The Ahwahnee Water Principles

Local Government Commission | July 1st, 2006

In 2004,the Local Government Commission set out to identify effective,least-cost economically and politically viable options for sustainable water resources management at

In 2004,the Local Government Commission set out to identify effective,least-cost economically and politically viable options for sustainable water resources management at the local level. The LGC invited respected water resource policy, management and planning professionals – with experience at the federal,state and local levels – to craft a set of land use principles which would provide guidance to local officials and communities concerned about sustaining future water supplies. The process of developing the Ahwahnee Water Principles mirrored the LGC’s earlier Ahwahnee Principles for Resource-Efficient Communities, which were released in 1991. The Ahwahnee Principles presented a blueprint for elected officials to create compact, mixed-use,walkable,transit-oriented developments in their local communities,and have since paved the way for growing acceptance and inclusion of “smart growth”and the “New Urbanism”in local and regional land-use policies and practices.

The Application of Ground-Water Flow Models as Predictive Tools—A Review of Two Ground-Water Models of Eastern Honey Lake Valley, California-Nevada

Geological Society of America (GSA) | January 9th, 1992

In the late 1980's Washoe County, Nevada, entered into an agreement with a private water development company to develop and export groundwater from the Nevada portion of

In the late 1980's Washoe County, Nevada, entered into an agreement with a private water development company to develop and export groundwater from the Nevada portion of the arid Honey Lake Valley to the rapidly growing Reno-Sparks area. The proposed project is known as the Truckee Meadows Project (TMP). Honey Lake Valley is 35 mi north of Reno, Nevada; but is located predominantly in California. Computer groundwater models of the valley were prepared by the USGS and the TMP proponents and presented to the Nevada State Engineer to evaluate the impacts of the proposed exportation of 15,000 ac-ft annually from eastern Honey Lake Valley. By using assumptions, numbers, and data which are not justified by the scientific data, both models place unreasonable and, in some instances, artificial constraints on the geology and hydrogeology of the groundwater system rather than allowing the geology and hydrogeology to constrain the models. Neither model is useful as a predictive tool. However, the major problems with the two models fall into two fundamentally different classes. The USGS model exceeded the technical limitations of the model code and made large, inappropriate adjustments to the water budget to compensate for these undetected errors. The TMP model used a water budget that was not technically justified or explained and placed the spatial distribution of ground-water recharge and discharge beyond the realm of hydrogeologic reality.  

The California water model: Resilience through failure

Hydrological Processes (Wiley) | March 21st, 2019

No earth resource is more abundant than water, but no other resources is more oversubscribed or a source of greater controversy. California, for example, generates an ave

No earth resource is more abundant than water, but no other resources is more oversubscribed or a source of greater controversy. California, for example, generates an average run-off of 100 km3/year, but the state's ecosystems and parts of its economy have been limited for decades with drought punctuated by years of exceptional rain or snowmelt and flooding. California has nonetheless managed to thrive, with 40 million people, agricultural production exceeding $45 billion/year, and the world's largest economy. Through droughts, floods, and constant tension between environmental protection and economic growth, California has evolved a diverse toolkit for managing its water. But ... is California's model of water management one of the world's greatest successes or instead a history of dismal failures?

The California Water Plan: Projected Use and Available Water Supplies to 2010

California Department of Water Resources (DWR) | December 15th, 1983

The case for strategic and managed climate retreat

American Association for the Advancement of Science (AAAS) | August 23rd, 2019

Faced with global warming, rising sea levels, and the climate-related extremes they intensify, the question is no longer whether some communities will retreat�

Faced with global warming, rising sea levels, and the climate-related extremes they intensify, the question is no longer whether some communities will retreat—moving people and assets out of harm’s way—but why, where, when, and how they will retreat. To the extent that retreat is already happening, it is typically ad hoc and focused on risk reduction in isolation from broader societal goals. It is also frequently inequitable and often ignores the communities left behind or those receiving people who retreat. Retreat has been seen largely as a last resort, a failure to adapt, or a one-time emergency action; thus, little research has focused on retreat, leaving practitioners with little guidance. Such a narrow conception of retreat has limited decision-makers’ perception of the tools available and stilted innovation. We propose a reconceptualization of retreat as a suite of adaptation options that are both strategic and managed. Strategy integrates retreat into long-term development goals and identifies why retreat should occur and, in doing so, influences where and when. Management addresses how retreat is executed. By reconceptualizing retreat as a set of tools used to achieve societal goals, communities and nations gain additional adaptation options and a better chance of choosing the actions most likely to help their communities thrive.

The Changing Nature of Atmospheric Rivers

American Meteorological Society (AMS) | March 15th, 2025

Atmospheric rivers (ARs) are expected to strengthen in a warming climate, largely due to the thermodynamic (moistening) effect. Here, we show that this trend is already e

Atmospheric rivers (ARs) are expected to strengthen in a warming climate, largely due to the thermodynamic (moistening) effect. Here, we show that this trend is already evident in historical reanalysis data using the AR Tracking Method Intercomparison Project (ARTMIP) tier 2 AR detection tools (ARDTs) and variants of our own global AR detection applied to ERA5, MERRA-2, and JRA-55 reanalysis data. Over the 1980–2019 (ARTMIP) and 1980–2023 (variants) periods, total AR area increased by 6%–9%. AR integrated water vapor (IWV) increased by 1.5%–2.5% while integrated vapor transport (IVT) increased by less than 1% and 850-hPa wind speed (|V850|) and vertically integrated moisture flux convergence (VIMFC) both decreased. IWV increases were the most robust overall. All trend magnitudes were sensitive to subsetting, with fixed-frequency subsets consisting of the most intense AR grid points showing larger increases of 3%–4% IVT, 4%–6% IWV, and 6%–10% VIMFC, this last opposing a decreasing AR-mean VIMFC trend likely associated with large area increases. For individual ARs, maximum IVT and IWV increased at ;3–63 and ;1.5–23 the rate of AR-mean values, respectively. Regional changes were often even larger, particularly for extreme events, though most geospatial trends had low detectability under a false discovery rate control framework. Ultimately, despite considerable ARDT and methodological diversity, we found robust consensus moistening and expansion of ARs between 1980 and 2023. However, further research is required to determine the extent to which these trends are affected by reanalysis observational assimilation changes. For example, previous studies indicate that certain reanalyses misrepresent 1980–94 atmospheric moistening and so may underestimate historical AR expansion and intensification rates.

