Title:
Data supporting the manuscript ‘Water isotopic composition traces source and dynamics of water supply in a semi-arid agricultural landscape'

Citation:
Mayernik, C., S. A. Ewing, R. Payn, W. A. Sigler, S. Leuthold, S. Fordyce, S. Keeshin, T. Koffman (2024). Data supporting the manuscript ‘Water isotopic composition traces source and dynamics of water supply in a semi-arid agricultural landscape', HydroShare, https://doi.org/10.4211/hs.01ad081983234d85b7cbf1f10ac961c1.	

The content of this resource includes data referenced in:
Mayernik, Caitlin M., Stephanie A. Ewing, W. Adam Sigler, Kelsey G. Jencso, Robert A. Payn. 2024. Water Isotopic Composition Traces Source and Dynamics of Water Supply in a Semi-Arid Agricultural Landscape. Hydrological Processes, https://doi.org/10.1002/hyp.15069. 

Abstract:
Data were collected at variable frequencies between 2012 and 2022. Rain water was collected from 2013 to 2016 near the towns of Stanford, Moccasin, and Moore, Montana, (USA) using precipitation collectors and mineral oil coating to limit evaporation (Product Alternatives, Inc.; Fergus Falls, MN). Snow water was collected in 2014 near Moore, Montana and from 2019 to 2022 near Moccasin, Montana using a 10 cm-diameter metal core inserted vertically in the snowpack to sample the entire snow column. Snow samples were sealed in Ziploc bags, weighed, and allowed to melt before thorough mixing and pouring an aliquot into 20 mL scintillation vials. A monthly precipitation composite sample was collected from 2021-2022 near Moccasin, Montana. Terrace soil water was collected from 2013 to 2016 in a privately owned field near Moore, Montana using porous cup tension lysimeters (PTFE/silica; Prenart Equipment; Frederiksberg, Denmark). Terrace groundwater was collected from 2013 to 2022 from wells and springs across the Moccasin terrace landform. Riparian groundwater and surface water were collected from 2020 to 2022 from three stream corridors on the Moccasin terrace. Stream water was collected from 2012 to 2022 from streams on the Moccasin terrace landform. All groundwater and surface water were sampled using a peristaltic pump (Geotech Environmental Equipment; Denver, CO) and pumped through a 0.45-μm capsule filter (Geotech Environmental Equipment; Denver, CO) into 20 mL glass scintillation vials. Data were collected to assess water isotopic compositions of precipitation and landscape water to understand soil, aquifer, and stream hydrological processes and integration of source waters in a semi-arid, non-irrigated agricultural landscape. 

Spatial coverage:
The general area sampled is represented by the bounding box, and the specific watershed within which we worked was the Judith River Basin (HUC-8: 10040103).

Description of Contents:
The file titled “JRW_precipCompilation_20230718.csv” contains measured d2H and d18O results for precipitation samples which include rain, snow, and a composite. 
The file titled “JRW_landscapeDomainCompilation_wLCexcess_20230718.csv” contains measured d2H and d18O results and calculated line conditioned excess values for water samples collected from terrace soils, terrace aquifers, riparian aquifers, and the streams. 

Methods: 
Water samples were analyzed for oxygen and hydrogen isotopic composition using integrated cavity output spectroscopy (Los Gatos Research; Mountain View, CA) at the Montana State University Environmental Analytical Laboratory (EAL). 
Isotopic composition uncertainty was determined by calculating the variance from the mean in the distribution of a population of the last four successful analytical injections repeated analyses of the sample, for samples analyzed 2015-2022. Calculated uncertainties were determined reasonable by comparison to USGS reference standards. For samples analyzed in 2014 and earlier: 2 ‰ uncertainty was applied to samples analyzed following standards USGS 46 and USGS 48, and a 1 ‰ value was applied at all others.
Further details on the methods of data collection are described in the manuscript that references this resource.

Licenses:
The data in this resource are licensed under the Creative Commons CC-0 1.0 Universal.
This work has been marked as dedicated to the public domain. See here for the full legal text: 
https://creativecommons.org/publicdomain/zero/1.0/

Contact:
Caitlin Mayernik, mitchellcm17@gmail.com