Droughts impede water balance recovery from fires in the Western United States

Nature Portfolio (Springer Nature) | January 2nd, 2024

A steady rise in fires in the Western United States, coincident with intensifying droughts, imparts substantial modifications to the underlying vegetation, hydrology and

A steady rise in fires in the Western United States, coincident with intensifying droughts, imparts substantial modifications to the underlying vegetation, hydrology and overall ecosystem. Drought can compound the ecosystem disturbance caused by fire, although how these compound effects on hydrologic and ecosystem recovery vary among ecosystems is poorly understood. Here we use remote sensing-derived high-resolution evapotranspiration (ET) estimates from before and after 1,514 fires to show that ecoregions dominated by grasslands and shrublands are more susceptible to drought, which amplifies fire-induced ET decline and, subsequently, shifts water flux partitioning. In contrast, severely burned forests recover from fire slowly or incompletely, but are less sensitive to dry extremes. We conclude that moisture limitation caused by droughts influences the dynamics of water balance recovery in post-fire years. This finding explains why moderate to extreme droughts aggravate impacts on the water balance in non-forested vegetation, while moisture accessed by deeper roots in forests helps meet evaporative demands unless severe burns disrupt internal tree structure and deplete fuel load availability. Our results highlight the dominant control of drought on altering the resilience of vegetation to fires, with critical implications for terrestrial ecosystem stability in the face of anthropogenic climate change in the West.

Drowned Memories: The Submerged Places of the Winnemem Wintu

Journal of the World Archaeological Congress (Springer) | July 7th, 2009

This article is a brief overview of an instance where landscape inundation has disconnected culture from place. The Winnemem Wintu, a Native American tribe in Northern Ca

This article is a brief overview of an instance where landscape inundation has disconnected culture from place. The Winnemem Wintu, a Native American tribe in Northern California, had most of their ancestral landscape along the McCloud River submerged by the construction of Shasta Dam just after World War II. The tribe’s remaining traditional cultural properties are under continual threat of loss and/or destruction, leaving the tribe’s ability to practice traditional ceremonies crippled by legal battles and fights against the continual assertion of United States hegemonic power over tribal cultural identity. As part of archaeological research on these submerged places, the tribe’s spiritual leader, Caleen Sisk-Franco, and Tribal Headman, Mark Franco, spoke with the author about these threats and how their culture must adapt to meet them.

Effects of montane watershed development on vulnerability of domestic groundwater supply during drought

Journal of Hydrology (Elsevier) | April 1st, 2020

Climate change is expected to reduce recharge to montane aquifers in the western United States, but it is unclear how this will impact groundwater resources in waters

Climate change is expected to reduce recharge to montane aquifers in the western United States, but it is unclear how this will impact groundwater resources in watersheds where intensive surface-water development has disrupted the natural hydrologic regime. To better understand sources of recharge and associated vulnerabilities of groundwater supply in this setting, we made a detailed geochemical survey of domestic wells finished in fractured bedrock throughout the Yuba and Bear River watersheds (Sierra Nevada foothills, northern California) during historic drought (2015–2016). Stable isotopes of water and noble gas recharge temperatures closely tracked atmospheric lapse rates across a broad elevation gradient (100–2000 m), indicating groundwater inputs are dominated by local precipitation that rapidly recharges fractured bedrock during the winter wet-season. However, nearly one-quarter of wells had water isotopes that were fractionated by evaporation and warm recharge temperatures, indicative of mixing with dry-season recharge by surface water. Monte Carlo mixing models suggest evaporation-impacted groundwater samples are mixtures of local rain with an average of 28% ± 13% from diverted surface water that can recharge bedrock aquifers during the dry-season by either irrigation return flow or seepage from extensive distribution infrastructure. Wells that received recharge subsidies from diverted surface water had elevated levels of nitrate and coliform bacteria compared to those replenished exclusively by local precipitation, which are more vulnerable to supply shortage during drought. It is important to consider the impacts of increased surface-water development on the quantity and quality of groundwater recharge in rapidly developing montane watersheds.

Estuary News, December 1998

San Francisco Estuary Partnership (SFEP) | December 15th, 1998

Evaluating GFS and ECMWF Ensemble Forecasts of Integrated Water Vapor Transport along the U.S. West Coast

American Meteorological Society (AMS) | October 28th, 2022

Atmospheric rivers (ARs) are long and narrow regions in the atmosphere of enhanced integrated water vapor transport (IVT) and can produce extreme precipitation and high s

Atmospheric rivers (ARs) are long and narrow regions in the atmosphere of enhanced integrated water vapor transport (IVT) and can produce extreme precipitation and high societal impacts. Reliable and skillful forecasts of landfalling ARs in the western United States are critical to hazard preparation and aid in decision support activities, such as Forecast-Informed Reservoir Operations (FIRO). The purpose of this study is to compare the cool-season water year skill of the NCEP Global Ensemble Forecast System (GEFS) and ECMWF Ensemble Prediction System (EPS) forecasts of IVT along the U.S. West Coast for 2017–20. The skill is analyzed using probability-over-threshold forecasts of IVT magnitudes ≥ 250 kg m−1 s−1 (P250) using contingency table skill metrics in coastal Northern California and along the west coast of North America. Analysis of P250 with lead time (dProg/dt) found that the EPS provided ∼1 day of additional lead time for situational awareness over the GEFS at lead times of 6–10 days. Forecast skill analysis highlights that the EPS leads over the GEFS with success ratios 0.10–0.15 higher at lead times > 6 days for P250 thresholds of ≥25% and ≥50%, while event-based skill analysis using the probability of detection (POD) found that both models were largely similar with minor latitudinal variations favoring higher POD for each model in different locations along the coast. The relative skill of the EPS over the GEFS is largely attributed to overforecasting by the GEFS at longer lead times and an increase in the false alarm ratio.

