Browsing by Author "Grant, Stanley B."

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    Addressing the Contribution of Indirect Potable Reuse to Inland Freshwater Salinization
    Bhide, Shantanu V.; Grant, Stanley B.; Parker, Emily A.; Rippy, Megan A.; Godrej, Adil N.; Kaushal, Sujay S.; Prelewicz, Gregory; Saji, Niffy; Curtis, Shannon; Vikesland, Peter J.; Maile-Moskowitz, Ayella; Edwards, Marc A.; Lopez, Kathryn; Birkland, Thomas A.; Schenk, Todd (2021-02-02)
    Inland freshwater salinity is rising worldwide, a phenomenon called the freshwater salinization syndrome (FSS). We investigate a potential conflict between managing the FSS and indirect potable reuse, the practice of augmenting water supplies through the addition of reclaimed wastewater to surface waters and groundwaters. From time-series data collected over 25 years, we quantify the contributions of three salinity sources—a wastewater reclamation facility and two rapidly urbanizing watersheds—to the rising concentration of sodium (a major ion associated with the FSS) in a regionally important drinking water reservoir in the Mid-Atlantic United States. Sodium mass loading to the reservoir is primarily from watershed runoff during wet weather and reclaimed wastewater during dry weather. Across all timescales evaluated, sodium concentration in the reclaimed wastewater is higher than in outflow from the two watersheds. Sodium in reclaimed wastewater originates from chemicals added during wastewater treatment, industrial and commercial discharges, human excretion, and down-drain disposal of drinking water and sodium-rich household products. Thus, numerous opportunities exist to reduce the contribution of indirect potable reuse to sodium pollution at this site, and the FSS more generally. These efforts will require deliberative engagement with a diverse community of watershed stakeholders and careful consideration of the local political, social, and environmental context.
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    The anthropogenic salt cycle
    Kaushal, Sujay S.; Likens, Gene E.; Mayer, Paul M.; Shatkay, Ruth R.; Shelton, Sydney A.; Grant, Stanley B.; Utz, Ryan M.; Yaculak, Alexis M.; Maas, Carly M.; Reimer, Jenna E.; Bhide, Shantanu V.; Malin, Joseph T.; Rippy, Megan A. (SpringerNature, 2023-10-31)
    Increasing salt production and use is shifting the natural balances of salt ions across Earth systems, causing interrelated effects across biophysical systems collectively known as freshwater salinization syndrome. In this Review, we conceptualize the natural salt cycle and synthesize increasing global trends of salt production and riverine salt concentrations and fluxes. The natural salt cycle is primarily driven by relatively slow geologic and hydrologic processes that bring different salts to the surface of the Earth. Anthropogenic activities have accelerated the processes, timescales and magnitudes of salt fluxes and altered their directionality, creating an anthropogenic salt cycle. Global salt production has increased rapidly over the past century for different salts, with approximately 300 Mt of NaCl produced per year. A salt budget for the USA suggests that salt fluxes in rivers can be within similar orders of magnitude as anthropogenic salt fluxes, and there can be substantial accumulation of salt in watersheds. Excess salt propagates along the anthropogenic salt cycle, causing freshwater salinization syndrome to extend beyond freshwater supplies and affect food and energy production, air quality, human health and infrastructure. There is a need to identify environmental limits and thresholds for salt ions and reduce salinization before planetary boundaries are exceeded, causing serious or irreversible damage across Earth systems.
