to protect and improve community members’ quality of life and health, to enhance stormwater management, city services and ecosystem health in the region, with a focus on mitigating the flooding, improving transportation, and to provide opportunities for potential economic growth. An additional content deliverable was created as well. This deliverable aims to address watershed health, providing recommendations for native plantings and other ecological components that will greatly improve the quality of the project sites’ encompassing watershed and existing landscape. Several policies, programs and funding initiatives have also been identified that aim to cover climate justice, environmental justice and community revitalization efforts through green actions. In order to best mitigate issues in these focus areas, the team has compiled extensive GIS analyses, community research and data related to all three areas of focus. In addition to an in depth analysis, a well constructed literature review was completed to enhance the qualitative data previously collected. Overall, this project has created an extensive development plan that will aid the City in revitalizing and improving the chosen community area.

Since the mid-1990s, an increase in annual cyanobacterial harmful algal blooms (HABs) in the Western Lake Erie Basin (WLEB) has driven a focus on nonpoint source (NPS) nutrient pollution in tributary watersheds, especially in the states of Michigan, Indiana and Ohio, and in the Canadian province of Ontario (EGLE et al., 2021; Green et al., 2023; Watson et al., 2016). Attention to the issue was intensified in 2014 when a HAB in WLEB led to a drinking water crisis in Toledo, Ohio, which spurred commitments by the governments of Ohio, Michigan, and Ontario to achieve a 40% reduction of phosphorus loading into the lake by the year 2025 (Snyder et al., 2015; Steffen et al., 2017). However, these states are not currently on track to meet their reduction targets. To address NPS loading into the lake, government attention turned to the approximately 7 million acres draining directly into the WLEB, as well as the region’s primary land use: agricultural production (OSU Extension, 2024). Agricultural production is associated with 70-90% of NPS phosphorus loading into WLEB (Wilson et al., 2019), which can be mitigated through the use of agricultural best management practices (BMPs) for conservation. In Michigan’s 2021 Adaptive Management Plan for Lake Erie, the state identifies and prioritizes 13 subwatersheds for data collection and evaluation toward increased BMP adoption. To explore a new approach in localized conservation planning, the Michigan Department of Agriculture and Rural Development (MDARD) partnered with the University of Michigan School for Environment and Sustainability (SEAS) to research the factors contributing to producer conservation choices in a select priority subwatershed. The Stony Creek (South Branch River Raisin), a HUC-12 component of the River Raisin watershed, was chosen for this research effort. Over a sixteen-month period, our team of five SEAS graduate students reviewed literature related to agricultural, social, biochemical, and economic aspects of WLEB algal blooms; performed informal outreach and information gathering through event participation and farm visits; conducted 12 stakeholder interviews with producers, community members, and local experts; developed an erosion risk map of the subwatershed through GIS analysis utilizing the RUSLE model; and formed a steering committee to direct the development of a Watershed Conservation Plan (WCP) for Stony Creek. Through these various research efforts and their respective results, we synthesized three Key Themes that affect BMP adoption in Stony Creek: 1. Socio-cultural influences and personal attitudes factor heavily in farmer decisionmaking around BMP adoption; 2. Simplicity and specificity of conservation programming play a large role in adoption rates of conservation practices; and 3. Financial incentives are necessary but not alone sufficient for improving BMP adoption rates. Within these three themes, we identified nine cross-cutting barriers and six motivators to conservation adoption in Stony Creek. Based on these barriers and motivators, we developed five key recommendations for improving BMP adoption in Stony Creek: 1. Increase and stabilize funding and support for Lenawee Conservation District; 2. Improve accessibility and simplicity of conservation programming; 3. Improve information and education efforts in Stony Creek concerning BMPs; 4. Enhance avenues for collaboration between producer communities, trusted organizations, and stakeholders to engage with cost-share policies; and 5. Develop a strategic approach to attract and retain younger producers in rural farming communities. Our research findings drove the completion of a Sub-Watershed Conservation Plan (WCP) for Stony Creek, guided by a steering committee of local producers and stakeholders in agricultural conservation and watershed management. In the Stony Creek WCP, we recommend precision agriculture practices (nutrient management, nutrient mass-balance calculations, and precision application of nutrients) and two suites of BMPs based on field topography. While our research findings and recommendations are specific to Stony Creek

Glioblastoma multiform (GBM) is an aggressive primary brain tumour. Despite treatment advances in recent years, outcomes remain poor. Disease progression tends to occur adjacent to the original tumour or surgical resection bed, usually within the radiotherapy planning field. This local recurrence and progression is believed to be the result of invasive disease in the surrounding tissue at the time of diagnosis and treatment, which is not currently detectable by conventional non-invasive methods. A number of novel therapies are currently under development which target specific aspects of the tumour behaviour, to try and improve outcomes from this devastating disease. Imaging biomarkers are under development, therefore, in order to provide a non-invasive assessment of tumour extent and behaviour, to provide bespoke image-guided therapies, and detect recurrence or treatment failure at the earliest opportunity. These are also of value in the context of novel therapeutics, which may have a very specific affect on an aspect of tumour behaviour that is not readily apparent on standard clinical imaging. Key to the progression of GBM is the invasion into surrounding white matter. This is followed by a period of tumour growth and subsequent angiogenesis in which microvasculature is produce that is distinct from the highly regulated blood-brain barrier. This thesis covers the development of suite of advanced magnetic resonance imaging (MRI) techniques aimed at characterising those very traits of GBM responsible for the aggressiveness and treatment resistance. Repeatability studies are undertaken to determine the performance of the biomarkers in healthy tissues, and also in a range of gliomas. Dynamic Contrast Enhanced (DCE-) and dynamic susceptibility-enhanced (DSC-)MRI are used to provide estimates of perfusion and permeability in the tumour. In order to address the reasons behind preferential invasion of the corpus callosum, they are used in conjunction with ASL to non-invasively map perfusion territories and watershed regions in the brain through perfusion timing parameters. Diffusion Tensor Imaging (DTI) and quantitative magnetisation transfer (qMT) are used to provide complementary information about white matter integrity, in order to identify changes occurring with glioma invasion as early as possible and direct image-guided treatments at presentation. Their complementary nature is assessed by comparing the two parameters simultaneously in white matter. Additionally, one of the qMT parameters which may be related to tissue pH is shown to be sensitive and specific for the detection of high-grade tumour tissue. Finally, a novel multiparametric imaging biomarker is introduced. Tumour surface mapping assesses the boundary between the solid tumour and surrounding tissue in order to identify areas of potential aggressiveness and invasion. Multiple imaging parameters can be combined to improve specificity and sensitivity. Using the diffusion-weighted imaging parameter, mean diffusivity (MD - also referred to as the apparent diffusion coefficient (ADC)), it is shown to be predictive of clinical outcome in a retrospective and prospective study, while a multiparametric example is given indicating the utility as a predicative biomarker for regions of progression and recurrence, and as potential spatial discriminator for image-guided therapies.

Urbanization alters the quality of the natural environment, with more land areas that were previously covered with forest are now being converted to built-up areas. As a result, watersheds are typically negatively impacted by urbanization. This study analyzed multiple water-quality variables (i.e., temperature, turbidity, pH, dissolved oxygen, and conductance) in 24 to 30 watersheds in the Atlanta, GA region during 2014 – 2021. To understand the impact of urbanization on water quality, monthly means, correlations, and linear regression were used to investigate the relationship between water quality variables and watersheds characteristics. Landcover characteristics such as developed land, imperviousness, population and housing densities, increased stream temperature, and conductance, while decreased DO levels and turbidity. High temperatures and low dissolved oxygen can affect water quality, rendering it unsuitable for various uses. It is recommended that this approach for water quality assessment be used in other metropolitan areas.

Riparian forests are unique ecosystems that act as transitional areas between land and water that are a vital part of a healthy and functional stream ecosystem. Due to the rapidly changing landscape, riparian forests are increasingly threatened by urban development, agriculture, and invasive species, which contributes to a trend of degrading water quality in Tennessee. To address declining riparian forest quality in the face of land-use changes, the purpose of this study was to develop a simple watershed prioritization model that identifies areas that are highly susceptible to poor water quality, and where riparian plantings would be most beneficial. This study consisted of a spatial analysis assessing connections between 3 land-cover types (Forest Cover, Impervious Cover, and Open Area) within HUC-12 watersheds and associated Tennessee Macroinvertebrate Index (TMI) scores, and a field analysis connecting land and riparian cover variables to resulting stream temperatures. The spatial analysis indicated that all three land-cover types were found to have a significant predictive relationship with TMI score outcomes, with greater predictive ability achieved when combining land-cover types into a single “score”. Assessment of stream temperatures in connection with adjacent riparian vegetation and upstream land-cover factors support the importance of forests in maintaining lower temperatures, as well as the contribution of urban development to higher temperatures with broader ranges. The results of the analysis and further review of literature informed the development of a watershed priority model that emphasizes the importance of targeting HUC-12 watersheds with higher levels of impervious surface and low forest cover for riparian restoration efforts. This model could be a helpful tool for the communication of water quality and urban forestry initiatives to public audiences.

