U.S. Department of Energy

Pacific Northwest National Laboratory

An Integrated View of Hydropower Impacts

This simplified schematic shows HEF-driven ecosystem functioning in riverine hydropower systems.

A new framework explains how hydropower triggers a cascade of hydrologic, biogeochemical, and ecological effects

The Science

A recent overview of river corridor science by researchers at Pacific Northwest National Laboratory (PNNL) argues that understanding the linkages between surface-subsurface hydrologic exchange flows (HEFs) and aquatic ecology are an overlooked aspect of riverine health. The authors, led by quantitative ecosystem ecologist Emily B. Graham, propose a new conceptual framework to discuss how the impacts of hydropower operations cascade via subsurface biogeochemistry from HEFs to river corridor food webs and, more holistically, to ecosystem health.

The Impact

Integrating subsurface hydrology and aquatic ecology through biogeochemical processes can improve our predictions of riverine health, particularly within dam-impacted systems with large HEFs.


A global boom is underway in building the large dams (over 50,000 so far) that supply water and power to farms and cities. Hydropower, in particular, has grown six-fold in recent years, and contributes 80 percent of the world’s renewable energy.

Scientists have investigated some impacts of hydropower, including river channelization, bank erosion, and changes in river sediment load. But research rarely connects these cross-disciplinary effects into a more holistic understanding of river corridor health. Specifically, we know very little about how dam-induced alterations to subsurface hydrology influence the ecological health of river corridor ecosystems.

To address this knowledge gap, the paper proposes a new and expanded conceptualization of river corridor health—a framework for improving our understanding of influential subsurface processes across a range of spatial and time scales. The authors propose numerous ways in which theses linked processes may play out. They also call on the scientific community to embrace the new integrative research framework in order to uncover missing conceptual linkages between HEFs, subsurface biogeochemistry, and the river corridor food webs that are crucial to ecosystem health.

In writing the paper, Graham acknowledged the challenge of “reviewing and synthesizing decades of research in a variety of disciplines—hydrology, food web ecology, and biogeochemistry.” She was joined by PNNL coauthors James C. Stegen, Maoyi Huang, Xingyuan Chen, and by senior author Timothy D. Scheibe.

As for the future: The authors and others in PNNL’s Subsurface Biogeochemical Research Scientific Focus Area (SFA), sponsored by the Department of Energy’s, Office of Science, Biological and Environmental Research program, continue work on major projects investigating the organic carbon chemistry and the spatiotemporal dynamics that the paper proposes are the keys to understanding river corridor health.

March 2019
| Pacific Northwest National Laboratory