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    Balancing the Water Budget: the effect of plant functional type on infiltration to harvest ratios in stormwater bioretention cells
    Krauss, Lauren Marie (Virginia Tech, 2021-01-19)
    Stormwater bioretention cells (BRCs) are a variety of green stormwater infrastructure with the potential to restore pre-urban water balance, provided they can be tailored to infiltrate and evapotranspire (i.e., harvest) urban runoff in proportions consistent with pre-urban hydrologic conditions. This paper evaluates their capacity to do so, focusing on evapotranspirative harvest, which is relatively understudied, and the capacity of CSR (Competitve, Stress-tolerant, and Ruderal) functional type to serve as an overarching framework characterizing the water use strategy of BRC plants. The goal is to determine if harvest (and therefore the ratio of urban runoff infiltrated to harvested; the I:H ratio) might be fine-tuned to meet pre-urban values in BRCs through informed manipulation of plant community composition. This study focuses on 3 critical plant water use traits, the turgor loss point, the point of incipient water stress, and maximum stomatal conductance. A global plant traits meta-analysis identified degree of plant competitiveness and stress tolerance as significant determinants of all three water use traits, with stem type (woody vs herbaceous) also being significant, but only for turgor loss point. Based on these results, six water use scenarios appropriate for plants with different CSR type/stem type combinations were developed. BRC plants spanning the range of CSR types necessary to actionize these scenarios were determined to be available in eight major climate zones of the coterminous US, suggesting that regulating plant water use in BRCs using CSR is likely feasible. Hydraulic simulations (Hydrus 1D) were conducted for each scenario in all eight climate zones and revealed significant differences in evapotranspirative harvest and I:H ratios in simulated BRCs. Competitive woody plants had the highest evapotranspiration and lowest I:H ratios; 1.5-1.8 times more evapotranspiration and a 1.6-2 times lower I:H ratio than stress tolerant herbaceous plants, on average, across climate zones. Despite these significant differences, no simulated BRC in any climate zone was capable of reproducing pre-urban I:H ratios, regardless of plant type. More water was infiltrated than harvested in all scenarios and climates with the inverse being true for all pre-urban conditions. This suggests that absent additional sources of harvest (e.g., use of BRC water for nonpotable purposes such as toilet flushing and outdoor irrigation, or adoption of novel BRC designs that promote lateral exfiltration, stimulating "extra" evapotranspiration from nearby landscapes), BRCs will be unable to restore pre-urban water balance on their own. If true, then using BRCs in combination with other green technologies (particularly those biased towards harvest), may be the best path forward for balancing urban water budgets.
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    Can Common Pool Resource Theory Catalyze Stakeholder-Driven Solutions to the Freshwater Salinization Syndrome?
    Grant, Stanley B.; Rippy, Megan A.; Birkland, Thomas A.; Schenk, Todd; Rowles, Kristin; Misra, Shalini; Aminpour, Payam; Kaushal, Sujay; Vikesland, Peter J.; Berglund, Emily; Gomez-Velez, Jesus D.; Hotchkiss, Erin R.; Perez, Gabriel; Zhang, Harry X.; Armstrong, Kingston; Bhide, Shantanu V.; Krauss, Lauren; Maas, Carly; Mendoza, Kent; Shipman, Caitlin; Zhang, Yadong; Zhong, Yinman (American Chemical Society, 2022-09-14)
    Freshwater salinity is rising across many regions of the United States as well as globally, a phenomenon called the freshwater salinization syndrome (FSS). The FSS mobilizes organic carbon, nutrients, heavy metals, and other contaminants sequestered in soils and freshwater sediments, alters the structures and functions of soils, streams, and riparian ecosystems, threatens drinking water supplies, and undermines progress toward many of the United Nations Sustainable Development Goals. There is an urgent need to leverage the current understanding of salinization's causes and consequences?in partnership with engineers, social scientists, policymakers, and other stakeholders?into locally tailored approaches for balancing our nation's salt budget. In this feature, we propose that the FSS can be understood as a common pool resource problem and explore Nobel Laureate Elinor Ostrom's social-ecological systems framework as an approach for identifying the conditions under which local actors may work collectively to manage the FSS in the absence of top-down regulatory controls. We adopt as a case study rising sodium concentrations in the Occoquan Reservoir, a critical water supply for up to one million residents in Northern Virginia (USA), to illustrate emerging impacts, underlying causes, possible solutions, and critical research needs.
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    Can Smart Stormwater Systems Outsmart the Weather? Stormwater Capture with Real-Time Control in Southern California
    Parker, Emily A.; Grant, Stanley B.; Sahin, Abdullah; Vrugt, Jasper A.; Brand, Matthew W. (2022-01-14)
    Stormwater capture systems have the potential to address many urban stormwater management challenges, particularly in water-scarce regions like Southern California. Here, we investigate the potential best-case limits of water supply and stormwater retention benefits delivered by a 10,000 m3 stormwater capture system equipped with real-time control (RTC) on a university campus in Southern California. Using a copula-based conditional probability analysis, two performance metrics (percent of water demand satisfied and the percent of stormwater runoff captured) are benchmarked relative to (1) precipitation seasonality (historical rainfall and a counterfactual in which the same average annual rainfall is distributed evenly over the year); (2) annual precipitation (dry, median, and wet years); and (3) three RTC algorithms (no knowledge of future rainfall or perfect knowledge of future rainfall 1 or 2 days in advance). RTC improves stormwater retention, particularly for the highly seasonal rainfall patterns in Southern California, but not water supply. Improvements to the latter will likely require implementing stormwater capture RTC in conjunction with other stormwater infrastructure innovations, such as spreading basins for groundwater recharge and widespread adoption of green stormwater infrastructure.
