The highest potential was identified in the Pacific Northwest Region (32%), followed by the Missouri Region (15%) and the California Region (9%). In total, the undeveloped NSD capacity is 84.7 GW, and the undeveloped NSD generation is estimated to be 460 TWh/year. When areas protected by federal legislation limiting the development of new hydropower (national parks, wild and scenic rivers, and wilderness areas) were excluded from the analysis, the estimated NSD capacity falls to 65.5 GW, slightly lower than the current existing U.S. conventional hydropower nameplate capacity (79.5 GW; NHAAP, 2013).

Undeveloped NSD generation with these areas excluded is estimated to be 347.3 TWh/year, roughly 128% of the average 2002–2011 net annual generation from existing plants (272 TWh/year; EIA, 2013). Since the assessment was designed to identify potential run-of-river projects, NSD stream-reaches have higher capacity factors (53%–71%), especially compared with conventional larger-storage peaking-operation projects that usually have capacity factors of around 30%.

—ORNL NSD assessment

Development potential by sub-basin. The New Stream-reach Development (NSD) Assessment analyzed more than 3 million stream-reaches, making it the most detailed evaluation of new US hydropower potential to date. Source: ORNL NSD. Click to enlarge.

The US Department of Energy (DOE) tasked ORNL with evaluating the new stream-reach development resource potential of more than 3 million US streams. Such a wide spatial scope required a methodology that can (1) resolve aggregate potential within hydrologic regions and electric power systems; and (2) enable the modeling of regional and national scenarios for existing and new electric power generation technology deployment through the development of curves for hydropower capacity cost versus supply.

ORNL designed a methodology containing three main components: (1) identification of stream-reaches with high energy density; (2) topographical analysis of promising stream-reaches to estimate the characteristics of potential inundations of reservoirs; and (3) environmental attribution to spatially join the energy potential of stream-reaches with information related to the natural ecological systems; social and cultural settings; and policies, management, and legal constraints.

Some of the environmental, technical and socioeconomic factors variables included:

• Endangered species;
• Federally protected lands;
• Water use and water quality concerns;
• Fishing and boating access.

In addition to voluminous new data and the methodology, the NSD assessment focuses specifically on undeveloped stream-reaches, unlike previous assessments that examined all types of streams without further breakdown (i.e., including river segments with existing hydropower plants or non-powered dams).

Hydropower makes up 7% of total US electricity generation and continues to be the US’ largest source of renewable electricity. Hydropower also provides reliable baseload power day and night, providing greater flexibility and diversity to the electric grid and allowing utilities to integrate intermittent renewable sources such as wind and solar power.

The NSD Assessment builds on a 2012 Energy Department assessment that found more than 12 GW of hydropower potential at the nation’s existing 80,000 non-powered dams. The results of the new resource assessment show that there are opportunities to develop new hydropower projects around the country, most of which would likely be smaller, run-of-river facilities that could utilize new low-impact designs and technologies.

Resources

• New Stream-reach Development: A Comprehensive Assessment of Hydropower Energy Potential in the United States