River ecosystems provide society with a broad range of goods and services including food, water, recreation, waste disposal, and energy. As a renewable energy source, hydropower has some desirable properties including minimal effects on carbon and air quality. Concerns center on how dam infrastructure alters other goods and services in regulated rivers. Opportunities for more-sustainable hydropower production occur when spatial decisions, including where hydropower dams should be located, which rivers to protect, and where to invest in mitigation measures such as fish passage or river restoration, are made from a broad vantage point. Such an undertaking requires tools from a variety of disciplines (e.g., economics, engineering, ecology). Drawing on case studies from several rivers, we show how various tools can be integrated to inform decisions about where dams are located (Penobscot River basin), where to provide fish passage or to re-establish upstream populations (Snake River basin), and how seasonal flows are shaped (San Joaquin River basin). Results were obtained either by combining optimization methods with applied simulation modeling of interactions between hydrosystems, physical habitat, and fish metapopulation dynamics, or by developing consensus among stakeholders.
Results/Conclusions
Simulations results for the Snake River highlighted the need for attention to source-sink dynamics and the need for either downstream passage or screening when establishing upstream populations. Optimization results in the San Joaquin River basin demonstrated tradeoffs and complementarities between energy and salmon objectives. In the Penobscot River basin, a consensus solution was reached that maintained total hydropower generation while increasing the amount of habitat accessible to migratory fish through selective removal of dams. We summarize efforts to assign ecological value to alternative options and argue that finding win-win options that provide correlated energy and ecological benefits will most likely result from decision problems formulated at the scale of large river basins. Done right, decisions involving hydropower should seek to maximize the ecological return on investment while ensuring long-term energy security.