Agricultural runoff is one of largest contributors of phosphorus (P), nitrogen (N), and sediment affecting freshwater systems in watersheds across the Northeastern U.S., including the Lake Champlain Basin in Vermont. Agricultural cropping systems, such as corn silage and haylands, used for dairy feed production have been shown to impact watershed hydrology and water quality. Agricultural best management practices (BMPs) have the potential to decrease runoff volumes and flow rates and the associated export of nutrients and sediment from agricultural fields. Many states in the Northeastern U.S., including Vermont, are beginning to require farmers to implement water quality BMPs and further improve risk evaluation of export of P in runoff using evolving P site assessment tools, such as the Phosphorus Index (P-Index). Quantifying the effects of BMPs on hydrologic and nutrient exports from fields is critical for informing site assessment tools that aid in the development of nutrient management plans and to help design agroecosystems that do not degrade water quality. However, there is a lack of data on the effects of BMPs on edge-of-field hydrologic and nutrient fluxes, especially in cold-climate regions with snow-melt induced runoff events. This thesis consists of four chapters, Chapter 1 is a comprehensive literature review on agricultural hydrology and water quality, BMP effectiveness, and P site assessment tools. Chapters 2 and 3 address research objectives related to the evaluation of BMP and P site assessment tool effectiveness. Chapter 4 is a summary of the conclusions drawn from the work done in Chapters 2 and 3, and suggestions for future work. Chapter 2 evaluates the effects of soil aeration prior to manure application on edge-of-field hydrology, water quality, and P fluxes in haylands with clay soils during both precipitation and snow-melt induced runoff events. Edge-of-field water quality monitoring techniques and passive-capillary lysimeter systems were used to continuously measure the losses of surface runoff, subsurface leachate, and the associated export of nutrients (total phosphorus, total dissolved phosphorus, total nitrogen, and total dissolved nitrogen) and total suspended solids resulting from runoff events year-round from 2012 to 2018. Annual P fluxes in the form of vegetative uptake and removal, manure additions, and soil test P were also recorded. Results from this study indicated that soil aeration had the potential to reduce nutrient and sediment exports from haylands with poorly-drained, high runoff producing soils in the Northeastern U.S. where winter freeze-thaw conditions exist. However, potential increases in surface and subsurface hydrologic flows can accompany these reductions; these implications should be considered before implementation. Chapter 3 identifies potential P-Index improvements through the representation of topographic controls on phosphorus (P) transport by comparing results from the Vermont P-Index (VT P-Index) and a more complex process-based model, TopoSWAT, across topographic regions in a small agricultural watershed (360 ha) in the Lake Champlain Basin. Scenarios of varying P management strategies were modeled for corn silage production fields with poorly-drained soils and rolling topography. Modeled outputs of P risk assessments and edge-of-field dissolved and particulate P losses were compared. Results from this study suggest that the VT P-Index could improve its ability to support farm nutrient management planning and other P-based management decisions by incorporating topographic controls of runoff production into its estimation of P transport.

Population growth, coupled with changing weather patterns, is straining water supplies, especially in the American Southwest. A multitude of tools, including additional storage, will be needed to meet water demand and supply gaps. The Animas-La Plata Project, a reservoir in southwest Colorado, provides a case study of how groups worked for nearly 70 years to solve a water problem: insufficient irrigation for agriculture. This qualitative case study addressed a lack of first-person narratives from those most involved. Its purpose was to gather stakeholder narratives and analyze them using Kingdon's three streams theory to address the extent to which the problem, policy, and political streams converged to open policy windows that resulted in a built facility. Purposeful sampling identified 11 organizational stakeholders with the highest seniority and longest association with the project. Transcribed data from structured interview questions were inductively coded and thematically analyzed. Key findings include identification of a major federal policy change in the late 1970s to 1980s that excluded escalated benefits of water projects. Within this same timeframe, necessary elements were present to open a policy window, the Colorado Ute Indian Water Rights Settlement, which resulted in project construction. If strategists can learn to predict the opening of policy windows "when the problem, policy, and political streams join" water resource planning and policy can be improved. Retrospective narrative analysis is a promising ex post audit and evaluation tool that policy analysts can use to assess program performance and lessons learned. Social change implications of the study are that its findings on the need for positive collaboration may prove valuable to those in management who seek to address water scarcity issues.

