The future role of dams in the United States of America

Storage and controlled distribution of water have been key elements of a human strategy to overcome the space and time variability of water, which have been marked by catastrophic droughts and floods throughout the course of civilization. In the United States, the peak of dam building occurred in the mid-20th century with knowledge limited to the scientific understanding and hydrologic records of the time. Ecological impacts were considered differently than current legislative and regulatory controls would potentially dictate. Additionally, future costs such as maintenance or removal beyond the economic design life were not fully considered. The converging risks associated with aging water storage infrastructure and uncertainty in climate in addition to the continuing need for water storage, flood protection, and hydropower result in a pressing need to address the state of dam infrastructure across the nation. Decisions regarding the future of dams in the United States may, in turn, influence regional water futures through groundwater outcomes, economic productivity, migration, and urban growth. We advocate for a comprehensive national water assessment and a formal analysis of the role dams play in our water future. We emphasize the urgent need for environmentally and economically sound strategies to integrate surface and groundwater storage infrastructure in local, regional, and national water planning considerations. A research agenda is proposed to assess dam failure impacts and the design, operation, and need for dams considering both paleo and future climate, utilization of groundwater resources, and the changing societal values toward the environment. Plain Language Summary Water storage and control have been key elements of a human strategy to overcome differences between water availability and water needs. The future promises changes to when and where water will be available and many regions in the USA will likely see an increase in the imbalance between existing water storage and evolving demands for water. This indicates the need for more storage or new dams to meet human and ecological needs. The current trend for removal of old, hazardous or unpopular dams now and into the future may impact regional groundwater outcomes, food and energy production, migration, and urban growth. We advocate for a formal analysis of the role dams play in the future of the USA's water landscape. We also stress the need for national water planning considerations to develop environmentally and economically sound strategies to integrate the management of surface and groundwater storage infrastructure in the USA.