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Forgrave R, Evenson GR, Golden HE, Christensen JR, Lane CR, Wu Q, D'Amico E, Prenger J. Wetland-mediated nitrate reductions attenuate downstream: Insights from a modeling study. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 370:122500. [PMID: 39299124 DOI: 10.1016/j.jenvman.2024.122500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2024] [Revised: 09/09/2024] [Accepted: 09/12/2024] [Indexed: 09/22/2024]
Abstract
Connections between agricultural runoff and excess nitrogen in the Upper Mississippi River Basin are well-documented, as is the potential role of constructed wetlands in mitigating this surplus nitrogen. However, limited knowledge exists about the "best" placement of these wetlands for downstream nitrogen reductions within a whole watershed context as well as how far downstream these benefits are realized. In this study, we simulate the cumulative impacts of diverse wetland restoration scenarios on downstream nitrate reductions in different subbasins of the Raccoon River Watershed, Iowa, USA, and spatially trace their relative effects downstream. Our simulated results underscore previous work demonstrating that the total area of wetlands and the wetland-catchment-to-wetland area ratio are both significant factors for determining the nitrate load reduction benefits of wetlands at subbasin scales. Simulated wetland conservation scenarios resulted in nitrate load decreases ranging from 7.5 to 43.2% of our baseline model loads. However, we found these wetland-mediated nitrate reduction benefits are quickly attenuated downstream: load reductions were <1% at the watershed outlet across all model scenarios, despite the magnitude of the subbasin-scale nitrate decreases. The relatively rapid attenuation of wetland effects is largely due to downstream nitrate load contributions from untreated subbasins. However, higher subbasin-scale nitrate reductions from wetland-based conservation practices resulted in longer downstream distances prior to attenuation. This study highlights the importance of considering the spatial location of constructed or restored wetlands relative to the area within the watershed where nitrogen reductions are most needed.
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Affiliation(s)
- Rebecca Forgrave
- Oak Ridge Institute for Science and Education (ORISE) Research Participation Program, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH, USA.
| | - Grey R Evenson
- Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH, USA
| | - Heather E Golden
- Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH, USA
| | - Jay R Christensen
- Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH, USA
| | - Charles R Lane
- Office of Research and Development, U.S. Environmental Protection Agency, Athens, GA, USA
| | - Qiusheng Wu
- Department of Geography and Sustainability, The University of Tennessee, Knoxville, TN, USA
| | - Ellen D'Amico
- Pegasus Technical Services, Inc. C/o, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH, USA
| | - Joseph Prenger
- Natural Resources Conservation Service, U.S. Department of Agriculture, Beltsville, MD, USA
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2
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Nietch CT, Hawley RJ, Safwat A, Christensen JR, Heberling MT, McManus J, McClatchey R, Lubbers H, Smucker NJ, Onderak E, Macy S. Implementing constructed wetlands for nutrient reduction at watershed scale: Opportunity to link models and real-world execution. JOURNAL OF SOIL AND WATER CONSERVATION 2024; 79:113-131. [PMID: 38994438 PMCID: PMC11235211 DOI: 10.2489/jswc.2024.00077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/13/2024]
Abstract
The negative effects of nutrient pollution in streams, rivers, and downstream waterbodies remain widespread global problems. Understanding the cost-effectiveness of different strategies for mitigating nutrient pollution is critical to making informed decisions and defining expectations that best utilize limited resources, which is a research priority for the US Environmental Protection Agency. To this end, we modeled nutrient management practices including residue management, cover crops, filter strips, grassed waterways, constructed wetlands, and reducing fertilizer in the upper East Fork of the Little Miami River, an 892 km2 watershed in southwestern Ohio, United States. The watershed is 64% agriculture with 422 km2 of row crops contributing an estimated 71% of the system's nutrient load. The six practices were modeled to treat row crop area, and among them, constructed wetlands ranked highest for their low costs per kilogram of nutrient removed. To meet a 42% phosphorus (P) reduction target for row crops, the model results suggested that the runoff from 85.5% of the row crop area would need to be treated by the equivalent of 3.61 km2 of constructed wetlands at an estimated cost of US$2.4 million annually (or US$48.5 million over a 20-year life cycle). This prompted a series of projects designed to understand the feasibility (defined in terms of build, treatment, and cost potential) of retrofitting the system with the necessary extent of constructed wetlands. The practicalities of building this wetland coverage into the system, while leading to innovation in unit-level design, has highlighted the difficulty of achieving the nutrient reduction target with wetlands alone. Approximately US$1.2 million have been spent on constructing 0.032 km2 of wetlands thus far and a feasibility analysis suggests a cost of US$38 million for an additional 0.409 km2. However, the combined expenditures would only achieve an estimated 13% of the required treatment. The results highlight the potential effectiveness of innovative design strategies for nutrient reduction and the importance of considering realistic field-scale build opportunities, which include accounting for acceptance among landowners, in watershed-scale nutrient reduction simulations using constructed wetlands.
