THE EFFECTS OF GEOTHERMAL FLUIDS ON SURFACE WATER QUALITY IN THE JEMEZ RIVER SYSTEM IN NORTHERN NEW MEXICO

Geothermal fluids flow into the Jemez river, northern New Mexico, from the Valles caldera. The river discharge levels (driven by both snowmelt pulses in the spring and monsoons in the summer) greatly influence the local downstream water quality. Water samples have been taken from a 43-kilometer reach of the Jemez River over the past decade. Methods included ‘campaign style’ bottle collections for laboratory chemical analysis of cation and metals, anion and alkalinity, and in situmonitoring of temperature, total dissolved solids, pH, conductance, and dissolved oxygen. Analyses along the studied reach do show three major and distinct geothermal input sites and continuous fluctuations in water quality due to seasonal snowpack melt, seasonal monsoons, meteoric influenced discharge rates, and the geothermal fluid inputs. At low river discharges, it is common for many of the constituent concentrations to exceed the Maximum Contaminant Levels, for example sulfate, TDS and arsenic. Alkalinity is also influenced by high CO2 levels of the geothermal discharges.

As influences from climate fluctuations continue, the importance of continuous real-time monitoring of the local water systems can be seen, more importantly if temperatures continue to climb and drought conditions persist. Streams of the arid Southwestern US are particularly susceptible to water quality degradation coupled to declines in surface water supply do to the widespread presence of deeply-derived, saline groundwater inputs.