SFS Annual Meeting

6/04/2024  |   10:30 - 10:45   |  Freedom Ballroom H/G

DEVELOPMENT AND APPLICATION OF RAPID STREAMFLOW DURATION ASSESSMENT METHODS Resource managers, regulators, and regulated entities need rapid, reach-scale methods to classify streamflow duration to implement and comply with many federal, state and local programs. The U.S. Environmental Protection Agency is working cooperatively with the U.S. Army Corps of Engineers and other partners to develop regional streamflow duration assessment methods (SDAMs) for nationwide coverage that use hydrological, geomorphological, biological and/or geospatial indicators, observable in a single visit to classify reaches as perennial, intermittent or ephemeral (https://www.epa.gov/streamflow-duration-assessment). Since hydrologic monitoring of non-perennial streams is limited, we deployed and maintained data loggers for up to two years to confirm streamflow duration class in study reaches, independent from observed indicators. We present published SDAMs covering the Arid West, Western Mountains, Great Plains, and Northeastern and Southeastern U.S. The methods resulted from multi-year studies conducted at reaches across the country and included the evaluation of 141 candidate indicators expected to control or respond to streamflow duration. Each regional SDAM has a unique set of indicators. Beta SDAMs were re-evaluated in light of public comments and additional data to develop final methods. The presentation will describe the process used to develop the SDAMs including data analysis steps, beta and final SDAMs developed to date and opportunities for more refined regionalization. Additionally, the presentation will discuss how the collection, management, analysis, and publication of these unique data sets can support applications across multiple management decisions and further study by others.

Brian Topping (Primary Presenter/Author), U.S. Environmental Protection Agency, topping.brian@epa.gov;

Rachel FertikEdgerton (Co-Presenter/Co-Author), U.S. Environmental Protection Agency , fertikedgerton.rachel@epa.gov;

Kristina Nicholas (Co-Presenter/Co-Author), ORISE Fellow at U.S. Environmental Protection Agency, Nicholas.Kristina@epa.gov;

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6/04/2024  |   10:45 - 11:00   |  Freedom Ballroom H/G

Weight of Evidence Approach to Assign Flow Regimes to Arizona Streams In the Arid West, many surface waters are non-perennial and classifying their flow regime is essential to making water quality standards and regulatory decisions. Arizona Department of Environmental Quality (ADEQ) assigns flow regimes to individual waterbodies to make these decisions and to ensure Arizona’s surface waters are being adequately protected. Currently, only 18% of Arizona’s surface waters have been assigned a flow regime, leaving 82%, more than 3,000 surface waters, with undetermined flow regimes. ADEQ developed a weight of evidence (WOE) approach to assign flow regimes that combines flow regime data from multiple data sources into a single flow regime result. Each data source is assigned a flow regime of either ephemeral, intermittent, at least intermittent, or perennial, and is assigned a numeric score based on the quality of data. The numeric scores within each flow regime category are combined and the flow regime category with the greatest score is assigned to the surface water. We validated the WOE approach by comparing the WOE flow regime of 51 water bodies to their known flow regimes that were either perennial (n = 18), intermittent (n = 17), or ephemeral (n = 16). The overall accuracy was 92% when we compared the WOE flow regime to the known validation flow regimes. Using the WOE approach, all perennial and intermittent validation sites were assigned correct flow regimes and 75% of ephemeral validation sites were assigned correct flow regimes. ADEQ plans to use the WOE approach to assign flow regime data gaps in Arizona.

Matt Robinson (Primary Presenter/Author), Arizona Department of Environmental Quality, Robinson.matt@azdeq.gov;

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6/04/2024  |   11:00 - 11:15   |  Freedom Ballroom H/G

Irrigation ditches as novel and ubiquitous non-perennial waterways that provide large energetic subsidies to terrestrial ecosystems via aquatic insect emergence Non-perennial waterways dominate river networks, comprising more than half of lotic ecosystems globally. Although little attention has been paid to these systems relative to those that are perennial, perhaps even less is known about the ecology of artificial (i.e. human constructed) novel waterways. In the western US, irrigation ditches are ubiquitous in arid river valleys and may contribute to regional biodiversity and ecosystem processes. We quantified the extent of the irrigation ditch network relative to other natural waterways in the Gallatin River valley (Montana, USA), and quantified the magnitude, phenology, and composition of aquatic insect emergence during the 2022 irrigation season. We found that non-perennial streams, both natural and artificial, dominated the surface-water network, representing over 70% of the total length. In addition, irrigation ditches constituted 34% and 30% of the total length and surface area of all waterways in the valley, respectively. Median daily insect emergence from ditches was 32.0 mg m-2 day-1, fairly consistent throughout the irrigation season, dominated by Diptera, and comparable in magnitude to emergence fluxes from nearby perennial streams. The phenology, cumulative biomass export, and proportion of EPT differed among ditches with varying water-use histories and distances from natural waterways. Using a Bayesian modelling approach, we estimated an emergence flux of 7.4 grams m-2 yr-1 from irrigation ditches, which represents more than 40 tons of biomass at the whole-network scale. Our study highlights the ubiquity of irrigation ditches in western US agricultural regions, and the important contribution of these novel ecosystems to aquatic-terrestrial subsidies.

