Effects on Water Resources

Wildfires pose a substantial risk to water supplies because they can lead to severe flooding, erosion, and delivery of sediment, nutrients, and metals to rivers, lakes, and reservoirs. The USGS works with federal and state land managers and local water providers to monitor and assess water quality after wildfires in order to help protect our Nation’s water resources.

Large wildfires have increased in size and frequency in the western United States over the past several decades. This has led to increased soil erosion and the transport of sediment containing nutrients into streams and reservoirs. Excess nutrients typically lead to the increased production of algae which can then lead to low levels of dissolved oxygen. This degrades the habitat for fish and...

The enhanced probability of catastrophic wildfires has increased our need to understand the risk of floods, erosion, and debris and contaminant transport in burned watersheds. This project investigates the relation between rainfall intensity and peak discharge; erosion and deposition processes; and water-quality impacts to minimize the loss of life and property resulting from post-wildfire floods.

The Rim Fire has burned over 400 square miles of the Tuolumne River and Merced River watersheds in central California and is now the 3rd largest wildfire in state history. The burn area is largely on the Tuolumne between Hetch Hetchy Reservoir and Don Pedro Reservoir, both of which serve as critical sources of drinking water and irrigation water to San Francisco Bay area and Central Valley...

Release Date: OCTOBER 15, 2018 USGS scientists have been pursuing a way to assess debris-flow hazards before a fire occurs.

About half of the water supply in the southwestern United States is supplied by water from forests, which generally yield higher quality water than any other source. Approximately 80 percent of the freshwater resources in the U.S. originate on forested land, and more than 3,400 public drinking-water systems are located in watersheds containing national forest lands (USDA, 2006). More than 12...

The 2012 Little Bear Fire burned 44,000 acres in the upper Rio Hondo Basin in south-central New Mexico. Landscape in the Basin ranges from mixed conifer forests at higher elevations (12,000 ft) to desert shrubland at lower (5,200 ft) elevations. Burned areas are at risk of substantial post-wildfire erosion and flash floods. USGS post-wildfire analysis estimated 70% of the burned area had a high...

The Las Conchas fire started on June 26, 2011, near the small community of Las Conchas in the Jemez Mountains of north-central New Mexico. When the fire was contained on August 3, 2011, it had burned 156,593 acres of mixed conifer, pinyon/juniper, and ponderosa forest. At the time, it was the largest wildfire in New Mexico history. Peak burn severity was extreme; over 60,000 acres of the total...

Flash flooding can be a destructive and life-threatening response of watersheds to intense rainfall events, particularly in sparsely­ vegetated, or burned watersheds. Studies have been conducted to estimate the magnitude of hydrologic responses of burned watersheds to rainfall events, however the time that it takes a flood to travel through a burned watershed and reach a critical or populated area...

The Las Conchas fire started on June 26, 2011, near the small community of Las Conchas in the Jemez Mountains of north-central New Mexico. When the fire was contained on August 3, 2011, it had burned 156,593 acres of mixed conifer, pinyon/juniper and ponderosa forest and at the time was the largest wildfire in New Mexico history. Peak burn severity was extreme; over 60,000 acres of the total...

Wildfire is a natural process in forest ecosystems, and occurs with varying frequencies and severities depending on landscape characteristics, climatic conditions, and the historical fire regime. Although attention often is focused on the potential damages from wildfire in the wildland-urban interface, wildfire also presents a threat to critical infrastructure including flood water conveyances and...

The project aimed to use existing models and data to understand how wildfires (number, size, and location) and land-use change will affect watersheds, and therefore water supply, under current conditions and future climates (through 2050) in the western U.S. The projected changes in temperature and precipitation are expected to affect water supply in two major ways: 1) decreased water availability