Interactions between snow cover and evaporation lead to higher sensitivity of streamflow to temperature

Nature Portfolio (Springer Nature) | December 4th, 2020

Estimates of potential evaporation often neglect the effects of snow cover on evaporation process. Here, we present a definition of potential evaporation that explicitly

Estimates of potential evaporation often neglect the effects of snow cover on evaporation process. Here, we present a definition of potential evaporation that explicitly accounts for landscapes that are partially covered by snow. We show that, in the presence of snowpack, our evaporation estimates differ from conventional methods that assume evaporation from a free water surface. Specifically, we find that conventional methods overestimate potential evaporation as well as aridity, taken as the ratio of atmospheric water demand to supply, in landscapes where snowfall is significant. With dwindling snow-cover, actual aridity increases, which could explain the reduction in streamflow with decreasing snowfall. We suggest that streamflow, and hence water availability, is more sensitive to temperature changes in colder than in warmer regions.

Investigating the Role of Snow Water Equivalent on Streamflow Predictability during Drought

American Meteorological Society (AMS) | October 20th, 2022

Snowpack provides the majority of predictive information for water supply forecasts (WSFs) in snow-dominated basins across the western United States. Drought conditions t

Snowpack provides the majority of predictive information for water supply forecasts (WSFs) in snow-dominated basins across the western United States. Drought conditions typically accompany decreased snowpack and lowered runoff efficiency, negatively impacting WSFs. Here, we investigate the relationship between snow water equivalent (SWE) and April–July streamflow volume (AMJJ-V) during drought in small headwater catchments, using observations from 31 USGS streamflow gauges and 54 SNOTEL stations. A linear regression approach is used to evaluate forecast skill under different historical climatologies used for model fitting, as well as with different forecast dates. Experiments are constructed in which extreme hydrological drought years are withheld from model training, that is, years with AMJJ-V below the 15th percentile. Subsets of the remaining years are used for model fitting to understand how the climatology of different training subsets impacts forecasts of extreme drought years. We generally report overprediction in drought years. However, training the forecast model on drier years, that is, below-median years (P15, P57.5], minimizes residuals by an average of 10%in drought year forecasts, relative to a baseline case, with the highest median skill obtained in mid- to late April for colder regions. We report similar findings using a modified National Resources Conservation Service (NRCS) procedure in nine large Upper Colorado River basin (UCRB) basins, highlighting the importance of the snowpack–streamflow relationship in streamflow predictability. We propose an “adaptive sampling” approach of dynamically selecting training years based on antecedent SWE conditions, showing error reductions of up to 20% in historical drought years relative to the period of record. These alternate training protocols provide opportunities for addressing the challenges of future drought risk to water supply planning.

Lahar Hazard Zones for Eruption-Generated Lahars in the Lassen Volcanic Center, California

U.S. Geological Survey (USGS) | September 25th, 2012

Lahars, Indonesian for volcanic mudflows or debris-flows, are a rapidly flowing mixture of rock debris and water that originates on the slopes of a volcano. Lahar generat

Lahars, Indonesian for volcanic mudflows or debris-flows, are a rapidly flowing mixture of rock debris and water that originates on the slopes of a volcano. Lahar generation requires an adequate source of water, abundant unconsolidated debris, steep slopes, significant relief, and a triggering mechanism (Vallance, 2000). Various triggering mechanisms include the rapid melting of snow and ice by pyroclastic flows, intense rainfall on loose volcanic rock deposits, a breakout of a lake dammed by volcanic deposits, and a debris avalanche.

