LAKEPORT >> The county approved on Tuesday of a $102,000 extension of a deal with UC Davis for sediment sampling and testing in Clear Lake.
Since 2009, the university’s environmental science and policy department has analyzed sediment for phosphorus and nitrogen, which contribute to excessive growth of cyanobacteria and algea, according to Lake County Water Resources Director Scott De Leon. Sampling and testing by other agencies began in 1992.
“Understanding this nutrient cycling is necessary in order to develop measure to improve summer conditions,” as well as “critical to understanding Clear Lake’s cyanobacteria blooms,” De Leon explained.
The agreement would extend the contract with UC Davis for three years and will cost a approximately $34,000 each year. The county provides a boat and staff to assist with the project, limiting costs to laboratory testing and other research expenses.
The previous agreement lasted from 2009 to 2014.
According to De Leon, samples are taken 10 times a year, conditions permitting, from three locations on the lake. Each sight has seven layers of sediment analyzed.
After analyzing all data collected since 1992, De Leon said “significant trends have been identified in the sediment chemistry.” Those trends were discussed in the most recent report by Lake County Water Resources Engineer Tom Smythe, which was compiled in October of last year. The report found that the greatest increases in phosphorus concentrations are in the Lower and Oaks Arms of the lake.
According to Smythe, the data also indicated that phosphorus cycling has continued to occur in the top 10 centimeters of sediments, with total concentration and mass, as well as solids content decreasing.
“This decrease is probably due to a reduction in external phosphorus loading from historical levels,” De Leon said.
However, the amount of phosphorus cycled from the sediments is “up to seven times the average annual phosphorus load,” Smythe said.
Last year, the county began analyzing nitrogen levels. Currently there is insufficient data to determine if there is an increasing or decreasing trend.
The Board of Supervisors approved the agreement with UC Davis with a 4-0 vote. District 3 Supervisor Jim Steele was not present.
Contact J. W. Burch, IV at 900-2022.
