The synoptic water stable isotope values were collected to compare summer baseflow water sources between 2 years with contrasting hydrologic conditions: 2015 was a year that lacked snowpack and had very low flow conditions and 2016 that had average incoming precipitation. The samples were collected roughly in the same stream network over 3 sampling campaigns in the 2nd to 5th order steams of Lookout, Mack, McRae, and Cold Creeks.
The synoptic water stable isotope values (2021, 2022) were collected to compare Summer baseflow water sources to water sources during wet months in the Fall and Spring. Sampling during these campaigns spanned smaller headwater streams to elucidate the influence of physiographic metrics on the spatial distribution of isotope data.
Samples collected every 3 weeks at selected locations targeted streams draining a broad range of drainage areas over contrasting geologic and geomorphologic conditions. Precipitation samples collected at three locations provide information about the water inputs to the Andrews Forest.
High frequency storm samples were collected at Mack Creek in order to investigate the performance of a flow partitioning tracer-based hydrological model calibrated using water stable isotopes and electrical conductivity.
The sampling locations in the Marys Rivers were selected to characterize the spatial variability in isotope ratios in streams draining different geologies.
The weekly stream samples (May 2022- May 2023) were collected from multiple locations along the main tributaries and selected headwater streams of the Lookout Creek watershed to investigate the spatiotemporal streamflow contributions of those selected watersheds, which have different basin sizes (drainage area) and elevations gradients.
Synoptic grab water samples were collected during multiple campaigns: July-September 2015, June 2016, September 2016, August 2021, and May-November 2022 including locations over a wide range of streams spanning 1st to 5th orders. Locations were at ~50- 100-meter intervals recorded using Gain 30x GPS unit.
Stream samples were collected every 3 weeks between 2014 and 2018 at Lookout, Mack and McRae Creeks and at WS01, WS02, WS07, and WS08. Bulk precipitation was collected every week (PRIMET) and every 3 weeks (H15MET) over the same period, and sampling at PRIMET continued to 2023.
Forty-four, streamflow grab samples were collected at Mack Creek every 4 hours using an automatic autosampler (ISCO-3700). Precipitation was sequentially sampled at the PRIMET benchmark station using a sequential rainfall sampler designed to collect up to 12, 200-mL water samples to characterize the temporal variability of water stable isotopes.
The grab samples in the Marys River were collected approximately monthly at 24 locations between 2015-2016.
The weekly grab samples collected in Lookout Creek and selected tributaries were collected at 10 sites between May 2022-April 2023. Some sites were added mid-study, so some data was collected over a shorter time frame. An attempt was made to sample each location every week, but some samples may be absent due to field conditions.
All water samples for isotopic analysis were collected and stored in 20-mL glass bottles with conical inserts without headspace and kept in dark at relatively cool conditions (<15°C) to avoid fractionation by evaporation until their analysis was conducted at the Watershed Processes Laboratory at Oregon State University.
