Shallow groundwater samples were collected since 2006 for routine analysis by ODEQ from 16 domestic wells (installation dating from the 1970s) and 23 ODEQ groundwater monitoring wells (installation dating between 2003-2006) across the SWV-GWMA. In 2012, sampling and analysis for water isotopes (δH2O:2H-H2O and 18O-H2O) were added to the monitoring program. At that time, ODEQ collected samples quarterly in all wells. However, in 2016, ODEQ decreased sampling frequency to once a year (May/June) for all 39 wells, while 12 wells continued to be sampled every quarter. At the same time, sampling and analysis for NO3- isotopes (δNO3-: 15N-NO3- and 18O-NO3-) were added to the monitoring program. This study reports on the monitoring results through 2019, which includes 8 years of water isotope and 4 years for nitrate isotope data. Data were added to include data collected through May 2024, adding 4 additional years.

This dataset is associated with the following publication: Weitzman, J., J.R. Brooks, P. Mayer, W. Rugh, and J. Compton. Coupling the dual isotopes of water (δ2H and δ18O) and nitrate (δ15N and δ18O): A new framework for classifying current and legacy groundwater pollution. Environmental Research Letters. IOP Publishing LIMITED, Bristol, UK, 16(4): 045008, (2021).