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Affiliation(s)
- C T Nietch
- US Environmental Protection Agency (USEPA) Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, Ohio
| | - R J Hawley
- Sustainable Streams, LLC, Louisville, Kentucky
| | - A Safwat
- Aptim Federal Services, LLC, Cincinnati, Ohio
| | - J R Christensen
- US Environmental Protection Agency (USEPA) Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, Ohio
| | - M T Heberling
- US Environmental Protection Agency (USEPA) Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, Ohio
| | - J McManus
- US Environmental Protection Agency (USEPA) Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, Ohio
| | - R McClatchey
- Clermont Soil and Water Conservation District, Owensville, Ohio
| | - H Lubbers
- Clermont County Office of Environmental Quality, Batavia, Ohio
| | - N J Smucker
- US Environmental Protection Agency (USEPA) Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, Ohio
| | - E Onderak
- Coldwater Consulting, LLC, Galena, Ohio
| | - S Macy
- Division of Parks and Watercraft, Ohio Department of Natural Resources, Columbus, Ohio
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3
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Zuidema S, Wollheim WM, Kucharik CJ, Lammers RB. Existing wetland conservation programs miss nutrient reduction targets. PNAS NEXUS 2024; 3:pgae129. [PMID: 38628600 PMCID: PMC11020223 DOI: 10.1093/pnasnexus/pgae129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 03/14/2024] [Indexed: 04/19/2024]
Abstract
Restoring wetlands will reduce nitrogen contamination from excess fertilization but estimates of the efficacy of the strategy vary widely. The intervention is often described as effective for reducing nitrogen export from watersheds to mediate bottom-level hypoxia threatening marine ecosystems. Other research points to the necessity of applying a suite of interventions, including wetland restoration to mitigate meaningful quantities of nitrogen export. Here, we use process-based physical modeling to evaluate the effects of two hypothetical, but plausible large-scale wetland restoration programs intended to reduce nutrient export to the Gulf of Mexico. We show that full adoption of the two programs currently in place can meet as little as 10% to as much as 60% of nutrient reduction targets to reduce the Gulf of Mexico dead zone. These reductions are lower than prior estimates for three reasons. First, net storage of leachate in the subsurface precludes interception and thereby dampens the percent decline in nitrogen export caused by the policy. Unlike previous studies, we first constrained riverine fluxes to match observed fluxes throughout the basin. Second, the locations of many restorable lands are geographically disconnected from heavily fertilized croplands, limiting interception of runoff. Third, daily resolution of the model simulations captured the seasonal and stormflow dynamics that inhibit wetland nutrient removal because peak wetland effectiveness does not coincide with the timing of nutrient inputs. To improve the health of the Gulf of Mexico efforts to eliminate excess nutrient, loading should be implemented beyond the field-margin wetland strategies investigated here.
