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Collaborators: Amanda Cox, Ph.D., P.E.; Ronaldo Luna, Ph.D., P.E.; Diana Meyers and Peter Kickham

Complex ground transportation networks coexist with dynamic river network systems and bridges are a common element at the intersections of these networks. A primary concern for bridge stability is scour, a turbulent physical process in which hydrodynamic forces (e.g., forces from water flow or wind) remove solid material (e.g. soil or rock). In fact, scour is the leading cause of bridge failure in the United States. Bridges that are susceptible to structural damage or failure from scour are termed 鈥渟cour critical鈥� bridges.

The objectives of this project are to:

• Provide the methodology used to determine soil/rock sampling locations and depths and the soil sampling and testing methods used
• Compare scour analysis results using data from different available hydraulic models
• Compare scour analyses to analyses of soil samples from the stream bed and to hydraulic model data
• Conduct a risk assessment, due to scour, for the bridges studied by the project

The research involves data collection from available sources, hydraulic modeling and field data collection. The field data collection consists of topographic and LiDAR surveys, bathymetric surveys, water velocity measurements and soil sampling. This study will contribute to a greater understanding of evaluating bridge scour and ultimately lead to improvements in bridge stability in the state of Missouri.

This is a collaborative project with Purdue University (PI), the University of Iowa (Co-PI), the University of Colorado 鈥� Boulder (Co-PI), and the NSF (sponsor).

Information on river shape, bed morphology and sediment load are critical to help inform research and management issues related to river channels. However, such information is not easily accessible and/or available in public domain. This project will create a web platform for aggregating, storing, sharing, and analyzing river-related scientific data. The proposed web platform, labeled RIMORPHIS, will serve as a clearing house for river morphology data that will help improve our overall understanding of national rivers鈥� health using scientifically rendered datasets.

RIMORPHIS can also support management of current and future issues of the nation鈥檚 stressed water resources. The data and tools developed for RIMORPHIS will create digital representations of three-dimensional river morphological structures of most U.S. rivers that can support fundamental research and practical needs related to stream rehabilitation, infrastructures design and food risk mitigation. Through this catalytic project, we will demonstrate how RIMORPHIS can improve river flow forecasts and produce accurate flood inundation maps that subsequently can help save lives and billions of dollars in flood damages.

This is a collaborative project with University of Portsmouth (PI), University of Nottingham (Co-PI) and U.S. Army Corps of Engineers (sponsor).

Rivers are dynamic systems that change over time in response to environmental and water management factors. River channels respond to disturbances in a variety of ways such as changing channel size, slope along the flow path and bed and bank materials. Forecasting these changes over many decades is challenging due to the variable nature of modeling input parameters (e.g., variable flow rates), uncertainty in computed sediment transport rates, and the complexity of how channels respond to having a surplus or deficit of sediment.

The goal of this project is to develop a tool to forecast changes in river form and riverbed material using a hybrid modeling approach. Existing sediment transport models are deterministic and lack complex channel response. The modeling tool being developed for this project is uncertainty-bounded and flexible to explore a range of possible future scenarios. As a hybrid model, it incorporates traditional process-based hydraulic and sediment transport models with a set of rules for how the channel responds to imbalances in sediment transport rates. Finally, the tool will provide a variety of indicators for various channel conditions.

This is a collaborative project with University of Iowa (Co-PI) and U.S. Army Corps of Engineers (sponsor).

Reservoirs are a vital component of our nation鈥檚 water-resources infrastructure, yet many reservoirs across the nation are slowly filling with sediment, reducing their effectiveness and increasing maintenance costs. Water-resources managers must develop sustainable sediment management plans for reservoirs to ensure the continuation of reservoir functions, which require reservoir capacity surveys to assess lost storage capacity and sedimentation rates.

The U.S. Army Corps of Engineers (USACE) has developed the Enhancing Reservoir Sedimentation Information for Climate Preparedness and Resilience (RSI) system to help evaluate aggradation trends, life expectancy and reservoir vulnerabilities to climate change. Survey data collected entail multiple methods, instruments and measurement protocols, which can lead to considerable differences in data that result in anomalies that require detection and correction before being permanently stored for further usage. Due to the large number of reservoirs in the RSI system and the numerous parameters that influence sedimentation, manual detection of data anomalies is a challenging, tedious and costly task.

