SOUTH-DAKOTA RESERVOIR REPORT

Last Updated: February 21, 2026

Across the nation, dams and reservoirs play a crucial role in water supply, flood control, irrigation, and hydroelectric power generation. The latest observations suggest that while some reservoirs are experiencing high storage levels, others are grappling with below-average water volumes, indicating localized surpluses and droughts.

For instance, Lake Winnipesaukee in New Hampshire is currently below its average gage height, sitting at 3 feet compared to the average of 3.77 feet. Similarly, the Wanaque Reservoir in New Jersey shows a notable deficit with current levels at 273 feet against an average of 293.25 feet. In contrast, the General Edgar Jadwin Reservoir in Pennsylvania is slightly above its average water surface elevation, suggesting an abundance in that region. Maurice R. at Union Lake Dam in New Jersey is experiencing significantly reduced streamflow, with a current flow of 192 ft³/s compared to the average of 296.72 ft³/s. In the West, Lake Powell, a critical water source spanning Arizona and Utah, is facing severe shortages with its storage plummeting to almost 40% of its average capacity. Similarly, California's Lake Mead, a barometer for the Southwest's water health, is also recording storage levels significantly below average.

These abnormal conditions can be attributed to a variety of factors, including fluctuating snowpack levels, river flows, and prolonged periods of dry weather affecting water inflow. The data underscores the importance of efficient water management strategies and the need for continued monitoring and adaptation to ensure water security amidst changing climatic conditions. As researchers and hydrologists seek to balance water needs with ecological conservation, these observations offer a snapshot of the ongoing challenges faced by the nation's reservoirs and dams.

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.