Hydrological and Meteorological Data
Four (2015) and two (2016) field stints of up to three weeks occurred during each open-channel season (05/18 – 09/17), with hydrological sampling balanced among other field priorities. Hydrological and meteorological stations were setup for continuous monitoring at 30 or 60 minute intervals (Figures 1 and 3). At the meteorological stations (854, 1425, and 1750 m asl), data loggers recorded air temperature, ground temperature (2 cm and 30 cm depth), and rainfall. The meteorological station at 854 m asl also recorded solar radiation and barometric pressure. Meteorological instrumentation is described in Broadman et al. (2019). At the hydrological stations, we used In-Situ TROLL 9500 (“TROLL”) instruments to measure water-pressure and turbidity, and Hobo Onset U20 (“Hobo”) instruments to measure water pressure. Additionally, time-lapse cameras photographed the hydrological stations hourly throughout the open-channel seasons. In Carnivore Creek, and during the 2015 season in Chamberlin Creek, the TROLL and Hobo instruments were secured in thalwegs of relatively stable reaches close to Lake Peters, upstream from where the main channel anabranches (CAR and CHBa on Figure 1). During the 2016 season in Chamberlin Creek, the instruments were secured farther upstream at the apex of the alluvial fan (CHBb on Figure 1). Turbidity data were used after removing erroneous data due to fouling or instrument dislodgement, resulting in discontinuous time-series. Unrecorded or erroneous stage data was infilled using regressions or photographic reconstructions where available (Broadman et al., 2019; Thurston, 2017). To generate statistics, unrecorded temperature data was also infilled using regressions (Appendix I), but only the original meteorological records were used for sediment modeling. SSCs in Carnivore and Chamberlin Creeks were sampled manually at the hydrological stations using a depth-integrated handheld sampler (US DH-48). The liquid volume of each sample was recorded, prior to filtering with GN-4 Metricel membrane disc filters (0.8 μm). Filters were later dried in a laboratory oven and weighed (± 0.01 mg). For discharge, we used a Hach FH950 portable velocity meter to measure current velocities and cross-sections near the hydrological stations. In the 2016 field season the velocity meter was inoperable, so only cross-section areas were used for calculating discharge (Broadman et al., 2019). The discharge data was used to construct stage-discharge rating curves and establish continuous discharge records (Broadman et al., 2019; Thurston, 2017).