Seasonal variation in total water storage in California inferred from GPS observations of vertical land motion

American Geophysical Union (AGU) | March 12th, 2014

GPS is accurately recording vertical motion of Earth's surface in elastic response to seasonal changes in surface water storage in California. California's mountains subs

GPS is accurately recording vertical motion of Earth's surface in elastic response to seasonal changes in surface water storage in California. California's mountains subside up to 12 mm in the fall and winter due to the load of snow and rain and then rise an identical amount in the spring and summer when the snow melts, the rain runs off, and soil moisture evaporates. We invert the GPS observations of seasonal vertical motions to infer changes in equivalent water thickness. GPS resolves the distribution of change in total water across California's physiographic provinces at a resolution of 50 km, compared to 200 km resolution from the Gravity Recovery and Climate Experiment. The seasonal surface water thickness change is 0.6 m in the Sierra Nevada, Klamath, and southern Cascade Mountains and decreases sharply to about 0.1 m east into the Great Basin and west toward the Pacific coast. GPS provides an independent inference of change in total surface water, indicating water storage to be on average 50% larger than in the NLDAS‐Noah hydrology model, likely due to larger changes in snow and reservoir water than in the model.

Sensitivity of Mountain Hydroclimate Simulations in Variable-Resolution CESM to Microphysics and Horizontal Resolution

American Geophysical Union (AGU) | July 31st, 2018

Snow monitoring at strategic locations improves water supply forecasting more than basin-wide mapping

Nature Portfolio (Springer Nature) | August 15th, 2025

In the Western United States, water supply forecasting has traditionally relied on snow water equivalent measurements at ground-based stations due to their strong correla

In the Western United States, water supply forecasting has traditionally relied on snow water equivalent measurements at ground-based stations due to their strong correlations with streamflow volume during spring and summer. However, stations are sparse and sample a small area, prompting interest in spatially complete – but costly – basin-wide mapping from airborne surveys or future satellite missions. Here we show that adding strategic measurements at snow hotspots – localized areas with untapped information for predicting streamflow – consistently outperforms spatially complete surveys that provide basin-average snowpack, both in basins with and without existing stations. While both improve forecast skill, hotspot monitoring increases correlations with streamflow volume by 11-14% (median) across 390 basins, compared to 4% from basin-wide surveys. These findings hold across snowpack datasets, skill metrics, and statistical models. The greatest gains in water supply prediction come from leveraging existing stations and expanding snow measurements to the right places, rather than everywhere.

State Climate Policy and Nature-based Solutions: A Match that Provides Multiple Benefits for Climate, Water, and More

Stanford University | August 17th, 2022

This report examines potential synergies between state climate policies and nature-based solutions that yield multiple benefits; outlines barriers to meeting that potenti

This report examines potential synergies between state climate policies and nature-based solutions that yield multiple benefits; outlines barriers to meeting that potential; and provides recommendations to accelerate the implementation of nature- based solutions with water benefits in state climate policies. It is not meant to be exhaustive, but to point out areas for further productive work. The audience is non-climate water practitioners working in the Colorado River Basin and state climate policy practitioners who may not be familiar with the opportunities nature-based solutions (NBS) provide for both climate and water. As a result, the report can be considered something of a primer or resource, including basic information about both fields to educate water practitioners as to what state climate plans entail, and to educate climate practitioners about the opportunity to include (and the necessity of including) NBS as part of their climate planning. The report’s intent is to illuminate an area where further engagement and technical work can help seize an opportunity to meet the climate and water challenges facing the Colorado River Basin states.

Storing and managing water for the environment is more efficient than mimicking natural flows

Nature Portfolio (Springer Nature) | June 27th, 2024

Strategic Forest Reserves can protect biodiversity in the western United States and mitigate climate change

Nature Portfolio (Springer Nature) | December 14th, 2021

Forest preservation is crucial for protecting biodiversity and mitigating climate change. Here we assess current forest preservation in the western United States using sp

Forest preservation is crucial for protecting biodiversity and mitigating climate change. Here we assess current forest preservation in the western United States using spatial data and find that beyond the 18.9% (17.5 Mha) currently protected, an additional 11.1% (10.3 Mha) is needed to achieve 30% preservation by 2030 (30 × 30). To help meet this regional preservation target, we developed a framework that prioritizes forestlands for preservation using spatial metrics of biodiversity and/or carbon within each ecoregion. We show that meeting this preservation target would lead to greater protection of animal and tree species habitat, current carbon stocks, future carbon accumulation, and forests that are important for surface drinking water. The highest priority forestlands are primarily owned by the federal government, though substantial areas are also owned by private entities and state and tribal governments. Establishing Strategic Forest Reserves would help protect biodiversity and carbon for climate adaptation and mitigation.

