Development of environmental instream flow standards for the state of Alabama: Comparison of historic flow, hydraulic, and physical habitat simulation methods

Authors: Sarah Praskievicz*, University of Alabama
Topics: Water Resources and Hydrology, Geomorphology, Biogeography
Keywords: aquatic ecology, environmental instream flows, hydrology
Session Type: Paper
Day: 4/10/2018
Start / End Time: 8:00 AM / 9:40 AM
Room: Jackson, Marriott, 5th Floor
Presentation File: No File Uploaded

Rivers provide both offstream and instream benefits to society, but flow regulation and withdrawals have altered the natural flow regime of many river systems. Legally enforceable environmental flow standards have been developed for many states in order to preserve the ecological benefits of rivers. In Alabama, the state with the highest levels of freshwater biodiversity and some of the highest concentrations of endangered and threatened aquatic taxa in the nation, no environmental flow standards currently exist. Environmental flow standards can be based on methods of varying capacity, ranging from simple metrics of historic flow to hydraulic methods to complex and data-intensive physical habitat simulation modeling. We estimated environmental flow requirements for five rivers in Alabama, representative of the state’s major interstate river basins and physiographic regions, using a range of methods. We used United States Geological Survey (USGS) gaging stations and the software program Indicators of Hydrologic Alteration (IHA) to calculate historic flow metrics. We used measured channel hydraulic properties to determine the inflection point in the relationship between discharge and wetted perimeter. Finally, we did intensive topographic surveying and substrate sampling and made repeated measurements of water depth and flow velocity at differing flow levels to parameterize a Physical Habitat Simulation (PHABSIM) model to simulate the usable habitat area under a range of flows. Our results can be used to determine which of the simpler historic flow and hydraulic methods, which can be easily applied at a regional or statewide scale, best approximate the physical habitat requirements of species.

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