The gauge and the chart readings are in tenths of a foot (1/10 foot = 1.2 inches). The first point on the chart, June 27, 2017, was when the gauge was first installed at the downstream end of the bridge abutment, i.e., the Little LCO side. The gauge was moved to the upstream end of the abutment, the Big LCO side, on 4/15/21. The difference in water level between the upstream and downstream positions varies considerably, but the average was calculated to be 3.9 inches based on multiple measurements at both positions made in 2020. Therefore, all measurements made before 4/15/21 were increased by 3.9 inches to estimate what they would have been had the gauge been located on the upstream end of the abutment.

Sawyer County is required by WDNR rules to maintain water levels between the maximum of 1.49 feet (1286.09 feet above sea level) and minimum of 0.99 feet (1285.59 feet above sea level). This is accomplished by opening the gates at the Billy Boy dam when the level exceeds the maximum, and closing the gates when the level falls below the minimum.

The actual effect of raising/lowering the gates at the Billy Boy dam is minimal for big LCO. The main effect is on the water level of the Billy Boy flowage and little LCO.