Strategic stream gauging network design for sustainable water management

Nature Portfolio (Springer Nature) | June 3rd, 2024

Stream gauging stations that monitor the flow of water in rivers and streams provide critical information to water managers, but biases and gaps in gauge placement, compo

Stream gauging stations that monitor the flow of water in rivers and streams provide critical information to water managers, but biases and gaps in gauge placement, compounded by gauge deactivations, limit our ability to track river flows and address global water challenges. Here we introduce an approach for identifying gauging sites to efficiently fill gaps in monitoring coverage within river networks while also addressing water management priorities, including reservoir operations, biodiversity conservation and hydroclimatic monitoring. Applying this approach to gauges in California, United States, we found substantial gaps in the stream monitoring network. Hypothetically reconfiguring gauges to locations that maximize coverage and representation of management objectives highlights the current network’s biases. Through the strategic reactivation and placement of additional gauges, we demonstrate how stream gauging networks can be designed to support sustainable water management.

Strategies for Managing the Colorado River in an Uncertain Future

Utah State University | January 11th, 2020

Colorado River managers and stakeholders face many uncertainties—issues such as climate change, future water demand, and evolving ecological priorities. Managers and st

Colorado River managers and stakeholders face many uncertainties—issues such as climate change, future water demand, and evolving ecological priorities. Managers and stakeholders are looking for new ways to communicate about uncertain future conditions, help cope with an uncertain future, and develop public policy when future conditions are highly uncertain. Historically, Colorado River managers have operated Lake Powell and Lake Mead under the assumption that the future natural flow regime of the Colorado River at Lee Ferry will resemble the previously observed regime, but most climate scientists believe that the flow regime is changing, and that future flows will be lower, more variable, and more uncertain.

Stream Flow and Losses of the Colorado River in the Southern Colorado Plateau

Utah State University | September 18th, 2020

A confounding uncertainty for predicting stream flow and losses in anticipation of renegotiation of the 2007 Interim Guidelines for Lower Basin Shortages concerns the acc

A confounding uncertainty for predicting stream flow and losses in anticipation of renegotiation of the 2007 Interim Guidelines for Lower Basin Shortages concerns the accuracy and precision of those data. Several key gages that are not used in CRSS and are not considered part of the standard network of gages used to manage the Colorado River offer critical insight into understanding future watershed conditions.

Summarizing Relationships among Landfalling Atmospheric Rivers, Integrated Water Vapor Transport, and California Watershed Precipitation 1982–2019

American Meteorological Society (AMS) | September 16th, 2022

Atmospheric rivers (ARs) are defined as corridors of enhanced integrated water vapor transport (IVT) and produce large fractions of annual precipitation in regions with c

Atmospheric rivers (ARs) are defined as corridors of enhanced integrated water vapor transport (IVT) and produce large fractions of annual precipitation in regions with complex terrain along the western coastlines of midlatitude continents (e.g., 30%–50% along the U.S. West Coast in California). This study investigates this relationship among landfalling ARs, IVT, and watershed mean areal precipitation (MAP) for a 38-yr period over California. On average, the daily average IVT magnitude at different coastal locations explains ∼34% of the variance in annual watershed MAP across 140 Hydrologic Unit Code 8 (HUC-8) watersheds with large spatial variability across California. Further investigation of the IVT magnitude and direction at coastal locations illustrated that accounting for water vapor transport direction increases the explained variance in annual MAP to an average of 45%, with highest values (∼65%) occurring in watersheds over Northern and coastal California. Similar investigation of the lower-tropospheric water vapor flux vector at 850 and 925 hPa revealed further increases in the explained variance in annual MAP to an average of >50%. The results of this study 1) emphasize the importance of both IVT direction and water vapor flux altitude to watershed MAP, 2) align well with previous studies for select locations that highlight the importance of upslope (i.e., lower tropospheric) water vapor flux during landfalling ARs and precipitation, and 3) motivate the development of AR-related and watershed-centric forecast tools that incorporate IVT direction and water vapor flux altitude parameters in addition to IVT magnitude.