SOUTH-DAKOTA RESERVOIR REPORT

Last Updated: December 24, 2025

The latest observations of the nation's dams and reservoirs present a mixed picture of water storage levels, with some areas experiencing surpluses due to recent inflows, while others face drought conditions with below-average water levels. Notably, major reservoirs such as Lake Powell in Arizona and Lake Mead in Nevada reveal a concerning trend, with storage levels falling significantly short of their historical averages, reflecting extended periods of drought and increased water demand in the Southwest. Conversely, California's Lake San Antonio has seen a surge in water levels, exceeding its average and demonstrating the variability of water supplies across different regions.

For water management researchers and hydrologists, the data underscores the importance of monitoring and adaptive management strategies to address the challenges posed by climate variability and human impact on water resources. Reservoirs like Lake Powell, currently at only 44% of average storage, and Lake Mead with less than half its average, are stark reminders of the long-term water scarcity issues facing the Colorado River Basin. Meanwhile, reservoirs such as California's Lake San Antonio, which now holds over twice its average storage, showcase the benefits of effective catchment during periods of heavy precipitation. The contrasting conditions highlight the need for dynamic management approaches that consider both the immediate and future water needs, in addition to the environmental and economic impacts of fluctuating water levels.

South Dakota has over 150 reservoirs and dams, with major reservoirs including Oahe, Sharpe, Francis Case, and Lewis and Clark. These reservoirs are fed by tributaries of the Missouri River, such as the James, White, and Cheyenne rivers. Snowpack in the Rocky Mountains, especially in Colorado and Wyoming, is a major source of water for these tributaries. Hydrology in the area is heavily influenced by seasonal trends, with high flows in the spring due to snowmelt and lower flows in the summer and fall. There have been several record high flows in recent years, including the historic flooding of the Missouri River in 2011. Drought conditions have also been an issue in some areas, leading to decreased water levels and increased concern for water use.

South Dakota has over 150 reservoirs and dams, with major reservoirs including Oahe, Sharpe, Francis Case, and Lewis and Clark. These reservoirs are fed by tributaries of the Missouri River, such as the James, White, and Cheyenne rivers. Snowpack in the Rocky Mountains, especially in Colorado and Wyoming, is a major source of water for these tributaries. Hydrology in the area is heavily influenced by seasonal trends, with high flows in the spring due to snowmelt and lower flows in the summer and fall. There have been several record high flows in recent years, including the historic flooding of the Missouri River in 2011. Drought conditions have also been an issue in some areas, leading to decreased water levels and increased concern for water use.