Constructed inland aquatic systems (e.g., reservoirs, ponds, lakes, canals) are managed to provide ecosystem services, such as drinking water supply, flood control, irrigation, hydropower generation, and recreation. These socioeconomically important systems are ecological and biogeochemical hotspots and are increasingly affected by anthropogenic disturbances and hydro-climatic fluctuations. Here, we invite research contributions that take the “pulse” of these constructed ecosystems to understand their physical, ecological, and biogeochemical responses to local and global changes. Research focused on past reconstructions, present observations, or future projections/forecasts of such responses are invited. We aim to use the session to bring together the broader scientific community to understand current conditions of constructed aquatic systems and identify future research needs and directions related to the management and conservation of these important ecosystems. As such, contributions from scientists studying all aspects of man-made ecosystems utilizing methodologies including, but not limited to, remote sensing, artificial intelligence, modeling, field surveys, long-term monitoring, experimental manipulations, or big data are encouraged.
Lead Organizer: Ruchi Bhattacharya, Dept. of Biological, Geological, & Environmental Sciences, Cleveland State University, OH, USA (ruchi.bhattacharya@gmail.com)
Co-organizers:
Xinyu Sun, Dept. of Fisheries and Wildlife, Michigan State University, MI, USA (16xs6@queensu.ca)
Carolina C. Barbosa, Ecosystem Science and Sustainability Department, Colorado State University, CO, USA (carolina.barbosa@colostate.edu)
Tonya Delsontro, Dept. of Earth & Environmental Sciences, University of Waterloo, ON, CA (tonya.delsontro@uwaterloo.ca)
Presentations
09:00 AM
INTEGRATING HIGH-FREQUENCY MONITORING AND FORECASTING TO QUANTIFY THE PREDICTABILITY OF RESERVOIRS (9090)
Primary Presenter: Cayelan Carey, Virginia Tech (cayelan@vt.edu)
How predictable are reservoir ecosystem dynamics? Reservoirs exhibit high levels of ecosystem variability, which affects the provisioning of water for drinking, hydropower, and irrigation. However, despite the ubiquity of reservoirs in the landscape and their critical role for society, the limits of ecological predictability in reservoirs are unknown. To address this gap, our team has launched VERA, the Virginia Ecoforecast Reservoir Analysis. VERA is an open forecasting challenge to predict physical, chemical, and biological variables at two water supply reservoirs before the data are collected, thereby enabling us to identify ecosystem predictability. VERA is integrated with state-of-the-art ecosystem monitoring led by the Virginia Reservoirs LTREB (Long-Term Research in Environmental Biology) program, which serves as a testbed for developing new approaches for data collection, access, and publishing. To date, >6200 forecasts have been submitted to VERA for 32 reservoir variables, with more forecasts submitted every day. Preliminary analyses demonstrate that physical ecosystem variables (e.g., water temperature) have substantially higher predictability than chemical or biological variables (e.g., dissolved oxygen, chlorophyll). Interestingly, predictability may be highest during periods of hypolimnetic anoxia. At www.ltreb-reservoirs.org, we provide forecast submission templates, a dashboard of updated forecast performance, and additional resources. We invite you to submit forecasts to the VERA Challenge to expand our understanding of reservoir ecosystem predictability!
09:15 AM
DEGASSING EMISSIONS IN A TEMPERATE HYDROPOWER RESERVOIR: EXPLORING SUB-ANNUAL VARIABILITY AND SENSITIVITY (8922)
Primary Presenter: Rachel Pilla, Oak Ridge National Laboratory (pillarm@ornl.gov)
Globally, human-made reservoirs are important ecosystems in inland water carbon processing. Reservoirs can be significant sources of methane (CH4) emissions, though temporal variability in emissions is uncertain given limited empirical studies. In many hydropower reservoirs, one pathway of CH4 emissions is via degassing, where deepwater intakes can pull water with high dissolved CH4 concentrations through turbines. When this water is removed from deepwater pressure and circulated during power generation, much of the dissolved CH4 is released (“degassed”) into the atmosphere. While this emissions pathway is understudied, a global modelling study suggested it can account for over one-third of greenhouse gas emissions from hydropower reservoirs. In 2023-2024, we conducted monthly sampling at Douglas Reservoir (Tennessee, USA) to quantify sub-annual temporal patterns in CH4 degassing and sensitivity to sampling date. Over this year, CH4 degassing emissions were highest in summertime due to CH4 accumulation in deep waters during thermal stratification. However, discharge was highly variable at daily to weekly time scales, meaning that degassing flux estimates were very sensitive to sampling date. For instance, discharge from a different date within one week of the original sampling date could have resulted in 85% lower to 82% higher CH4 degassing estimates. Understanding the variability in degassing fluxes at sub-annual scales is necessary to improve estimates of CH4 emissions from hydropower reservoirs and understand their role in global carbon processing.
