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Water extinguishes fire, but how does fire affect water? (Part 1 of 2)

Fetched 2026-07-13 08:01 from californiawaterblog.com

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Reading Summary: “Water extinguishes fire, but how does fire affect water? (Part 1 of 2)”

Key Facts

Who Is Affected

Policy/Legal Angle

Blog Angles

  1. The data gap problem: Big Chico Creek had to be excluded entirely due to missing gage data — how many other critical California watersheds lack real-time monitoring, and what does that cost us in post-disaster assessment capability?
  2. Compounding fire effects: Mill and Deer Creeks burned in both the 2021 Dixie Fire and the 2024 Park Fire — does repeated burning amplify runoff changes beyond what single-fire research predicts, and are water managers planning for that?
  3. The cliffhanger question: This Part 1 sets up the key comparison but withholds the streamflow results — the Part 2 data on peak flows and timing differences will be the actionable story for water supply planners and flood managers to watch.

Full Text

Water extinguishes fire, but how does fire affect water? (Part 1 of 2)

Wildfires in California are increasing in frequency and intensity, resulting in a greater extent of areas being directly burned or otherwise impacted in recent years. I work for a water resources consulting firm called Davids Engineering (DE), and we have an office in Chico in the beautiful Sacramento Valley. Our region has been severely impacted by some large fires in recent years. The Camp Fire in 2018 was unprecedented, burning over 18,000 structures (roughly ~85%) in the nearby foothill town of Paradise and, propelled by strong winds, roaring out of the foothills down onto Chico’s doorstep before being contained. It was the deadliest wildfire in U.S. history in over 100 years . Then the Dixie Fire in 2021 was the largest single-source fire in recorded California history. More recently, in 2024, the Park Fire started on the edge of Chico and very quickly expanded, burning over 429,000 acres to the north . Figure 1 below shows flames and smoke rising from the Park Fire, the day it began, seen in a photo taken from the outskirts of Chico.

We don’t work with wildfires at DE. We often work with irrigated agriculture and environmental water users in the Central Valley (not an area prone to wildfires), but even on the valley floor, the water supplies that we and our clients rely on are impacted by these wildfires.

At a very young age (before we can spell either “water” or “fire”), we learn that water extinguishes fire. However, out of professional curiosity, we wanted to zoom out, and at a much larger scale, ask the reverse question: how does fire affect water? How do these large wildfires impact our water systems, supplies, and the water cycle?

We will not address water quality issues related to fire 1 but will focus solely on water quantity. Our specific research question is: How is storm runoff affected by wildfire?

We attempted to answer the question by:

  1. Evaluating local precipitation records pre- and post-fire to identify similar large precipitation events that would result in substantial runoff and streamflow.

  2. Comparing hourly streamflow records to identify differences in peak flow and timing between pre- and post-fire conditions.

We considered the 2024 Park Fire, and the watersheds most impacted by the Park Fire that we considered were Big Chico Creek, Deer Creek, and Mill Creek. The United States Geological Service (USGS) has maintained stream gages on Deer Creek and Mill Creek for several decades, providing a rich dataset for analysis. Unfortunately, Big Chico Creek was excluded from the analysis due to a lack of streamflow data (although it has historical USGS data ). The Battle Creek watershed to the north of Mill Creek also has a USGS stream gage, and its streamflow record was evaluated as a control.

We calculated the percentage of watersheds burned using fire perimeters from Cal Fire and the USGS StreamStats tool to delineate the watershed area above the gaging locations on Deer, Mill, and Battle Creeks (and the historical gage location on Big Chico Creek) 2 .

For our three impacted watersheds, our evaluation showed the largest impact to the Mill Creek watershed, then the Big Chico Creek watershed, and the smallest impact to the Deer Creek watershed (with most of the upper watershed outside of the Park Fire perimeter). Portions of the upper Mill and Deer Creek watersheds also burned in the Dixie Fire in 2021 (so we included their perimeters as well). The Battle Creek watershed (our control) was least impacted, with the Park Fire only crossing its southern edge in a few locations. These results are summarized below in Table 1.

Table 1. Total area and area within fire perimeters for watersheds of interest.

Precipitation data were accessed through the California Irrigation Management Information System (CIMIS) website maintained by the Department of Water Resources (DWR) . The closest station to the area of interest with sufficient data was the Gerber South station (Station No. 222) , located in the Sacramento Valley south of the City of Red Bluff, to the west of the Park Fire burn area. It includes hourly data from August 2014 through the present 3 . The fire perimeters, watersheds, stream gages, and CIMIS station are depicted in Figure 2.

The first major rain event after the Park Fire was a BIG one. CIMIS recorded it lasting for nearly three days from 11/20/2024 to 11/22/2024 (70 hours total). It produced 4.25” of rain with an average and peak intensity of 0.06” and 0.19” per hour, respectively.

