Virginia flow-ecology modeling results—An initial assessment of flow reduction effects on aquatic biota

Abstract

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit http://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov/.Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Application of a New Species‐Richness Based Flow Ecology Framework for Assessing Flow Reduction Effects on Aquatic Communities

“…With August MMF conditions, IFIM sites larger than the RCC breakpoint had stable or increasing median percent change in habitat with 20% flow reductions (Figure 6a); however, all 24 IFIM sites had habitat loss when flows were below the 10 th percentile flow in summer months (Figure 6b). It follows that during extreme low flow as habitat is reduced species richness may also be reduced, corroborating the findings of Rapp and Reilly (2017) that many species responses were highly correlated with alterations of summer‐month low‐flow statistics.…”

“…Percent habitat change for all species studied was negative (indicating habitat loss) in August, September, and October ( Figure S4). Across all IFIM sites, August and September flows had the greatest rates of habitat loss with flow reduction, further supporting the use of August flows as an indicator of risk of habitat loss or richness change (Krstolic et al 2006;Armstrong et al 2011;Kennen et al 2012;Krstolic and Ramey 2012;Knight et al 2014;Commonwealth of Virginia 2015;McManamay and Frimpong 2015;Rapp and Reilly 2017). With a 20% flow reduction, most of the IFIM sites with MAF <900 ft 3 /s had a median habitat-loss condition in August, and the majority of IFIM sites with MAF >900 ft 3 /s had a median habitat-gain ( Figure 6).…”

“…The RCC postulates the predictive strength of drainage area (DA), streamflow, or stream order in determining richness or density in aquatic communities (Schlosser 1987;Beecher et al 1988;Angermeier and Schlosser 1989;Walters et al 2003;Filipe et al 2010;Pracheil et al 2013;Vander Vorste et al 2017). Numerous studies are consistent with the RCC, that streams with higher streamflow volume have the potential to support richer fish assemblages, and have found that fish and benthic macroinvertebrates show negative responses to flow reductions (Freeman and Marcinek 2006;Dewson et al 2007;D€ oll and Zhang 2010;Poff and Zimmerman 2010;Armstrong et al 2011;Rolls et al 2012;Gido et al 2013;McManamay et al 2013;Carlisle et al 2014;Kennen et al 2014;Knight et al 2014;Brooks and Haeusler 2016;Rapp and Reilly 2017;Vander Vorste et al 2017). Instead of examining the suite of typical ecological flow statistics like base flow index or seven-day low flow, we sought to examine potential fish response to a net reduction in mean annual flow (MAF).…”

“…The "space-for-time" approach requires paired biological samples with modeled streamflow. This approach was used to estimate ecological responses to flow alteration in Virginia (Rapp and Reilly 2017), but representative, suitable paired biological and hydrological locations were not abundant, and habitat change was not quantified. ELOHA has the potential to be less expensive and time consuming than IFIM models, but suffers from limitations in flow-model accuracy, lack of prealteration flow data, and low data density.…”

elfgen: A New Instream Flow Framework for Rapid Generation and Optimization of Flow–Ecology Relations

“…The term species-discharge relationship (SDR) is commonly used to describe the increase in ecological diversity with streamflow and is often represented as a continuous curve with some suggesting a piecewise model (Xu et al 2016). Additional previous research has found that fish and benthic macroinvertebrate communities exhibit negative responses to decreases in streamflow magnitude (Dewson et al 2007; D€ oll and Zhang 2010; Poff and Zimmerman 2010;Armstrong et al 2011;Carlisle et al 2012;Rolls et al 2012;Gido et al 2013;Kennen et al 2014;Knight et al 2014;Brooks and Haeusler 2016;Rapp and Reilly 2017). In light of these most basic stream size-ecology relations, studies have begun to advocate the use of SDRs to predict changes in fish species richness resulting from decreases in streamflow (Jowett et al 2005;Xenopoulos et al 2005;Xenopoulos and Lodge 2006;D€ oll and Zhang 2010;Iwasaki et al 2012).…”