The primary objective of the research project was to develop methods to identify anomalous data (likely erroneous) within the RSI system using machine learning algorithms. A secondary goal of the study was to use the RSI data along with supplementary data sources in conjunction with machine-learning to estimate sedimentation rates.

Data from the RSI system were analyzed to quantify capacity loss between consecutive reservoir surveys. A filtering process was developed to identify potentially erroneous survey data. Then, a survey of available supplemental data was conducted and a composite dataset was assembled. To further identify anomalous data, two machine learning methods were used: the automated anomaly detection (AAD) method and the Kolmogorov-Smirnov and Efron (KSE) method. Finally, the composite dataset was used with regression, machine learning and artificial intelligence methods to develop models for predicting capacity loss as a function of several reservoir and drainage basin properties.

This project will enhance our understanding of the role that river sediments play in controlling downstream nutrient loading, eutrophication and hypoxia and will help provide the foundation to enable future monitoring of sediment-related nutrient fluxes through ground-based remote sensing cameras. The Mississippi River makes an ideal study site because it features intensive agricultural land use, drains ~40% of the contiguous United States and has delivered excessive nutrient loads to the Gulf of Mexico that have led to eutrophic conditions. Our study will explore the potential for suspended and riverbed sediments to sequester excess nutrients from agriculture that enter rivers and may ultimately be delivered to the global ocean. We will correlate our sediment chemical data with depth modeling and remote sensing. Depth modeling will help identify the particle sizes which transport nutrients and where they are transported in the water column.

These efforts could be relevant to mechanical (flow turbulence) influences on nutrient and sediment attachment. Thus, there is potential to 鈥渆ngineer鈥� rivers (i.e., increase or decrease turbulent characteristics) to either reduce or increase the amount of nutrients that attach to sediments. Our remote sensing work will allow us to determine the overall input of nutrients in the suspended load to the ocean across space and time. Our study will be the first to explore the link between problems with nutrient loading and long-term sediment transport trends in the Mississippi River, allowing us to better estimate nutrient loads to the Gulf of Mexico. These efforts will inform ongoing management strategies to mitigate problems with marine dead zones.

Agricultural land use is essential for food production, but intensively managed landscapes can considerably alter the 鈥渃ritical zone,鈥� which is the thin, life-supporting layer of Earth鈥檚 surface from the tops of the trees to the bottom of the groundwater. Excess inputs of nutrients from chemical fertilizers and manures used in agriculture that enter aquatic environments can trigger algal blooms, which can have severe impacts on humans and ecosystems. Successful management of nutrient pollution requires understanding river systems, which transport excess nutrients to the ocean but can also sequester or transform them in the water column, channel bed sediments, floodplains or reservoirs.

We investigated the role of reservoirs in controlling water quality in agricultural critical zones and found that reservoir bed sediments can act as both nutrient sinks or sources for rivers. A long-term nutrient mass balance for an Illinois reservoir showed that sediment processes consistently removed nitrogen pollution from the water column over time. Phosphorus contamination was initially stored in reservoir sediments, but this storage capacity was exhausted and legacy phosphorus was subsequently released from the reservoir. Thus, reservoirs in agricultural critical zones can act as a sink for nitrogen but can change from a sink to a source for phosphorus over decadal timescales. Our study showed that agricultural reservoirs could become important sources for nutrient pollution in the future.

Collaborators: Carly Finegan-Dronchi, M.S., and Elizabeth Hasenmueller, Ph.D.

Untreated wastewater entering the environment through leaking infrastructure, faulty septic systems and sewer overflows threatens both human and aquatic health. Water managers need low cost field methods to detect wastewater contamination in real time to promptly employ mitigation strategies. While wastewater is traditionally detected in the environment using chemical or microbial tracers that allow it to be distinguished from natural water, these analyses are often expensive and performed in the lab. Optical brighteners, synthetic brightening compounds present in laundry detergents and paper products, are emerging as ideal tracers of wastewater because they can be quickly and inexpensively detected in the field.

