Application of the ELOHA Framework to Regulated Rivers in the Upper Tennessee River Basin: A Case Study

Abstract

In order for habitat restoration in regulated rivers to be effective at large scales, broadly applicable frameworks are needed that provide measurable objectives and contexts for management. The Ecological Limits of Hydrologic Alteration (ELOHA) framework was created as a template to assess hydrologic alterations, develop relationships between altered streamflow and ecology, and establish environmental flow standards. We tested the utility of ELOHA in informing flow restoration applications for fish and riparian communities in regulated rivers in the Upper Tennessee River Basin (UTRB). We followed the steps of ELOHA to generate univariate relationships between altered flows and ecology within the UTRB. By comparison, we constructed multivariate models to determine improvements in predictive capacity with the addition of non-flow variables. We then determined whether those relationships could predict fish and riparian responses to flow restoration in the Cheoah River, a regulated system within the UTRB. Although ELOHA provided a robust template to construct hydrologic information and predict hydrology for ungaged locations, our results do not suggest that univariate relationships between flow and ecology (step 4, ELOHA process) can produce results sufficient to guide flow restoration in regulated rivers. After constructing multivariate models, we successfully developed predictive relationships between flow alterations and fish/ riparian responses. In accordance with model predictions, riparian encroachment displayed consistent decreases with increases in flow magnitude in the Cheoah River; however, fish richness did not increase as predicted 4 years after restoration. Our results suggest that altered temperature and substrate and the current disturbance regime may have reduced opportunities for fish species colonization. Our case study highlights the need for interdisciplinary science in defining environmental flows for regulated rivers and the need for adaptive management approaches once flows are restored.

Accounting for environmental flow requirements in global water assessments

“…The advantage of habitat simulation models is that they take into consideration riverine ecosystems; however, data collection can be costly and time-consuming. Habitat simulation models also need to be recalibrated when they are applied to a different region and are usually species-specific (McManamay et al, 2013).…”

Quantitative Assessment of Flow Regime Alteration Using a Revised Range of Variability Methods

“…The ELOHA framework, which is used to find relationships between flow regime alteration and ecological responses in order to define environmental flow [41], includes four scientific steps: (1) building a hydrologic foundation, (2) classifying river types, (3) assessing flow alterations, and (4) determining flow-ecology relationships. Flow alteration assessment is central to the ELOHA framework.…”

Putting Flow–Ecology Relationships into Practice: A Decision-Support System to Assess Fish Community Response to Water-Management Scenarios

“…The Ecological Limits of Hydrologic Alteration (ELOHA) [31] is commonly cited as a general framework for discerning flow-ecology relationships, but it provides little guidance on how these relationships can be operationalized to support specific and localized water-management decisions. For example, recent applications of the ELOHA framework have either produced flow-ecology relationships [36][37][38][39] or have prescribed general flow standards for particular river systems [40,41] but have not provided objective, quantitative frameworks for translating particular water-management decisions (e.g., withdrawal permits, and dam releases) into predicted hydrologic or ecological outcomes. Although substantial science exists on ecological effects of flow alteration [16,42], this understanding is often not specific enough to be readily translated into usable DSS [17], such that the "implementation" phase of ELOHA (lower left corner of figure 1 in [31]) remains a challenge.…”

“…This DSS directly addresses priorities of the National Park Service [53] and was developed in the prevailing management context (a partially regulated river system) and scale (local watershed) at which water-allocation decisions are commonly made [38]. The DSS allows simultaneous evaluation of multiple components of the hydrologic and water-infrastructure system, including withdrawals for municipal water supply, effluent discharges from wastewater treatment, inter-basin water transfer, and dam operation protocols, representing some of the many socio-economic, regulatory, and technical considerations that must be weighed by water-resource managers [54,55].…”