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Affiliation(s)
- Shan Zuidema
- Earth Systems Research Center, University of New Hampshire, Durham, NH 03824, USA
| | - Wilfred M Wollheim
- Earth Systems Research Center, University of New Hampshire, Durham, NH 03824, USA
- Department of Natural Resources, University of New Hampshire, Durham, NH 03824, USA
| | - Christopher J Kucharik
- Department of Plant and Agroecosystem Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Richard B Lammers
- Earth Systems Research Center, University of New Hampshire, Durham, NH 03824, USA
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4
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McLellan EL, Suttles KM, Bouska KL, Ellis JH, Flotemersch JE, Goff M, Golden HE, Hill RA, Hohman TR, Keerthi S, Keim RF, Kleiss BA, Lark TJ, Piazza BP, Renfro AA, Robertson DM, Schilling KE, Schmidt TS, Waite IR. Improving ecosystem health in highly altered river basins: a generalized framework and its application to the Mississippi-Atchafalaya River Basin. FRONTIERS IN ENVIRONMENTAL SCIENCE 2024; 12:1-19. [PMID: 38516348 PMCID: PMC10953731 DOI: 10.3389/fenvs.2024.1332934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/23/2024]
Abstract
Continued large-scale public investment in declining ecosystems depends on demonstrations of "success". While the public conception of "success" often focuses on restoration to a pre-disturbance condition, the scientific community is more likely to measure success in terms of improved ecosystem health. Using a combination of literature review, workshops and expert solicitation we propose a generalized framework to improve ecosystem health in highly altered river basins by reducing ecosystem stressors, enhancing ecosystem processes and increasing ecosystem resilience. We illustrate the use of this framework in the Mississippi-Atchafalaya River Basin (MARB) of the central United States (U.S.), by (i) identifying key stressors related to human activities, and (ii) creating a conceptual ecosystem model relating those stressors to effects on ecosystem structure and processes. As a result of our analysis, we identify a set of landscape-level indicators of ecosystem health, emphasizing leading indicators of stressor removal (e.g., reduced anthropogenic nutrient inputs), increased ecosystem function (e.g., increased water storage in the landscape) and increased resilience (e.g., changes in the percentage of perennial vegetative cover). We suggest that by including these indicators, along with lagging indicators such as direct measurements of water quality, stakeholders will be better able to assess the effectiveness of management actions. For example, if both leading and lagging indicators show improvement over time, then management actions are on track to attain desired ecosystem condition. If, however, leading indicators are not improving or even declining, then fundamental challenges to ecosystem health remain to be addressed and failure to address these will ultimately lead to declines in lagging indicators such as water quality. Although our model and indicators are specific to the MARB, we believe that the generalized framework and the process of model and indicator development will be valuable in an array of altered river basins.
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Affiliation(s)
| | | | - Kristen L. Bouska
- U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, WI, United States
| | - Jamelle H. Ellis
- Theodore Roosevelt Conservation Partnership, Washington, DC, United States
| | - Joseph E. Flotemersch
- U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, OH, United States
| | - Madison Goff
- School for Environment and Sustainability, University of Michigan, Ann Arbor, MI, United States
| | - Heather E. Golden
- U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, OH, United States
| | - Ryan A. Hill
- U.S. Environmental Protection Agency, Office of Research and Development, Corvallis, OR, United States
| | - Tara R. Hohman
- Audubon Upper Mississippi River, Audubon Center at Riverlands, West Alton, MO, United States
| | | | - Richard F. Keim
- School of Renewable Natural Resources, Louisiana State University, Baton Rouge, LA, United States
| | - Barbara A. Kleiss
- Department of River Coastal Science and Engineering, Tulane University, New Orleans, LA, United States
| | - Tyler J. Lark
- Center for Sustainability and the Global Environment, University of Wisconsin, Madison, WI, United States
| | | | | | - Dale M. Robertson
- U.S. Geological Survey, Upper Midwest Water Science Center, Madison, WI, United States
| | - Keith E. Schilling
- IIHR-Hydroscience and Engineering, University of Iowa, Iowa City, IA, United States
| | - Travis S. Schmidt
- U.S. Geological Survey, Wyoming-Montana Water Science Center, Helena, MT, United States
| | - Ian R. Waite
- U.S. Geological Survey, Oregon Water Science Center, Portland, OR, United States
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5
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Kirk L, Compton JE, Neale A, Sabo RD, Christensen J. Our national nutrient reduction needs: Applying a conservation prioritization framework to US agricultural lands. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 351:119758. [PMID: 38086118 PMCID: PMC10851882 DOI: 10.1016/j.jenvman.2023.119758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 11/21/2023] [Accepted: 12/01/2023] [Indexed: 01/14/2024]
Abstract
Targeted conservation approaches seek to focus resources on areas where they can deliver the greatest benefits and are recognized as key to reducing nonpoint source nutrients from agricultural landscapes into sensitive receiving waters. Moreover, there is growing recognition of the importance and complementarity of in-field and edge-of-field conservation for reaching nutrient reduction goals. Here we provide a generic prioritization that can help with spatial targeting and applied it across the conterminous US (CONUS). The prioritization begins with identifying areas with high agricultural nutrient surplus, i.e., where the most nitrogen (N) and/or phosphorus (P) inputs are left on the landscape after crop harvest. Subwatersheds with high surplus included 52% and 50% of CONUS subwatersheds for N and P, respectively, and were located predominantly in the Midwest for N, in the South for P, and in California for both N and P. Then we identified the most suitable conservation strategies using a hierarchy of metrics including nutrient use efficiency (proportion of new nutrient inputs removed by crop harvest), tile drainage, existing buffers for agricultural run-off, and wetland restoration potential. In-field nutrient input reduction emerged as a priority because nutrient use efficiency fell below a high but achievable goal of 0.7 (30% of nutrients applied are not utilized) in 45% and 44% of CONUS subwatersheds for N and P, respectively. In many parts of the southern and western US, in-field conservation (i.e., reducing inputs + preventing nutrients from leaving fields) alone was likely the optimal strategy as agriculture was already well-buffered. However, stacking in-field conservation with additional edge-of-field buffering would be important to conservation strategies in 35% and 29% of CONUS subwatersheds for N and P, respectively. Nutrient use efficiencies were often high enough in the Midwest that proposed strategies focused more on preventing nutrients from leaving fields, managing tile effluent, and buffering agricultural fields. Almost all major river basins would benefit from a variety of nutrient reduction conservation strategies, underscoring the potential of targeted approaches to help limit excess nutrients in surface and ground waters.
