Water Quality & The Las Conchas Fire


Climate change manifests itself in major changes to the terrestrial landscape of New Mexico. The New Mexico EPSCoR project is providing a very detailed picture of the effects of a major forest fire on the water quality, hydrology, and ecology of an important source of freshwater for the State of New Mexico. Continuous monitoring is critical to describe the timing and magnitude of and the controls on these highly variable parameters. Better understanding of controls on water quality variability can help management in the face of climate change.


One component of the current New Mexico EPSCoR project is the effect of climate change on water quality in the forested mountain catchments of New Mexico. The Las Conchas fire in the Jemez Mountains in June and July of 2011 was the largest recorded fire in New Mexico history and burned approximately 80% of one of our primary research catchments (East Fork Jemez River). The fire burned with variable intensity throughout the catchment with forested areas generally seeing higher intensity fire. The primary research site along the East Fork Jemez was spared from the fire and provides excellent background information on water quality before the fire. New state-of-the-art instrumentation in the East Fork Jemez River and the shallow groundwater system along the river offer the opportunity for detailed characterization of water quality before and after the Las Conchas fire.

Post-fire impacts to streams and rivers have begun with the onset of the monsoons in late July of 2011. Massive erosion events with major changes in total suspended sediments, conductivity, total phosphorus, total nitrogen, and total ammonia have occurred in the East Fork Jemez River, Rio San Antonio, and Indios Creek. Major fish kills have been documented in the Rio San Antonio and Indios Creek. Trout have been particularly severely affected with 95% or greater mortality. Native non-game fish have survived in somewhat greater numbers. Post-fire changes in water quality in the East Fork Jemez River have been measured using continuously measuring in situ instruments installed as part of the New Mexico EPSCoR project. Major responses to July and August precipitation events include increased turbidity, conductivity, phosphate, and nitrate.


Rapid return to baseflow conditions for all events (particularly post-fire monsoons) highlights the important role precipitation plays in delivering solutes and sediment to rivers. Non-monsoonal events result in increased NO3- and turbidity. Post-fire monsoonal events resulted in increased NO3-, PO43-, SC, turbidity, and decreased DO and pH, and data indicate subsurface dominated flowpaths for all events.

Sources: Cliff Dahm, UNM; Lauren Sherson, UNM; Natalie Willoughby, NM EPSCoR
Image provided by: Cliff Dahm, cdahm@sevilleta.unm.edu