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.

Supplement to the 2007 Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for Lake Powell and Lake Mead

U.S. Bureau of Reclamation (USBR) | May 6th, 2024

This ROD revises the 2007 Interim Guidelines for the near-term operation of Glen Canyon and Hoover Dams to address the potential for continued low-runoff conditions in th

This ROD revises the 2007 Interim Guidelines for the near-term operation of Glen Canyon and Hoover Dams to address the potential for continued low-runoff conditions in the Basin. Reclamation has concluded that the potential impacts of low-runoff conditions pose unacceptable risks to routine operations of Glen Canyon and Hoover Dams during the remainder of the interim period (through the end of the 2026 operating year) and that modified operating guidelines need to be expeditiously developed.

Sustainable Management of a Water Reservoir System Facing Climate Uncertainty

Social Science Research Network (SSRN) | November 27th, 2024

Water scarcity is a growing global issue. It affects even highly developed regions like California, the world's fifth largest economy, where years of severe droughts inte

Water scarcity is a growing global issue. It affects even highly developed regions like California, the world's fifth largest economy, where years of severe droughts interspersed with unusually wet seasons have caused societal debates over the management of the water resources stored in the state's extensive reservoir system. This paper presents a strategic optimization model for the long-term, sustainable management of such a system. Introducing a new modeling paradigm based on cycles of stochastic length, defined by the event when all reservoirs are simultaneously full, we avoid the limitations of traditional models and obtain sustainable management policies. To address the unpredictable effect of climate change on future water supply, we adopt a distributionally robust framework where nature chooses adverse inflow distributions. This leads to a stochastic shortest path problem under distributional ambiguity. Using tools from stochastic dynamic programming and aggregation methods, we obtain policy insights and overcome the curse of dimensionality typically associated with systems models. In a case study for California's Sacramento River Basin, we report suboptimality gaps between 3% and 15%, with our sustainable management policy reducing average cycle shortage costs by 40% compared to the current policy, demonstrating the significant cost saving potential.

Tahoe: State of the Lake Report 2025

University of California, Davis (UC Davis) | July 18th, 2025

UC Davis has conducted research at Lake Tahoe since 1950, and scientists from UC Davis Tahoe Environmental Research Center have been monitoring conditions at the lake con

UC Davis has conducted research at Lake Tahoe since 1950, and scientists from UC Davis Tahoe Environmental Research Center have been monitoring conditions at the lake continuously since 1968. This has created a unique document of change for one of the world’s most iconic and vulnerable lakes.

Taming wildfires in the context of climate change: The case of the United States

Organisation for Economic Co-operation and Development (OECD) | January 22nd, 2024

Shifts in climate cycles (e.g., Pacific Decadal Oscillation, El Niño-Southern Oscillation), combined with ongoing changes in drought, temperature and snowmelt, together,

Shifts in climate cycles (e.g., Pacific Decadal Oscillation, El Niño-Southern Oscillation), combined with ongoing changes in drought, temperature and snowmelt, together, have contributed to the overall warmer, drier conditions that fuel extreme wildfires (Environmental Protection Agency, 2022[4]; Kitzberger et al., 2007[10]; Westerling, 2016[11]). The period with the largest increase in area burned coincides with many of the warmest years on record nationwide (Environmental Protection Agency, 2022[4]). Such changes are especially visible in the western United States, where the peak extent of area burned now occurs about one month earlier than just two decades ago. Other factors including longer dry seasons and drier soils and vegetation are increasingly creating the conditions for catastrophic wildfires (Environmental Protection Agency, 2022[4]; US Global Change Research Program, 2018[9]). Wildfires are also further spreading into areas historically unaccustomed to fire, including high elevation areas in the west of the country (Figure 1.2) (OECD, 2023[2]; Alizadeh et al., 2021[12]), which may be less prepared for wildfires and potentially harmed by its impacts.