Antibiotic resistance is a serious health threat around the world. Millions of individuals are infected with antibiotic-resistant bacteria yearly, and thousands die from previously curable illnesses. Although antibiotic resistance occurs naturally, misuse of antibiotics accelerates the loss of their effectiveness. Public health campaigns focusing on antibiotic awareness have not effectively communicated and educated the public on this health crisis. New efforts to combat antibiotic resistance are urgently needed. This dissertation focuses on the ecological and public health components of antibiotic resistance research that must be addressed to decelerate antibiotic resistance. A new interdisciplinary theoretical framework was developed to Connect Antibiotic Resistance to the Environment (CARE). The CARE theoretical framework is the first framework that includes chemical cross-resistance and place-based engagement. Researchers can use the CARE framework to conduct scientific studies and communicate their findings to individuals who live and work near research areas. The CARE theoretical framework was applied to the Blue Marsh Watershed in Reading, Pennsylvania, to explore two real-world applications: (a) A Level III multimedia environmental modeling program was used to determine areas where chemical cross-resistance could occur in the Blue Marsh Watershed. Threecommonly used herbicides, 2,4-D, dicamba, and glyphosate, were modeled to accumulate in the water and sediment of the Blue Marsh Watershed. Low concentrations of these chemicals can potentially expose bacteria to an environment where chemical cross-resistance may occur. (b) This dissertation also applied the CARE theoretical framework to assess the chemical and microbial characteristics of the Blue Marsh Watershed. High concentrations of nitrates, phosphates, Escherichia coli, and Enterococcus spp. were prevalent throughout the watershed, indicating that the Blue Marsh Watershed would be an ideal environment to look for antibiotic-resistant bacterial populations. Future studies will apply the CARE theoretical framework to determine if antibiotic-resistant microorganisms are present in the watershed and also communicate the scientific findings from this dissertation to individuals who live, work, and recreate in and around the Blue Marsh Watershed.

Impervious surfaces are the greatest contributors to degradation of water quality and large volumes of stormwater runoff. Green infrastructure is the holistic solution to this problem which not only reduces flooding but also actively moves towards achievement of larger environmental goals. Green infrastructure has the co-benefits of reducing the heat island effect, traffic calming, beautifying the neighbourhood, improving the canopy within the city, the creation of parks and even supports economic development. The City of Falls Church is deeply concerned with the pressing matter of flood control due to the threats to human life and property in recent flooding events. The polluted waters of Falls Church also contribute to a highly impaired watershed- the Chesapeake Bay. This thesis recognizes the environmental crisis caused by polluted runoff and places equal emphasis upon reducing runoff as well as improving water quality. In order to mitigate the effects of inundation, it is most critical to intervene at the source of locations which create the most runoff and pollution. The thesis provides a systematic methodology of identifying such areas and intervening in them. The watershed which contains the downtown area of Falls Church has the greatest amount of impervious surfaces and the highest rate of stormwater runoff. The two intersecting streets of S. Maple Avenue and Annandale Road are identified as the location of intervention after tabulating a confluence of stormwater and public realm factors. S. Maple Avenue is a part of the Falls Church bike network and is also designated to become a civic great street. Meanwhile, Annandale Road has the potential to play an active role in collection and management of stormwater. Annandale Road runs along the watershed boundary as well as crosses several tributaries which are low points in the watershed. Furthermore, there is a dynamic urban character to the street as it transitions from a residential zone to the commercial zone. Both streets present excellent possibilities for road diets, pedestrianization and traffic calming which bolsters the implementation of stormwater management in the public realm.

In the past several decades, soil water erosion and runoff in agricultural regions across the Midwestern United States have contributed to significant A-horizon soil losses, declining soil productivity, and the widespread impairment of water resources. Rising temperatures and changes in precipitation trends have the potential to significantly impact future soil water erosion and runoff in the Midwest, yet relatively few studies have attempted to quantify these impacts. To help expand this area of research, the Water Erosion Prediction Project (WEPP) Model was used to quantify growing season soil water erosion and runoff for a baseline period (1965-2019) and two future periods (2020-2059 & 2060-2099) in agricultural hillslopes across three Minnesota HUC12 watersheds. Future daily weather inputs were generated for WEPP using downscaled daily climate projections from two CMIP5 climate models (HadGEM2-CC and GFDL-ESM2G) and three emissions scenarios (RCP 4.5, RCP 6.0, and RCP 8.5). The climate scenarios were combined with varying adoption rates of perennial crops, conservation tillage systems, and cover crops in order to determine the effectiveness of these mitigation strategies in reducing future soil loss and runoff. When the baseline management scenario was used, most future climate scenarios showed decreases in runoff (34-58%), soil loss (3.3-40%), and the number of hillslopes with unsustainable soil loss (1-8%). However, there were also moderate to significant increases in runoff (17-38%), soil loss (4.2-40%), and the number of hillslopes with unsustainable soil loss (+3%) in several of the moderate emissions scenarios (RCP 4.5 and RCP 6.0). Watersheds with steep slopes and widespread conventional row crop systems had a significantly greater number of hillslopes with unsustainable soil losses, even if runoff and soil loss were projected to decrease in the future. Additionally, growing season runoff and edge-of-field sediment delivery values required to meet TSS total maximum daily loads (TMDLs) were only met in the highest emissions scenarios (RCP 8.5) where future soil loss and runoff significantly decreased. In order to mitigate agricultural runoff and unsustainable soil losses in Minnesota under current and future climates, we recommend implementing a combination of perennial alfalfa cropping systems and reduced tillage systems across hillslopes in watersheds with widespread steep slopes and conventional row cropping systems. However, requirements for TSS TMDLs were still only met in the highest emissions scenarios when these systems were implemented into the majority of hillslopes. As a result, additional off-site mitigation measures will likely be required in at-risk watersheds to meet TSS TMDLs and soil conservation goals under most future climates.

Water quality of a stream or river is influenced by the surrounding landscape and vegetation. The Normalized Difference Vegetation Index (NDVI) is commonly used to characterize landcover and vegetation density. Benthic macroinvertebrates are ubiquitous in freshwater streams and are excellent indicators of the quality of freshwater habitats. Data from one NDVI remote sensing flight and one macroinvertebrate sampling event for eight wadeable stream study sites in the National Ecological Observatory Network (NEON) were acquired. Proportions of high, moderate, and sparse vegetation were calculated for each stream watershed using ArcGIS. Functional feeding groups and tolerance values were assigned to macroinvertebrate taxa. The Fourth-corner and RLQ methods of analysis, available in the ade4 package for R software, were used to evaluate the relationships of macroinvertebrate traits with environmental variables. Hypothesis testing using Model 6 in the ade4 package resulted in p-values of 0.066 and 0.057 for global (overall) significance. Mean NDVI values of moderately vegetated areas and proportion of sparse vegetation were found to be significant to percent shredders at alpha ≤ 0.05. Results of these methods of analysis, when combined with traditional macroinvertebrate sampling metrics, show that NDVI can be a useful, additional tool to characterize a watershed and its effects on macroinvertebrate community composition and structure.

The argument could be made that there is nothing more valuable on the planet than water. Our lives depend upon it. Climate change is already having an impact on the United States (US) and water stress will be one of the problems we increasingly face in coming decades. Regional research has shown that one or another part of the conterminous US (CONUS) is expected to experience an annual deficit or a surplus in runoff. Further studies have looked at changing patterns over the CONUS as a whole. Other research has focused on a particular season. This work addresses a gap in the research by analyzing water stress across the CONUS by climate region, seasonally, for each watershed. We used the widely deployed Water Supply Stress Index (WaSSI) to analyze the CONUS at the Hydrologic Unit Code eight (HUC8) scale. The aim of this work was to determine if there would be a significant change in trend of runoff from one season to the next, for each climate region. We first analyzed the projections for twenty global climate models through WaSSI, under two Intergovernmental Panel on Climate Change (IPCC) representative concentration pathways (RCP) emissions scenarios, RCP 4.5, an intermediate scenario, and RCP 8.5, a high stress scenario. The next phase of analysis focused on finding the global climate model which demonstrated the closest parallel with the historical data for the same time period. From these results, graphs were produced for every HUC8, for every season, under both RCPs. This data were then analyzed using Kendall's Tau to determine regionally significant trends. The trends for every climate region, under both RCPs, were then mapped in ArcMap to create a series of data visualizations so that the results would be easily accessible and understandable to decision-makers and lay people alike. The final phase of the research analyzed projected population changes across the CONUS in conjunction with the seasonal climate region results to underscore those cities and regions most vulnerable to water stress due to increased population. It is critical that we address the needs of our communities as water stress increases. This work will serve as a useful tool to water managers across the country.

Economic input-output (I-O) and watershed models provide useful results but when seeking to integrate these systems, the structural, spatial, and temporal differences between these models must be carefully considered. To reconcile these differences, a hydrologic-economic modeling framework is designed to couple an economic model with a watershed model. A physically constrained, I-O model, RCOT, is used to represent the economic system in this framework because it provides sectoral detail for a regional economy and calculates physical resource quantities used by these sectors. Uniquely, it also allows for technology options for all sectors and minimizes the resource use based on environmental constraints imposed by the watershed, which adds complexity to the representation of the economic system and its interactions with the watershed system. To represent the watershed system in this framework, the Hydrological Simulation Program-Fortran (HSPF) is used. An HSPF model has been calibrated to represent the hydrological processes of Cedar Run Watershed by the Occoquan Watershed Monitoring Laboratory (OWML). Thus, the capabilities of this framework are demonstrated using strategic scenarios developed to examine future development patterns that may occur within Fauquier County, northern Virginia, and its local basin, Cedar Run Watershed. The scenarios evaluate both the downstream and seasonal impacts on water flow and nitrogen concentration within the watershed, and the changes made within the economic system in response to these impacts. For these scenarios, the most efficient solution is the one that minimizes the use of resource inputs within the economic sectors, including developed land, water withdrawn, and applied nitrogen, which in turn inform watershed health. The scenario results demonstrate that this coupled hydrologic-economic modeling framework can overcome the spatial differences of the individual models and can capture the interactions between watershed and economic systems at a temporal resolution that expands the types of questions one can address beyond those that can be analyzed using these models separately.