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    Contextualization and Sodium Diet Implications of Occoquan Reservoir Salinization
    Shipman, Caitlin Mariah (Virginia Tech, 2023-03-17)
    Freshwater salinization syndrome is a rising threat globally which results in increased ion concentrations in inland freshwaters. This syndrome threatens healthy aquatic ecosystems and can alter the perception of the potability of finished drinking water. The Occoquan Reservoir, located in Northern Virginia, is a freshwater system that is facing rising salinization. Stakeholders for the reservoir have been convened to address these rising salinization concerns. Among these stakeholders, there are a variety of viewpoints on the significance of the salinization, which is preventing a high level of convergence around this threat. To assist in contextualizing this system, empirical cumulative distribution functions were generated from data gathered from various governmental sources and compared the reservoir's watershed and finished drinking water ion concentrations. These analyses show that the watershed and finished drinking water have some of the highest concentrations of sodium and chloride statewide. Additional investigations determined the trend of sodium increases in finished drinking water since the 1980s. Monte Carlo simulations were ran to determined whether there would be risks to human from ingesting this water should this trend continued. Results from these analyses greatly varied due to the wide range in drinking water ingestion rates. The purpose of these analyses is to assist with stakeholder convergence around the level of threat salinization poses to the reservoir and to initiate discussions of what an acceptable threshold for management could be.
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    Environmental Impact Bonds: a common framework and looking ahead
    Brand, M. W.; Quesnel, K.; Saksa, P.; Ulibarri, N.; Bomblies, A.; Mandle, L.; Allaire, M.; Wing, O.; Tobin-de la Puente, J.; Parker, E. A.; Nay, J.; Sanders, Brett F.; Rosowsky, D.; Lee, J.; Johnson, K.; Gudino-Elizondo, N.; Ajami, N.; Wobbrock, N.; Adriaens, P.; Grant, Stanley B.; Wright, S.; Gartner, T.; Knight, Z.; Gibbons, J. P. (2021-07-27)
    A frequent barrier to addressing some of our world’s most pressing environmental challenges is a lack of funding. Currently, environmental project funding largely comes from philanthropic and public sources, but this does not meet current needs. Increased coordination and collaboration between multiple levels and sectors of government, in addition to private sector funding, can help address the environmental funding challenge. New financial tools and strategies can enable this transition and facilitate uptake of innovative solutions. One such mechanism, the Environmental Impact Bond (EIB), is an emerging financial tool with the potential to transformthe environmental funding landscape. However, these financial instruments are not well understood or recognized beyond those actively involved in EIB projects or in the field of conservation finance. As EIBs gain momentum, there is a clear need for a common framework, including definitions and nomenclature, research needs, and outlook for the future. In this paper, we define EIB mechanics, elucidate the difference between EIBs and Green Bonds, and propose a common vocabulary for the field. Drawing on first-hand experience with the few EIBs which have been deployed, we review and assess lessons learned, trends, and paths for the future. Finally, we propose a set of future targets and discuss research goals for the field to unify around. Through this work, we identify a concrete set of research gaps and objectives, providing evidence for EIBs as one important tool in the environmental finance toolbox.
