Saylorville Lake, Water Supply

Rock Island District
Published Oct. 1, 2021
Saylorville Lake and Dam

Saylorville Lake and Dam


Saylorville Lake, Johnston, Iowa


Water supply storage contract with the State of Iowa. A contract was awarded in 1982 between the State of Iowa and the United States of America to allow the State 18.86% of usable storage space in Saylorville Lake between elevations of 812 NGVD29 and 836 NGVD29. The storage space was estimated to be approximately 14,900 acre-feet of water and the State has the right to request water from this reserve to be released from Saylorville Dam Outlet Works during periods of drought and low flow in the Des Moines River. Water supply for downstream utilities is released through Red Rock Dam Outlet Works.

Des Moines Water Works withdraws water directly from the Des Moines River at Prospect Park and from two wells below the riverbed south of Sycamore Access. Des Moines Water Works supplies potable water to over 500,000 customers in the Des Moines metropolitan area.


A report completed in 2014 indicated the 1982 usable storage estimate of 14,900 acre feet had been reduced to 11,940 acre feet of usable storage due to sedimentation in the reservoir. Computer simulations indicate that water supply reliability of 99% is still maintained, but with a slight decrease in the ability to release water to meet downstream water quality targets. Sediment surveys are performed every 7-10 years to assess the current storage capability. Sedimentation resurveys use GIS methods paired with bathymetric surveys and LiDAR.


Contract is in effect for the life of the project. The contract was originally entered into May 26, 1982. The State of Iowa has paid the joint-use construction costs. Annual O&M costs are still required from the State of Iowa.

Additional Information


OM - Operations and Maintenance

Water Supply Act of 1958

Summarized Project Costs

Estimated Federal Cost

$ N/A

Estimated Non-Federal Cost

$ N/A

Estimated Total Project Cost

$ N/A

Allocations Prior to FY2022

$ N/A

FY2021 Allocation


FY2022 Allocation


FY2022 President’s Budget


FY2022 Total Capability



Major Work Item Current Year

FY2022: Project is in operation; contract administration.