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Affiliation(s)
- Lily Kirk
- Oak Ridge Institute for Science and Education - US Environmental Protection Agency (EPA), 109 T.W. Alexander Drive, Durham, NC, 27709, USA.
| | - Jana E Compton
- US EPA, Office of Research and Development, Center for Public Health and Environmental Assessment, Pacific Ecological Systems Division, Corvallis, OR, 97330, USA
| | - Anne Neale
- US EPA, Office of Research and Development, Center for Public Health and Environmental Assessment, Public Health and Environmental Systems Division, Durham, NC, USA
| | - Robert D Sabo
- US EPA, Office of Research and Development, Center for Public Health and Environmental Assessment, Health and Environmental Effects Division, Washington, DC, USA
| | - Jay Christensen
- US EPA, Office of Research and Development, Center for Environmental Measurement and Modeling, Watershed and Ecosystem Characterization Division, Cincinnati, OH, USA
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6
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Zuidema S, Liu J, Chepeliev MG, Johnson DR, Baldos ULC, Frolking S, Kucharik CJ, Wollheim WM, Hertel TW. US climate policy yields water quality cobenefits in the Mississippi Basin and Gulf of Mexico. Proc Natl Acad Sci U S A 2023; 120:e2302087120. [PMID: 37844248 PMCID: PMC10614783 DOI: 10.1073/pnas.2302087120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 08/31/2023] [Indexed: 10/18/2023] Open
Abstract
We utilize a coupled economy-agroecology-hydrology modeling framework to capture the cascading impacts of climate change mitigation policy on agriculture and the resulting water quality cobenefits. We analyze a policy that assigns a range of United States government's social cost of carbon estimates ($51, $76, and $152/ton of CO2-equivalents) to fossil fuel-based CO2 emissions. This policy raises energy costs and, importantly for agriculture, boosts the price of nitrogen fertilizer production. At the highest carbon price, US carbon emissions are reduced by about 50%, and nitrogen fertilizer prices rise by about 90%, leading to an approximate 15% reduction in fertilizer applications for corn production across the Mississippi River Basin. Corn and soybean production declines by about 7%, increasing crop prices by 6%, while nitrate leaching declines by about 10%. Simulated nitrate export to the Gulf of Mexico decreases by 8%, ultimately shrinking the average midsummer area of the Gulf of Mexico hypoxic area by 3% and hypoxic volume by 4%. We also consider the additional benefits of restored wetlands to mitigate nitrogen loading to reduce hypoxia in the Gulf of Mexico and find a targeted wetland restoration scenario approximately doubles the effect of a low to moderate social cost of carbon. Wetland restoration alone exhibited spillover effects that increased nitrate leaching in other parts of the basin which were mitigated with the inclusion of the carbon policy. We conclude that a national climate policy aimed at reducing greenhouse gas emissions in the United States would have important water quality cobenefits.
