- Water Resources
- Clear Lake
Clear Lake is the largest, natural freshwater lake in California with 68 square miles of surface area. Clear Lake is very productive and scenic, a lush paradise for fish and wildlife. The high productivity of the Clear Lake Basin attracted Native Americans early in their settlement of North America. Archeological evidence indicates human habitation around Clear Lake for the last 12,000 years.
Known as the Bass Capital of the West, Clear Lake supports large populations of bass, crappie, bluegill, carp and catfish. Two-thirds of the fish caught in Clear Lake are largemouth bass, with a record of 17.52 pounds. Bass fishing and fishing tournaments held on Clear Lake bring fishermen and women from all over California and other States. In addition to fish, there is abundant wildlife within the Basin. There are year-round populations of:
- Blue herons
- Bald eagles
The Basin also supports abundant populations of deer, bear, mountain lion, raccoon and other animals. The expansive warm, water of Clear Lake makes it popular for watersports, such as:
- Water skiing
- Boat races
- Jet skiing
With its scenic beauty, clean air and abundant wildlife, Clear Lake is an excellent place to slow down, enjoy nature study, photography or just plain loafing.
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 National Geodetic Vertical Datum (NGVD)). The following chart relates the Rumsey gauge reading to the National Geodetic Vertical Datum of 1929 (1929 NGVD). Full lake is established as 7.56 feet on the Rumsey gauge (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 the Rumsey to NGVD Conversion Chart (PDF).