4.3.2. Data Collection & Analysis

The MWQI discrete monitoring network has changed little since the CALFED years (Figure 1), with routine monitoring locations sampling for bromide, TOC, DOC, nutrients, standard minerals, and chlorophyll on a monthly basis [78,116]. The total number of discrete monitoring locations may change year to year based on need of special studies. The MWQI program discontinued publication of its annual data reports after water year 2009; however, the program continues to make its data available online through the CDWR

Water Data Library. Representative time series of discrete sample bromide and TOC data from Banks Pumping Plant are shown in Figure 3.

**Figure 3.** Representative data from the MWQI Program at the Banks Station: (**a**) Bromide (Br−) and (**b**) TOC. Data are downloaded from the California Water Data Library (WDL Water Quality Data (ca.gov), accessed 21 July 2021).

The MWQI program was expanded during 2002–2006 with the initiation of real time data collection and water quality forecasting. The key elements of this expansion include construction and on-going management of real time monitoring sites, systematic production of water quality forecasts, and management and dissemination of information generated by the program expansion [24]. The objective of this program expansion was to enhance the ability of drinking water treatment plant operators to make informed operational decisions based on observed and forecasted changes in Delta water quality [117].

Five real time monitoring stations are operated and maintained by the MWQI program; four of the stations are located in the Delta and one is located south of the Delta (Figure 1). The Delta stations include Hood (located on the Sacramento River near the town of Hood upstream of most Delta influences—see Figure A4 in Appendix A), Vernalis (located on the San Joaquin River near the town of Vernalis upstream of most Delta influences), Banks Pumping Plant (located at the head of the SWP), and Jones Pumping Plant (located at the head of the Delta-Mendota Canal, which provides water to the CVP). The southern station, Gianelli, is located along the SWP at the Gianelli Pumping-Generating Plant on O'Neill Forebay below San Luis Reservoir. Data, collected from 46 field sensors at the five monitoring stations, measure several key water quality constituents, with organic carbon (both TOC and DOC) and bromide being the primary focus. Of the 46 sensors, 31 are operated by the MWQI program while the remaining sensors are operated by other entities such as the U.S. Geological Survey, the San Luis Delta Mendota Water Authority, and other CDWR programs. Table 1 summarizes MWQI real time station names, California Data Exchange Center (CDEC) identifications, and water quality parameters collected by the MWQI program and other entities; parameters collected by other entities are referred to as "non-program" parameters in the table.


#### **Table 1.** MWQI Real Time Stations and Parameters.

Note: Abbreviations and definitions: EC = electrical conductivity (surrogate for salinity); TOC = total organic carbon; DOC = dissolved organic carbon; FDOM = Fluorescent Dissolved Organic Matter (refers to the fraction of organic matter that fluoresces). Algal fluorescence refers to the detection of cyanobacterial and algal cells via measurement of fluorescence from specific pigments.

Although the MWQI program discontinued measurement of UV-254 as a surrogate for organic carbon, efforts continue to find a useful real time surrogate. Recent efforts have focused on the use of fluorescence of dissolved organic matter (FDOM) as a real time surrogate for DOC; preliminary results appear promising [118]. The U.S. Geological Survey has been using FDOM sensors in the Delta since 2014 and has found it to be a strong predictor of DOC concentration [119,120]. Real time monitoring data, along with the daily water quality report, are posted on the SWC RTDF web page at http://rtdf.info/ (accessed on 8 October 2022). This web page provides links to CDWR's Water Data Library, CDEC, and the daily MWQI water quality report.
