The Importance of Interflow to Groundwater Recharge in a Snowmelt-Dominated Headwater Basin

American Geophysical Union (AGU) | May 23rd, 2019

Understanding the sensitivity of groundwater generation to climate in a mountain system is complicated by the tight coupling of snow dynamics to vegetation and topogr

Understanding the sensitivity of groundwater generation to climate in a mountain system is complicated by the tight coupling of snow dynamics to vegetation and topography. To address these feedbacks, we combine LiDAR-derived snow observations with an integrated hydrologic model to quantify spatially and temporally distributed water fluxes across varying climate conditions in a Colorado River headwater basin. Results indicate annual groundwater flow is an important and stable source of stream water. However, interflow decreases during drought as a function increased plant water use and the relative fraction of groundwater to streams increases. Seasonal snowmelt and vegetation water use regulate small recharge rates in the lower portions of the basin, but snowmelt transported via interflow from high mountain ridges toward convergent topographic zones define preferential recharge in the upper subalpine. Recharge in this zone appears decoupled from annual climate variability and resilient to drought. 

The Northern California 2018 Extreme Fire Season

American Meteorological Society (AMS) | February 19th, 2020

The fire season of 2018 was the most extreme on record in Northern California in terms of the number of fatalities (95), over 22,000 structures destroyed, and over 600,00

The fire season of 2018 was the most extreme on record in Northern California in terms of the number of fatalities (95), over 22,000 structures destroyed, and over 600,000 ha burned. The most deadly and destructive fire in California history, the Camp Fire, occurred in Butte County in the Sierra Nevada foothills in early November, and caused 85 fatalities and destroyed nearly 19,000 structures. The largest fire complex in state history, the Mendocino Complex, which included the Ranch fire, the largest single fire in state history, burned nearly 186,000 ha. It occurred in July and August, killing one firefighter. In western Shasta County nearly 138,000 ha burned from July through September in the Carr, Hirz, and Delta Fires. These fires caused multiple closures of Interstate 5 and exhibited some of the most extreme fire behavior ever observed in California. The Carr Fire caused eight fatalities, including two firefighters and two workers supporting firefighting efforts, burned over 1,100 homes in west Redding, caused the evacuation of one-third of the city, and produced an extreme fire vortex with an Enhanced Fujita scale rating between 136 to 165 mph, making it arguably the strongest tornado type event in state history, and one of the strongest documented cases in the world (Lareau et al. 2018).

The Rainfall Intensity-Duration Control of Debris Flows After Wildfire

American Geophysical Union (AGU) | May 23rd, 2023

The season for large fires in Southern California is projected to lengthen in a changing climate

Nature Portfolio (Springer Nature) | February 17th, 2022

Southern California is a biodiversity hotspot and home to over 23 million people. Over recent decades the annual wildfire area in the coastal southern California region h

Southern California is a biodiversity hotspot and home to over 23 million people. Over recent decades the annual wildfire area in the coastal southern California region has not significantly changed. Yet how fire regime will respond to future anthropogenic climate change remains an important question. Here, we estimate wildfire probability in southern California at station scale and daily resolution using random forest algorithms and downscaled earth system model simulations. We project that large fire days will increase from 36 days/year during 1970–1999 to 58 days/year under moderate greenhouse gas emission scenario (RCP4.5) and 71 days/year by 2070–2099 under a high emission scenario (RCP8.5). The large fire season will be more intense and have an earlier onset and delayed end. Our findings suggest that despite the lack of a contemporary trend in fire regime, projected greenhouse gas emissions will substantially increase the fire danger in southern California by 2099.

The State of the Sierra Nevada’s Forests

Sierra Nevada Conservancy | October 2nd, 2014

There is a growing understanding that many Sierra Nevada forests are not healthy and that overgrown forests are susceptible to disease and intense wildfire. There is like

There is a growing understanding that many Sierra Nevada forests are not healthy and that overgrown forests are susceptible to disease and intense wildfire. There is likewise broad consensus that science-based ecological restoration of our Sierra Nevada forests must be dramatically increased in order stem the tide of large, uncharacteristic wildfires. These wildfires threaten the very lifeblood of California -- the forested watersheds of the Sierra Nevada. The State of Sierra Nevada’s Forests Report identifies the wide range of benefits provided by our Sierra Nevada forests and watersheds that are at risk: The Region is the origin of 60% of California’s developed water supply. These watersheds are the primary source of fresh water flowing into the Sacramento-SanJoaquin Delta, California’s water “hub.” The forests of the Sierra Nevada store massive amounts of carbon, assisting in the state’sefforts to combat climate change. The forests and watersheds provide crucial habitat to hundreds of species. The area provides world-class recreational opportunities enjoyed by millions from around the world. The Region is a major producer of wood products and hydro-electric power. Key findings of this report include the following: The United States Forest Service Region 5 (USFS) estimates that between six and nine million acres of lands for which they have management responsibility are in need of restoration. In order to return these lands to ecological health, a two to three times increase in the pace and scale of ecological restoration must occur. The amount of area consumed by fire in the Sierra Nevada continues to increase. More land has burned in the first four-and-a-half-years of this decade than seven entire decades in the past. Between 1984 and 2010, there was a significant increase in the number of acres within a forest fire burning at high-intensity, from an average of 20% in mid-1980s to over 30% by 2010. High-intensity burn areas can experience runoff and erosion rates five to ten times greater than low- or moderate-intensity burn areas. The sediment that is carried in the runoff not only degrades water quality and damages infrastructure, it fills reservoirs, reducing storage capacity. The 2013 Rim Fire, the largest fire in the recorded history of the Sierra Nevada, burned 257,000 acres, almost 40% of which was at high intensity. Estimates are that that fire produced the same amount of greenhouse gas emissions that 2.3 million vehicles produce in a year.