Riverkeepers and environmental groups currently face the complex task of defending watersheds. In Georgia, these efforts are complicated by the vast geographical and racial diversity within the state. This study examined the riverkeepers and environmental groups need to improve advocacy abilities to defend communities they serve from poor water quality, what communities in Georgia are being impacted by poor water quality, what disconnects exist between riverkeepers, environmental groups, and governmental agencies, and how COVID-19 has challenged the riverkeepers and environmental groups. Using qualitative interviews with eleven riverkeepers and environmentalists, the findings suggest that collaboration with riverkeepers, enforcement of current policy, defending communities of color, and educating the public on water quality are all critical to maintaining watersheds in Georgia. Minoritized groups, instances of environmental racism, and other challenges presented barriers to water conservation. The riverkeepers and environmental groups provided strategies to address these barriers and improve water quality.

In many rural areas in arid and semi-arid regions, balancing agricultural and environmental water demands is a key challenge facing resource managers, which is complicated by the interconnection of groundwater and surface water resources. In California, water management decisions are increasingly supported by hydrologic models, but these can often provide confusing or overwhelming amounts of information. The Scott River watershed (HUC8 18010208), a 2,109 square km undammed rural basin in northern California, was used as a case study to develop a suite of tools, informed by a groundwater-surface water model, for water managers, including: 1) a hydrologic proxy for the ecological success of a key aquatic species; 2) applying a quantitative multi-benefit framework (i.e., incorporating ecological, agricultural, and cost objectives) to an existing groundwater planning process; and 3) two locally-tailored, seasonal, quantitative predictions of fall-season watershed behavior as a complement to historically-used water year type categories. Chapter 1 aims to quantify hydrologic conditions that support persistence of the Scott Valley coho salmon (Oncorhynchus kisutch) run. We applied the functional flows framework to characterize the hydrology of each water year measured at a key long-term stream gauge. Taking advantage of a nearly two-decade ecological monitoring dataset, we built linear models to predict coho salmon reproductive success using combinations of one and two hydrologic metric predictors. We used an ensemble of the three best linear models to formulate a Hydrologic Benefit function, summarizing the ecological services provided by the hydrology in different seasons into a single index value per water year.In Chapter 2, we apply a multi-benefit framework to a portfolio of management actions, which were proposed for the Scott Valley jurisdiction during the recent development of a long-term Groundwater Sustainability Plan (GSP). We developed a summary statistic or proxy for each of the three primary policy objectives in the GSP (environmental, agricultural, and project cost). We then used them to summarize the results of 40 management scenarios developed for the Groundwater Sustainability Plan (GSP) in Scott Valley in Northern California, which were simulated using an existing integrated surface- and groundwater model. We found that a trade-off in benefits for fish and farms was evident in every category of infrastructure investment (a proxy for project cost), though greater infrastructure investment can achieve some reductions in this trade-off. Additionally, although the GSP management priorities emphasized infrastructure investments, both infrastructure-based and regulatory approaches fell within the Pareto-optimal set of management options under a strict application of these objective functions. Finally, regarding regulatory actions, management interventions targeted at low-flow periods produced a more efficient gain in environmental flow value per cost in agricultural productivity.In Chapter 3, we propose methods to predict, approximately five months in advance, two key hydrologic metrics in the Scott River watershed. Both metrics are intended to quantify the transition from the dry to the wet season, to characterize the severity of a dry year and support seasonal adaptive management. The first metric is the minimum 30-day dry season baseflow volume, V_min, which occurs at the end of the dry season (September-October) in this Mediterranean climate. The second metric is the cumulative precipitation, starting Sept. 1st, necessary to bring the watershed to a "full" or "spilling" condition (i.e. initiate the onset of wet season storm- or baseflows) after the end of the dry season, referred to here as P_spill. As potential predictors of these two values, we assess maximum snowpack, cumulative precipitation, the timing of the snowpack and precipitation, spring groundwater levels, spring river flows, reference ET, and a subset of these metrics from the previous water year. We find that, though many of these predictors are correlated with the two metrics of interest, of the predictors considered here, the best prediction for both metrics is a linear combination of the maximum snowpack water content and total October-April precipitation. These two linear models could reproduce historic values of V_min and P_spill with an RMSE of 1.4 Mm3 / 30 days (19.4 cfs) and 20.7 mm (0.8 inches), respectively.The tools developed for this case study could be of value for other local jurisdictions with similar features, including a Mediterranean and/or intermontane (snow-fed) climate, an undammed watershed, and challenges balancing agricultural and environmental water needs. The method for empirically deriving the highest-priority hydrologic functions for a threatened species could be used in other watersheds (if sufficient ecological data records are available) to evaluate trade-offs and support water management decisions in human-altered novel ecosystems. The development of basin-specific objective functions, especially ones using output from existing hydrologic models, could help quantify management decision trade-offs and improve stakeholder communication in ongoing water planning efforts throughout the region. And finally, although careful consideration of baseline conditions used as a basis for prediction is necessary, seasonal predictive indices could be used by governance entities to support adaptive management in an uncertain future climate.

Stormwater runoff response in a complex coastal-urban basin varies with the changes in climatic and land cover drivers. This thesis aims to assess the runoff responses to variation in climatic and land cover variables and perform a sensitivity analysis in complex coastal-urban basins. The Buffalo San Jacinto Basin (BUSJ) of southeast Texas, USA was considered a pilot study area for this research. BUSJ is a heavily urbanized coastal basin, draining an area of 3132 km2 through the City of Houston, Texas into the northern Gulf of Mexico, USA. A process-based hydrological model was developed with fine spatio-temporal resolutions for the basin by using U.S. Environmental Protection Agency (EPA)’s Storm Water Management Model 5.1. The model was calibrated and validated with historically measured streamflow data from January 1 to December 31, 2020 (termed 2020). Rainfall and evapotranspiration were selected to represent the key climatic drivers, whereas surface imperviousness represented the major land cover drivers. These stormwater drivers were perturbed by -30 to +30% (with 5 percentage points increments) from their reference 2020 baseline values. The results indicated predominant and varying seasonal sensitivities of stormwater runoff to the changes in rainfall. Evapotranspiration changes led to consequential, but much fewer changes in the runoff than that of rainfall. However, runoff had stronger sensitivities to the changes in imperviousness, compared to that due to evapotranspiration in this heavily urbanized coastal basin. The quantified runoff sensitivities can provide important guidance for stormwater infrastructure management, improvement and development to achieve resilience and sustainability in the City of Houston and other areas along the northern Gulf of Mexico, USA and similar coastal-urban regions around the world.

The Huff Run Watershed, located in Mineral City, Ohio, was mined for coal, limestone, and clay from 1853 to the late 1970s. Mine spoil is left scattered on the surface of about one third of the watershed, contributing to metal leaching to the watershed. Although the mine spoil has had time to become vegetated, camouflaging itself among the native landscape, the disturbed pyrite from coal layers is exposed to water and oxygen leading to a chain of chemical reactions, resulting in the production of potentially acidic and metal-rich porewater, which can infiltrate into the groundwater and streams. Remediation efforts for this watershed have totaled around 4.5 million dollars, but most of the remediation is focused on the point sources of contamination. Runoff from the spoil is a nonpoint source of contamination, and most areas are left untreated. These untreated areas can affect the immediate area and many kilometers downstream of the leaching. For this project, soil samples were collected from a vegetated mine spoil hill and a vegetated shale hill in this watershed, to make a physical and chemical comparison of the soils and their pore water. Solid phase characterization included particle size analysis, bulk X-ray powder diffraction, and loss on ignition (LOI). Soil pore water was collected from suction lysimeters installed at different depths (10, 40, 80, and 120 cm) at the two sites. Field-based water quality analyses included pH, dissolved oxygen (DO), electrical conductivity, and temperature; collected samples were analyzed for metals by inductively coupled plasma-optical emission spectrometry (ICP-OES), anions by ion chromatography, and dissolved organic carbon (DOC). The speciation of Al, Fe, and Mn was also determined by a sequential extraction procedure. The particle size distribution showed a sandy loam, with an overall average of 4.4% clay, 47.7% silt, and 47.9% sand in the high wall (HW) and 6.3% clay, 41.8% silt, and 51.9% sand in the mine spoil (MS). The bulk mineralogy was dominated by quartz (30.6 – 43.3 % HW; 27.5 – 49% MS) and muscovite (34.9 – 42.6% HW; 29.1 – 45.0 MS). LOI values ranged from 4.27– 8.53% in the HW and 5.35– 15.48% in the MS, with the LOI being fairly uniform throughout the vertical profile in the HW and found in high percentages of the MS in areas of residual coal. DOC values were highest in the first 10 cm of the HW (91.45 ± 23.61 mg/L), 5 times higher than the first 10 cm of the MS. Although mineralogy and particle size analysis between the two sampling sites were very similar, metal leaching and mobility were different based upon whether organics were plant-derived such as the thick organic layer on the native hill, or vs. rock-derived organics from the residual coal in layers found from 50 – 100 cm in the mine spoil hill. Aqueous Al, Fe, and Cu were highest in the first 10 cm of the HW, indicating that they are readily released from soil into solution when exposed to plant-derived organic matter, and at this depth and location increased in concentration over the field season (were fairly constant at other locations). Aqueous Mn, Ni, and Zn were found in higher concentrations in the MS. Mn and Ni concentrations at both sites and all depths decreased over the field season and Zn did not show a temporal trend. Evidence of coal in the mine spoil is found through higher LOI values (approximately 10% in MS vs. 5% in HW), and extractable Fe and Mn having its highest concentrations at depths where rock-derived organics were highest, lower levels of dissolved oxygen, and overall higher concentrations of extractable Al, Fe, and Mn. Al, Fe, and Mn were all found in highest concentrations in the reducible fraction, indicating the formation of (oxy)hydroxides after pyrite dissolution in the MS. Using the results, there is potential to quantify the amount of metal leaching from non-point source mine spoil hills the and pH changes that take place during the months of May – October and evaluate the potential for metal leaching over greater lengths of time.

