SOUTH-DAKOTA RESERVOIR REPORT

Last Updated: January 12, 2026

The overall status of the nation's dams and reservoirs reflects a diverse range of storage levels, with some bodies of water experiencing above-average storage while others fall below historic averages. Notably, several key reservoirs show significant variances that may impact regional water management and ecosystems.

For instance, Lake Mead in Nevada – a critical water source for millions in the Southwest – is considerably below its average storage capacity at 8,671,468 acre-feet, a stark contrast to its historic average of 17,984,398.93 acre-feet. Similarly, Elephant Butte Reservoir in New Mexico holds just 188,909 acre-feet compared to an average of 829,181.99 acre-feet, signaling potential water scarcity issues. On the flip side, Lake San Antonio in California stands at a surplus with 270,863 acre-feet against an average of 132,675.92 acre-feet, reflective of recent hydrologic events or management strategies that have resulted in increased storage.

These disparities in reservoir levels underscore the complex interplay between climatic variables, such as precipitation and snowpack melt, and human interventions like water consumption and reservoir management. Hydrologists and water managers must continuously monitor these changing conditions to ensure sustainable water allocation and maintain ecological balance, particularly in regions facing drought conditions or those with reservoirs atypically high for the season.

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.