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    Five state factors control progressive stages of freshwater salinization syndrome
    Kaushal, Sujay S.; Mayer, Paul M.; Likens, Gene E.; Reimer, Jenna E.; Maas, Carly M.; Rippy, Megan A.; Grant, Stanley B.; Hart, Ian; Utz, Ryan M.; Shatkay, Ruth R.; Wessel, Barret M.; Maietta, Christine E.; Pace, Michael L.; Duan, Shuiwang; Boger, Walter L.; Yaculak, Alexis M.; Galella, Joseph G.; Wood, Kelsey L.; Morel, Carol J.; Nguyen, William; Querubin, Shane Elizabeth C.; Sukert, Rebecca A.; Lowien, Anna; Houde, Alyssa Wellman; Roussel, Anais; Houston, Andrew J.; Cacopardo, Ari; Ho, Cristy; Talbot-Wendlandt, Haley; Widmer, Jacob M.; Slagle, Jairus; Bader, James A.; Chong, Jeng Hann; Wollney, Jenna; Kim, Jordan; Shepherd, Lauren; Wilfong, Matthew T.; Houlihan, Megan; Sedghi, Nathan; Butcher, Rebecca; Chaudhary, Sona; Becker, William D. (Wiley, 2022-03-16)
    Factors driving freshwater salinization syndrome (FSS) influence the severity of impacts and chances for recovery. We hypothesize that spread of FSS across ecosystems is a function of interactions among five state factors: human activities, geology, flowpaths, climate, and time. (1) Human activities drive pulsed or chronic inputs of salt ions and mobilization of chemical contaminants. (2) Geology drives rates of erosion, weathering, ion exchange, and acidification-alkalinization. (3) Flowpaths drive salinization and contaminant mobilization along hydrologic cycles. (4) Climate drives rising water temperatures, salt stress, and evaporative concentration of ions and saltwater intrusion. (5) Time influences consequences, thresholds, and potentials for ecosystem recovery. We hypothesize that state factors advance FSS in distinct stages, which eventually contribute to failures in systems-level functions (supporting drinking water, crops, biodiversity, infrastructure, etc.). We present future research directions for protecting freshwaters at risk based on five state factors and stages from diagnosis to prognosis to cure.
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    Freshwater salinization syndrome limits management efforts to improve water quality
    Maas, Carly M.; Kaushal, Sujay S.; Rippy, Megan A.; Mayer, Paul M.; Grant, Stanley B.; Shatkay, Ruth R.; Malin, Joseph T.; Bhide, Shantanu V.; Vikesland, Peter J.; Krauss, Lauren; Reimer, Jenna E.; Yaculak, Alexis M. (Frontiers, 2023-09-22)
    Freshwater Salinization Syndrome (FSS) refers to groups of biological, physical, and chemical impacts which commonly occur together in response to salinization. FSS can be assessed by the mobilization of chemical mixtures, termed “chemical cocktails”, in watersheds. Currently, we do not know if salinization and mobilization of chemical cocktails along streams can be mitigated or reversed using restoration and conservation strategies. We investigated 1) the formation of chemical cocktails temporally and spatially along streams experiencing different levels of restoration and riparian forest conservation and 2) the potential for attenuation of chemical cocktails and salt ions along flowpaths through conservation and restoration areas. We monitored high-frequency temporal and longitudinal changes in streamwater chemistry in response to different pollution events (i.e., road salt, stormwater runoff, wastewater effluent, and baseflow conditions) and several types of watershed management or conservation efforts in six urban watersheds in the Chesapeake Bay watershed. Principal component analysis (PCA) indicates that chemical cocktails which formed along flowpaths (i.e., permanent reaches of a stream) varied due to pollution events. In response to winter road salt applications, the chemical cocktails were enriched in salts and metals (e.g., Na+, Mn, and Cu). During most baseflow and stormflow conditions, chemical cocktails were less enriched in salt ions and trace metals. Downstream attenuation of salt ions occurred during baseflow and stormflow conditions along flowpaths through regional parks, stream-floodplain restorations, and a national park. Conversely, chemical mixtures of salt ions and metals, which formed in response to multiple road salt applications or prolonged road salt exposure, did not show patterns of rapid attenuation downstream. Multiple linear regression was used to investigate variables that influence changes in chemical cocktails along flowpaths. Attenuation and dilution of salt ions and chemical cocktails along stream flowpaths was significantly related to riparian forest buffer width, types of salt pollution, and distance downstream. Although salt ions and chemical cocktails can be attenuated and diluted in response to conservation and restoration efforts at lower concentration ranges, there can be limitations in attenuation during road salt events, particularly if storm drains bypass riparian buffers.
