THE WATER QUALITY CHALLENGE: USING NEW TECHNOLOGY TO TRACK TECTONIC SALINITY SOURCES TO SURFACE AND GROUND WATER

In the arid Southwest, saline surface water and brackish groundwater pose particular problems in water quality for water management. The contribution of deep groundwaters to near-surface hydrologic systems (streams and shallow unconfined aquifers) is often overlooked. Quantitative forecasting of the effects of climate change (diminishing surface flows) on water quality depends on our understanding of these deep inputs. The Jemez and Rio Salado watersheds in northern New Mexico are classic examples of arid-region salinization due in part to tectonic inputs (deep fluids emerging along fault conduits). These hydrologic systems are important both to local constituencies (including a mix of private, tribal and public lands) as well as regional managers because of their contribution to the middle Rio Grande system, and as recharge components to Sandoval County and the northwestern part of the Albuquerque groundwater basin. Under base flow conditions deep groundwater inputs to the Jemez along fault pathways result in high salinity and arsenic contents. Climate change scenarios predicting reduced snowpack and changes in runoff timing, linked to a solute loading/discharge model, highlight serious water quality concerns for the Jemez. Three sets of data are presented to demonstrate how a quantitative loading model for particular solutes of concern (in this case, sulfate and arsenic) can be integrated with climate change scenarios. (1) Traditional ‘campaign’ water sampling over the 2006-2012 water years along a 60 km reach of the Jemez shows that during low flow the salinity, sulfate concentration, and arsenic concentration all exceed designated use limits. (2) The deployment of continuous sensors for temperature, salinity, pH, and dissolved oxygen in the Jemez in 2010-2012 provides information on coupling of discharge, temperature, dissolved oxygen, pH and specific conductance at a highly resolved timescale. (3) Preliminary results from two geophysical surveys (both a Distributed Temperature Sensor (DTS) deployment in the Rio Salado and an ERI survey across the Nacimiento fault indicate diffuse leakage from the fault system into the shallow alluvial aquifer). Combined, these results indicate the need for a wider application of environmental sensors in hydrologic systems to inform water management decisions.