Evidence of Landlocked Chinook Salmon Populations in California

North American Journal of Fisheries Management (Taylor & Francis) | November 10th, 2015

Natural reproduction of adfluvial Chinook Salmon Oncorhynchus tshawytscha has been documented in their native and introduced range but not in California, the southern end

Natural reproduction of adfluvial Chinook Salmon Oncorhynchus tshawytscha has been documented in their native and introduced range but not in California, the southern end of their native range. A combination of anecdotal evidence and survey data suggests that successful spawning by Chinook Salmon reared in California reservoirs could be common. The planted juveniles are often from different basins and are genetically distinguishable from local salmon populations below reservoirs. Consequently, the possibility of behavioral and genetic interactions may lead to complications of restoration efforts via trap and haul programs. The full extent of this phenomenon needs to be documented before trap and haul programs are initiated to reintroduce salmon above reservoirs.

Excavation and Embankment by Water Power

Scientific American | July 24th, 1886

I wish to call the attention of the Society to a plan by which large excavations and embankments can be cheaply made —which is especially applicable to earthen dams

I wish to call the attention of the Society to a plan by which large excavations and embankments can be cheaply made —which is especially applicable to earthen dams— by simply applying the method used in the hydraulic mines that have been so largely developed in California. The system, in brief, is discharging the water under a vertical head of from 100 to 300 feet against the bank to be excavated. The momentum of the water cuts the bank, the material of which is conveyed by it into the flume, and thence by it to the place at which it is to be discharged. This point of discharge is generally in some water course or river, which soon becomes dammed by a perfectly water-tight dam, which remains intact and tight until it is destroyed, or partially so, by the winter's flood washing away the material from the top.

Feather River Salmonid Habitat Improvement Project Proposed Mitigated Negative Declaration

California Department of Water Resources (DWR) | October 6th, 2022

An initial study/proposed mitigated negative declaration (IS/MND) has been prepared to assess the proposed project’s potential effects on the physical environment and t

An initial study/proposed mitigated negative declaration (IS/MND) has been prepared to assess the proposed project’s potential effects on the physical environment and the significance of those effects. Based on the analysis conducted in the IS, DWR has determined that the proposed project would not have any significant adverse effects on the environment because environmental commitments and mitigation measures would be implemented to reduce impacts to a less-than-significant level.

Flood Size Increases Nonlinearly Across the Western United States in Response to Lower Snow-Precipitation Ratios

American Geophysical Union (AGU) | December 20th, 2019

Many mountainous and high-latitude regions have experienced more precipitation as rain rather than snow due to warmer winter temperatures. Further decreases in the annual

Many mountainous and high-latitude regions have experienced more precipitation as rain rather than snow due to warmer winter temperatures. Further decreases in the annual snow fraction are projected under continued global warming, with potential impacts on flood risk. Here, we quantify the size of streamflow peaks in response to both seasonal and event-specific rain-fraction using stream gage observations from watersheds across the western United States. Across the study watersheds, the largest rainfall-driven streamflow peaks are >2.5 times the size of the largest snowmelt-driven peaks. Using a panel regression analysis of individual precipitation and snowmelt events, we show that the empirical streamflow response grows approximately exponentially as the liquid precipitation input increases, with rain-dominated runoff leading to proportionately larger streamflow increases than snowmelt or mixed rain-and-snow runoff. We find that the response to changes in rain percentage is largest in the wettest watersheds, where wet antecedent conditions are important for increasing runoff efficiency. Similarly, the effect of rain percentage is larger across watersheds in the Northwest and West regions compared to watersheds in the Northern Rockies and Southwest regions. Overall, as a higher percentage of precipitation falls as rain, increases in the size of rainfall-driven and “rain-on-snow”-driven floods have the potential to more than offset decreases in the size of snowmelt-driven floods.

Forest Management (Resource Management Strategy)

California Department of Water Resources (DWR) | July 29th, 2016

Forest lands in California, the majority of which are in the middle to high elevation foothills and mountains, produce a diverse array of resources such as water, timber,

Forest lands in California, the majority of which are in the middle to high elevation foothills and mountains, produce a diverse array of resources such as water, timber, native vegetation, fish, wildlife, and livestock, and outdoor recreation. However, the water produced by these forests has economic value that equals or exceeds that of any other forest resource (Krieger 2001; California Department of Forestry and Fire Protection 2003). Most of California’s major rivers and a substantial portion of its runoff originate in these forests; therefore, most of California’s major water development projects are tied strongly to forested watersheds. Forest management activities can affect water quantity and quality. This strategy focuses on forest management activities, on both public and privately-owned forest lands, whose goals specifically include improvement of the availability and quality of water for downstream users.