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    From yards to cities: a simple and generalizable probabilistic framework for upscaling outdoor water conservation behavior
    Grant, Stanley B.; Duong, Kimberly; Rippy, Megan A.; Pierce, Gregory; Feldman, David; Zanetti, Enrique; McNulty, Amy (2020-05)
    Outdoor watering of lawns accounts for about half of single-family residential potable water demand in the arid southwest United States. Consequently, many water utilities in the region offer customers cash rebates to replace lawns with drought tolerant landscaping. Here we present a parcel-scale analysis of water savings achieved by a 'cash-for-grass' program offered to 60 000 homes in Southern California. The probability a resident will participate in the program, and the lawn area they replace with drought tolerant landscaping, both increase with a home's outdoor area. The participation probability is also higher if a home is occupied by its owner. From these results we derive and test a simple and generalizable probabilistic framework for upscaling water conservation behavior at the parcel-scale to overall water savings at the city- or water provider-scale, accounting for the probability distribution of parcel outdoor areas across a utility's service area, climate, cultural drivers of landscape choices, conservation behavior, equity concerns, and financial incentives.
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    Longitudinal stream synoptic monitoring tracks chemicals along watershed continuums: a typology of trends
    Kaushal, Sujay S.; Maas, Carly M.; Mayer, Paul M.; Newcomer-Johnson, Tammy A.; Grant, Stanley B.; Rippy, Megan A.; Shatkay, Ruth R.; Leathers, Jonathan; Gold, Arthur J.; Smith, Cassandra; McMullen, Evan C.; Haq, Shahan; Smith, Rose; Duan, Shuiwang; Malin, Joseph; Yaculak, Alexis; Reimer, Jenna E.; Newcomb, Katie Delaney; Raley, Ashley Sides; Collison, Daniel C.; Galella, Joseph G.; Grese, Melissa; Sivirichi, Gwendolyn; Doody, Thomas R.; Vikesland, Peter J.; Bhide, Shantanu V.; Krauss, Lauren; Daugherty, Madeline; Stavrou, Christina; Etheredge, MaKayla; Ziegler, Jillian; Kirschnick, Andrew; England, William; Belt, Kenneth T. (Frontiers, 2023-06-09)
    There are challenges in monitoring and managing water quality due to spatial and temporal heterogeneity in contaminant sources, transport, and transformations. We demonstrate the importance of longitudinal stream synoptic (LSS) monitoring, which can track combinations of water quality parameters along flowpaths across space and time. Specifically, we analyze longitudinal patterns of chemical mixtures of carbon, nutrients, greenhouse gasses, salts, and metals concentrations along 10 flowpaths draining 1,765 km2 of the Chesapeake Bay region. These 10 longitudinal stream flowpaths are drained by watersheds experiencing either urban degradation, forest and wetland conservation, or stream and floodplain restoration. Along the 10 longitudinal stream flowpaths, we monitored over 300 total sampling sites along a combined stream length of 337 km. Synoptic monitoring along longitudinal flowpaths revealed: (1) increasing, decreasing, piecewise, or no trends and transitions in water quality with increasing distance downstream, which provide insights into water quality processes along flowpaths; (2) longitudinal trends and transitions in water quality along flowpaths can be quantified and compared using simple linear and non-linear statistical relationships with distance downstream and/or land use/land cover attributes, (3) attenuation and transformation of chemical cocktails along flowpaths depend on: spatial scales, pollution sources, and transitions in land use and management, hydrology, and restoration. We compared our LSS patterns with others from the global literature to synthesize a typology of longitudinal water quality trends and transitions in streams and rivers based on hydrological, biological, and geochemical processes. Applications of LSS monitoring along flowpaths from our results and the literature reveal: (1) if there are shifts in pollution sources, trends, and transitions along flowpaths, (2) which pollution sources can spread further downstream to sensitive receiving waters such as drinking water supplies and coastal zones, and (3) if transitions in land use, conservation, management, or restoration can attenuate downstream transport of pollution sources. Our typology of longitudinal water quality responses along flowpaths combines many observations across suites of chemicals that can follow predictable patterns based on watershed characteristics. Our typology of longitudinal water quality responses also provides a foundation for future studies, watershed assessments, evaluating watershed management and stream restoration, and comparing watershed responses to non-point and point pollution sources along streams and rivers. LSS monitoring, which integrates both spatial and temporal dimensions and considers multiple contaminants together (a chemical cocktail approach), can be a comprehensive strategy for tracking sources, fate, and transport of pollutants along stream flowpaths and making comparisons of water quality patterns across different watersheds and regions.
