USING STABLE ISOTOPES AND CONTINUOUS SENSORS TO TRACK GEOTHERMAL SALINITY CONTRIBUTIONS THAT IMPAIR SURFACE AND GROUNDWATER QUALITY, JEMEZ RIVER, NM

In the southwestern US, the contribution of groundwaters (including geothermal systems) to streams and shallow unconfined aquifers is often underappreciated. Quantitative forecasting of the effects of climate change (and accompanying diminished surface flows) on water quality depends on our understanding of these deep inputs. The Jemez watershed in the Jemez Mountains, northern New Mexico is a classic example of arid-region salinization due in part to inputs from geothermal waters associated with the Quaternary Valles Caldera. This watershed has also recently been impacted by major fire disturbance and associated water quality impairments. The water quality of the Jemez system is important both to local stakeholders (including private, tribal and public land managers) as well as regional resource managers because of the sustained contribution to the middle Rio Grande system, and as recharge components to Sandoval County and the northwestern part of the Albuquerque groundwater basin.

We report here on two long-term datasets (1) Traditional ‘campaign’ water sampling over the 2006-2017 water years along a 60 km reach of the Jemez showing stable isotope variations, as well as a multi-year higher-frequency (weekly) stable isotope suite. Stable isotopes of water (D, O) and selected conservative solutes (e.g. chloride) can be used for hydrograph separation. (2) The multi-year deployment of continuous sensors for temperature, salinity, pH, and dissolved oxygen in the Jemez in 2010-2013 provides information on coupling of discharge, temperature, dissolved oxygen, pH and specific conductance at a highly resolved timescale. Specifically, specific conductance is inversely related to discharge. Combined, these results indicate the need for a wider application of environmental sensors in hydrologic systems to inform water management decisions. Climate change scenarios predicting reduced snowpack and changes in runoff timing, linked to a solute loading/discharge model and our hydrochemical data, highlight serious water quality concerns for the Jemez river and the downstream stakeholders.