Nate Heili (Primary Presenter/Author), Montana State University , nheili42@gmail.com;

Wyatt Cross (Co-Presenter/Co-Author), Montana State University, wyatt.cross@montana.edu ;

Kieran Wilder (Co-Presenter/Co-Author), Montana State University, kieranwilder2@gmail.com;

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6/04/2024  |   11:15 - 11:30   |  Freedom Ballroom H/G

MUTLI-SCALE DRIVERS OF FLOW INTERMITTENCY IN A REGULATED DESERT RIVER Fluvial ecosystems are vital for biodiversity and human welfare but face increasing threats from flow intermittency caused by climate change and other human activities. To better understand drivers of flow intermittency, we analyzed long-term and spatially explicit river drying data from the Rio Grande, a regulated river in the North American desert southwest that was historically perennial but is now persistently intermittent. We examined the spatial structure and influences of in-channel infrastructure, river discharge, and weather on flow intermittency using multivariate autoregressive state space (MARSS) models and 12 years of daily discharge and drying observations. We define weather as inter and intra-annual variability in precipitation and temperature. River diversion rates at dams and irrigation return flows significantly structure the spatial occurrence of flow intermittency, but fine-scale factors (e.g., transmission losses) at distances <= 7 kilometers (km) are more influential predictors of drying. We did not detect influences of temperature and precipitation at the reach scale (~150 km) but they were significant at each of three the subreach scales we investigated. At all subreach scales, the effect size of temperature exceeds that of precipitation by 2.5 times and was the strongest predictor of drying. Overall, our analysis shows that scale-sensitive models can inform environmental flow management strategies aimed at mitigating negative effects of climate change and water extraction.

Eliza Gilbert (Primary Presenter/Author), University of New Mexico, egilbe01@unm.edu;

Thomas Turner (Co-Presenter/Co-Author), University of New Mexico, turnert@unm.edu;

Melanie Moses (Co-Presenter/Co-Author), University of New Mexico, melaniem@unm.edu;

Alex Webster (Co-Presenter/Co-Author), University of New Mexico, awebster2@unm.edu;

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6/04/2024  |   11:30 - 11:45   |  Freedom Ballroom H/G

TEACHING FRESHWATER SCIENCE WITHOUT ANY WATER: CHALLENGES AND OPPORTUNITIES FOR INCORPORATING INTERMITTENT AND EPHEMERAL RIVERS INTO STREAM ECOLOGY COURSES Intermittent and ephemeral streams comprise the majority of stream networks and are increasing in many regions due to climate change and water abstraction. An appropriately trained workforce is needed to propertly manage such systems. However, many courses and textbook emphasize perennial systems when explaining stream ecology concepts and field methods. In addition, providing experiential learning in freshwater science can be challenging in arid and semi-arid regions where most easily accessible streams are intermittent or ephemeral. I discuss how several core stream ecology concepts and important field skills for employment in freshwater careers are challenging to teach, with an emphasis on undergraduate stream ecology laboratory courses. Examples include longitudinal connectivity, measurement of discharge, and habitat classification. I also highlight how lack of flowing water can be advantageous, such as the ability to easily examine and measure properties of streambed sediments and clear examples of hyporheic flow in spatially intermittent streams. Strategies for delivering aquatic experiential learning opportunities in intermittent and ephemeral streams will be discussed, drawing from experience with an aquatic science lab course at the University of Texas at San Antonio campus, where easily accessible stream channels are mostly dry with only isolated pools of water present most of the year. Finally, I will discuss opportunities for better incorporating the full diversity of flow conditions into lotic freshwater education, an important step for training new freshwater scientists and managers who will be tasked with managing intermittent and ephemeral systems.

Brian Laub (Primary Presenter/Author), The University of Texas at San Antonio, laubbriang@gmail.com;

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6/04/2024  |   11:45 - 12:00   |  Freedom Ballroom H/G

Dry gets wetter, wet gets drier: Counterintuitive changes in stream drying driven by cross-scale interactions among regional and global hydrologic processes Non-perennial streams are globally widespread and increasingly common. In many river basins, the spatial and temporal patterning of stream drying emerges from cross-scale interactions among local, regional and global hydrologic processes. Here, we evaluated how changes in stream flow and river network connectivity might be influenced by interactions between global-scale climate change and regional aridity. We modeled stream flow in stream networks across the continental United States for current and future climate scenarios to investigate how drivers of connectivity across spatial scales interact. We found that while nine of eleven stream networks had increased flow in the future, only four stream networks showed increased network connectivity. Changes in the number of days annually that the stream networks were very highly or very poorly connected varied with aridity. More arid networks tended to have more high connectivity days in the future while more mesic networks tended to have more low connectivity days in the future. Our findings overall highlight how cross-scale interactions between climate change and aridity drove predictable changes in network connectivity. The ability to predict future changes in connectivity improves our ability to anticipate the consequences of climate change and manage ecosystems in a changing world.

Megan C. Malish (Primary Presenter/Author), University of Oklahoma, megan.malish@ou.edu;

Shang Gao (Co-Presenter/Co-Author), University of Arizona, shanggao@arizona.edu;

Daniel Allen (Co-Presenter/Co-Author), Penn State, daniel.c.allen@psu.edu;

Thomas Neeson (Co-Presenter/Co-Author), University of Oklahoma, neeson@ou.edu;

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