Tribal-Traditional Ecological Knowledge and the Use of Fire

California Department of Water Resources (DWR) | September 9th, 2014

A memo written by Ron W. Goode, Tribal Chairman, North Fork Mono Tribe on Traditional Ecological Knowledge and the use of fire.  This document was part of the reference

A memo written by Ron W. Goode, Tribal Chairman, North Fork Mono Tribe on Traditional Ecological Knowledge and the use of fire.  This document was part of the reference documents included with the California Water Plan 2013 Update.

Twentieth-century shifts in forest structure in California: Denser forests, smaller trees, and increased dominance of oaks

National Academy of Sciences (NAS) | January 20th, 2015

Valuing the benefits of forest restoration on enhancing hydropower and water supply in California's Sierra Nevada

Science of the Total Environment (Elsevier) | March 15th, 2023

Forest restoration through mechanical thinning, prescribed burning, and other management actions is vital to improving forest resilience to fire and drought across the We

Forest restoration through mechanical thinning, prescribed burning, and other management actions is vital to improving forest resilience to fire and drought across the Western United States, and yields benefits that can be monetized, including improvements in water supply and hydropower. Using California's Sierra Nevada as a study area, we assess the water and energy benefits of forest-restoration projects. By using a scalable top-down approach to track annual evapotranspiration following forest disturbance, coupled with hydropower simulations that include energy-price information, and marginal prices for water sales, we project the potential economic benefits of hydropower and water sales accruing to water-rights holders. The results found that water-related benefits from strategically planned fuels-reduction treatments now being carried out can be sufficient to offset costs of management actions aimed at forest restoration, especially in the face of climate change. Our findings justified investments in restoring forests and reinforce the central role of water and hydropower providers in partnerships for management of source-water watersheds. Results also highlighted the importance of accurate, scalable data and tools from the hydrology and water-resources community.

Walker River Atlas

California Department of Water Resources (DWR) | June 1st, 1992

The Walker River has its headwaters in California's high Sierras north of Mono Lake and terminates in a desert lake in Nevada. The Walker is a relatively small river

The Walker River has its headwaters in California's high Sierras north of Mono Lake and terminates in a desert lake in Nevada. The Walker is a relatively small river by California standards, in places resembling more stream than river, but is an important water source to arid western Nevada. The river's existence is best known to local residents and to devotees of trout fishing; travelers through the eastern Sierras are more apt to be familiar with the celebrated attractions of Lake Tahoe to the north and Mono Lake to the south.

Water Reliability in the West - 2021 SECURE Water Act Report

U.S. Bureau of Reclamation (USBR) | January 4th, 2021

The Bureau of Reclamation (Reclamation) is the largest wholesaler of water in the country. Reclamation delivers water for municipal, agricultural, tribal, and environment

The Bureau of Reclamation (Reclamation) is the largest wholesaler of water in the country. Reclamation delivers water for municipal, agricultural, tribal, and environmental water uses, including providing one out of five farmers in the Western United States (West) with irrigation water for 10 million acres of farmland that produce 60 percent of the Nation’s vegetables and 25 percent of its fruits and nuts. The Omnibus Public Land Management Act of 2009 (Public Law 111-11), Subtitle F of Title IX of the Act (Science and Engineering to Comprehensively Understand and Responsibly Enhance [SECURE] Water Act) recognizes that changes to temperature, precipitation (rainfall and snowfall), and the timing and quantity of snowpack and runoff pose a significant challenge to the protection and use of water resources. Every 5 years, Reclamation submits a report to Congress under the SECURE Water Act that analyzes projected risks to water supplies in the West using the best available science and highlights collaborative efforts to mitigate those risks. This Water Reliability in the West - 2021 SECURE Water Act Report (2021 Report) provides a West-wide assessment of expected changes to water supplies, uses, and demands; highlights progress; and describes actions taken to increase water supply reliability since the 2016 SECURE Water Act Report. Reclamation has a broad range of programs and projects that help increase the reliability of water and power deliveries. Our activities include science and research, planning, infrastructure sustainability, efficient hydropower production, and on-the-ground actions to increase reliable water supplies to meet water demands. These activities are undertaken in collaboration with our customers, stakeholders, and partners. In the West, competing demands for water for farms, cities, Tribes, the environment, recreation, hydropower, and other uses can lead to conflict. Conflict escalates particularly during droughts, which are expected to be more frequent and severe with climate change. Fostering strong relationships is essential to carry out Reclamation’s everyday operations, conduct long-term planning efforts, and avoid unnecessary conflicts. Reclamation operators and planners rely on information about precipitation, snowpack, streamflow, temperatures, water demands, and groundwater to make informed decisions. Reclamation’s 2021 West-Wide Climate and Hydrology Assessment (2021 Assessment) builds on our 2011 and 2016 West-wide assessments of future temperature and precipitation change by using several complementary approaches, including analyses based in paleohydrology derived from tree rings (dendochronology) that help answer this question: “If droughts in the distant past were to occur today, how would water systems perform?” With our Federal, State, Tribal, and local partners, we address challenges resulting from climate change and shifting demographics. We use a multi-faceted approach to support reliable water and hydropower deliveries; to help maintain healthy ecosystems; to protect federally-listed fish, wildlife, and plants, as well as designated critical habitat; and to manage risks (e.g., droughts, floods, and fires). Implementing the SECURE Water Act has served as a catalyst for collaboration and innovation, improving our understanding of climate change impacts to water resources and our ability to address those impacts.