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Affiliation(s)
- Shan Zuidema
- Earth Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH03824
| | - Jing Liu
- Department of Agricultural Economics, Purdue University, West Lafayette, IN47907
| | - Maksym G. Chepeliev
- Department of Agricultural Economics, Purdue University, West Lafayette, IN47907
| | - David R. Johnson
- Department of Political Science, Purdue University, West Lafayette, IN47907
- School of Industrial Engineering, Purdue University, West Lafayette, IN47907
| | - Uris Lantz C. Baldos
- Department of Agricultural Economics, Purdue University, West Lafayette, IN47907
| | - Steve Frolking
- Earth Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH03824
| | - Christopher J. Kucharik
- Department of Plant and Agroecosystem Sciences, University of Wisconsin-Madison, Madison, WI53706
| | - Wilfred M. Wollheim
- Earth Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH03824
- Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH03824
| | - Thomas W. Hertel
- Department of Agricultural Economics, Purdue University, West Lafayette, IN47907
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7
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Lane CR, D’Amico E, Christensen JR, Golden HE, Wu Q, Rajib A. Mapping global non-floodplain wetlands. EARTH SYSTEM SCIENCE DATA 2023; 15:2927-2955. [PMID: 37841644 PMCID: PMC10569017 DOI: 10.5194/essd-15-2927-2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2023]
Abstract
Non-floodplain wetlands - those located outside the floodplains - have emerged as integral components to watershed resilience, contributing hydrologic and biogeochemical functions affecting watershed-scale flooding extent, drought magnitude, and water-quality maintenance. However, the absence of a global dataset of non-floodplain wetlands limits their necessary incorporation into water quality and quantity management decisions and affects wetland-focused wildlife habitat conservation outcomes. We addressed this critical need by developing a publicly available "Global NFW" (Non-Floodplain Wetland) dataset, comprised of a global river-floodplain map at 90 m resolution coupled with a global ensemble wetland map incorporating multiple wetland-focused data layers. The floodplain, wetland, and non-floodplain wetland spatial data developed here were successfully validated within 21 large and heterogenous basins across the conterminous United States. We identified nearly 33 million potential non-floodplain wetlands with an estimated global extent of over 16×106 km2. Non-floodplain wetland pixels comprised 53% of globally identified wetland pixels, meaning the majority of the globe's wetlands likely occur external to river floodplains and coastal habitats. The identified global NFWs were typically small (median 0.039 km2), with a global median size ranging from 0.018-0.138 km2. This novel geospatial Global NFW static dataset advances wetland conservation and resource-management goals while providing a foundation for global non-floodplain wetland functional assessments, facilitating non-floodplain wetland inclusion in hydrological, biogeochemical, and biological model development. The data are freely available through the United States Environmental Protection Agency's Environmental Dataset Gateway (https://gaftp.epa.gov/EPADataCommons/ORD/Global_NonFloodplain_Wetlands/, last access: 24 May 2023) and through https://doi.org/10.23719/1528331 (Lane et al., 2023a).
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Affiliation(s)
- Charles R. Lane
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Measurement and Modeling, Athens, Georgia, USA
| | - Ellen D’Amico
- Pegasus Technical Service, Inc. c/o U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, Ohio, USA
| | - Jay R. Christensen
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, Ohio, USA
| | - Heather E. Golden
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, Ohio, USA
| | - Qiusheng Wu
- Department of Geography & Sustainability, University of Tennessee, Knoxville, Tennessee, USA
| | - Adnan Rajib
- Hydrology and Hydroinformatics Innovation Lab, Department of Civil Engineering, University of Texas at Arlington, Arlington, Texas, USA
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8
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Evenson GR, Golden HE, Christensen JR, Lane CR, Kalcic MM, Rajib A, Wu Q, Mahoney DT, White E, D'Amico E. River Basin Simulations Reveal Wide-Ranging Wetland-Mediated Nitrate Reductions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:9822-9831. [PMID: 37345945 PMCID: PMC10633752 DOI: 10.1021/acs.est.3c02161] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/23/2023]
Abstract
River basin-scale wetland restoration and creation is a primary management option for mitigating nitrogen-based water quality challenges. However, the magnitude of nitrogen reduction that will result from adding wetlands across large river basins is uncertain, partly because the areal extent, location, and physical and functional characteristics of the wetlands are unknown. We simulated over 3600 wetland restoration scenarios across the ∼450,000 km2 Upper Mississippi River Basin (UMRB) depicting varied assumptions for wetland areal extent, physical and functional characteristics, and placement strategy. These simulations indicated that restoring wetlands will reduce local nitrate yields and nitrate loads at the UMRB outlet. However, the projected magnitude of nitrate reduction varied widely across disparate scenario assumptions─e.g., restoring 4500 km2 of wetlands (i.e., 1% of UMRB area) decreased mean annual nitrate loads at the UMRB outlet between 3 and 42%. Higher magnitude nitrate reductions correlated with best-case assumptions, particularly for characteristics controlling nitrate loading rates to the wetlands. These results show that simplified claims about basin-scale wetland-mediated water quality improvements discount the breadth of possible wetland impacts across disparate wetland physical and functional conditions and highlight a need for greater clarity regarding the likelihood of these conditions at river basin scales.
