The Water and Atmospheric Resources Monitoring Program's Reservoir Observation Network is a group of cooperating lake operators who report month-end water surface levels of reservoirs operated by their facility. Some of the operators also report monthly system pumpage, representing water usage. Most of the lakes included in the WARM network are Public Water Supply reservoirs. Lake level data at some of the lakes is collected and posted by automated equipment; otherwise, observations are reported to ISWS manually each month by the facility operators.
Currently, month-end lake levels at about two dozen reservoirs are reported each month in the ISWS Illinois Water and Climate Summary. These lakes are located mainly in the southern half of Illinois, where Public Water Supplies that rely on impounded surface water are more prevalent. The ISWS WARM network has collected 15 to 30 years of lake level data from selected lakes. To inquire about data availability, contact ISWS Water Resources Data and Information Services staff.