Flood analyses have historically been conducted using the stationarity principle, which assumes a constant hydrological regime within a river system. This research echoed previous studies challenging the assumption of stationarity for the purposes of flood analyses. The Greenbrier River watershed in West Virginia fit criteria for questioning the stationarity principle as it experienced dramatic forest harvesting activities in the late 1800s and has suffered deadly floods in the last four decades. This research questioned the stationarity assumption by testing hydrological data using Pearson’s and Pettitt’s tests. Additionally, two scenarios were developed to spatially model runoff travel time for a forested and deforested watershed. Stationarity was confirmed for the Greenbrier River. The study showed no evidence of non-stationarity in the hydrological time series of the river, despite widespread changes in land use across the study period. Similarly, spatial modeling of total runoff travel time estimation between watershed scenarios did not drastically vary.

Watershed planners and decision makers need tools to determine which best management practices (BMPs) are most effective at reducing nitrate pollution in the Root River Basin of southeastern Minnesota. The Root River Field to Stream Partnership is monitoring three subwatersheds of the Root River (Headwaters, Crystal Creek, and Bridge Creek) for flow and nutrient flux. Additionally, an individual agricultural field in each subwatershed is also being monitored. The Soil and Water Assessment Tool (SWAT) used data from these monitored sites to attempt to create calibrated hydrology and nitrate flux models. Inputs for modeling were obtained using publicly available sources for land cover, soils, elevation, and weather data. Model calibration for hydrology and nitrate flux was done via the trial and error method. Accurate hydrology models were produced for both the Headwaters and Crystal Creek subwatersheds, but a good nitrate model was produced only for the Headwaters due to several complications from underlying karst features in the Crystal and Bridge Creek subwatersheds that were difficult to account for using the SWAT model. Accurate SWAT models could not be developed for Bridge Creek and the field sites. The Headwaters model was then run using ten combinations of BMP scenarios to determine their effectiveness at reducing nitrate losses. Reducing nitrogen fertilizer application rates to economical rates and splitting applications of nitrogen resulted in a fourteen and sixteen percent decrease in nitrate losses, respectively. Applying nitrogen only in the spring and placing filter strips on steeply sloping agricultural land reduced nitrate flux by six percent each.

Coastal communities face threats of flooding associated with episodic storm events and high tides that are increasing in severity and frequency due to climate change and sea level rise (SLR). The Mid-Atlantic U.S. is experiencing SLR at rates faster than the global average, especially in Hampton Roads, Virginia where the rate of SLR is accelerating due to land subsidence. Adaptation plans for coastal flooding are mostly made at the municipality level, ignoring the propagation of water across its administrative boundaries. Impact assessment at the watershed scale identifies areas where municipalities will need to collaborate to mitigate the flood impact. The main purpose of this project was to evaluate the impact of flooding among watersheds in Hampton Roads and identify those most at risk that overlap one or more municipal boundary. Additionally, this research assessed the impact on land use/cover and population throughout the Hampton Roads region and within a case study watershed. To meet these objectives, we used U.S. Army Corps of Engineers 50-year floodplain and NOAA intermediate SLR scenarios for 2030, 2060, and 2090 to calculate the percent land area inundated for each watershed in Hampton Roads. Further, we assessed the flood impact on populations and specific land use/covers throughout the region for each SLR scenario, as well as within the Elizabeth River watershed. Key findings show that five watersheds will see a greater increase in inundated area than the surrounding watersheds, with two that overlap multiple municipalities. The anticipated land use impacts indicate significant inundation of land occupied by military, followed by commercial, industrial, and wetland covers both in Hampton Roads and within the Elizabeth River watershed. These findings not only highlight the need for more synchronized collaboration on adaptation between municipalities in Hampton Roads, but also provide a framework for the impact assessments in similar settings globally.

Billions of dollars are invested annually in stream restoration in the United States. However, three centuries of landscape modification have fundamentally altered riverine ecosystems, and some current widespread stream restoration methods do not account for this. The restoration projects studied in this project removed legacy sediments and regraded the streams and banks to achieve a more historically accurate stream system, an anastomosing wetland-stream complex. This project analyzed historical water depth and precipitation data to determine the effect of the restoration on the hydrology of the system. A significant difference in the relationship between water depth and precipitation at all study sites pre-restoration to post-restoration was found. It was also found that post-restoration, rainfall led to a lesser increase in water level than pre-restoration, suggesting that floodplains were saturated and peak velocity was lowered, thus lowering erosion potential. Stream restoration methods should adjust their focus from aesthetic improvement to improvement ecological function and recreate streams as we now know they existed historically.

The Occoquan Reservoir is part of the largest indirect potable reuse systems in the United States. It in an important water supply source for the Northern Virginia area, as well as, an ecological and recreational area. Furthermore, the Occoquan Reservoir protects the water quality of the Chesapeake Bay because it acts as a trap for sediments and pollutants. Continuous water quality monitoring and evaluation is critical to preserve this important water resource. Reservoir water quality can be affected by the delivery of pollutants from point and nonpoint sources, potentially causing problems such as eutrophication, excess salinization, presence of compounds that affect human and aquatic health. Different management strategies have been implemented at the Occoquan Reservoir to nutrient loading into the reservoir and address eutrophication issues, including nitrate addition to hypolimnetic waters and installation of a hypolimnetic oxygenation system. The goal of this study is to assess how current management strategies implemented in the Occoquan Reservoir have affected the water quality from 1973 to 2019, with particular emphasis on the data since 2003. This analysis of the Occoquan Reservoir and its tributary watershed includes the evaluation of hydrometeorological data and morphometric characteristics; establishment of long-term trends for water quality constituents; and determination of the trophic state of the reservoir. Data from water samples from four different stations located at the Occoquan Reservoir and four stations located throughout the Occoquan tributary watershed were analyzed for nutrients, principal ions and metals, synthetic organic compounds (SOCs), and other water quality parameters. Long-term water quality trends were determined using Mann-Kendall test and relationship between constituents was evaluated using Principal Component Analysis (PCA). Trophic state of the reservoir was assessed using Carlson's Trophic State Index (TSI), Vollenweider Model, and Rast, Jones, and Lee's Model. Results indicate the Occoquan Reservoir is a eutrophic waterbody. However, the nitrate management strategy and the installation of the hypolimnetic system have improved reservoir water quality, reducing concentrations of nutrients and metals.

Knowledge of nitrate sources and pathways in karst basins remains incomplete and hinders management of nutrients that cause algae blooms and degrade municipal water supply. However, the increased availability of optical, ultraviolet nitrate sensors allows advancement of nitrate source and transfer for water managers. A concept model is hypothesized for nitrate transfer during hydrologic events and baseflow that considers the multiple porosity of karst. To test the concept model, 15-minute nitrate sensor data is collected with submersible underwater nutrient analyzers over a multi-year period from two locations in a karst basin in the inner bluegrass region of central Kentucky, USA. Data results carried through quality assurance and quality control methods suggests fluctuations in nitrate and provides evidence of karst pathways with varying porosity. The inner bluegrass nitrate sensor results are compared with data from other karst basins in the United States, including the carbonate karst and their aquifers in Kentucky, Arkansas, Virginia and Maryland. Meta-analysis results from hydrographs, chemographs and hysteresis show evidence of nitrate transfers in karst including: a piston effect at the onset of an event as water stored in fractures and conduits is displaced by new water; a quick response during or just after storm event peaks that quickly dilutes nitrate levels in water; a concentrating effect after an event as high nitrate levels stored in soil water dominate transport; and a nitrate recession curve as nitrate stored in rock matrix become a larger contributor to nitrate flux. Mass balance un-mixing simulation was carried out to quantify nitrate sources for the inner bluegrass basin. The amount of water and nitrate load associated with the nitrate sources was quantified for four seasons and revealed the importance of the intermediate flow/fracture network pathway in transporting the majority of nitrate load. The piston flush occurring at the beginning of storm events was also noteworthy generating greater than 10% of the nitrate load. A reservoir model was formulated to represent the nitrate transfer processes for prediction. The reservoir model showed more insight including the impact of seasonality and sinkhole concentration on the distribution of water while at the same time showed the efficacy of the approach. New information from the reservoir modelling included the volume of water and nitrate stored in the karst aquifer, and these estimates will be useful for concerns of algal bloom proliferation at different times of the year.

