GEOTHERMAL CONTRIBUTIONS TO WATER CHEMISTRY IN THE JEMEZ RIVER: IMPLICATIONS FOR WATER QUALITY MANAGEMENT IN THE RIO GRANDE, NEW MEXICO

The Rio Grande originates in the mountains of Colorado and flows south through New Mexico and Texas before reaching the Gulf of Mexico. High elevation snowpack from the San Juan, Sangre de Cristo, and Jemez mountain ranges is responsible for more than one half of the dependable surface water supply delivered to the Rio Grande. Understanding hydrologic processes relating to snowmelt and climate change is critical in water management from the water quality and quantity perspective.

The Jemez River in New Mexico is a snowmelt-driven system that feeds into the Rio Grande north of Albuquerque. Water chemistry in the Jemez River is influenced by precipitation in the Jemez watershed and geothermal spring inputs associated with the Valles Caldera that emerge along faults. Water samples were collected seasonally between 2006 and 2009 to investigate the hydrothermal impacts on water quality across the annual hydrograph. Data indicate that the springs are the most influential solute load to the river system water chemistry, particularly during periods of low flow. Increased loading of cations and anions from upstream to downstream is observed and appears to be independent of runoff that changes seasonally. Data also suggest that TDS, sulfate, and arsenic potentially exceed EPA drinking water standards during low flow conditions (<30-50 cfs).

Climate change is expected to result in the alteration of precipitation and stream flow distributions throughout the year. If the timing and magnitude of discharge events change as predicted, we expect the water chemistry that is delivered to the Rio Grande to be altered concurrently. Salinization of the Rio Grande is a major issue that increases exponentially downstream, making it important to understand how water chemistry delivered from tributaries, such as the Jemez River, may be changing. These waters also recharge the regional groundwater aquifer within the Albuquerque basin. Observations of Jemez River salt and metal loadings are compared to continuous conductivity data in both the Rio Grande and mountainous headwaters of the Jemez River. In addition, monthly water quality data collected from multiple headwater streams in the Jemez watershed are analyzed to better understand the spatial and temporal relationship between water quality and discharge.