Unfortunately, it is impossible to produce an apples-to-apples (or raindrop-to-raindrop) comparison of this rain event to one before the Park Fire, as every storm is unique, but we did our best to find the closest one. Going back more than 10 years to August 2014, we identified 22 other precipitation events that produced at least 1.5” of rain 4 . For each of these, we extracted the total duration, total precipitation, average intensity, and peak hourly intensity to identify the most similar event. The parameters were scaled to a common reference system using z-scores (greater weight was applied to total precipitation), and the Euclidean distance was calculated in four-dimensional space to find the event closest in distance to the 11/20/24 event.

The closest event occurred on 2/12/2019. It produced the second highest total precipitation for all events (3.65”), but it only lasted about half as long (37 hours) and thus had a relatively higher average intensity of 0.10” per hour (peak intensity was 0.27” per hour). The two events track closely initially and then diverge more later. A plot of the hourly precipitation across both of these events is included in Figure 3 below 5 .

And with that, we’ll close this week on a bit of an unresolved cliffhanger… Tune in next week when we’ll look at the storm runoff results for these two events and reflect on what we learn.

This blog is the first in a two-part series evaluating impacts of wildfire on streamflows. This first blog post introduces the research question, study approach, and geographic context, along with identifying similar pre- and post-fire precipitation events. Next week, the second blog post will analyze streamflows resulting from the pre- and post-fire precipitation events and summarize findings.

Brandon Ertis is a Senior Engineer at Davids Engineering and a proud UC Davis graduate. After living in Chico for the better part of a decade, he now lives in the Sierra Nevada mountains of California, within walking distance of Lake Tahoe (albeit a pretty long walk) with his beautiful wife and two wonderful kids. He thinks life is a big messy adventure that is full of meaning and purpose.

Study design, data analysis, and development of materials were led by Brandon Ertis, but with notable contributions from Davids Engineering team members Ji Yeow Law, Dylan Diep, and Gento Shimamura. Let the record note that Gento Shimamura is also a UC Davis graduate 😊.

  1. However, for “fun” we did collect some water samples from Big Chico Creek to compare visual clarity before, during, and after the first major precipitation/runoff event following the Park Fire in November 2024 , with some stark results ( DE, 2024 ).

  2. We did not consider burn severity as a factor in this analysis, although it obviously influences storm runoff after wildfires. The USGS has analyzed this ( Moody, 2012 ) and the analytical method they developed is available in a beta-version of StreamStats for fires from 2023 and earlier. Available at: https://streamstats.usgs.gov/national-beta/

  3. There is also a Gerber station (Station No. 8) very close to Gerber South to the north that is no longer active, but includes data from 1982 through 2014. There was a coordinated transition from Gerber to Gerber South, as each station includes a few days of overlapping data in 2014.

  4. Interestingly, the 11/20/24 event actually had the highest total precipitation of all 23 events during this 10-year period. A simplifying assumption in our analysis is that the precipitation measured at the South Gerber station is representative of precipitation across all watersheds. The southernmost point of the Deer Creek watershed is more than 40 miles from the northernmost point of the Battle Creek watershed, so precipitation patterns and intensity across them likely varied to some degree and correspondingly influenced the runoff patterns observed.

  5. Another notable difference between these two events (which is not accounted for in the analysis) is that the 11/20/2024 event was first major rain event of the water year, while the 2/12/2019 event happened in the middle of winter (well into the water year).

Davids Engineering (2024). Examining water quality at Big Chico Creek and Little Chico Creek (Website Post). Published on November 27, 2024. Available at: https://davidsengineering.com/examining-water-quality-at-big-chico-creek-and-little-chico-creek/

Knapp, E.E., Valachovic, Y.S., Quarles, S.L. et al. (2021). Housing arrangement and vegetation factors associated with single-family home survival in the 2018 Camp Fire, California. fire ecol 17 , 25. https://doi.org/10.1186/s42408-021-00117-0

Li, S., Banerjee, T. (2021). Spatial and temporal pattern of wildfires in California from 2000 to 2019. Sci Rep 11 , 8779. https://doi.org/10.1038/s41598-021-88131-9

Martinez, Gina (2018). The California Fire That Killed 48 People Is the Deadliest U.S. Wildfire in a Century. Time Magazine. November 14, 2018. https://time.com/5453710/california-camp-fire-deadliest-wildfires-us-history/ . Note: The Camp Fire ultimately resulted in 85 confirmed fatalities ( Cal Fire ).

Moody, J.A. (2012). An analytical method for predicting postwildfire peak discharges: U.S. Geological Survey Scientific Investigations Report 2011–5236, 36 p. https://pubs.usgs.gov/sir/2011/5236/

National Park Service (NPS). Lassen Volcanic National Park – Fire History: Dixie Fire webpage. Available at: https://www.nps.gov/lavo/learn/nature/dixie-fire.htm

Turco, M., Abatzoglou, J.T., Herrera, S., Zhuang, Y., Jerez, S., Lucas, D.D., AghaKouchak, A., & Cvijanovic, I. Anthropogenic climate change impacts exacerbate summer forest fires in California, Proc. Natl. Acad. Sci. U.S.A. 120 (25) e2213815120, https://doi.org/10.1073/pnas.2213815120 (2023).

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