2022 McKinney rain-on-wildfire event, dissolved oxygen sags, and a fish kill on the Klamath River, California

Jennifer A. Curtis; Grant Johnson; Josh Cahill; Laurel Genzoli; Clifford Dahm; Liam N. Schenk; John Oberholzer

doi:10.1038/s41598-025-08179-9

Home/Archive/USGS

USGS · 70269532

2022 McKinney rain-on-wildfire event, dissolved oxygen sags, and a fish kill on the Klamath River, California

Jennifer A. Curtis·Grant Johnson·Josh Cahill·Laurel Genzoli·Clifford Dahm·Liam N. Schenk·John Oberholzer

View original source ↗Export metadata ↓

Abstract

The longitudinal propagation of water-quality and ecological impairments in rivers during and after wildfires remain poorly understood. In Northern California, the 2022 McKinney Fire burned 243 km 2 of the Klamath National Forest, with 83% of the burned area classified as moderate to high severity. During the active wildfire, a high-intensity monsoonal rain event triggered sediment-laden flooding and runoff-initiated debris flows, causing extreme water-quality impairments and a 95 km fish kill zone along the main-stem Klamath River. This rain-on-wildfire event produced a flood wave that outpaced a sediment pulse, diminishing the dilution effect of the floodwaters. A network of high-frequency water-quality sensors recorded water-quality impairments that propagated 296 km downstream. Impairments at the nearest monitoring station, situated 71 km downstream from the fire perimeter, included dissolved oxygen sags to zero (anoxia) for 5.25 h, turbidity spikes exceeding 1000 FNU, a doubling of specific conductance from 175 to 415 µS/cm (at 25 °C), and pH anomalies of 0.5 units from 7.8 to 7.3. This novel rain-on-wildfire event triggered the first flush of fire-scar material during an active wildfire, resulting in water-quality impairments unprecedented in the historical monitoring data for the river spanning 2012 to 2022. This study provides new insights into the potential role of rain-on-wildfire events in generating extreme downstream water-quality and ecological impairments in a more fire-prone future.

Explore related subjects

Scientific Reports Article

Source-reported bounding extent: 41.86910985623359° to 42.00661546335127° latitude; -122.63359944859491° to -122.18203511324225° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Jennifer A. Curtis, Grant Johnson, Josh Cahill, Laurel Genzoli, Clifford Dahm, Liam N. Schenk, John Oberholzer. 2025-07-09. 2022 McKinney rain-on-wildfire event, dissolved oxygen sags, and a fish kill on the Klamath River, California. https://doi.org/10.1038/s41598-025-08179-9

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Spontaneous combustion of metal sulfide minerals and implications for seafloor massive sulfide mining

Metal sulfide minerals are abundant phases in many environments on earth, including seafloor massive sulfide (SMS) deposits, which occur at hydrothermal vents throughout the global ocean. These deep-sea settings are currently undergoing exploration for potential future mining. Here, we describe rocks from Escanaba Trough on the southern Gorda Ridge that underwent spontaneous combustion during laboratory processing. We compared the mineralogy, composition, and thermogravimetric behavior of the combusting samples to rocks from the same location that did not combust. We then used thermodynamic analyses to evaluate the exothermic nature of different metal sulfide oxidation reactions. The combusting rocks are primarily composed of nanocrystalline marcasite pseudomorphing blades of primary pyrrhotite. These altered, nanocrystalline rocks are less stable than their primary predecessors. Typically, recrystallization decreases reactivity as minerals trend towards steady state; however, both of the combusting samples we characterized are secondary, and demonstrate the instability of this metastable intermediate phase. Further, thermodynamic calculations indicate that metal sulfide oxidation is more exothermic when oxygen serves as the oxidant, as occurs in seawater or air. The distinct mineralogy, texture, and setting of SMS deposits in the modern oceans thus suggests a greater potential for self-heating in comparison to their ancient analogues.

Scientific Reports↗

USGS2026

Modelling potential areas of human-wildlife conflict using community-based data: A case study of black bears (Ursus americanus) in Massachusetts

Human-wildlife conflict has intensified with the continued expansion of human populations into natural habitats. American black bears ( Ursus americanus ) are increasingly coming into contact with people, particularly as bears return to areas where they were previously extirpated. Citizen science offers a promising tool for predicting where such conflicts might occur by providing large-scale data on human-wildlife interactions. We used citizen science observations to model areas of overlap between humans and bears in Massachusetts. Additionally, we created a distribution model by integrating designed research data with citizen science data. Through simulations, we evaluated how to best augment citizen science with designed research data to enhance species distribution modeling. Our model showed high sensitivity in detecting areas where humans and bears overlap, with high housing density and proximity to roads predicting overlap. The inclusion of designed research data improved accuracy of distribution in less-populated areas, although some bias remained. When simulating behavioral differences between urban and forest-dwelling bears, strategic designed research data helped detect elusive forest bears, which are less likely to be observed by people. Overall, incorporating citizen science into conflict models can lead to better predictions of where interactions will occur and therefore will be a helpful tool for developing management strategies as human-wildlife conflict increases.

Massachusetts↗

USGS2026

Rewilding the upper Klamath River Basin: Rapid recolonization of Chinook salmon following the world’s largest dam removal

Habitat fragmentation is a global driver of decline in biodiversity, yet evaluations of ecological response following re-connection remain rare. In 2024, four hydroelectric dams on the Klamath River were removed, reconnecting over 640 km of anadromous habitat and marking the largest dam removal project completed to date. We used a stationary high-resolution multi-beam imaging SONAR to quantify adult Chinook salmon ( Oncorhynchus tshawytscha ) passage into newly reopened reaches during the first two migratory seasons following dam removal. An estimated 7,742 (95% CI: 7,702–7,778) Chinook salmon migrated upstream in 2024 and 13,310 (95% CI: 12,876–13,733) in 2025, representing 18–19% of fish returning to the Klamath River Basin. Within this period, Chinook salmon recolonized 88% of their documented historical distribution, expanding into 345 km of reconnected habitats and reaching elevations of up to 1,250 m. Recolonization required fish to swim through dam removal sites, complex hydraulic corridors and engineered fishways, demonstrating the propensity for rapid recolonization at basin scale despite these challenges. These findings provide the first quantitative assessment of salmon response to the world’s largest dam removal and demonstrate how reconnection can catalyze large-scale recolonization in historically fragmented river networks.

California, Oregon↗