Wildfire Impacts on Groundwater Aquifers: A Case Study of the 1996 Honey Boy Fire in Beaver County, Utah, USA

Benjamin T Johnk,David C Mays

doi:10.3390/w13162279

Abstract

It is well known that wildfires destroy vegetation and form soil crusts, both of which increase stormwater runoff that accelerates erosion, but less attention has been given to wildfire impacts on groundwater aquifers. Here, we present a systematic study across the contiguous United States to test the hypothesis that wildfires reduce infiltration, indicated by temporary reductions in groundwater levels. Geographic information systems (GIS) analysis performed using structured queried language (SQL) categorized wildfires by their proximity to wells with publicly available monitoring data. Although numerous wildfires were identified with nearby monitoring wells, most of these data were confounded by unknown processes, preventing a clear acceptance or rejection of the hypothesis. However, this analysis did identify a particular case study, the 1996 Honey Boy Fire in Beaver County, Utah, USA that supports the hypothesis. At this site, daily groundwater data from a well located 790 m from the centroid of the wildfire were used to assess the groundwater level before and after the wildfire. A sinusoidal time series adjusted for annual precipitation matches groundwater level fluctuations before the wildfire but cannot explain the approximately two-year groundwater level reduction after the wildfire. Thus, for this case study, there is a correlation, which may be causal, between the wildfire and temporary reduction in groundwater levels. Generalizing this result will require further research.

Highlights

One of the biggest challenges in environmental hydrology is to prevent and control damage caused by wildfires
The current study addressed the following question: can one detect changes in groundwater levels at a particular well before and after a wildfire? Knowing how aquifers may be affected by wildfires can help to answer three questions: (1) is there a significant change in soil infiltration after a wildfire? (2) Is soil permeability restored to pre-wildfire levels given enough time? (3) What long-term effects may a wildfire have on groundwater?
One well met all the search criteria, so given the paucity o provoking case study that will constitute the remainder of the results

Summary

Introduction

One of the biggest challenges in environmental hydrology is to prevent and control damage caused by wildfires. Wildfires are occurring more frequently and with greater intensity [1,2,3,4,5,6] resulting from climate change, power line construction within heavily wooded areas, and the lack of forest management practices [7] This increase in frequency and intensity is important for environmental hydrology because wildfires trigger flash floods [8,9], debris flows [1,10], and erosion [4,5,11,12], erosion per area decreases with area as larger catchments provide more opportunity to trap eroded sediment [10]. On this key point the literature is nearly unanimous, there are a number of reports where fires increased infiltration rates [18,23], an unusual observation that presumably results from the variable effects of wildfire on soil water repellency

Methods

Results

Conclusion