09:30 AM
METHANE DYNAMICS IN RESTORED AND CONSTRUCTED AGRICULTURAL WETLANDS (9370)
Primary Presenter: Tonya DelSontro, University of Waterloo (tdelsontro@gmail.com)
Wetlands provide valuable ecosystem services like nutrient retention and carbon sequestration and are thus recognized as potential nature-based solutions for regions that could benefit from such services. There has been policy-driven creation or restoration of wetlands on agricultural lands of southwestern Ontario to help mitigate nutrient runoff into Lake Eerie and the now regular occurrence of harmful algal blooms. While many of these wetlands have proven to efficiently limit nutrient runoff in the greater Lake Eerie watershed, the trade-off of these wetlands being significant methane emitters has not adequately been assessed. Here we thoroughly investigate methane dynamics in 18 restored or constructed wetlands in southwestern Ontario, focusing on the spatial and temporal variability of methane emissions as well as constraining methane oxidation – the primary consumptive process of this potent greenhouse gas. Using multiple oxidation models along with the carbon and hydrogen isotopic fractionation of methane, we reveal the extent of oxidation in these shallow, eutrophic, polymictic manmade waterbodies. Understanding the consumption of methane in these purposely made systems is crucial for a comprehensive conceptual model of their ecosystem functioning as a nature-based solution.
09:45 AM
CONTROLS ON METHANE EMISSIONS FROM US RESERVOIRS DERIVED FROM A NATIONAL-SCALE MEASUREMENT CAMPAIGN (9478)
Primary Presenter: Jake Beaulieu, United States Environmental Protection Agency (Beaulieu.Jake@epa.gov)
Following guidance from the Intergovernmental Panel on Climate Change, methane (CH4) emissions from U.S. reservoirs are included in the Inventory of U.S. Greenhouse Gas Sources and Sinks. U.S. reservoirs are estimated to emit 1,094 kt CH4 y-1 and are the sixth largest anthropogenic CH4 source in the country. However, this estimate is based on default emission factors—making the accuracy of this estimate uncertain. To improve the inventory estimate, we measured CH4 emissions at 108 reservoirs using a spatially balanced survey design across the conterminous U.S. Ebullitive and diffusive emissions were measured at 15-25 locations in each reservoir during a 48-hour period between June 1 and September 15, 2018-2023. All reservoirs emitted CH4, with a mean emission rate of 134 mg CH4 m-2 d-1 (Inter Quartile Range: 18-110 mg CH4 m-2 d-1). These data, along with those from an additional 39 U.S. reservoirs where we measured emissions using identical methods, comprise the largest inter-reservoir GHG dataset ever assembled using consistent measurement methods. Initial data analysis suggest that emission rates are related to watershed properties (soil erodibility), reservoir morphology (water depth), productivity (chlorophyll a concentration), and regional effects such as sulfate concentrations in the Great Plains. We anticipate our analysis will identify drivers that can be used to estimate emission rates at unsampled locations for inclusion in EPA’s U.S. Greenhouse Gas Inventory.
10:00 AM
Assessment of Drivers of Water Clarity in Virginia Reservoirs (9467)
Primary Presenter: Jackson Barnett, Virginia Commonwealth University (barnettj8@vcu.edu)
Water clarity is ecologically important in aquatic ecosystems, as reduced light penetration is associated with submerged aquatic vegetation declines and algal abundance increases. Clarity is often impaired by excess sediments associated with land disturbance, or increased algal presence due to nutrient overabundance. We measured total suspended solids (TSS), chlorophyll-a (CHLa), and chromophoric dissolved organic matter (CDOM) in seven Virginia reservoirs to better understand their roles in regulating light attenuation (kd). Among study sites, there was an average kd of 1.85 m-1 with values in the range of 0.57 to 4.04 m-1. The photic depths of sites were between 1.14 and 8.10 m with an average of 2.48 m across sites. CDOM was the best predictor of kd across sites (R² = 0.66), accounting for 35.4% ± 0.03% of attenuation on average. Residual variation after removing CDOM effects, was strongly correlated with TSS (R² = 0.96). We estimate that, on average, TSS accounts for 52.8% ± 0.01% of light attenuation across sites. CDOM accounts for 33.3% more attenuation in Coastal Plain sites when compared to Piedmont lakes. Conversely, TSS accounts for 26.1% more attenuation in Piedmont sites than in Coastal Plain lakes. Greater topographic variation and sediment yields in Virginia's Piedmont region may explain the strong influence of TSS on lake clarity in this region. In contrast, CHLa has insignificant effects on attenuation across sites, suggesting clarity is primarily driven by natural processes like organic leaching, and by sediment transport, rather than algae abundance.
10:15 AM
Decoding Spatial Nutrient Dynamics in Reservoirs: The Role of Climate and Landscape Features (9609)
Primary Presenter: Ruchi Bhattacharya, Cleveland State University (ruchi.bhattacharya@gmail.com)
Reservoirs are ubiquitous and form a critical part of the aquatic continuum. These constructed ecosystems provide essential ecosystem services and are recognized as hotspots for nutrient cycling. However, reservoirs are undergoing significant changes due to shifts in hydro-climatic regimes and alterations in land use, making it crucial to understand the spatial and seasonal variability in their nutrient dynamics. Despite their importance, reservoirs are understudied compared to riverine and natural lake ecosystems, with routine monitoring efforts often concentrated near dam sites and during summer months. In this study, I leverage spatially resolved water quality data from reservoirs to quantify the spatial heterogeneity in nutrient cycling. I also examine how hydro-climatic conditions and landscape characteristics, such as mean depth, the watershed-to-reservoir area ratio, and human disturbances, influence nutrient dynamics within reservoirs. Finally, I discuss current research needs and highlight directions for future studies to improve our understanding of reservoir ecosystems. This work underscores the importance of expanding monitoring efforts across various seasons and spatial scales to better manage and preserve these vital aquatic systems.
SS28A - Taking the pulse of constructed ecosystems: past, present, and future
Description
Time: 9:00 AM
Date: 29/3/2025
Room: W206A