Assessing potential effects of changes in water use with a numerical groundwater-flow model of Carson Valley, Douglas County, Nevada, and Alpine County, California

U.S. Geological Survey (USGS) | July 1st, 2012

Assessing the accuracy of OpenET satellite-based evapotranspiration data to support water resource and land management applications

Nature Portfolio (Springer Nature) | January 15th, 2024

Remotely sensed evapotranspiration (ET) data offer strong potential to support data-driven approaches for sustainable water management. However, practitioners require rob

Remotely sensed evapotranspiration (ET) data offer strong potential to support data-driven approaches for sustainable water management. However, practitioners require robust and rigorous accuracy assessments of such data. The OpenET system, which includes an ensemble of six remote sensing models, was developed to increase access to field-scale (30 m) ET data for the contiguous United States. Here we compare OpenET outputs against data from 152 in situ stations, primarily eddy covariance flux towers, deployed across the contiguous United States. Mean absolute error at cropland sites for the OpenET ensemble value is 15.8 mm per month (17% of mean observed ET), mean bias error is −5.3 mm per month (6%) and r2 is 0.9. Results for shrublands and forested sites show higher inter-model variability and lower accuracy relative to croplands. High accuracy and multi-model convergence across croplands demonstrate the utility of a model ensemble approach, and enhance confidence among ET data practitioners, including the agricultural water resource management community.

Assessing the Microclimate Effects and Irrigation Water Requirements of Mesic, Oasis, and Xeric Landscapes

Hydrology (MDPI) | June 10th, 2022

Urban irrigation is an essential process in land–atmosphere interactions. It is one of the uncertain parameters of urban hydrology due to various microclimates. This s

Urban irrigation is an essential process in land–atmosphere interactions. It is one of the uncertain parameters of urban hydrology due to various microclimates. This study investigated the microclimate effects and irrigation water requirements of three landscape types in an arid region of Phoenix, AZ. The microclimate effect encompassed surface temperature, air temperature, and wind speed. The simulations of the three landscapes were conducted using ENVI-met software for the hottest day of the year (23 June 2011). The simulated model was validated using ground data. Results show that the mesic landscape induced cooling effects, both in the daytime and nighttime, by reducing surface and air temperatures. However, the mesic landscape showed highwater consumption because of a high leaf area density. The oasis landscape showed 2 degrees C more daytime cooling than the mesic landscape, but the nighttime warming (surface temperature) was comparable to the xeric landscape. The potential irrigation water requirement was 1 mm/day lower than the mesic landscape. Moreover, microclimate conditions varied spatially in each neighborhood. The xeric landscape showed lower wind speeds and air temperatures between the buildings. The wind speed variations in the three landscapes were inconclusive due to differences in building orientations and discrepancies in trees’ heights. The findings can have implications for restricting the municipal irrigation budget. In addition, they can help water managers in choosing a landscape in urban areas. Urban scientists can adapt the methodology to quantify urban ET in arid regions.

Assessment of Interconnected Subbasins

Butte County | June 30th, 2017

The Sustainable Groundwater Management Act (SGMA) requires groundwater sustainability agencies (GSAs) to develop groundwater sustainability plans (GSPs) that achieve sust

