SOUTH-DAKOTA RESERVOIR REPORT

Last Updated: December 22, 2025

Across the nation, dams and reservoirs play a vital role in water supply, flood control, and ecosystem management. However, these critical resources are subject to the whims of weather, climate change, and human demand. The latest observations reveal a mixed picture, with some reservoirs experiencing surpluses due to above-average precipitation, while others face drought conditions, reflecting irregularities in snowpack melting and river flows.

For instance, Lake Powell in Arizona, the second-largest man-made reservoir in the country by maximum water capacity, is currently facing significantly low water levels with only about 44% of its average storage reported, a stark illustration of the prolonged drought impacting the Colorado River Basin. Contrastingly, Lake San Antonio in California is experiencing a surplus, holding nearly double the average storage, likely due to recent heavy rains. Similarly, New Melones Reservoir in California has a storage level well above its average, which could be beneficial in addressing the state's water needs amidst variable climatic conditions. Strategic management of these water resources is more crucial than ever, as water management authorities strive to balance environmental sustainability with the demands of urban development, agriculture, and recreation. The data underscores the importance of continued monitoring and adaptive reservoir management in the face of increasingly unpredictable weather patterns.

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.