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Affiliation(s)
- Grey R Evenson
- Center for Environmental Measurement and Modeling, Office of Research and Development, United States Environmental Protection Agency, Cincinnati, Ohio 45268, United States
| | - Heather E Golden
- Center for Environmental Measurement and Modeling, Office of Research and Development, United States Environmental Protection Agency, Cincinnati, Ohio 45268, United States
| | - Jay R Christensen
- Center for Environmental Measurement and Modeling, Office of Research and Development, United States Environmental Protection Agency, Cincinnati, Ohio 45268, United States
| | - Charles R Lane
- Center for Environmental Measurement and Modeling, Office of Research and Development, United States Environmental Protection Agency, Athens, Georgia 30605, United States
| | - Margaret M Kalcic
- Biological Systems Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Adnan Rajib
- Hydrology and Hydroinformatics Innovation Lab, Department of Civil Engineering, University of Texas at Arlington, Arlington, Texas 76019, United States
| | - Qiusheng Wu
- Department of Geography and Sustainability, University of Tennessee at Knoxville, Knoxville, Tennessee 37996, United States
| | - David Tyler Mahoney
- Civil and Environmental Engineering, J.B. Speed School of Engineering, University of Louisville, Louisville, Kentucky 40292, United States
| | - Elaheh White
- Oak Ridge Institute for Science and Education c/o United States Environmental Protection Agency, Office of Research and Development, Cincinnati, Ohio 45268, United States
| | - Ellen D'Amico
- Pegasus Technical Services Incorporated c/o United States Environmental Protection Agency, Office of Research and Development, Cincinnati, Ohio 45268, United States
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9
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Mahoney D, Christensen J, Golden H, Lane C, Evenson G, White E, Fritz K, D’Amico E, Barton C, Williamson T, Sena K, Agouridis C. Dynamics of streamflow permanence in a headwater network: Insights from catchment-scale model simulations. JOURNAL OF HYDROLOGY 2023; 620:129422. [PMID: 39211483 PMCID: PMC11360430 DOI: 10.1016/j.jhydrol.2023.129422] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
The hillslope and channel dynamics that govern streamflow permanence in headwater systems have important implications for ecosystem functioning and downstream water quality. Recent advancements in process-based, semi-distributed hydrologic models that build upon empirical studies of streamflow permanence in well-monitored headwater catchments show promise for characterizing the dynamics of streamflow permanence in headwater systems. However, few process-based models consider the continuum of hillslope-stream network connectivity as a control on streamflow permanence in headwater systems. The objective of this study was to expand a process-based, catchment-scale hydrologic model to better understand the spatiotemporal dynamics of headwater streamflow permanence and to identify controls of streamflow expansion and contraction in a headwater network. Further, we aimed to develop an approach that enhanced the fidelity of model simulations, yet required little additional data, with the intent that the model might be later transferred to catchments with limited long-term and spatially explicit measurements. This approach facilitated network-scale estimates of the controls of streamflow expansion and contraction, albeit with higher degrees of uncertainty in individual reaches due to data constraints. Our model simulated that streamflow permanence was highly dynamic in first-order reaches with steep slopes and variable contributing areas. The simulated stream network length ranged from nearly 98±2% of the geomorphic channel extent during wet periods to nearly 50±10% during dry periods. The model identified a discharge threshold of approximately 1 mm d-1, above which the rate of streamflow expansion decreases by nearly an order of magnitude, indicating a lack of sensitivity of streamflow expansion to hydrologic forcing during high-flow periods. Overall, we demonstrate that process-based, catchment-scale models offer important insights on the controls of streamflow permanence, despite uncertainties and limitations of the model. We encourage researchers to increase data collection efforts and develop benchmarks to better evaluate such models.