To test the utility of optical brighteners as standalone and in situ wastewater tracers, optical brightener levels were compared with traditional wastewater indicators (e.g., B, F-, E. coli, microbial source tracking) in a suburban watershed (Fishpot Creek near St. Louis, Missouri). Stream samples were collected monthly across the watershed (26 sites) and weekly from a single outlet site from June 2019 to October 2020 to understand the utility of optical brighteners as tracers. Three mixing models using our wastewater tracers assessed the wastewater fraction in streamflow across the basin. Optical brightener values in the watershed were 6.3 - 59.7 RFU for the monthly samples, while influent wastewater averaged 142.7 卤 56.5 RFU. A significant (伪 = 0.05), positive correlation between optical brighteners and E. coli existed, but a low r value of 0.3 for the correlation suggested other sources of E. coli to the watershed (e.g., wildlife, pet waste). Of the wastewater tracers we used, only optical brighteners had a significant, positive correlation with wastewater infrastructure density (r = 0.6), indicating their utility to detect wastewater. Our mixing models also showed a significant, positive correlation between the wastewater fraction and sewer pipe density at each site. While using optical brighteners as wastewater tracers has limitations (e.g., photodecay, organic matter interferences), we find that they are more robust tracers than traditional wastewater indicators. Thus, optical brighteners are a good screening tool for identifying wastewater contributions to the environment.

Microplastic (plastic < 5 mm in size) contamination is ubiquitous and has been found in environments ranging from deep ocean floors to Artic Sea ice. Microplastics are concerning emerging contaminants because they degrade slowly, are highly mobile, and can be easily consumed by wildlife. Once ingested by organisms, microplastics can cause both physical tissue damage as well as toxicity due to adsorption of other contaminants (e.g., heavy metals, organic compounds) on their surfaces. Microplastic research has mainly focused on marine settings, but has more recently expanded to surface freshwater systems. However, only one previous study has quantified microplastic pollution in groundwater. Thus, the potential for microplastic contamination of groundwater systems is understudied, and the role of land use in microplastic sourcing and transport to aquifers is unknown. Understanding the origins and extent of microplastic pollution in groundwater systems is critical because these reservoirs are often used as drinking water resources. Microplastic surveys of groundwater resources are a necessary first step in understanding the possible negative consequences to human health. Furthermore, karst environments often host fragile ecosystems (e.g., cave wildlife) and aquifers can discharge groundwater to surface water systems. Organisms in both subsurface and surface environments may be impacted by deteriorating groundwater quality due to plastic pollution.

The proposed study will assess microplastic loads in karst groundwater springs in Missouri across a range of land uses, including the highly urbanized St. Louis metropolitan area as well as agriculturally-dominated and rural landscapes in central and southern Missouri. The research will also provide novel information on how microplastic contamination is transported to and through groundwater systems, which will help inform land managers for debris mitigation strategies. The proposed study will constitute a novel and important contribution to our understanding of the distribution of microplastics in water resources, which is essential to ensure both human and ecosystem health.

Collaborators: Teresa Baraza, M.S., and Elizabeth Hasenmueller, Ph.D.

Carbonate critical zones (CZs) are often characterized by the presence of dissolution features in bedrock that lead to high connectivity between the surface and subsurface. Carbonate aquifers can therefore be highly susceptible to anthropogenic contamination compared to aquifers in silicate CZs. Microplastics (plastic < 5 mm) are emerging contaminants that are ubiquitous in the environment. Because they degrade slowly and are highly mobile, microplastics can travel long distances and be easily ingested by wildlife. Microplastic research mainly focuses on marine and surface freshwater environments, with groundwater systems remaining understudied.

Thus, our study identifies microplastic sources and transport mechanisms through an aquifer in a carbonate CZ. We continuously monitored in situ water quality (e.g., temperature, specific conductivity, pH) and level for a stream issuing from a cave hosted in St. Louis Limestone (Cliff Cave; St. Louis, Missouri) from February 2020 to February 2021. We also collected water samples under a range of flow conditions, employing both weekly and high frequency flood sampling (four flood events total). Samples were analyzed for microplastic content and characteristics as well as other analytes (e.g., total suspended solids (TSS), ion chemistry, O and H isotopes). Microplastics were found in all samples, with concentrations of 2.1 鈥� 82.5 counts/L. For all microplastics, the dominant morphology was fiber (93.0%) and the most common color was clear (59.7%). Total microplastic concentrations had significant, positive correlations with water level and TSS (R2 > 0.18; p < 0.05) but significant, negative correlations with specific conductivity and pH (R2 > 0.17 p < 0.05).

