Status, trends and significance of American hydropower in the changing energy landscape

Highlights: • Hydropower-based energy contributes > 10% of the total energy generation. • 65% of all hydro-dams is comprised of "small" dams that generate 3.5% of the total hydroelectricity. • The mean age of hydropower dams in the U.S. is 60.48 ± 0.70. • The total nameplate capacity of hydroenergy in the conterminous U.S. is 102.7 GW. -- Abstract: Despite the considerable contribution of hydropower in driving the American economy for over a century, the rationale for hydropower in the U.S. energy mix needs to be reassessed in the context of advanced science and technology. Other alternative-yet-cheaper energy resources have been identified and hazards associated with aging hydro-dams have escalated in recent years. Furthermore, research has shown more negative environmental consequences associated with hydro-dams—and dams in general. To compare the contribution of hydro-electricity to the total energy production in the U.S., and to identify its regional distribution and contemporary patterns, we conducted a systematic analysis of large-scale multi-year data from U.S. federal agencies and tallied the nameplate capacities of major hydro-dams against their existing energy production values. We found that despite continuous efforts at upgrading hydro-facilities, since 2000 the mean contribution of hydroelectricity has remained less than 10% of the total generated energy in the U.S. and has been declining since then. Based on our results, we conclude that reservoir- and dam-based hydroelectricity may not be an efficient energy resource—at least from the American perspective, and perhaps it is timely to consider promoting other non-conventional renewable resources for energy production.