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Affiliation(s)
- D.T. Mahoney
- Department of Civil and Environmental Engineering, University of Louisville, Louisville, KY
| | - J.R. Christensen
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, OH
| | - H.E. Golden
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, OH
| | - C.R. Lane
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Measurement and Modeling, Athens, GA
| | - G.R. Evenson
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, OH
| | - E. White
- U.S. Geological Survey, Data Science Branch, Integrated Information Dissemination Division, Denver, CO
| | - K. Fritz
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, OH
| | - E. D’Amico
- Pegasus Corporation c/o U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, OH
| | - C. Barton
- Department of Natural Resources and Environmental Science, University of Kentucky, Lexington, KY
| | - T. Williamson
- U.S. Geological Survey, OH-KY-IN Water Science Center, Louisville, KY
| | - K. Sena
- Lewis Honors College, University of Kentucky, Lexington, KY
| | - C. Agouridis
- College of Agriculture, Food and Environment, University of Kentucky, Lexington, KY
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Christensen JR, Golden HE, Alexander LC, Pickard BR, Fritz KM, Lane CR, Weber MH, Kwok RM, Keefer MN. Headwater streams and inland wetlands: Status and advancements of geospatial datasets and maps across the United States. EARTH-SCIENCE REVIEWS 2022; 235:1-24. [PMID: 36970305 PMCID: PMC10031651 DOI: 10.1016/j.earscirev.2022.104230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Headwater streams and inland wetlands provide essential functions that support healthy watersheds and downstream waters. However, scientists and aquatic resource managers lack a comprehensive synthesis of national and state stream and wetland geospatial datasets and emerging technologies that can further improve these data. We conducted a review of existing United States (US) federal and state stream and wetland geospatial datasets, focusing on their spatial extent, permanence classifications, and current limitations. We also examined recent peer-reviewed literature for emerging methods that can potentially improve the estimation, representation, and integration of stream and wetland datasets. We found that federal and state datasets rely heavily on the US Geological Survey's National Hydrography Dataset for stream extent and duration information. Only eleven states (22%) had additional stream extent information and seven states (14%) provided additional duration information. Likewise, federal and state wetland datasets primarily use the US Fish and Wildlife Service's National Wetlands Inventory (NWI) Geospatial Dataset, with only two states using non-NWI datasets. Our synthesis revealed that LiDAR-based technologies hold promise for advancing stream and wetland mapping at limited spatial extents. While machine learning techniques may help to scale-up these LiDAR-derived estimates, challenges related to preprocessing and data workflows remain. High-resolution commercial imagery, supported by public imagery and cloud computing, may further aid characterization of the spatial and temporal dynamics of streams and wetlands, especially using multi-platform and multi-temporal machine learning approaches. Models integrating both stream and wetland dynamics are limited, and field-based efforts must remain a key component in developing improved headwater stream and wetland datasets. Continued financial and partnership support of existing databases is also needed to enhance mapping and inform water resources research and policy decisions.
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Affiliation(s)
- Jay R. Christensen
- Center for Environmental Measurement and Modeling, Office of Research and Development, US Environmental Protection Agency, Cincinnati, OH 45268, USA
| | - Heather E. Golden
- Center for Environmental Measurement and Modeling, Office of Research and Development, US Environmental Protection Agency, Cincinnati, OH 45268, USA
| | - Laurie C. Alexander
- Center for Public Health and Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, Washington DC 20460 USA Region 10, US Environmental Protection Agency, Portland, OR 97205, USA
| | | | - Ken M. Fritz
- Center for Environmental Measurement and Modeling, Office of Research and Development, US Environmental Protection Agency, Cincinnati, OH 45268, USA
| | - Charles R. Lane
- Center for Environmental Measurement and Modeling, Office of Research and Development, US Environmental Protection Agency, Athens, GA, 30605 USA
| | - Marc H. Weber
- Center for Public Health and Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, Corvallis, OR 97333 USA
| | - Rose M. Kwok
- Office of Wetlands, Oceans, and Watersheds, Office of Water, US Environmental Protection Agency, Washington, DC 20460, USA
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Tschikof M, Gericke A, Venohr M, Weigelhofer G, Bondar-Kunze E, Kaden US, Hein T. The potential of large floodplains to remove nitrate in river basins - The Danube case. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 843:156879. [PMID: 35753454 DOI: 10.1016/j.scitotenv.2022.156879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 06/17/2022] [Accepted: 06/18/2022] [Indexed: 06/15/2023]
Abstract
Floodplains remove nitrate from rivers through denitrification and thus improve water quality. The Danube River Basin (DRB) has been affected by elevated nitrate concentrations and a massive loss of intact floodplains and the ecosystem services they provide. Restoration measures intend to secure and improve these valuable ecosystem services, including nitrate removal. Our study provides the first large-scale estimate of the function of large active floodplains in the DRB to remove riverine nitrate and assesses the contribution of reconnection measures. We applied a nutrient emission model in 6 river systems and coupled it with denitrification and flooding models which we adapted to floodplains. The floodplains have the capacity to eliminate about 33,200 t nitrate-N annually, which corresponds to 6.5 % of the total nitrogen emissions in the DRB. More nitrate is removed in-stream at regular flow conditions than in floodplain soils during floods. However, increasing frequently inundated floodplain areas reveals greater potential for improvement than increasing the channel network. In total, we estimate that 14.5 % more nitrate can be removed in reconnected floodplains. The largest share of nitrogen emissions is retained in the Yantra and Tisza floodplains, where reconnections are expected to have the greatest impact on water quality. In absolute numbers, the floodplains of the lower Danube convert the greatest quantities of nitrate, driven by the high input loads. These estimates are subject to uncertainties due to the heterogeneity of the available input data. Still, our results are within the range of similar studies. Reconnections of large floodplains in the DRB can, thus, make a distinct contribution to improving water quality. A better representation of the spatial configuration of water quality functions and the effect of floodplain reconnections may support the strategic planning of such to achieve multiple benefits and environmental targets.