The spread of human settlement has imperiled fresh waterbodies; however, it has also led to the generation of novel water conservation strategies, including the reuse of treated wastewater, or effluent. Effluent reuse is an increasingly common aspect of watershed management, and thus far, research has been concentrated on its effects to water quality and efforts to describe effects to wildlife species have been relatively piecemealed. In this study, we evaluate the overlap between wastewater treatment plants and federal and state-listed endangered and threatened wildlife species in order to present a holistic view of the intersection of effluent and species management and the potential need for effluent considerations in species conservation. We show that there is substantial overlap between the presence of species and the presence of treatment plants in California watersheds, and with this overlap, a large potential for unintended consequences. As such, species conservation goals should be considered when making decisions related to effluent reuse.

Urban stormwater runoff has become of increasing concern as urban sprawl has increased over decades. With more impervious surfaces, stormwater quickly passes into freshwater ecosystems with little to no water percolating into the soil. Even if there are not impervious surfaces, stormwater may pass over agricultural lands where nitrogen and phosphorus are easily available to flow into aquatic environments. Management plans are now using different strategies to filter out sediment and nutrients before they enter lotic or large lentic ecosystems. These small ponds or constructed wetlands have larger pieces of sediment settle before they have an opportunity to flow into a larger water body. While this has shown to be a successful and useful tool to filter out materials, horizontal (lateral) movement of water during flood events has become a concern. Species in a wetland can migrate in and out of the wetland into a lentic or lotic ecosystem, returning for refuge and breeding habits. If the wetland and larger water body become cut off they develop their own line of succession. The purpose of this study is to understand and characterize the water quality between an urban stormwater wetland and the headwaters of the Hocking River. Evaluate differences of biotic assemblages in the two water bodies and present information to the neighboring AHA! A Hands-On Adventure A Children’s Museum. These goals are done by conducting: fish, invertebrate, crayfish and field parameter tests.

Accurately predicting sediment delivery has been a long-standing problem in the field of water resource management. Many different watershed equations and models have been developed such as the Universal Soil Loss Equation (USLE), the Geo-spatial interface for the Water Erosion Prediction Program (GeoWEPP) and many more, however, these models have not always been able to reliably predict in-stream sediment loads. In this study, two scales, watershed and site level, are used to understand where sediment transported in-stream is being produced. At the watershed scale, USLE was used to estimate sediment yield and then different factors such as connectivity topographic indices were applied as discount factors in an attempt to improve these estimates. The different parameters were then compared to turbidity to determine the level of accuracy of each method. It was found that USLE is not able to predict in-stream turbidity levels in the study area watersheds in Virginia and North Carolina. An implicit assumption of USLE is that runoff is produced on steeper slopes and that sediment production occurs on these hillslopes. However, it was found that flatter-sloped areas were highly correlated with in-stream turbidity. It was also found that in-channel and site-specific parameters such as bank height/slope and level of confinement at higher flows were more accurate predictors of in-stream sediment levels. Overall, turbidity and in-stream sediment levels are not well predicted by models that employ USLE. The distribution of runoff source areas, and channel/bank properties appear to be good predictors of sediment production at the watershed scale. These results indicate that sediment production and transport, as conceptualized by common models and equations, often associate sediment source areas with geomorphic and hydrologic processes in ways that are not consistent with the results of this study. Our results show that sediment is most likely being sourced from the channels and in stream areas.

Nitrate concentrations have been increasing throughout the globe, primarily due to heightened agricultural activity. Nitrate concentrations in Bazile Creek, located in Northeastern Nebraska, have been steadily rising since the early 2000s. Groundwater nitrate concentrations within the Bazile Creek watershed are high (> 10 mg/L nitrate-N), and there is strong connectivity between groundwater and surface water systems. This study aimed to better understand temporal nitrate concentration variability within the watershed through sampling tributaries and the main channel during baseflow conditions. Nitrate source was also investigated though the use of dual δ15N and δ18O nitrate isotopes, with samples collected seasonally and after three summer rain events. Surface water nitrate and nitrate isotope results were then analyzed along with sub-watershed land use and soils characteristics in order to draw conclusions on input pathways. Average surface water nitrate concentrations between sites ranged from 2.7 mg/L to 15.3 mg/L, and nitrate concentrations were found to be significantly different between sites. On the main channel, nitrate concentrations were greatest in the winter. Ammonium from fertilizer was found to be the nitrate source, both seasonally and after rain events. Denitrification was detected, and was greatest in the spring. Analysis of sub-watershed land use revealed a positive correlation between nitrate concentration and watershed area as cultivated cropland. Soils were predominantly well or excessively drained throughout the study area. The results of this study suggest that ammonium from fertilizer applied to fields near Bazile Creek leached into the water table, eventually entering streams as groundwater discharge. Advisors: Troy E. Gilmore & Aaron R. Mittelstet

Beaver dams are known to alter the thermal regime of ponds, streams, and adjacent subsurface waters. Downstream of a dam, stream temperature is influenced by increased exchange with the hyporheic zone, which may cool and buffer the stream’s diel temperature cycles. Concurrently, reduced shading in the beaver forage zone is likely to increase heat flux at the stream-atmosphere boundary. The dynamics of these processes can be analyzed to understand how stream temperature is affected on diel time scales, as well as longitudinally at distances downstream from the dam. At two beaver dam-impacted stream sites in the Knife River Watershed in Minnesota, USA, I monitored in-stream and shallow subsurface flow and temperature during low-flow summer conditions. I used a dye tracer test, vertical heat transport modelling, and soil characterization to estimate flux through the streambed at multiple locations. Temperature, stream flow, and atmospheric data were also collected throughout the summer from the two sites. A one-dimensional model of longitudinal stream temperature, calibrated to in-stream temperature measurements, was developed to determine which physical parameters and heat flux components have the greatest influence on stream temperature. The model was then used to demonstrate how these changes persist downstream, as well as to simulate stream temperature under potential future site conditions. These findings increase scientific understanding of stream temperature regime in the context of beaver dam-altered watersheds.

Forest cover disturbance, climate change, and their interaction can alter how catchments store and process water, which has ramifications for all aspects of the hydrologic cycle, including flood risk, channel geomorphology, and water quality. Catchments in the boreal-temperate transition zone may be especially vulnerable to these factors. While streams in this glaciated region have low-topographic relief and may originate from expansive wetlands, much of the past research on forest disturbance-streamflow relationships comes from regions where landscape characteristics and subsequent hydrological function is substantially different, e.g. mountainous regions with bedrock close to the soil surface. Further, most work investigating the forest-streamflow relationship occurs at small spatial scales (< 10 km2). I seek to fill a knowledge gap by 1) creating a new conceptual model for how forest cover change affects sediment yield in managed temperate forested catchments that accounts for how sediment yield responds to altered catchment hydrology, 2) developing a new approach to peak-flow analysis using paired catchment experiments at the Marcell Experimental Forest (MEF) in north-central Minnesota, and 3) investigating how forest cover change and climate affect peak flows and water yield in large (> 10 km2) catchments in Minnesota. My results indicate that in low-relief glaciated regions, glacial geology controls sediment yield response to forest harvesting; forest harvesting may affect large peak flows by altering the occurrence probabilities of large peaks at the small catchment scale; and streamflow in larger catchments is largely controlled by climate variation, with land cover a minor yet discernable driver of peak flows and water yield. These results are framed within a new forest harvesting/water quality framework that holistically accounts for all sources of increased sediment yield after forest harvesting in diverse landscapes. Please note that multiple of these chapters are under peer review in scientific journals as of August 2020, and those versions will supersede this dissertation for purposes of citations.

Excessive nutrient loading from watersheds causes nutrient enrichment and water quality issues in very small streams to large rivers. Nutrient enrichment is exacerbated by urbanization and agricultural land use; however, the magnitude of the problem differs by regional landscape and environmental characteristics. Currently, we do not understand how regional variables moderate these relationships. Thus, the overall objective of this thesis was to investigate how regional landscape and environmental variables moderate developed land cover–stream nutrient relationships across the United States. The first study examined how climate and land use influences the scaling of phosphorus, total nitrogen, ammonia and nitrate loads for very large regions (Mid-Atlantic, Upper Mississippi, Ohio and Missouri) of the U.S. Results show the scaling relationships of nutrient loads with watershed size depends on the nutrient species and differed by region; the magnitude of the relationships was greater in wetter climates and developed watersheds. The second study determined 1) whether the relationships between urban and agricultural land cover intensity and concentrations of phosphorus, total nitrogen, ammonia and nitrate across the U.S., differed by ecoregion, and 2) whether regional landscape and environmental factors explained those differences. The relationships were found to differ by ecoregion and the differences were moderated by regional agriculture, topography and climate where stream nutrients increased more rapidly with anthropogenic land use in regions with high agricultural land use, wetter climates and flatter topography. The study findings will enable water quality managers create region-specific water management strategies for streams impacted by excessive nutrient loads.

