Clear Lake

What is Rumsey?
The natural level of Clear Lake has been maintained by the Grigsby Riffle, which is a rock sill located at the confluence of Cache and Seigler Creeks near Lower Lake. The natural low water level of Clear Lake was established as "Zero Rumsey" and all subsequent lake measurements are based on this elevation.

Zero Rumsey is equivalent to 1318.256 feet (1929 NGVD). The chart below relates the Rumsey gage reading to the National Geodetic Vertical Datum of 1929 (1929 NGVD). Full lake is established as 7.56 feet on the Rumsey gage (7.56’R; 1325.82 NGVD). Flood monitor stage is 8.0’R (1326.3 NGVD); flood stage is recognized as 9.0’R (1327.3 NGVD) and the 100 year flood event is established as 12’R (1330.3 NGVD).

Download Rumsey to NGVD Conversion Chart