Designing flows to enhance ecosystem functioning in heavily altered rivers

K.R. Bestgen, N LeRoy Poff, Daniel Baker, B.P. Bledsoe, David M. Merritt, Mark Lorie, G.T. Auble, John Sanderson, Boris C. Kondratieff

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

More than a century of dam construction and water development in the western United States has led to extensive ecological alteration of rivers. Growing interest in improving river function is compelling practitioners to consider ecological restoration when managing dams and water extraction. We developed an Ecological Response Model (ERM) for the Cache la Poudre River, northern Colorado, USA, to illuminate effects of current and possible future water management and climate change. We used empirical data and modeled interactions among multiple ecosystem components to capture system-wide insights not possible with the unintegrated models commonly used in environmental assessments. The ERM results showed additional flow regime modification would further alter the structure and function of Poudre River aquatic and riparian ecosystems due to multiple and interacting stressors. Model predictions illustrated that specific peak flow magnitudes in spring and early summer are critical for substrate mobilization, dynamic channel morphology, and overbank flows, with strong subsequent effects on instream and riparian biota that varied seasonally and spatially, allowing exploration of nuanced management scenarios. Instream biological indicators benefitted from higher and more stable base flows and high peak flows, but stable base flows with low peak flows were only half as effective to increase indicators. Improving base flows while reducing peak flows, as currently proposed for the Cache la Poudre River, would further reduce ecosystem function. Modeling showed that even presently depleted annual flow volumes can achieve substantially different ecological outcomes in designed flow scenarios, while still supporting social demands. Model predictions demonstrated that implementing designed flows in a natural pattern, with attention to base and peak flows, may be needed to preserve or improve ecosystem function of the Poudre River. Improved regulatory policies would include preservation of ecosystem-level, flow-related processes and adaptive management when water development projects are considered.

Original languageEnglish
Article numbere02005
Pages (from-to)1-45
Number of pages45
JournalEcological Applications
Volume30
Issue number1
DOIs
Publication statusPublished - 1 Jan 2020

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peak flow
baseflow
ecosystem
river
ecosystem function
overbank flow
channel morphology
dam construction
adaptive management
environmental assessment
prediction
bioindicator
development project
low flow
mobilization
biota
water management
dam
substrate
water

Cite this

Bestgen, K. R., Poff, N. L., Baker, D., Bledsoe, B. P., Merritt, D. M., Lorie, M., ... Kondratieff, B. C. (2020). Designing flows to enhance ecosystem functioning in heavily altered rivers. Ecological Applications, 30(1), 1-45. [e02005]. https://doi.org/10.1002/eap.2005
Bestgen, K.R. ; Poff, N LeRoy ; Baker, Daniel ; Bledsoe, B.P. ; Merritt, David M. ; Lorie, Mark ; Auble, G.T. ; Sanderson, John ; Kondratieff, Boris C. / Designing flows to enhance ecosystem functioning in heavily altered rivers. In: Ecological Applications. 2020 ; Vol. 30, No. 1. pp. 1-45.
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Bestgen, KR, Poff, NL, Baker, D, Bledsoe, BP, Merritt, DM, Lorie, M, Auble, GT, Sanderson, J & Kondratieff, BC 2020, 'Designing flows to enhance ecosystem functioning in heavily altered rivers', Ecological Applications, vol. 30, no. 1, e02005, pp. 1-45. https://doi.org/10.1002/eap.2005

Designing flows to enhance ecosystem functioning in heavily altered rivers. / Bestgen, K.R.; Poff, N LeRoy; Baker, Daniel; Bledsoe, B.P.; Merritt, David M.; Lorie, Mark; Auble, G.T.; Sanderson, John; Kondratieff, Boris C.

In: Ecological Applications, Vol. 30, No. 1, e02005, 01.01.2020, p. 1-45.

Research output: Contribution to journalArticle

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T1 - Designing flows to enhance ecosystem functioning in heavily altered rivers

AU - Bestgen, K.R.