Shallow groundwater flow in the critical zone of steep headwater mountain catchments is often assumed to mimic surface topography. However, groundwater flow is influenced by other variables, such as the elevation of the water table and subsurface hydraulic conductivity, which can result in temporal variations in both magnitude and direction of flow. In this study, I investigated the temporal variability of groundwater flow in the soil zone (solum) within the critical zone of a headwater catchment at the Hubbard Brook Experimental Forest in North Woodstock, NH. Groundwater levels were continuously monitored throughout several seasons (March 2019 to Jan 2020) in a network of wells comprising three hillslope transects within the upper hillslopes of the catchment. Five clusters of three wells per cluster were screened from 0.18 – 1.1 m depth at the base of the solum. Water levels were also monitored in five deeper wells, screened from 2.4 - 6.9 m depth within glacial sediments of the C horizon. I conducted 47 slug tests across the well network to determine hydraulic properties of the aquifer materials surrounding each well. In addition, our team conducted a large-scale auger investigation mapping soil horizon depths and thicknesses. Results show that the magnitude of hydraulic gradients and subsurface hydrologic fluxes varied at each site with respect to changing water-table elevation, having a maximum range of 0.12 m/m and 9.19 x 10-6 m/s, respectively. The direction of groundwater flow had an arithmetic mean deviating from surface topography by 2-10 degrees, and a total range that deviated from surface topography by as much as 51 degrees. During lower water table regimes, groundwater flow direction deviated from the ground surface, but under higher water table regimes, in response to recharge events, flow direction mimicked surface topography. Within most of the well clusters, there is an observable connection between the slope direction of the top of the C horizon and the direction of groundwater flow during lower water table regimes. Slug test results show the interquartile range of saturated hydraulic conductivity (Ksat) within the C horizon (1.5×10-7 to 9.8×10-7 m/s) is two orders of magnitude lower than the interquartile range of Ksat values within the solum (2.9×10-5 to 5.2×10-5 m/s). Thus, the C horizon is on average a confining unit relative to the solum that may constrict groundwater flow below the solum. Additionally, results from the larger scale auger investigation suggest that deviations in subsurface topography of the C horizon may be generalizable at the larger hillslope scale. Overall, these results indicate that 1) shallow groundwater flow direction and magnitude within this headwater catchment are dynamic and can deviate from surface topography, and 2) the subsurface topography of the C horizon can influence groundwater flow direction. These results imply that temporal dynamics of groundwater flow direction and magnitude should be considered when characterizing subsurface flow in critical zone studies. Additionally, knowledge of subsurface topography of confining units may provide constraints on the temporal variability of groundwater flow direction.

Climate change may have a variety of impacts on Midwest USA agriculture, including impacts to water quality, soil erosion, and nutrient loss. Existing and future climate scenarios were modeled in the Le Sueur watershed using the Soil & Water Assessment Tool (SWAT) to compare the watershed outflow and nutrient concentration outflows under those scenarios. The Le Sueur watershed, in south-central Minnesota, USA, is approximately 1,112 square miles, 87% of which is agriculture. The agriculture land is predominantly in corn and soybean rotations. Much work has been done using global climate models to predict the climate impacts from anthropogenic climate changes, resulting in predictions that the Midwest will experience increased temperatures, increased precipitation in the winter months, and decreased precipitation in the summer months. Minnesota has already documented an increase in extreme rainfall events. These events can cause flooding, damage land and property, and impact agricultural production. This analysis uses six global climate model (GCM) projections from the Coupled Model Intercomparison Project Phase 5 (CMIP5) for the Le Sueur River watershed area. The magnitude of change of five weather inputs; maximum temperature, minimum temperature, relative humidity, solar radiation, and wind speed, was averaged over three future climate time periods (2006-2029, 2030-2059, and 2060-2099) for two emissions scenarios, RCP 4.5 and 8.5. Average changes were applied to local weather in the Weather Input for Nonpoint Data Simulations (WINDS) model to simulate local climate projections. Predictions from WINDS are used in SWAT, to investigate watershed response to climate change in the Le Sueur River watershed.

Rapid growth and climate change are two main challenges that the majority of the cities of the United States currently face. For this reason, it is time for cities to use smart and multidisciplinary techniques to address these challenges. To present an example, this study proposes ideas and strategies on how to manage stormwater runoff to reduce some of the impacts of floods. The consequences of stormwater are often hardly noticed until it is too late. In Texas, the cities have become hotter than before and are predicted to become more intolerable in the future. Hotter temperatures increase the frequency of storms annually, and with an increase in the number of storms comes heavy rainfall. In turn, heavy rainfall and an increase in impervious cover due to population growth can be the worst nightmare for the cities of Texas. One of the sustainable techniques that few cities in the USA are implementing to overcome the issues of managing stormwater runoff is Green Streets. Green Streets allow the public right of way (ROW) to manage stormwater runoff with comparatively very affordable solutions than other longtime expensive grey infrastructures. As the concept of Green Street is new, not many cities have this program implemented. However, the cities that have implemented them agree that it has not only helped to reduce the impact of floods, but it has also greatly improved the quality of the surrounding neighborhoods. The objective of this report is to investigate the challenges regarding stormwater management at three levels—Macro (Colorado River Watershed-the city of Austin), Meso (the Shoal Creek Watershed), and Micro (Clay Street), and help the city of Austin implement a Green Street program. This study can act as an information guide, providing steps to be taken to implement green streets for the City of Austin where no such program yet exists. It will provide recommended strategies to the city to tackle some of the climate issues highlighted in the “Atlas 14” Report and reduce the risks of flooding and polluted waters due to the increase in impervious cover

Midwestern wetlands can provide a variety of ecosystem services to the surrounding landscape including nutrient retention. Although wetlands are often times sinks for phosphorus (P), accumulation of P in wetland soils, referred to as legacy phosphorus, can affect water quality when flushed out of a system. The prevention, management, or removal of stored soil P within treatment wetlands can be challenging for land managers, but P may be stored within plant biomass and removed by harvesting. In Minnesota, a small-scale edge-of-farm treatment wetland (Granada treatment wetland), a micro-scale experiment of 30 mesocosm wetland systems (University of Minnesota, St. Paul campus), and a large-scale flood water storage impoundment (North Ottawa Impoundment) were assessed. In the small scale Granada treatment wetland and the St. Paul mesocosm experiments, harvested wetland vegetation was compared in autumn for P retention within the above ground biomass. A wet prairie vegetation mix from the Granada treatment wetland was sampled from each cell within the wetland and various native Minnesota plants were tested in the mesocosms at different times of the year. The monoculture species in the mesocosm experiments ultimately removed more P per biomass than the wet prairie mixes at the Granada treatment wetland. Biomass was not witnessed to be a direct indicator of P removal per the species studied in our experiments. The time of season of harvest and correlated phosphorus content was found to be an indicative factor for phosphorus removal potential. The Granada treatment wet prairie vegetation mix removed phosphorus each season through harvesting in the fall with approximately 2.3 kg/ha removed by vegetation in 2017 and 3.2 kg/ha removed in 2018. From the 2017-2018 mesocosm experiments, both Schoenoplectus tabernaemontani and Scirpus fluviatilis removed approximately 1.6 g of P per tank or up to approximately 12 kg/ha of P. Both bulrush species removed more P than Calamagrostis canadensis, Spartina pectinata, and Carex stricta. In the large scale North Ottawa Impoundment (NOI), a 2014 Typha x glauca harvest was analyzed for P removal potential in which results indicated up to 2,564 kg of P removal from biomass harvesting, or approximately 3.11 kg/ha. Each site was also monitored for soil legacy phosphorus reductions. In the 2018 St. Paul mesocosm soil analysis, reductions of soil P after plant harvest significantly exceeded loading of P. This may indicate potential for legacy phosphorus reduction by removing vegetation. Harvesting vegetation in treatment wetlands based on phosphorus content within the shoots of selected species can be a successful management practice to reduce phosphorus accumulation over time. Currently, treatment wetland vegetation harvesting is not widely practiced in Midwestern agricultural watersheds; if treatment wetland design and harvests were cost-effective and compatible with surrounding farm systems, there may be potential for widespread application of harvesting vegetation for P removal. Harvesting treatment wetland vegetation annually may aid in reducing legacy phosphorus content within soil and may further prevent water quality degradation within agricultural watersheds at different scales.

