The recent storm raised the lake level about 6 inches on the Rumsey Gauge. Whereas the rain was good news, a lot more is needed to end the drought.
Recently a pair of fishermen at a local tackle shop got into a discussion about the Rumsey Gauge, which is unique to Clear Lake because just about all other bodies of water are measured by the their elevation above sea level.
For example, when Indian Valley Reservoir is full the surface of the lake is 1,502 feet above sea level. Right now Indian Valley Reservoir is 1,355 feet. Clear Lake is unique in that its elevation is measured at 1,318.26 feet, which is zero on the Rumsey Gauge. The lake level is based on that figure, which can be confusing because the lake is considered full when it is 7.56 feet on the Rumsey Gauge, which is actually 1,325.82 feet above sea level.
The altitude above or below sea level measures just about all lakes, however, the Rumsey Gauge measures the lake level of Clear Lake. Many people don't know how the Rumsey Gauge came into being. Prior to the building of the Cache Creek Dam in 1914, outflow from Clear Lake into Cache Creek was controlled by a rock ledge called the "Grigsby Riffle." The riffle is a rock ledge located in a narrow canyon on Cache Creek about three miles from Clear Lake. Before the dam was built, water would normally cease to flow over the riffle during the summer months.
In 1872, Captain Rumsey decided to register the lake level at Clear Lake but he needed to come up with a standard. He decided that when water ceased to flow over the riffle it would be called "Zero Rumsey." When water was above the riffle it would be called plus Rumsey, such as 1 foot, 2 feet and so on. Below the riffle, the lake level would be measured as a minus on the Rumsey Gauge. All measurements were based on zero Rumsey at the Grigsby Riffle. However, the actual gauge is located in Lakeport and it's used as a reference to the actual depth at the riffle, not the depth at Lakeport.
To this day, the lake level is still measured by the Rumsey Gauge. For example, Tuesday's official reading of the lake level was 1.02 feet on the Rumsey Gauge, but the actual depth of water at the gauge in Lakeport was a little more than 2 feet. That means at the Grigsby Riffle the depth of the water is just a little more than a foot.
As for the individual who started the Rumsey Gauge, he was actually Captain Dewitt C. Rumsey and he was from Yolo County. In 1852, he was a trail boss on cattle drives in the West. From what I have researched that's where he received the title of "Captain." In those days it was common to call the trail boss captain. Captain Rumsey was an important part of the history of Lake County. In fact, he founded the town of Rumsey, which is located on Highway 16 in Yolo County. He also bought property in Lakeport and Rumsey Bay on Clear Lake is named after him. He started the Rumsey Gauge in 1872. The actual location of the Rumsey Gauge is on Esplanade Avenue in Lakeport. Up to a few years ago the gauge was physically read each day by the county, but now the U.S. Geological Survey Agency reads the gauge by remote telemetry.
Clear Lake is considered full when it reaches 7.56 feet on the Rumsey Gauge. Averaging high water levels between 1873 and 1920 derived that number. When the lake is full it holds approximately 1,155,000 acre-feet of water. An acre-foot of water is equal to approximately 326,000 gallons. When the lake level drops to zero on the Rumsey Gauge, the lake holds 842,000 acre-feet. That means between zero and 7.56 feet there is 313,000 acre-feet of water in the lake. Yolo County's allotment is 150,000 acre-feet of water when the lake is full. That adds up to about 3 1/2 feet of water on the Rumsey Gauge. However, when the lake is somewhere between full and 3.22 feet on the Rumsey Gauge as of May 1, Yolo County's water allotment is less. Yolo County gets no water if the lake level is below 3.22 feet on May 1. In addition, about 3.1 feet of water is lost because of evaporation. If it's a hot summer, the evaporation rate can be much higher. Yolo County can't take its full allotment all at once. There is a monthly discharge rate that has been established. Also, Yolo County can't draw any water after Oct. 31.