Forest Fire Effects on Water Quality


Las Conchas and Thompson Ridge Fires: Effects on Water Quality


Water Quality in San Antonio Creek, July 2011

chart of water quality parameters

The biggest impact of forest fires on water quality happens as a result of flooding after the fire. In New Mexico, the fire season in spring and early summer is generally followed by the monsoon season in mid to late summer, when up to several inches of rain can fall in a very short time. Landscapes that have been burned are prone to erosion because of the loss of groundcover to hold the soil in place and a change in the soil itself due to expose to high temperatures. During a post-fire monsoon rain, ash and debris is washed into streams and the chemical profile of the streams is drastically changed. Decreased water quality has impacts on the biota that live in the stream as well as downstream users.

In July 2011, during a flood after the Las Conchas Fire, scientists measured water quality in San Antonio Creek in the Valles Caldera, see “Floodwater” in the chart below. They compared these results to baseline data, see the “Normal” column. Having access to water quality data from both before and after the fire allows scientists a unique opportunity to study the effect of forest fire on water quality.


Bob Parmenter, Valles Caldera National Preserve; Cliff Dahm, University of New Mexico, New Mexico, USA

San Antonio Creek, Valles Caldera National Preserve
About the Researchers: 

Dr. Bob Parmenter is the Preserve Scientist for the Valles Caldera Trust in northern New Mexico and is responsible for organizing and coordinating the research, inventory and monitoring programs on the Valles Caldera National Preserve. He is a member of the Valles Caldera Trust's executive management team and the NM EPSCoR science team.

Dr. Parmenter's research interests include studies on ecosystem disturbance, climatic influences on plant and animal populations, successional processes, plant-animal interactions, predator-prey relationships of both vertebrates and invertebrates, decomposition and nutrient cycling, and the ecology of zoonotic diseases (specifically hantavirus, plague, and West Nile virus).


Reading the Graph

1. How is the water quality that was measured during flooding different from the normal baseline water quality?

2. Calculate the percent increase for each component. Which component had the most drastic change?

Making Inferences

3. The lethal concentration of ammonia for trout is 0.5 to 0.8 mg/L. Predict what happened to the trout that were in the stream at the time of the post-fire flooding. Use evidence from the chart to support your claim.

Digging Deeper

4. According to scientists doing research in the Valles Caldera, there is some evidence that native fish populations are recovering better from the effects of the post-fire flooding than are non-native species. What is one possible explanation for this?

click here to view the answers.