Abstract: Snowpack accumulation and melt dynamics, and soil moisture storage (SMS) play a critical role in regulating stressed regional water supplies in the southern Alberta Rockies. However, these processes are sensitive to impacts from forest cover losses by timber harvesting and associated land disturbance. While numerous studies have investigated effects of clearcut harvesting, few studies have evaluated the comparative effects of alternative forest-harvesting methods on spatial and temporal snowpack accumulation-melt and subsequent growing season soil moisture dynamics, resulting in a knowledge gap about how current alternative or new/novel strategies influence these key hydrological processes. Spatio-temporal patterns of snowpack accumulation/melt and SMS were assessed from 2016-2018 in the three sub-watersheds located in the Crowsnest Pass, Alberta that were harvested using three different forest-harvesting strategies (clear-cut with tree retention, strip-shelterwood, and partial cut harvesting). Snowpack and SMS were measured in each harvest and adjacent undisturbed forest stands using a series of linear transects. Snow depth and water equivalent (SWE) was measured every 14-21 days from the period of peak snowpack through snow disappearance, and SMS monitored at the same frequency thereafter using time domain reflectometry (TDR) to measure soil water storage at 0-20 cm and 20-60 cm depths. Differences in snowpack accumulation and melt and SMS were evaluated in the context of measured differences in microclimate and modeled solar radiation forcing. Results from this study showed peak snow accumulation increased by 43% in harvested strips, and 28% in the partial-cut relative to corresponding forested reserves, while snowpacks in north and south facing clearcut were either not different or significantly less. Differences in solar radiation due to slope orientation and shading by retained trees produced highly varied patterns of snow accumulation and melt creating within-harvest differences in snow disappearance timing of up to 20 days. Subsequent seasonal SMS was also generally increased by harvesting due to reduced water losses from tree transpiration. However, the duration and magnitude of differences in SMS varied among harvests and soil layer depths over wet and dry years, which was attributed to differences in the ability of specific harvest cutting-patterns to moderate surface soil moisture losses. Across both study years, increased SMS after harvesting was greatest in SS (39%) followed by CC (~25% across both north- and south-facing hillslopes), and PC (~19%) for the two soil layers considered (0-20, and 20-60 cm). Results from this study demonstrate key differences in the comparative ability of specific patterns of tree retention to moderate spatial patterns of snow accumulation and melt and seasonal SMS, and strongly reinforce past research on the importance of interactions between forest cover, slope-orientation, and solar radiation in controlling spatial and temporal water-balance. These findings provide new information on relationships between alternative forest harvesting methods and snowpack and SMS dynamics needed to help evaluate integrated forest-water management strategies in this vital water supply region.

The purpose of this research is to investigate the predominant sources and processes that influence runoff in the watersheds that interact with hydraulic structures in different climate systems. The predominant sources in three basins were analyzed: The San Juan-Chama River System in the USA, the Manduriacu, and Coca Codo Sinclair hydropower systems in Ecuador. This field study is based on the identification of the predominant sources in the watershed by the comparison of the isotopic signature between the seasonal variation of water sources to the surface water samples in different stream order tributaries. The results exposed that there are three different predominant runoff sources in the three watersheds during the year: a) waterheads in Manduriacu, b) local sources in Coca Codo Sinclair and c) snowpack sources in San Juan-Chama. Also, the predominant processes are: a) altitude effect in the Manduriacu and Coca Codo Sinclair and b) seasonal effect in the waterheads in San Juan-Chama. Moreover, the findings of this study support the applications of stable isotopes values to identify the dominant physical processes and primary sources in a watershed at a natural scale.

This is a study of the influence of the various land use practices on water quality parameters of Mill Creek Watershed that flows north from Columbiana County, then through Boardman Township and Mill Creek Park, before finally merging with the Mahoning River in Youngstown, Ohio. Land uses in the Mill Creek sub-watershed vary from residential to urban industrial as well as from agricultural to forested and recreational areas. Water samples were collected from eleven different points of Mill Creek. Various physical, chemical and biological water quality parameters like temperature, DO, pH, ammonia, soluble reactive phosphorous, nitrate-nitrogen, TSS, VSS, TDS, VDS, Total Coliform, E.coli and BOD were measured using standard methods. Graphical representations showed the difference in the averages of different water quality parameters before and after rain events. Inverse distance weighted (IDW) interpolation techniques were used to represent the spatial dispersion of nutrients, solids and bacteria at the scale of whole watershed. Different types of land cover i.e., herbaceous land, forest, developed areas, cultivated crops, open water and wetlands of Mill Creek Watershed are used in this study.Principal Component Analysis (PCA) of water quality parameters shows a positive correlation of the potential runoff from impervious surfaces and cultivated land with the concentrations of ammonia, TSS, E.coli, VSS and Coliform. On the other hand, percentage of forest does not depict any trend with the concentrations of ammonia, TSS, E.coli, VSS and Coliform. Principal Component Analysis with whole data covering 2016-2018 indicate that the high precipitation events in summer 2016 diverged from high precipitation events in the fall. Excluding the high precipitation events from summer of 2016 results implications that are similar to that of 2017-18. Thus, high precipitation events of summer 2016 apparently produced water parameters similar to that of low flow conditions. This study shows that the runoff from cultivated land and impervious surfaces has negative impact on the water quality of the watershed. Beside runoff from impervious surfaces and cultivated land, input of nutrients, bacteria and solids from the tributaries of the Mill Creek River might be contributing to reduced water quality in Mill Creek River. It is recommended to expand the sampling into the tributaries of the Mill Creek River.

At present, it is evident that there is a shift from rural to an urban settlement which results in high demand for residential buildings and other urban infrastructure. Blue – Green Infrastructure (BGI) is a system of using blue (water) and green (nature) to address urban and environmental challenges. The purpose of this study is to evaluate the environmental, social, and economic benefits of blue-green infrastructure in an urbanized area in Pittsburgh, Pennsylvania, USA. The study involves the utilization of Geographic Information System (GIS) to determine water quality level resulting from nonpoint source pollution through acquiring elevation data; watershed; and processing the elevation data through performing appropriate watershed delineation for the study area. Different landscape models (i-Tree Design, i-Tree Landscape) were explored to determine the different benefits attached to BGI Infrastructure aside aesthetic and refuge benefits from the Landscape Performance Series database. The i-Tree Landscape gives one an idea of areas where particulate matter and atmospheric gases exist, and areas to prioritize planting of trees. A pilot scale-site was chosen from the discovered areas to prioritize plantation with the help of some selected criteria. Five design patterns (Green Parks, Riverfront, Activity Nodes, Green Parking, and Green Streets) were adopted an I-Tree Design model was used to get the pre and post environmental and economic benefits of trees on a 10-yr. expectation plan. The water quality model, I discovered areas that have high total suspended solids (TSS) level giving one an idea on the water quality of the area. The areas pointed out as areas to prioritize planting by the i- Tree Landscape model also has a high TSS level from the GIS delineation to further justify the outcomes of the two models used. sustainable design concepts were provided on how to practice/ incorporate blue-green infrastructure in areas that need interventions towards creating a balance between the built and natural environment.

The Saco River watershed, spanning two states and more than 23 municipalities, is home to a complex political and social fabric. A range of governments, economies, and activities exist in different sections of the watershed. To explore the possibilities for creating a Saco River watershed collaborative, this nonpartisan, independent assessment of current values, aspirations, and issues in the watershed and perceptions of collaboration was conducted. It is intended to inform and advise anyone living and/or working in the Saco River watershed who aspires to greater collaboration. It is also intended to provide insights to the existing Saco Watershed Collaborative that has taken shape over the same time period as this project.The research team utilized three methods in this assessment: a literature review of elements of successful collaboration in natural resource management, semi-structured interviews with 52 individuals representing 30 organizations in the watershed,and case profiles of nine existing watershed collaboratives in New England and elsewhere that face analogous issues or arose in similar contexts. When asked what they valued most about the Saco River watershed, interviewees cited recreation, clean water, biophysical attributes, aesthetic qualities, and the water's use for drinking and irrigation. Interviewees held many aspirations for the watershed. These included a future where the unique ecology and high-quality water are protected, particularly via better land management practices, more land conservation, recreation that does not degrade the river, and more coordinated and credible science to inform decision makers. Shared valuesand aspirationscan provide afoundationfor collaboration. Interviewees mentioned a wide array of issues related to the Saco River watershed, including recreation, development, dams and fish passage, and water extraction. Given the wide range of issues, a collaborative should prioritize which issues it seeks to address, in addition to engaging with individuals and organizations that have differing jurisdiction over and capacities to address these issues. Though interviewees expressed a clear interest in creating a collaborative organization to improve communication and coordination between individuals and organizations, they had an array of ideas about what purpose{s) such an organization might serve.These included bolstering networking and information sharing; influencing the behavior of others through education, advising governments, and advocacy; and enabling watershed-scale management by integrating an ecosystem perspective into decision making. A collaborative should discuss these varying ideas about potential roles and decide which purpose{s) to adopt. Finally, while most interviewees have not given much prior thought to a collaborative's potential structure, interviewees wanted any process that might be established to be credible and transparent in order to ensure trust that the collaborative would fairly attend to their interests and the watershed's well-being.

