2.2 Hydrometric Field Measurements and Conservative Tracer Injection
At all eleven sites, we monitored water level at 15-minute intervals from May 01, 2018 through September 30, 2018 using either TruTrack Capacitance Rods or HOBO U20L Pressure Transducers. To capture relative stage dynamics, we standardized mean daily stage as a z-score by normalizing mean daily stage by the seasonal (i.e., May-September) mean and standard deviation of water levels across the period of record at each individual site. Precipitation (2018 water year total: 645 mm) and snow water equivalent (2018 peak: 401 mm) records were obtained from the Wild Basin SNOTEL, #1042, (2914 m), located within the watershed.
To determine how river-floodplain connectivity changed as a function of streamflow we conducted instantaneous NaCl injection experiments at high (June 13, 2018) and low flows (July 30, 2018). We injected NaCl into the main stem of the river, 125m upstream from Inflow, and monitored the change in specific conductance (SC) over time (i.e., the breakthrough curve, BTC) at six downstream locations (Table 1) using Campbell CS547A-L conductivity loggers. We calculated modal velocity (Vm) as the time to peak (TTP) divided by the flow path distance from the injection site (DISTf) to the monitoring site.