Advanced wastewater treatment plants have complex biological kinetics, time variant influent rates and long processing times. The modeling and operation control of wastewater treatment plant gets complicated due to these characteristics. However, a robust operational system for a wastewater treatment plant is necessary to increase the efficiency of the plant, reduce energy cost and achieve environmental discharge limits. These discharge limits are set by the National Pollutant Discharge Elimination System (NPDES) for municipal and industrial wastewater treatment plants to limit the amount of nutrients being discharged into the aquatic systems. This document summarizes the research to develop a supervisory operational and control system for the Valrico Advanced Wastewater Treatment Plant (AWWTP) in the Hillsborough County, Florida. The Valrico AWWTP uses biological treatment process and has four oxidation ditches with extended aeration where simultaneous nitrification and denitrification (SND) takes place. Each oxidation ditch has its own anaerobic basin where in the absence of oxygen, the growth of microorganisms is controlled and which in return also helps in biological phosphorus removal. The principle objective of this research was to develop a working model for the Valrico AWWTP using BioWin which mimics the current performance of the plant, predicts the future effluent behavior and allows the operators to take control actions based on the effluent results to maintain the discharge permit limits. Influent and experimental data from online and offline sources were used to tune the BioWin model for the Valrico Plant. The validation and optimization of the BioWin model with plant data was done by running a series of simulations and carrying out sensitivity analysis on the model which also allowed the development of operation policies and control strategies. The control strategies were developed for the key variables such as aeration requirements in the oxidation ditch, recycle rates and wastage flow rates. A controller that manipulates the wasting flow rate based on the amount of mixed liquor suspended solids (MLSS) was incorporated in the model. The objective of this controller was to retain about 4500-4600 mg/L of MLSS in the oxidation ditch as it is maintained by the Valrico Plant. The Valrico AWWTP recycles around 80% of their effluent and hence, the split ratios were adjusted accordingly in the model to recycle the desired amount. The effluent concentrations from the BioWin model for the parameters such as Total Nitrogen (TN), Ammonia, Nitrate, Nitrite, Total Kjeldahl Nitrogen (TKN) complied with the discharge limits which is usually less than 2 mg/L for all the parameters.

In coastal urban regions, underground stormwater treatment units are suitable infrastructure options because they take less space where premium land is expensive. Even then, they should be accessible and ideally small enough to fit into existing stormwater networks. Since 2003, the City of Tampa and Florida’s Department of Transportation (FDOT) have installed 47 baffle boxes into the city’s stormwater pipe networks. Baffle boxes are underground stormwater treatment structures designed to capture sediments and floating debris. Since their deployment, many challenges regarding their practical sediment capturing performance was raised by the city. The objective of this research was to evaluate the effects of rainfall, land use, and maintenance on the sediment trapping efficiency of the baffle boxes and identify solutions to enhance their performance. This was addressed through site visits, sediment accumulation measurements and analysis of historical and field data. The results of these measurements and analysis were then compared to rainfall intensity, catchment characteristics, size and type of the units. During the preliminary site visits and sediment measurements it was observed that most of the units located in the south of Tampa were inundated by backflows from Tampa Bay. Survey information collected from inspection crew members also showed that resuspension of trapped sediments frequently occurs in these units. Concerning operation and maintenance (O&M), it was indicated that units mounted with screens are costly and difficult to clean-out. Additionally, it was found that 80% of the units have very small trap inlets and lack the baffle structures needed to slow down and settle sediments. Historical sediment measurements and O&M practices were analyzed to calculate the overall performance of the units. The analysis of the data determined the sediments captured, the resuspension rate, and yearly cost of maintenance for different types of baffle boxes. Rainfall intensity and land use and land cover (LULC) data for each catchment of the units was correlated to the performance of the units. The LULC data used impervious fraction and tree canopy area of the catchments to project sediment and leaf matter accumulation within the units. This research study found that total daily rainfall intensity is a good predictor of sediment accumulation. Cleanout crews can use this relationship to conduct their work efficiently and to promptly react to occurring rainfall events. Thus, the prediction of sediments accumulated from rainfall events and the coordination of clean-out trucks can optimize O&M practices. It was also determined that large-sized (24-40 in) units and those with three chambers (baffles) perform better at trapping sediments. Thus, installing baffles in units within the large-sized ones can enhance their performance. The study also found that baffle boxes mounted with screens can individually take up to eight hours to cleanup which makes them costly and difficult. This can be detrimental for municipalities to follow up on their O&M practices effectively. Therefore, to alleviate the clean out complexity and reduce maintenance expenditures complementary practices such as bag filters need to be explored and implemented for trials