Urban development significantly increases water temperatures within watersheds, primarily from the construction of impervious surfaces for buildings and pavement. While thermally enriched runoff can be harmful to aquatic life, available research and guidance on predicting these effects is limited. The goal of this assessment is to provide guidance on how to achieve necessary temperature regimes that meet aquatic health criteria for sensitive species such as trout. To address this need, the Minnesota Urban Heat Export Tool (MINUHET) and U.S. Environmental Protection Agency's Storm Water Management Model (SWMM) models were utilized to simulate hourly streamflow, water temperature, and heat flux in an urban watershed in Blacksburg, VA for typical summer periods using continuous-based simulation. SWMM and MINUHET were combined in a unique, hybrid approach that emphasized each model's strengths, i.e., SWMM for runoff and streamflow, and MINUHET for water temperature. The watershed is 14.1 km², and is portion of Stroubles Creek located near downtown Blackburg, Virginia and the main campus of Virginia Tech. Streamflow, water temperature, and climate data were acquired from Virginia Tech StREAM Lab (Stream Research, Education, and Management) monitoring stations. SWMM and MINUHET were calibrated manually for the summers of 2016, and were validated for the summer of 2015. Model sensitivity analyses revealed that simulations were especially sensitive to imperviousness (SWMM predicted streamflow as outputs) and dew point temperature (MINUHET predicted water temperatures as outputs), both resulted in increased outputs of SWMM and MINUHET models, respectively. Model performance in simulating streamflow was evaluated using Nash-Sutcliffe Efficiency (NSE) and correlation (R²). NSE and R² values were 0.65 and 0.7 for the SWMM Model and 0.57 and 0.55 for the MINUHET model during the validation period, indicating that SWMM performed better than MINUHET in streamflow simulation. Streamflow temperatures were simulated using MINUHET with a NSE and R² statistical values of 0.58, and 0.83, respectively, demonstrating a satisfactory simulation of water temperature. Heat loads were simulated using the MINUHET and Hybrid models, demonstrating less Percent BIAS of the Hybrid approach in simulation of watershed total heat load than MINUHET alone. Furthermore, a number of practices were implemented to reduce thermal loading within a watershed. These included infiltration practices, methods for decreasing absorption of thermal energy primarily by reducing albedo, and increased vegetation canopies. An index titled Percentage of Time Temperature Exceeded 21°C Threshold (PTTET) for trout habitat was used to represent the effectiveness of thermal mitigation practices. Installing concrete pavement (thermal diffusivity: 15×10-7 m²/s, pavement thickness: 0.20 m, and heat capacity: 4.0×106 J/m³⋅°C) and Acrylic Coated Galvalume (ACG) roofs for all pavement and roofs, respectively, in the watershed reduced heat load by 45%, and the PTTET index declined 4.5%. Installing bioretention with 61 cm of media thickness, and soil-media infiltration rate of 25 mm/hr. for 53 selected parking lots in the watershed, resulted in 11.1% reduction in watershed heat load and 1.4% reduction in PTTET. Planting forest canopies for the entire pervious area of the watershed, sufficient to shade 90% of all lands, resulted in reduction in heat load by 24% and PTTET by 4.6%.

San Diego is known for its temperate Mediterranean climate and beaches; however, human activities that compromise water quality degrade environmental conditions and impose economic and social costs. Urban runoff is one of the most serious threats to San Diego's coastal water quality, contributing to harmful algal blooms, low dissolved oxygen concentrations and impacts on economically important marine and estuarine taxa. Nutrients and toxins originate from residential, agricultural and industrial sources, and the land usage within watersheds determines their loadings. Economic development that improves human well being may either benefit water quality or further contamination of coastal ecosystems. The purpose of this study was to identify relationships between chemical and isotopic indicators of water quality and land usage and watershed socioeconomics composition. I found that areas with low socioeconomic status (SES), mostly in the southern watersheds, exhibited lower water quality scores based on composite indices. Interestingly, coverage of open, developed, impermeable or agricultural land uses was not directly correlated with water quality as I expected. Overall, water quality declined in southern watersheds where residents have the poorest socioeconomic status. My thesis suggests that anthropogenic activity and low socioeconomic status contribute to poor water quality and contamination of coastal environments. The role of economic development in transforming land use and affecting water quality needs to be evaluated in relation to other hydrologic factors that determine export of nutrients from watersheds to the ocean.

The Mill Creek Watershed (MCW) is located in Mahoning and Columbiana Counties,Ohio. It is a 47,000 acre sub-watershed of the Mahoning River watershed. The main surface stream is Mill Creek which starts in Fairfield Township, Columbiana County and continues until it reaches the Mahoning River just west of downtown Youngstown. Mill Creek runs through Mahoning County’s largest metropolitan park, Mill Creek MetroPark (MCMP). Mill Creek is approximately 39 kilometers long with a mixture of land use types ranging from heavily industrialized and residential to agriculture and mixed forests. The impact of land use practices and aging infrastructure in the Mill Creek Watershed have resulted in various water quality concerns related to human and ecological health. Local water quality issues include bacteria (and other pathogens) from animal waste, combined sewer overflows (CSOs) and failing septic systems; nutrients from urban and agricultural land uses; and sediment loading from erosion and construction. Project objectives are to establish a monitoring program for this watershed. Initial evaluation of MCW monitoring sites, based on specific watershed land uses and inputs (point and non-point) was identified. Twelve sites of concern were selected for water chemical, biological and physical analysis. To establish a control, baseline samples (low flow) were taken during dry periods of rainfall. To assess the effects of land uses in the watershed water samples were collected 24-48 hours after a significant rainfall (>1.9 cm). SPSS analyses were performed using Spearman correlation and ANOVA on SPSS. Soluble reactive phosphate was most prevalent upstream where land use was predominately agricultural. Total and fecal coliforms counts were greatest during the October 21 storm event. During that event, coliform counts were highest, specifically, upstream where agricultural land use dominated and in the Mahoning River where there is larger industrial and residential land use. Precipitation events did not appear to have an influence on any parameters other than total and fecal coliforms. Metals found within the watershed included calcium, potassium, magnesium, sodium, phosphorus, and sulfur. Results of the monitoring program will educate the public on water quality issues and the influence of watershed activity on water quality. Importantly, it will also provide data to Mill Creek MetroParks and the Mahoning County District Board of Health to improve its management of waters coming into and leaving the park.

A watershed management plan was created for the Lower East Fork watershed in 2003 by the Clermont Soil and Water Conservation District. Watershed management plans describe the condition of water resources within a watershed and outline problems and solutions for improving impaired resources. The Ohio EPA conducted a biological study on the Lower East Fork Little Miami River and select tributaries in 2012. To fulfill the requirements of Miami University’s Master of Environmental Science degree, I accepted a practicum to update Chapter 4 (Water Resource Quality) of the Lower East Fork Watershed Management Plan. This has given me the opportunity to become familiar with the many components of watershed management and assessment, which is very useful for future career goals.

Urbanization has been associated with the degradation of streams, and a consequence of forest to urban land transition is a change in streamflow. Therefore, the purpose of this thesis is to examine the impacts of land-cover change in ten different watersheds in the rapidly urbanizing Atlanta, GA USA metropolitan area. Streamflow and precipitation data for a 30-year period (1986-2016) were analyzed in conjunction with land cover data from 1992, 2001, and 2011. Big Creek and Suwanee Creek experienced the most urbanization and increases (20%) in streamflow and runoff, and high flow (>95th percentile of flow) days doubled and increased 85%, respectively. Precipitation-adjusted streamflow for Peachtree Creek and Flint River decreased about 17%. Runoff ratios for South River were the highest among all watersheds, even the Etowah River, which remained moderately forested and had the most precipitation and slope.

Globally, human activities are altering nutrient biogeochemical cycles. The impact of humans on silicon (Si) cycles remains largely unexplored. Understanding the cycle of Si is important because weathering of siliceous rocks is a substantial sink of atmospheric carbon. Additionally, Si is required by diatoms. Diatoms form the base of important socioeconomic food webs, responsible for ~50% of oceanic net primary production, and deliver atmospheric carbon to ocean sediments as part of the ocean’s biological pump. My dissertation aims to assess the role of anthropogenic activities in altering Si cycling across the land-ocean continuum. Chapter 2 focuses on how assimilation of biogenic silica (BSi) by trees may be impacted by projected changes in climate. Using samples collected during a multi-year, snow removal experiment, I show that increased frequency and duration of soil freezing in winter significantly decreased (-28%) BSi in sugar maple (Acer saccharum) fine roots compared to control plots. Importantly, I observed that fine roots are a previously undescribed pool of BSi within sugar maples, accounting for 29% of total sugar maple BSi while only 4% of sugar maple biomass. Chapter 3 examines the origin and fate of Si within wastewater for the City of Boston. I determined the total dissolved silica (DSi) load in wastewater influent (69,500 kmol DSi year-1), then parsed the total DSi flux between Si contributions of sewage (49%), groundwater infiltration (39%), and surface runoff inflow (12%). In Chapter 4, I study the DSi load carried by treated effluent. I determined that effluent load (67,800 kmol DSi year-1) is not statistically different from influent load, indicating that wastewater treatment does not remove DSi. In Chapter 5 I demonstrate how humans impact concentrations of DSi in urban groundwater. Groundwater DSi increases with human presence and urban areas have significantly higher concentrations of DSi compared to groundwater conditions along the Massachusetts coast. I demonstrate that historic variables defining fill techniques, fill material, and pre-fill land-use out preform geologic variables in predicting urban groundwater DSi concentrations. This dissertation highlights human alterations to biological assimilation, fate, and effects of Si in sewage, and centuries-long subsurface Si impacts that perturb the distribution and availability of a nutrient intimately tied to water quality and climate.

The (dis)connectivity of sediment, defined as the detachment and transport of sediment from source to sink between geomorphic zones, is a major control on sediment transport rates but has seldom taken precedence in sediment transport models that focus on assessment of sediment impacts on water supply. A watershed-scale sediment transport model was formulated that incorporates sediment (dis)connectivity knowledge and subroutines and predicts sediment flux through coupling with an excessive shear stress erosion equation. The intersecting probabilities of sediment supply, detachment, transport, and (dis)connectivity produce the probability of sediment connectivity for a watershed or region of a watershed. The integration of the net watershed probability of sediment connectivity yields an estimate of the active watershed area in terms of sediment transport when multiplied times the entire watershed area. The sediment transport model was tested for a bedrock controlled catchment in the Southeastern United States for which extensive historic water and sediment flux data was available. It is expected that the model presented here can be used as a tool to assess the regional impacts of natural and anthropogenic sources of (dis)connectivity on sedimentation rates that lead to problems such as reservoir sedimentation and water quality degradation.