Our findings indicate that microplastic transport is enhanced during floods in karst systems, when dilute and sediment-rich surface runoff enters aquifers through sinkholes and fractures. Antecedent moisture conditions may also play a role in microplastic transport because floods occurring after dry periods tend to have higher microplastic loads compared to floods following wetter conditions, even when peak stage values are comparable. Our study gives new insight into how microplastic contamination is transported to and through carbonate CZs, which will help inform debris mitigation strategies.

Collaborators: Natalie F. Hernandez, M.S., and Elizabeth A. Hasenmueller, Ph.D.

Microplastics, 1 渭m 鈥� 5 mm plastic particles, are ubiquitous global contaminants. The debris is concerning to human and ecological health due to ingestion by a range of species and presence in commonly consumed human foods and beverages. To regulate microplastics effectively, we must understand their sources, storage and transport. Small urban streams connect city plastic sources to rivers and the global ocean. These systems experience extreme changes in flow, exhibiting floods that may dramatically enhance sediment and contaminant transport, followed by periods of low discharge when debris may be stored. Erratic flow in urban streams suggests dynamic partitioning of microplastics across sediment and water, influencing stream storage and transport. Our research characterizes the role of an urban stream (Deer Creek near St. Louis, Missouri) in microplastic storage and transport across time and space. Samples were collected March to August 2021 from a single site weekly at low flow and at high frequency during a flood. Microplastics and other geochemical parameters were measured and compared with discharge to assess potential plastic sources including particle suspension within the catchment (e.g., using total suspended solids (TSS)) and wastewater inputs (e.g., using fluoride and optical brighteners (whiteners in laundry detergent)).

Microplastics were found in most samples (93%; n = 27) with the highest concentration (35.9 particles/L) found near peak flood flow. For all plastics, the dominant shape was fiber (88%) and common colors were clear (34%) and blue (33%). Total microplastics in flow lower than or near the stream鈥檚 average of 0.36 m3/s exhibited no correlations with other geochemical parameters. However, preliminary flood data indicate enhanced microplastic concentrations during high discharge (flow up to 4.87 m3/s) when TSS was elevated. Microplastics in floods are likely sourced from a combination of surface runoff inputs and resuspension of bed sediments. Ongoing analyses of temporal and spatial water and sediment samples will identify sources, storage and transport of plastic debris across the basin, seasons and floods. Our study results will clarify how microplastics partition between sediment and water in variable hydrologic conditions, with implications for export downstream.

Collaborators: Crystal Bell, M.S.; Craig Adams, Ph.D., P.E., F.ASCE; Rachel Rimmerman, MBA

Many different filtration technologies are employed in areas of the world without centralized drinking water systems. Some of these technologies remain effective for long periods of time (with proper maintenance), while others have been shown to actually degrade water quality after relatively short periods of time. Further, different filters are designed to address varied treatment objectives with respect to biological, chemical and physical water quality parameters. This project is focused on testing both commonly used water treatment technologies and water quality analytical methods employed with the objective to develop guidance recommendations. 

The WATER Institute faculty and staff provide mentorship, expertise and support for the SLU student organization Billikens for Clean Water, with the goal of raising awareness around water crises locally and globally and partnering for community impact around water issues. Most recently, the group has worked closely with partners in Belize on household drinking water initiatives in a community without a centralized drinking water system. They have also partnered with Belizean educators to host water quality education workshops. 

The WATER Institute served on the Missouri Filter First Coalition steering committee throughout 2021-2022, which included Great Rivers Environmental Law Center, Metropolitan Congregations United and Environment Missouri. The Coalition raised awareness about the issue and advocated for passage of a Missouri bill addressing lead levels in school drinking water throughout the 2022 legislative session. The policy passed the state legislature in spring 2022 with overwhelming bipartisan support and was signed into law by Governor Parsons in June 2022. The bill will increase protections for Missouri schoolchildren by requiring testing for and filtering of lead in school drinking water outlets.