Water security requires that sufficient quantities of water be available at critical times. This is particularly challenging for high-intensity urban and agricultural settings. In underdeveloped nations, streamflow is commonly the preferred water source, as it is readily available and delivered cost-free to users. Yet, the sources of these critical streamflows are often unknown. This issue is salient in the Northern Andes, where basic knowledge of controlling factors for the quantity, quality, and timing of runoff is lacking. High-elevation headwaters are the primary catchment areas in the Northern Andes, but the extent of water providing to municipalities in the Northern Andes is unknown. In this study, the contribution of water derived from the upper watershed to the streamflow in the Tulúa River which supplies water to 200,000 people in the city of Tulúa was quantified. The river runs 72 km through urban, agricultural, and industrial land use in the Central Cordillera of the Colombian Andes. We collected 32 and 34 water samples in August and November, respectively. The water samples were representative of high-elevation headwaters runoff, shallow groundwater discharge, and streamflow throughout the watershed. Samples were analyzed for dissolved constituents and stable isotopes. The dissolved constituents were used in mass-balance mixing models to identify the source of streamflow in the lower watershed of the Tulúa River, where it the river supports a large municipality. Results indicate that approximately 50% surface runoff largely originates as high-elevation headwater runoff, including high-elevation settings where páramos dominate the land cover. These findings underscore the need for source-water protection efforts in the upper watershed, including the páramos. This project serves as a model for other páramo derived watersheds, where source-water protection is a critical challenge.

Uncertainties were analyzed in three areas (remote sensing, dendroclimatology, and climate modeling) relevant to current water resources management. First, the research investigated the relationships between remotely sensed and in situ Snow Water Equivalent (SWE) datasets in three western U.S. basins. Agreement between SWE products was found to increase in lower elevation areas and later in the snowpack season. Principal Components Analysis (PCA) revealed two distinct snow regions among the datasets and Singular Value Decomposition (SVD) was used to link both data products with regional streamflow. Remotely sensed SWE was found to be sufficient to use in statistically based forecast models in which magnitude did not affect results. Second, the research investigated the dendroclimatic potential of a critical flood control and hydropower region in the southeastern U.S. (Tennessee Valley) using climate division precipitation and regional tree-ring chronology datasets. Tennessee Valley May–July precipitation was reconstructed from 1692 to 1980 (289 years) using a stepwise linear regression model (R2 = 0.56). Weibull analysis illustrated that the Tennessee Valley reconstruction model developed generally underestimated extreme precipitation and overestimated average precipitation. The longest May–July drought occurred over 10 consecutive years (1827–1836). Instrumental records indicated that the two most recent droughts (1985–1988 and 2006–2008) ranked second and third in severity in the past three centuries. Third, past, present, and future patterns and extremes in streamflow within the North Platte River Basin were investigated. A streamflow reconstruction dating back to 1383 using tree rings was created to provide a proxy for the long-term variability in the region. Projected streamflow datasets from the Community Climate System Model (CCSM) were gathered to acquire future insight of the hydroclimatic variability within the North Platte River Basin (NRPB). Drought analysis revealed that 2002–2008 was one of the driest periods in the past 600 years. Multiple CCSM projections suggest that in the future, drier (5th percentile) years will become wetter relative to 1970–1999 CCSM hindcasts. Future average (50th percentile) and wet (95th percentile) years may yield statistically higher streamflow compared to those seen in the historical (1383–1999) record, suggesting potential anthropogenic influence beyond the historic natural variability.