The Collapse of Pelagic Fishes in the Upper San Francisco Estuary: El Colapso de los Peces Pelagicos en La Cabecera Del Estuario San Francisco

American Fisheries Society (AFS) | January 9th, 2007

Although the pelagic fish community of the upper San Francisco Estuary historically has shown substantial variability, a recent collapse has captured the attention of res

Although the pelagic fish community of the upper San Francisco Estuary historically has shown substantial variability, a recent collapse has captured the attention of resource managers, scientists, legislators, and the general public. The ecological and management consequences of the decline are most serious for delta smelt (Hypomesus transpacificus), a threatened species whose narrow range overlaps with large water diversions that supply water to over 25 million people. The decline occurred despite recent moderate hydrology, which typically results in at least modest recruitment, and investments of hundreds of millions of dollars in habitat restoration and environmental water allocations to support native fishes. In response to the pelagic fish collapse, an ambitious multi-agency research team has been working since 2005 to evaluate the causes of the decline, which likely include a combination of factors: stock-recruitment effects, a decline in habitat quality, increased mortality rates, and reduced food availability due to invasive species.

The cost of alternative urban water supply and efficiency options in California

Environmental Research Communications (IOP) | May 28th, 2019

Urban communities, farms, businesses, and natural ecosystems depend upon adequate, reliable, and affordable supplies of clean water. As populations and economies

Urban communities, farms, businesses, and natural ecosystems depend upon adequate, reliable, and affordable supplies of clean water. As populations and economies grow and as climatic changes alter both water supply and demand, traditional options for meeting freshwater needs are becoming less available, reliable, and effective. As we approach peak water constraints on traditional water supplies, more efforts needed to reduce water demands through a wide range of conservation and efficiency technologies and policies, and to develop alternative, non-traditional water sources. A key factor in the adoption of these strategies is their economic feasibility; yet, only limited and often confusing data are available on their relative costs. To fill this gap, this analysis evaluates the costs of four groups of alternatives for urban supply and demand based on data and analysis in the California context: stormwater capture; water recycling and reuse; brackish and seawater desalination; and a range of water conservation and efficiency measures. We also describe some important co-benefits or avoided costs, such as reducing water withdrawals from surface water bodies or polluted runoff in coastal waterways. While difficult to quantify, such benefits are economically relevant, and we highlight areas where further research and analysis are needed to improve estimates presented here. All of the water- use efficiency options are far less costly than traditional or alternative supply systems with the exception of some of the most expensive landscape water reduction options. The water treatment and reuse systems and the urban stormwater capture projects are more costly per unit of water produced but still less expensive than seawater desalination—the most expensive option evaluated.

The Cost of Alternative Water Supply and Efficiency Options in California

Pacific Institute | October 13th, 2016

The Cost of Alternative Water Supply and Efficiency Options in California is the first comprehensive analysis to examine the cost of various strategies throughout the sta

The Cost of Alternative Water Supply and Efficiency Options in California is the first comprehensive analysis to examine the cost of various strategies throughout the state to augment local water supplies and reduce water demand in urban areas. The study uses methods developed in the field of energy economics to determine the “levelized” costs of each supply and demand management option. The study finds that the cost of new supplies in California is highly varied. Large stormwater capture projects are among the least expensive of the water supplies examined, with a median cost of about $590 per acre-foot. By contrast, seawater desalination, with a median cost of $2,100 per acre-foot for large projects and $2,800 per acre-foot for smaller projects, is among the most expensive water supply option. Brackish water desalination is much less expensive due to lower energy and treatment costs. Generally, the cost of recycled water is in between that of stormwater capture and seawater desalination. Non-potable reuse – which treats water for irrigation and other non-drinking purposes – is typically less expensive than indirect potable reuse due to the lower treatment requirements; however, the cost of building or expanding a separate “purple pipe” distribution system to deliver non-potable water may be such that indirect potable reuse could be more cost effective. Nonetheless, the study finds that urban water conservation and efficiency are the most cost-effective ways to meet current and future water needs. Indeed, many residential and non-residential measures have a “negative cost,” which means that they save the customer more money over their lifetime than they cost to implement.

The critical role of humidity in modeling summer electricity demand across the United States

Nature Portfolio (Springer Nature) | April 3rd, 2020

Cooling demand is projected to increase under climate change. However, most of the existing projections are based on rising air temperatures alone, ignoring that

Cooling demand is projected to increase under climate change. However, most of the existing projections are based on rising air temperatures alone, ignoring that rising temperatures are associated with increased humidity; a lethal combination that could significantly increase morbidity and mortality rates during extreme heat events. We bridge this gap by identifying the key measures of heat stress, considering both air temperature and near-surface humidity, in characterizing the climate sensitivity of electricity demand at a national scale. Here we show that in many of the high energy consuming states, such as California and Texas, projections based on air temperature alone underestimates cooling demand by as much as 10–15% under both present and future climate scenarios. Our results establish that air temperature is a necessary but not sufficient variable for adequately characterizing the climate sensitivity of cooling load, and that near-surface humidity plays an equally important role.