AU - Poff, N LeRoy

AU - Baker, Daniel

AU - Bledsoe, B.P.

AU - Merritt, David M.

AU - Lorie, Mark

AU - Auble, G.T.

AU - Sanderson, John

AU - Kondratieff, Boris C.

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N2 - More than a century of dam construction and water development in the western United States has led to extensive ecological alteration of rivers. Growing interest in improving river function is compelling practitioners to consider ecological restoration when managing dams and water extraction. We developed an Ecological Response Model (ERM) for the Cache la Poudre River, northern Colorado, USA, to illuminate effects of current and possible future water management and climate change. We used empirical data and modeled interactions among multiple ecosystem components to capture system-wide insights not possible with the unintegrated models commonly used in environmental assessments. The ERM results showed additional flow regime modification would further alter the structure and function of Poudre River aquatic and riparian ecosystems due to multiple and interacting stressors. Model predictions illustrated that specific peak flow magnitudes in spring and early summer are critical for substrate mobilization, dynamic channel morphology, and overbank flows, with strong subsequent effects on instream and riparian biota that varied seasonally and spatially, allowing exploration of nuanced management scenarios. Instream biological indicators benefitted from higher and more stable base flows and high peak flows, but stable base flows with low peak flows were only half as effective to increase indicators. Improving base flows while reducing peak flows, as currently proposed for the Cache la Poudre River, would further reduce ecosystem function. Modeling showed that even presently depleted annual flow volumes can achieve substantially different ecological outcomes in designed flow scenarios, while still supporting social demands. Model predictions demonstrated that implementing designed flows in a natural pattern, with attention to base and peak flows, may be needed to preserve or improve ecosystem function of the Poudre River. Improved regulatory policies would include preservation of ecosystem-level, flow-related processes and adaptive management when water development projects are considered.

AB - More than a century of dam construction and water development in the western United States has led to extensive ecological alteration of rivers. Growing interest in improving river function is compelling practitioners to consider ecological restoration when managing dams and water extraction. We developed an Ecological Response Model (ERM) for the Cache la Poudre River, northern Colorado, USA, to illuminate effects of current and possible future water management and climate change. We used empirical data and modeled interactions among multiple ecosystem components to capture system-wide insights not possible with the unintegrated models commonly used in environmental assessments. The ERM results showed additional flow regime modification would further alter the structure and function of Poudre River aquatic and riparian ecosystems due to multiple and interacting stressors. Model predictions illustrated that specific peak flow magnitudes in spring and early summer are critical for substrate mobilization, dynamic channel morphology, and overbank flows, with strong subsequent effects on instream and riparian biota that varied seasonally and spatially, allowing exploration of nuanced management scenarios. Instream biological indicators benefitted from higher and more stable base flows and high peak flows, but stable base flows with low peak flows were only half as effective to increase indicators. Improving base flows while reducing peak flows, as currently proposed for the Cache la Poudre River, would further reduce ecosystem function. Modeling showed that even presently depleted annual flow volumes can achieve substantially different ecological outcomes in designed flow scenarios, while still supporting social demands. Model predictions demonstrated that implementing designed flows in a natural pattern, with attention to base and peak flows, may be needed to preserve or improve ecosystem function of the Poudre River. Improved regulatory policies would include preservation of ecosystem-level, flow-related processes and adaptive management when water development projects are considered.

KW - NEPA policy change

KW - algae

KW - aquatic insects

KW - channel geomorphology

KW - climate change

KW - designed flow regime

KW - fish

KW - hydrology

KW - modeling

KW - probabilistic Bayesian Network model

KW - riparian community

KW - water development

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Bestgen KR, Poff NL, Baker D, Bledsoe BP, Merritt DM, Lorie M et al. Designing flows to enhance ecosystem functioning in heavily altered rivers. Ecological Applications. 2020 Jan 1;30(1):1-45. e02005. https://doi.org/10.1002/eap.2005