Section 303(d) of the Clean Water Act (CWA) requires states to assess and list all streams that do not meet water quality criteria for their designated use classes. In Tennessee, the Tennessee Department of Environment and Conservation (TDEC) uses macroinvertebrate surveys to assess the condition of streams designated for “fish and aquatic life” and the progress of targeted waterbodies toward meeting established standards for sediment. As of yet, no substrate metric has been established to monitor water quality or to document progress toward water quality improvement with respect to fish and aquatic life in Tennessee. A substrate metric that could be efficiently measured and would represent the needs of aquatic species would be valuable for monitoring streams with known sediment impairment to detect water quality improvement. The objectives of this study were to (1) investigate the relationships between riffle substrates and benthic macroinvertebrate data, provided by TDEC; (2) assess the potential use of substrate metrics as a monitoring tool for benthic habitat status; and (3) examine variation in riffle substrates over time in the Ridge and Valley Ecoregion of Tennessee. Bed and interstitial sediment were characterized at sites corresponding with TDEC macroinvertebrate sampling stations. Bed sediment characteristics were significantly correlated with benthic macroinvertebrate data; however, interstitial fines yielded no significant correlations with benthic macroinvertebrate data. Substrate metrics did not differ significantly between varying levels of impairment; however, they did differ significantly when all impaired sites were combined into a single impairment group. The lack of significant differences between varying classes of reach impairment suggests that substrate metrics may not be able to distinguish impairment at the level necessary for monitoring impairment. However, substrate metrics may be of potential use in monitoring sites where impairment is less ambiguous. To investigate change in riffle substrate over time, three sites were monitored over the course of a year. Preliminary observations showed little change in riffle substrate during the study period, suggesting that seasonal restrictions on substrate surveys are unneccessary.

Cypress Creek is an urbanizing watershed in the Gulf Coast region of Texas that contributes the largest inflow of urban runoff containing suspended solids to Lake Houston, the primary source of drinking water for the City of Houston. Historical water quality data was statistically analyzed to characterize the watershed and its pollutant sources. It was determined that the current sampling program provides limited information on the complex behaviors of pollutant sources in both dry weather and rainfall events. In order to further investigate the dynamics of pollutant export from Cypress Creek to Lake Houston, fully distributed hydrologic and water quality models were developed and employed to simulate high frequency small storms. A fully distributed hydrologic model, Vflo(TM) , was used to model streamflow during small storm events in Cypress Creek. Accurately modeling small rainfall events, which have traditionally been difficult to model, is necessary for investigation and design of watershed management since small storms occur more frequently. An assessment of the model for multiple storms shows that using radar rainfall input produces results well matched to the observed streamflow for both volume and peak streamflow. Building on the accuracy and utility of distributed hydrologic modeling, a water quality model was developed to simulate buildup, washoff, and advective transport of a conservative pollutant. Coupled with the physically based Vflo(TM) hydrologic model, the pollutant transport model was used to simulate the washoff and transport of total suspended solids for multiple small storm events in Cypress Creek Watershed. The output of this distributed buildup and washoff model was compared to storm water quality sampling in order to assess the performance of the model and to further temporally and spatially characterize the storm events. This effort was the first step towards developing a fully distributed water quality model that can be widely applied to a wide variety of watersheds. It provides the framework for future incorporation of more sophisticated pollutant dynamics and spatially explicit evaluation of best management practices and land use dynamics. This provides an important tool and decision aid for watershed and resource management and thus efficient protection of the sources waters.

To slow climate change, humans should take immediate and widespread action. One way to slow climate change is by switching to switch to renewable power plants such as solar fields. Recently, pioneering companies have built solar fields on water bodies. This study found that such a pairing of water and solar could increase production efficiency by 8-10% through panel cooling, save millions of liters of water from evaporation, and produce energy with under-utilized space.

The groundwater in agricultural karst areas is susceptible to contamination from organic soil amendments and pesticides. During major storm events during 2011, dye traces were initiated using sulphorhodamine-B, fluorescein and eosine in a groundwater recharge area where manure was applied to the ground. Fecal coliform samples were collected from significant storm events from January-September 2011. Water samples and geochemical data were collected every four hours before, during, and between the storm events from a waterfall in Crumps cave flowing from the known recharge area to track the transport and residence time of the epikarst water and organic soil amendments during variable flow conditions. Two dataloggers at the same waterfall were set up to collect 10-minute data, which included pH, specific conductivity, temperature, and discharge. Total rainfall amount and other surface meteorological data were collected from a rain station located above the cave. Cave water samples were collected for the analysis of anions, cations, bacterial count, and the presence of dye. The dye traces show variability in the characteristics of epikarstic response and flowpaths. The changes in geochemistry indicate simultaneous storage and transport of meteoric water through epikarst pathways into the cave, with rapid transport of bacteria occurring through the conduits that bypass storage. Fecal coliform counts were elevated all through the study period indicating survivability in soils through the seasons. The results indicate that significant precipitation events affect the storage properties and rapidly impact the various pathways and timing of contaminant transport through the epikarst zone, eventually allowing these contaminants to be transported unfiltered in to the groundwater supply. This study shows that current best management practices in karst lands need to be revisited to incorporate areas that do not have surface runoff but where contaminants are transported by seepage into local aquifer.