The Sustainable Groundwater Management Act (SGMA) requires groundwater sustainability agencies (GSAs) to develop groundwater sustainability plans (GSPs) that achieve sustainable groundwater management within 20 years of adoption. All critically overdrafted basins must adopt GSPs by January 31, 2020; all other medium and high priority basins must complete GSPs by January 31, 2022. Since many subbasins are hydrologically connected to adjoining subbasins, sustainable groundwater management will require accounting for groundwater interactions with adjoining subbasins. Often, adjoining subbasins will use different analytical methods or apply different levels of technical rigor. Many GSAs are concerned that different methodologies for developing interbasin flows can lead to different results that will call into question the ability to achieve sustainability and would potentially create issues with SGMA compliance. This effort evaluated opportunities and barriers for agencies to account for interconnected basin dynamics through the collaboration of technical experts focused on a portion of the northern Sacramento Valley Integrated Regional Water Management (NSVIRWM) Plan area. As interbasin flows (i.e., groundwater flow between interconnected basins) cannot be directly measured, the project reviewed available tools to investigate how they may or may not be suitable for use in estimating interbasin flows within the region. This process highlighted areas for local agencies to consider in addressing interbasin issues, developed a framework for analysis in other areas of the state, and identified areas where the state and federal government can assist local agencies implementing SGMA. This report is developed to provide summary level information appropriate for decision makers, with more detailed technical information and examples provided in the appendices or by reference. Interbasin flow is groundwater entering or exiting a defined subbasin through its boundaries in the subsurface and may vary significantly in space and time based on the dynamics of inflow and outflow from the basins. Interbasin flows are driven by differences in groundwater levels (i.e. head gradients) across the basin boundary. Groundwater levels are, in turn, impacted by processes on the land surface. Land use and crop acreages drive water demand in a subbasin and indirectly drive groundwater pumping, which has a direct effect on groundwater levels (i.e., groundwater heads). The direction and magnitude of interbasin flow depends on the groundwater head gradient across the basin boundary and the conductivity of the aquifer materials. It is widely recognized that the groundwater subbasins in the Sacramento Valley, and throughout the Central Valley, are interconnected to varying degrees. The Sacramento Valley Groundwater Basin includes many subbasins, extends over a wide geographic area, and includes numerous established and eligible GSAs. With interconnected subbasins, management decisions and actions in one subbasin may influence one or more adjoining subbasins. Such influence may positively or negatively impact sustainability. Thus, interbasin flows become critical to both GSAs’ development of GSPs and to DWR reviewing GSPs.

Assessment of Interconnected Subbasins: Regional Collaboration and Model Selection Process

Groundwater Resources Association of California (GRA) | October 3rd, 2017

In basins with complex spatial and temporal variations in water budget components, integrated groundwater-surface water modeling is the best approach to quantify and eval

In basins with complex spatial and temporal variations in water budget components, integrated groundwater-surface water modeling is the best approach to quantify and evaluate interbasin groundwater flows.

Assumptions and Estimates for California Water Plan Update 2018

California Department of Water Resources (DWR) | April 13th, 2017

The California Water Plan (Water Plan) is the State government’s strategic plan for sustainably managing and developing water resources statewide for current and future

The California Water Plan (Water Plan) is the State government’s strategic plan for sustainably managing and developing water resources statewide for current and future generations. The Water Plan development process provides a planning framework for elected officials, agencies, tribes, water and resource managers, businesses, academia, stakeholders, and the public to collaborate on findings and recommendations and make informed decisions regarding California’s water future. The goal for each update of the Water Plan is to receive broad input and support from Californians, meet California Water Code (Water Code) requirements, guide State investments, and advance integrated water management and regional sustainability.  This draft report and the related data posted online comprise the Draft Assumptions and Estimates Report (Draft A&E Report) for California Water Plan Update 2018 (Update 2018). The Draft A&E Report presents key assumptions and estimates, data and data sources, and companion plans that will be considered for the preparation of Update 2018. The report increases the transparency of the Water Plan process by disclosing the data, tools, methods, and references used to prepare Update 2018. This report meets Water Code requirements, which stipulate that the California Department of Water Resources (DWR) must publish the Water Plan’s assumptions and estimates one year prior to the plan’s publication, as well as provide an opportunity for public review and comment. Water code requirements for the Draft A&E Report are presented below.  The Draft A&E Report also describes the approach DWR is taking to improve the analytical tools and data being used to develop Update 2018. DWR will continue to update Draft A&E Report content online during the remainder of the Update 2018 development process. A draft glossary for Update 2018 is included as part of this report, and the final version of that glossary will be published as a component of Update 2018. The final data and data sources will be included in the Update 2018 reference and technical information. 

Atmospheric Rivers Impacting Northern California Exhibit a Quasi-Decadal Frequency

American Geophysical Union (AGU) | July 26th, 2021

In Northern California, much of the precipitation and surface water comes from atmospheric rivers–corridors of moisture transport from the tropics. The frequency of atm

In Northern California, much of the precipitation and surface water comes from atmospheric rivers–corridors of moisture transport from the tropics. The frequency of atmospheric rivers is cyclical, with periods of water surplus and deficit in the region that repeat every 10–17 years. While many social and political factors influence water resource distribution, understanding the climate factors that regulate water availability is important for managing water in the future. Using data from observations and modeling experiments, the pronounced wet/dry cycle in this area of the Western United States is mainly attributed to regular fluctuations in sea surface temperatures in the tropical Pacific Ocean. This analysis provides a potential source of predictability for atmospheric river frequency, and thus water availability, years before a winter season.