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    Modeling the Effects of Turbulence on Hyporheic Exchange and Local-to-Global Nutrient Processing in Streams
    Grant, Stanley B.; Gomez-Velez, Jesus D.; Ghisalberti, Marco (2018-09)
    New experimental techniques are allowing, for the first time, direct visualization of mass and momentum transport across the sediment-water interface in streams. These experimental insights are catalyzing a renaissance in our understanding of the role stream turbulence plays in a host of critical ecosystem services, including nutrient cycling. In this commentary, we briefly review the nature of stream turbulence and its role in hyporheic exchange and nutrient cycling in streams. A simple process-based model, borrowed from biochemical engineering, provides the link between empirical relationships for grain-scale turbulent mixing and nutrient processing at reach, catchment, continental, and global scales.
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    A One-Dimensional Model for Turbulent Mixing in the Benthic Biolayer of Stream and Coastal Sediments
    Grant, Stanley B.; Gomez-Velez, Jesus D.; Ghisalberti, Marco; Guymer, Ian; Boano, Fulvio; Roche, Kevin; Harvey, Judson (2020-12)
    In this paper, we develop and validate a rigorous modeling framework, based on Duhamel's Theorem, for the unsteady one-dimensional vertical transport of a solute across a flat sediment-water interface (SWI) and through the benthic biolayer of a turbulent stream. The modeling framework is novel in capturing the two-way coupling between evolving solute concentrations above and below the SWI and in allowing for a depth-varying diffusivity. Three diffusivity profiles within the sediment (constant, exponentially decaying, and a hybrid model) are evaluated against an extensive set of previously published laboratory measurements of turbulent mass transfer across the SWI. The exponential diffusivity profile best represents experimental observations and its reference diffusivity scales with the permeability Reynolds number, a dimensionless measure of turbulence at the SWI. The depth over which turbulence-enhanced diffusivity decays is of the order of centimeters and comparable to the thickness of the benthic biolayer. Thus, turbulent mixing across the SWI may serve as a universal transport mechanism, supplying the nutrient and energy fluxes needed to sustain microbial growth, and nutrient processing, in the benthic biolayer of stream and coastal sediments.
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    Predicting Solute Transport Through Green Stormwater Infrastructure With Unsteady Transit Time Distribution Theory
    Parker, E. A.; Grant, Stanley B.; Cao, Y.; Rippy, Megan A.; McGuire, Kevin J.; Holden, P. A.; Feraud, M.; Avasarala, S.; Liu, H.; Hung, W. C.; Rugh, M.; Jay, J.; Peng, J.; Shao, S.; Li, D. (2021-02)
    In this study, we explore the use of unsteady transit time distribution (TTD) theory to model solute transport in biofilters, a popular form of nature-based or "green" storm water infrastructure (GSI). TTD theory has the potential to address many unresolved challenges associated with predicting pollutant fate and transport through these systems, including unsteadiness in the water balance (time-varying inflows, outflows, and storage), unsteadiness in pollutant loading, time-dependent reactions, and scale-up to GSI networks and urban catchments. From a solution to the unsteady age conservation equation under uniform sampling, we derive an explicit expression for solute breakthrough during and after one or more storm events. The solution is calibrated and validated with breakthrough data from 17 simulated storms at a field-scale biofilter test facility in Southern California, using bromide as a conservative tracer. TTD theory closely reproduces bromide breakthrough concentrations, provided that lateral exchange with the surrounding soil is accounted for. At any given time, according to theory, more than half of the water in storage is from the most recent storm, while the rest is a mixture of penultimate and earlier storms. Thus, key management endpoints, such as the pollutant treatment credit attributable to GSI, are likely to depend on the evolving age distribution of water stored and released by these systems.
