title: Application of Effective Discharge Analysis to Environmental Flow Decision-Making.
abstract: Well-informed river management decisions rely on an explicit statement of objectives, repeatable analyses, and a transparent system for assessing trade-offs. These components may then be applied to compare alternative operational regimes for water resource infrastructure (e.g., diversions, locks, and dams). Intra- and inter-annual hydrologic variability further complicates these already complex environmental flow decisions. Effective discharge analysis (developed in studies of geomorphology) is a powerful tool for integrating temporal variability of flow magnitude and associated ecological consequences. Here, we adapt the effectiveness framework to include multiple elements of the natural flow regime (i.e., timing, duration, and rate-of-change) as well as two flow variables. We demonstrate this analytical approach using a case study of environmental flow management based on long-term (60 years) daily discharge records in the Middle Oconee River near Athens, GA, USA. Specifically, we apply an existing model for estimating young-of-year fish recruitment based on flow-dependent metrics to an effective discharge analysis that incorporates hydrologic variability and multiple focal taxa. We then compare three alternative methods of environmental flow provision. Percentage-based withdrawal schemes outcompete other environmental flow methods across all levels of water withdrawal and ecological outcomes.
authors.affiliation: Environmental Laboratory, U.S. Army Engineer Research and Development Center, Athens, GA, USA. kyle.mckay@usace.army.mil.
authors.forename: S Kyle
authors.initials: SK
authors.lastname: McKay
authors.affiliation: Patuxent Wildlife Research Center, U.S. Geological Survey, Athens, GA, USA.
authors.forename: Mary C
authors.initials: MC
authors.lastname: Freeman
authors.affiliation: Odum School of Ecology, University of Georgia, Athens, GA, USA.
authors.forename: Alan P
authors.initials: AP
authors.lastname: Covich
mesh_terms: D000818:Animals; D003657:Decision Making; D004784:Environmental Monitoring / Q000379:methods*; D005399:Fishes / Q000145:classification / Q000254:growth & development; D005845:Georgia; D062070:Hydrology; D008962:Models, Theoretical; D045483:Rivers; D012621:Seasons; D014872:Water Movements; D062066:Water Resources / Q000600:supply & distribution
keywords: Flow regime; Functional-equivalent discharge; Hierarchical linear models; Trait-based models; Water management