Landslide-channel feedbacks amplify channel widening during floods

Nature Portfolio (Springer Nature) | January 24th, 2025

Local hydraulics influence habitat selection and swimming behavior in adult California Central Valley Chinook salmon at a large river confluence

Fisheries Research (Elsevier) | February 2nd, 2023

Long-term climate and competition explain forest mortality patterns under extreme drought

Ecology Letters (Wiley) | December 20th, 2016

Rising temperatures are amplifying drought‐induced stress and mortality in forests globally. It remains uncertain, however, whether tree mortality across drought‐stri

Rising temperatures are amplifying drought‐induced stress and mortality in forests globally. It remains uncertain, however, whether tree mortality across drought‐stricken landscapes will be concentrated in particular climatic and competitive environments. We investigated the effects of long‐term average climate [i.e. 35‐year mean annual climatic water deficit (CWD)] and competition (i.e. tree basal area) on tree mortality patterns, using extensive aerial mortality surveys conducted throughout the forests of California during a 4‐year statewide extreme drought lasting from 2012 to 2015. During this period, tree mortality increased by an order of magnitude, typically from tens to hundreds of dead trees per km2, rising dramatically during the fourth year of drought. Mortality rates increased independently with average CWD and with basal area, and they increased disproportionately in areas that were both dry and dense. These results can assist forest managers and policy‐makers in identifying the most drought‐vulnerable forests across broad geographic areas.

Los Angeles Department of Water and Power 2016 Annual Owens Valley Report

Los Angeles Department of Water & Power (LADWP) | December 1st, 2015

This report includes Los Angeles Department of Water and Power’s (LADWP) proposed Owens Valley operations plan for the first six months of the 2016-17 runoff year, an u

This report includes Los Angeles Department of Water and Power’s (LADWP) proposed Owens Valley operations plan for the first six months of the 2016-17 runoff year, an update on Owens Valley conditions, the current status of LADWP’s environmental mitigation projects, and the status of other studies, projects, and activities.

Los Angeles Department of Water and Power 2018 Annual Owens Valley Report

Los Angeles Department of Water & Power (LADWP) | December 1st, 2017

This report includes Los Angeles Department of Water and Power’s (LADWP) proposed Owens Valley Operations Plan for the 2018-2019 Runoff Year, an update on Owens Valley

This report includes Los Angeles Department of Water and Power’s (LADWP) proposed Owens Valley Operations Plan for the 2018-2019 Runoff Year, an update on Owens Valley conditions, and the current status of LADWP’s environmental mitigation projects and other legal obligations under the Agreement between the County of Inyo and the City of Los Angeles and its Department of Water and Power on a Long-Term Groundwater Management Plan for Owens Valley and Inyo County (Water Agreement); the 1991 Environmental Impact Report Water from the Owens Valley to Supply the Second Los Angeles Aqueduct, 1970 to 1990, 1990 Onward, Pursuant to a Long Term Groundwater Management Plan (1991 EIR); the Laws Type E transfer; the 1997 Memorandum of Understanding between the City of Los Angeles Department of Water and Power, County of Inyo, the California Department of Fish and Game, the California State Lands Commission, the Sierra Club, and the Owens Valley Committee (1997 MOU), the August 2004 and March 2010 Amended Stipulations and Orders in Case No. S1CVCV01-29768.

Management of the Colorado River: Water Allocations, Drought, and the Federal Role

Congressional Research Service (CRS) | April 4th, 2024

From its headwaters in Colorado and Wyoming to its terminus in the Gulf of California, the Colorado River Basin covers more than 246,000 square miles. The basin spans sev

From its headwaters in Colorado and Wyoming to its terminus in the Gulf of California, the Colorado River Basin covers more than 246,000 square miles. The basin spans seven U.S. states (Wyoming, Colorado, Utah, New Mexico, Arizona, Nevada, and California) and two countries (the United States and Mexico). Pursuant to federal law, the Bureau of Reclamation (Reclamation), a component of the Department of the Interior (DOI), plays a prominent role in the management of the basin’s waters. In the Lower Basin (i.e., Arizona, Nevada, and California), Reclamation also serves as water master on behalf of the Secretary of the Interior, a role that elevates the status of the federal government in basin water management. The federal role in managing Colorado River water is magnified by the multiple federally owned and operated water storage and conveyance facilities in the basin, which provide low-cost water and hydropower supplies.

Management of the Colorado River: Water Allocations, Drought, and the Federal Role

Congressional Research Service (CRS) | September 7th, 2022