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    Re‐envisioning stormwater infrastructure for ultrahazardous flooding
    Sanders, Brett F.; Grant, Stanley B. (Wiley, 2020-03)
    Ultrahazardous flooding (UHF) occurs on low relief topography at the foot of mountain catchments and is characterized by rapid-onset, high-velocity flood flows, large fluxes of sediment and debris, and unpredictable flow paths. 20th century stormwater infrastructure seeks to contain UHF, up to a design level, using combinations of basins, reservoirs and flood control channels. However, these flood control elements may increase the risk of disasters due to: (a) increasingly frequent and intense wildfires that amplify streamflow and debris fluxes beyond infrastructure design capacity; (b) aging and underfunded infrastructure which is susceptible to clogging and failure during extreme events; and (c) expansive urban development where communities are relatively heavily on gray (hardened “levee effect.” 20th century stormwater infrastructure for UHF has also left communities with a legacy of social and environmental challenges including poor water quality, degraded habitats, high maintenance costs, unrealized urban amenities, and altered sediment fluxes. Adopting the Los Angeles Metropolitan Region as a type-locality for UHF, we propose a new paradigm for stormwater infrastructure based on the concept of erodible flood corridors. Our vision aims for greater sustainability and resilience to extreme events based on congruency with natural processes, conservation of resources and associated ecosystem services, minimization of flood exposure and vulnerability, and avoidance of legacy risk and energy intensive practices.
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    The sanitary sewer unit hydrograph model: A comprehensive tool for wastewater flow modeling and inflow-infiltration simulations
    Perez, Gabriel; Gomez-Velez, Jesus D.; Grant, Stanley B. (Elsevier, 2023-12-08)
    Sanitary sewer systems are critical urban water infrastructure that protect both human and environmental health. Their design, operation, and monitoring require novel modeling techniques that capture dominant processes while allowing for computationally efficient simulations. Open water flow in sewers and rivers are intrinsically similar processes. With this in mind, we formulated a new parsimonious model inspired by the Width Function Instantaneous Unit Hydrograph (WFIUH) approach, widely used to predict rainfall-runoff relationships in watersheds, to a sanitary sewer system consisting of nearly 10,000 sewer conduits and 120,000 residential and commercial sewage connections in Northern Virginia, U.S.A. Model predictions for the three primary components of sanitary flow, including Base Wastewater Flow (BWF), Groundwater Infiltration (GWI), and Runoff Derived Infiltration and Inflow (RDII), compare favorably with the more computationally demanding industry-standard Storm Water Management Model (SWMM). This novel application of the WFIUH modeling framework should support a number of critical water quality endpoints, including (i) sewer hydrograph separation through the quantification of BWF, GWI, and RDII outflows, (ii) evaluation of the impact of new urban developments on sewage flow dynamics, (iii) monitoring and mitigation of sanitary sewer overflows, and (iv) design and interpretation of wastewater surveillance studies.
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    Solute Transport Through Unsteady Hydrologic Systems Along a Plug Flow-To-Uniform Sampling Continuum
    Grant, Stanley B.; Harman, Ciaran J. (American Geophysical Union, 2022-08-22)
    Unsteady transit time distribution (TTD) theory is a promising new approach for merging hydrologic and water quality models at the catchment scale. A major obstacle to widespread adoption of the theory, however, has been the specification of the StorAge Selection (SAS) function, which describes how the selection of water for outflow is biased by age. In this paper we hypothesize that some unsteady hydrologic systems of practical interest can be described, to first-order, by a “shifted-uniform” SAS that falls along a continuum between plug flow sampling (for which only the oldest water in storage is sampled for outflow) and uniform sampling (for which water in storage is sampled randomly for outflow). For this choice of SAS function, explicit formulae are derived for the evolving: (a) age distribution of water in storage; (b) age distribution of water in outflow; and (c) breakthrough concentration of a conservative solute under either continuous or impulsive addition. Model predictions conform closely to chloride and deuterium breakthrough curves measured previously in a sloping lysimeter subject to periodic wetting, although refinements of the model are needed to account for the reconfiguration of flow paths at high storage levels (the so-called inverse storage effect). The analytical results derived in this paper should lower the barrier to applying TTD theory in practice, ease the computational demands associated with simulating solute transport through complex hydrologic systems, and provide physical insights that might not be apparent from traditional numerical solutions of the governing equations.
