What is the Rumsey Scale? In 1872, a poineer named Captain Rumsey established the low point of the Gribsby Riffle sill — a rockledge locaed at the confluence of Cache and Siegler Creeks in Lower Lake — as “Zero Rumsey.” All subsequent lake measurements are based on this elevation. Zero Rumsey is equivalent to 1,318.256 feet elevation above sea level.

The highest recorded lake level was 13.66 Rumsey in 1890, while the lowest was -3.5 Rumsey in 1920. Typically the lake varies from an average 1.6 to 6.75 Rumsey each year. The lake is considered full at 7.56 Rumsey; when Clear Lake is full it has a surface area of 43.790 acres and contains 1,155,000 acre feet of water. At Zero the surface area is 39,170 acres with a capacity of 842,000 acre-feet. Flood levels vary, but warnings are issued at 9 Rumsey..

Sea Wall at Library Park

Click Here for the current water level of Clear Lake.

Click Here for more information about the historic levels of Clear Lake.

Click Here for an article about Clear Lake water levels in the Record Bee.

Click Here for more information about the Rumsey Scale and pictures.