1. Continuous 15-minute flow data collection methods: To measure the level and velocity used to calculate flows, we used a SonTek IQ Plus Acoustic Doppler Current Profiler (ADCP) that we placed on the bottom of the channel opening(s) of each wetland. The ADCPs use five up-looking beams to calculate level and velocity and data was reported at 15-minute intervals. We calculated flow using the methods of Levesque and Oberg (2012) and used cubic spline interpolation to estimate missing flow data up to six hours; gaps larger than six hours could not be estimated.
2. Continuous 15-minute water quality sonde data collection methods: Basic water quality parameters were collected every 15-minutes using YSI EXO 2 water quality sondes. The sondes were mounted within the opening to adjacent water body of each wetland, except Blacklock, to collect temperature, specific conductance, turbidity, dissolved oxygen, and total chlorophyll data. We followed the YSI EXO User Manual collection and calibration methods for the first three wetlands. For the last wetland, Westervelt, we followed a modification of the Wagner Method (Wagner, Boulger Jr., Oblinger, & Smith, 2006) for verifying sonde data.
3. Discrete water quality grab sample data collection methods: Grab samples were collected weekly by sampling pole or by wading out near the sonde with a clean bottle. Samples were analyzed for chlorophyll a and total suspended solids. We also recorded temperature, specific conductance, dissolved oxygen, and turbidity at the time of collection with YSI ProPlus handheld meters and Hach 2100Q Turbidimeters at the first three wetlands. For the last wetland, Westervelt, we used YSI EXO 1 water quality sondes to record field measurements. This data was combined with continuous sonde data to estimate continuous data for chlorophyll a and total suspended solids.
4. 25-hour autosampler water quality event data collection methods: We used ISCO 6712 autosamplers deployed at the opening of each wetland to collect hourly water quality data over a 25-hour period. Each one was outfitted with 1.8 L glass bottles, PTFE lined tubing, and a CPVC coated weighted strainer. The intake was either attached to a stake or a float and weight set up in the mouth of each wetland, depending on the water depth, to keep the intake submerged but at least a foot above the sediment. We used the flow data to calculate and composite four flow-weighted tides, two floods and two ebbs per tidal cycle. The composited water samples were analyzed for unfiltered and filtered total mercury, unfiltered and filtered methylmercury, total and dissolved organic carbon, and total suspended solids.
5. Mercury sample collection methods: All mercury samples were collected using the EPA’s “clean hands, dirty hands” method. Glass sample bottles were purchased from suppliers that acid clean and double bag each bottle according to the EPA’s “Specifications and Guidance for Contaminant-Free Sample Containers” publication. All other equipment that came in contact with mercury samples was acid cleaned by DWR staff and stored in clean resealable plastic bags before use.
6. Methods references:
Levesque, V. A., & Oberg, K. A. (2012). Computing discharge using the index velocity method. Techniques and Methods 3-A23, U.S. Geological Survey, Reston, Virginia.
Wagner, R. J., Boulger Jr., R. W., Oblinger, C. J., & Smith, B. A. (2006). Guidelines and standard procedures for continuous water-quality monitors – Station operation, record computation, and data reporting. Techniques and Methods 1-D3, U.S. Geological Survey, Reston, Virginia.