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    Stormwater biofilter response to high nitrogen loading under transient flow conditions: Ammonium and nitrate fates, and nitrous oxide emissions
    Feraud, Marina; Ahearn, Sean P.; Parker, Emily A.; Avasarala, Sumant; Rugh, Megyn B.; Hung, Wei-Cheng; Li, Dong; Van De Werfhorst, Laurie C.; Kefela, Timnit; Hemati, Azadeh; Mehring, Andrew S.; Cao, Yiping; Jay, Jennifer A.; Liu, Haizhou; Grant, Stanley B.; Holden, Patricia A. (Pergamon-Elsevier, 2022-12-17)
    Nitrogen (N) in urban runoff is often treated with green infrastructure including biofilters. However, N fates across biofilters are insufficiently understood because prior studies emphasize low N loading under laboratory conditions, or use “steady-state” flow regimes over short time scales. Here, we tested field scale biofilter N fates during simulated storms delivering realistic transient flows with high N loading. Biofilter outflow ammonium (NH4+-N) was 60.7 to 92.3% lower than that of the inflow. Yet the characteristic times for nitrification (days to weeks) and denitrification (days) relative to N residence times (7 to 30 h) suggested low N transformation across the biofilters. Still, across 7 successive storms, total outflow nitrate (NO3−-N) greatly exceeded (3100 to 3900%) inflow nitrate, a result only explainable by biofilter soil N nitrification occurring between storms. Archaeal, and bacterial amoA gene copies (2.1 × 105 to 1.2 × 106 gc g soil−1), nitrifier presence by16S rRNA gene sequencing, and outflow δ18O-NO3− values (-3.0 to 17.1 ‰) reinforced that nitrification was occurring. A ratio of δ18O-NO3− to δ15N-NO3− of 1.83 for soil eluates indicated additional processes: N assimilation, and N mineralization. Denitrification potential was suggested by enzyme activities and soil denitrifying gene copies (nirK + nirS: 3.0 × 106 to 1.8 × 107; nosZ: 5.0 × 105 to 2.2 × 106 gc g soil−1). However, nitrous oxide (N2O-N) emissions (13.5 to 84.3 μg N m −2 h −1) and N2O export (0.014 g N) were low, and soil nitrification enzyme activities (0.45 to 1.63 mg N kg soil−1day−1) exceeded those for denitrification (0.17 to 0.49 mg N kg soil−1 day−1). Taken together, chemical, bacterial, and isotopic metrics evidenced that storm inflow NH4+sorbs and, along with mineralized soil N, nitrifies during biofilter dry-down; little denitrification and associated N2O emissions ensue, and thus subsequent storms export copious NO3−-N. As such, pulsed pass-through biofilters require redesign to promote plant assimilation and/or denitrification of mineralized and nitrified N, to minimize NO3−-N generation and export.
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    Unifying Advective and Diffusive Descriptions of Bedform Pumping in the Benthic Biolayer of Streams
    Grant, Stanley B.; Monofy, Ahmed; Boano, Fulvio; Gomez-Velez, Jesus D.; Guymer, Ian; Harvey, Judson; Ghisalberti, Marco (2020-09-01)
    Many water quality and ecosystem functions performed by streams occur in the benthic biolayer, the biologically active upper (similar to 5 cm) layer of the streambed. Solute transport through the benthic biolayer is facilitated by bedform pumping, a physical process in which dynamic and static pressure variations over the surface of stationary bedforms (e.g., ripples and dunes) drive flow across the sediment-water interface. In this paper we derive two predictive modeling frameworks, one advective and the other diffusive, for solute transport through the benthic biolayer by bedform pumping. Both frameworks closely reproduce patterns and rates of bedform pumping previously measured in the laboratory, provided that the diffusion model's dispersion coefficient declines exponentially with depth. They are also functionally equivalent, such that parameter sets inferred from the 2D advective model can be applied to the 1D diffusive model, and vice versa. The functional equivalence and complementary strengths of these two models expand the range of questions that can be answered, for example, by adopting the 2D advective model to study the effects of geomorphic processes (such as bedform adjustments to land use change) on flow-dependent processes and the 1D diffusive model to study problems where multiple transport mechanisms combine (such as bedform pumping and turbulent diffusion). By unifying 2D advective and 1D diffusive descriptions of bedform pumping, our analytical results provide a straightforward and computationally efficient approach for predicting, and better understanding, solute transport in the benthic biolayer of streams and coastal sediments.