Atmospheric rivers impacting western North America in a world with climate intervention

Nature Portfolio (Springer Nature) | May 18th, 2022

Atmospheric rivers (ARs) impacting western North America are analyzed under climate intervention applying stratospheric aerosol injections (SAI) using simulations produce

Atmospheric rivers (ARs) impacting western North America are analyzed under climate intervention applying stratospheric aerosol injections (SAI) using simulations produced by the Whole Atmosphere Community Climate Model. Sulfur dioxide injections are strategically placed to maintain present-day global, interhemispheric, and equator-to-pole surface temperatures between 2020 and 2100 using a high forcing climate scenario. Three science questions are addressed: (1) How will western North American ARs change by the end of the century with SAI applied, (2) How is this different from 2020 conditions, and (3) How will the results differ with no future climate intervention. Under SAI, ARs are projected to increase by the end of the 21st century for southern California and decrease in the Pacific Northwest and coastal British Columbia, following changes to the low-level wind. Compared to 2020 conditions, the increase in ARs is not significant. The character of AR precipitation changes under geoengineering results in fewer extreme rainfall events and more moderate ones.

Atmospheric rivers in 20 year weather and climate simulations: A multi-model, global evaluation

American Geophysical Union (AGU) | June 1st, 2017

Atmospheric rivers (ARs) are narrow, elongated, synoptic jets of water vapor that play importantroles in the global water cycle and meteorological/hydrological extremes.

Atmospheric rivers (ARs) are narrow, elongated, synoptic jets of water vapor that play importantroles in the global water cycle and meteorological/hydrological extremes. Increasing evidence shows that ARs have signatures and impacts in many regions across different continents. However, global-scalecharacterizations of AR representations in weather and climate models have been very limited. Using a recently developed AR detection algorithm oriented for global applications, the representation of AR activities in multi-decade weather/climate simulations is evaluated. The algorithm is applied to 6-hourly(daily) integrated water vapor transport (IVT) from 22 (2) global weather/climate models that participated inthe Global Energy and Water Cycle Experiment Atmospheric System Study–Year of Tropical Convection Multimodel Experiment, including four models with ocean-atmosphere coupling and two models with super parameterization. Multiple reanalysis products are used as references to help quantify model errors inthe context of reanalysis uncertainty. Model performance is examined for key aspects of ARs (frequency,intensity, geometry, and seasonality), with the focus on identifying and understanding systematic errors insimulated ARs. The results highlight the range of model performances relative to reanalysis uncertainty inrepresenting the most basic features of ARs. Among the 17 metrics considered, AR frequency, zonal IVT, fractional zonal circumference, fractional total meridional IVT, and three seasonality metrics have consistently large errors across all models. Possible connections between AR simulation qualities and aspects of model configurations are discussed. Despite the lack of a monotonic relationship, the importance of model horizontal resolution to the overall quality of AR simulation is suggested by the evaluation results.

Attributing Extreme Events to Climate Change: A New Frontier in a Warming World

Cell Press | June 19th, 2020

The emerging field of extreme event attribution (EEA) seeks to answer the question: ‘‘Has climate change influenced the frequency, likelihood, and/or severity

The emerging field of extreme event attribution (EEA) seeks to answer the question: ‘‘Has climate change influenced the frequency, likelihood, and/or severity of individual extreme events?’’ Methodological advances over the past 15 years have transformed what was once an unanswerable hypothetical into a tractable scientific question—and for certain types of extreme events, the influence of anthropogenic climate change has emerged beyond a reasonable doubt. Several challenges remain, particularly those stemming from structural limitations in process-based climate models and the temporal and geographic limitations of historical observations. However, the growing use of large climate-model ensembles that capture natural climate variability, fine-scale simulations that better represent underlying physical processes, and the lengthening observational record could obviate some of these concerns in the near future. EEA efforts have important implications for risk perception, public policy, infrastructure design, legal liability, and climate adaptation in a warming world.