The total watershed for Elm Lake is approximately 165,240 acres, including 59,520 acres that drain into Pheasant Lake, another reservoir on the Elm River located approximately 4 miles north of Elm Lake.
Elm Lake is classified as a drinking water supply for the city of Aberdeen.
The city uses Elm Lake as a storage reservoir for dry periods and has the legal right to the top 12 feet of the pool below the crest of the dam. Water can be released from the lake through draw-down tubes in the earthen embankment. The water flows down the Elm River approximately 30 miles where the city of Aberdeen pumps the water into their treatment plant. Elm Lake was one of the top priorities of the Section 319 Nonpoint Source Control Program for South Dakota, and when the conservation district was approached about the assessment they accepted sponsorship of the project. EPA granted the money to the State of South Dakota for the water quality assessment.