Trends in Dissolved Organic Carbon (DOC) in the Sacramento-San Joaquin Delta

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Water from the Sacramento-San Joaquin Delta contains high concentrations of disinfection byproduct-forming (DBP-forming) materials when treated for potable use. DBPs form when dissolved organic compounds (DOC) in water react with disinfectants such as chlorine and ozone during the water treatment process. The amount of DBPs that form is a function of both the amount and source of the DOC, both of which can vary significantly over a period of days. Epidemiological studies have linked several DBPs to increased occurrence of bladder cancer, miscarriages, and leukemia. Treated Delta water frequently exceeds DBP concentrations permitted by U.S. Environmental Protection Agency regulations.

A variety of natural and anthropogenic processes affect the concentration and composition of DOC in the Delta, some of which are likely to be affected by CalFed actions. Presently, there is little information available regarding historic levels and trends in the amount and composition of DOC released from, for example, in-channel biological production, wetlands, agricultural sources, island drains and the myriad of other DOC sources present in a system as large and complex as the Delta and its watersheds. A quantitative understanding of these processes is an important part of a CalFed solution to drinking water issues. In addition, assessment of the impact of CalFed Delta changes and integrated storage solutions on water users requires that DOC changes be monitored. To quantify potential changes, the baseline levels and current trends must be characterized and understood.

These goals are achieved by analysis of existing time-series data of a variety of types. The techniques used to analyze the data include spectral analysis and multiple parameter regression. Published reports include information on the baseline, trends, and major factors affecting DOC in the Delta, and on evaluating predictive/statistical models for quantitative assessment of changes and recommending effective monitoring solutions.