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Affiliation(s)
- Martin Tschikof
- Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Gregor-Mendel-Straße 33, 1180 Vienna, Austria; WasserCluster Lunz, Dr. Kupelwieser-Promenade 5, 3293 Lunz am See, Austria.
| | - Andreas Gericke
- Leibniz Institute of Freshwater Ecology and Inland Fisheries Berlin, Justus-von-Liebig-Straße 7, 12489 Berlin, Germany.
| | - Markus Venohr
- Leibniz Institute of Freshwater Ecology and Inland Fisheries Berlin, Justus-von-Liebig-Straße 7, 12489 Berlin, Germany.
| | - Gabriele Weigelhofer
- Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Gregor-Mendel-Straße 33, 1180 Vienna, Austria; WasserCluster Lunz, Dr. Kupelwieser-Promenade 5, 3293 Lunz am See, Austria.
| | - Elisabeth Bondar-Kunze
- Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Gregor-Mendel-Straße 33, 1180 Vienna, Austria; WasserCluster Lunz, Dr. Kupelwieser-Promenade 5, 3293 Lunz am See, Austria; Christian Doppler Laboratory for Meta Ecosystem Dynamics in Riverine Landscapes - Research for sustainable River Management, Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Gregor-Mendel-Straße 33, 1180 Vienna, Austria.
| | - Ute Susanne Kaden
- UFZ - Helmholtz Centre for Environmental Research, Department of Conservation Biology and Social-Ecological Systems, Permoserstraße 15, 04318 Leipzig, Germany.
| | - Thomas Hein
- Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Gregor-Mendel-Straße 33, 1180 Vienna, Austria; WasserCluster Lunz, Dr. Kupelwieser-Promenade 5, 3293 Lunz am See, Austria; Christian Doppler Laboratory for Meta Ecosystem Dynamics in Riverine Landscapes - Research for sustainable River Management, Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Gregor-Mendel-Straße 33, 1180 Vienna, Austria.
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Abstract
AbstractWatershed resilience is the ability of a watershed to maintain its characteristic system state while concurrently resisting, adapting to, and reorganizing after hydrological (for example, drought, flooding) or biogeochemical (for example, excessive nutrient) disturbances. Vulnerable waters include non-floodplain wetlands and headwater streams, abundant watershed components representing the most distal extent of the freshwater aquatic network. Vulnerable waters are hydrologically dynamic and biogeochemically reactive aquatic systems, storing, processing, and releasing water and entrained (that is, dissolved and particulate) materials along expanding and contracting aquatic networks. The hydrological and biogeochemical functions emerging from these processes affect the magnitude, frequency, timing, duration, storage, and rate of change of material and energy fluxes among watershed components and to downstream waters, thereby maintaining watershed states and imparting watershed resilience. We present here a conceptual framework for understanding how vulnerable waters confer watershed resilience. We demonstrate how individual and cumulative vulnerable-water modifications (for example, reduced extent, altered connectivity) affect watershed-scale hydrological and biogeochemical disturbance response and recovery, which decreases watershed resilience and can trigger transitions across thresholds to alternative watershed states (for example, states conducive to increased flood frequency or nutrient concentrations). We subsequently describe how resilient watersheds require spatial heterogeneity and temporal variability in hydrological and biogeochemical interactions between terrestrial systems and down-gradient waters, which necessitates attention to the conservation and restoration of vulnerable waters and their downstream connectivity gradients. To conclude, we provide actionable principles for resilient watersheds and articulate research needs to further watershed resilience science and vulnerable-water management.
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