California's Water Supply Strategy: Adapting to a Hotter, Drier Future

California Department of Water Resources (DWR) | August 16th, 2022

California's Water Supply Strategy: Adapting to a Hotter, Drier Future

Office of Governor Gavin Newsom | August 11th, 2022

California’s Most Significant Droughts: Comparing Historical and Recent Conditions

California Department of Water Resources (DWR) | February 2nd, 2015

This report was prepared in response to the dry conditions of 2012-14 (Figure 1.1) and particularly in response to the very dry hydrology of water year 2014. Water year 2

This report was prepared in response to the dry conditions of 2012-14 (Figure 1.1) and particularly in response to the very dry hydrology of water year 2014. Water year 2014 ranked as the third driest on record in terms of statewide precipitation, with the three-year period of water years 2012-14 ranking as the driest consecutive three-year period on record in terms of statewide precipitation. Continuing dry hydrology in 2015 raises questions about the similarity of present conditions to those of prior droughts and changes in observed impacts as California’s population increases and new institutional requirements are put in place. The purpose of this report is to compare present conditions with California’s most significant droughts of statewide scope, to help answer questions about the comparative severity of drought hydrology and drought impacts. The report also summarizes lessons learned and commonalities seen in the state’s most severe historical droughts.

California’s Severe Drought Has Only Marginal Impacts on Food Prices

University of California Giannini Foundation of Agricultural Economics | May 14th, 2015

The extreme drought that has gripped California over the past several years is causing onerous adjustments in the natural and human environments. Agriculture, which uses

The extreme drought that has gripped California over the past several years is causing onerous adjustments in the natural and human environments. Agriculture, which uses much of the state’s water, is at the center of many of these arduous responses. The 2015 impacts of the continuing drought are still underway, but in this special Agriculture and Resource Economics Update issue, we project responses and consequences within agriculture and more broadly. In this issue, Hanak and Mount put this drought in the context of California’s history and put agriculture in the context of water institutions, management, and distribution throughout the state. Next, Medellin-Azuara and co-authors develop detailed, and albeit preliminary, assessments of 2015 irrigation water distribution. They estimate a cut to agriculture of about 8.8 million acre-feet, or about 30% of what might be available in a normal year. (This number may be an underestimate given recent events.) During droughts, farms increase groundwater pumping. The authors estimate that farmers and ranchers will replace about 6.2 million acre-feet of lost surface water deliveries with costly increases in groundwater pumping, where possible in 2015. Another painful response to drought is to leave land idle. The authors estimate about 564,000 more acres, mostly field crop land in the Central Valley (including irrigated pastures), will be idled in 2015. This too may be an underestimate. USDA reported on June 30, that 2015 California acreage of “principal crops,” (defined as field crops such as hay, grains, oilseeds, cotton and potatoes) is about 900,000 acres below the 2013 total of about four million acres. Over this period, tree nut and tomato acreage increased by about 180,000 acres. So, even accounting for the steady shift to tree nuts and some other higher revenue per acre (and per acre-foot) crops, there is a strong indication of severely accelerated reductions in field crop acreage in California. The economic toll of the drought is fewer jobs and smaller value of output and economic contribution that would have otherwise occurred. Based on 564,000 idled acres, Howitt et al. estimates farm revenue losses of $1.8 billion, economy-wide revenue losses of $2.7 billion, and 18,600 fewer jobs due to the agricultural drought. That these economic impacts are not even larger is a testament to the extraordinary efforts and innovations by farmers, and others in California agriculture. Idling land, shifting water across crops, and using each acre-foot more economically all have led to smaller losses of revenue and jobs, and only very small price increases for consumers.

California’s Water: Managing Droughts

Public Policy Institute of California (PPIC) | October 1st, 2016

California is prone to multi-year droughts. Diverse, coordinated approaches are needed to stretch our water supply, ensure safe drinking water for at-risk communities

California is prone to multi-year droughts. Diverse, coordinated approaches are needed to stretch our water supply, ensure safe drinking water for at-risk communities, and protect the natural environment during dry periods. This brief describes the major effects of drought, and outlines adaptation strategies to manage them. This publication is part of a briefing kit that summarizes a dozen of the state’s most pressing water management issues.

Causes of extreme ridges that induce California droughts

American Meteorological Society (AMS) | February 15th, 2017

California droughts are often caused by high-amplitude and persistent ridges near and off the west coast of North America without apparent connections with ENSO. Here wi

California droughts are often caused by high-amplitude and persistent ridges near and off the west coast of North America without apparent connections with ENSO. Here with a hierarchy of climate models, it is demonstrated that extreme ridges in this region are associated with a continuum of zonal wavenumber-5 circumglobal teleconnection patterns that originate from midlatitude atmospheric internal dynamics. Although tropical diabatic heating anomalies are not essential to the formation and maintenance of these wave patterns, certain persistent heating anomalies may double the probability of ridges with amplitudes in the 90th percentile occurring on interannual time scales. Those heating anomalies can be caused by either natural variability or possibly by climate change, and they do not necessarily depend on ENSO. The extreme ridges that occurred during the 2013/14 and 2014/15 winters could be examples of ridges produced by heating anomalies that are not associated with ENSO. This mechanism could provide a source of subseasonal-tointerannual predictability beyond the predictability provided by ENSO.

Causes of the 2011‐14 California Drought

American Meteorological Society (AMS) | September 15th, 2015

The causes of the California drought during November–April winters of 2011/12–2013/14 are analyzed using observations and ensemble simulations with seven atmo

The causes of the California drought during November–April winters of 2011/12–2013/14 are analyzed using observations and ensemble simulations with seven atmosphere models forced by observed SSTs. Historically, dry California winters are most commonly associated with a ridge off the west coast but no obvious SST forcing. Wet winters are most commonly associated with a trough off the west coast and an El Niño event. These attributes of dry and wet winters are captured by many of the seven models. According to the models, SST forcing can explain up to a third of California winter precipitation variance. SST forcing was key to sustaining a high pressure ridge over the west coast and suppressing precipitation during the three winters. In 2011/12 this was a response to a La Niña event, whereas in 2012/13 and 2013/14 it appears related to a warm west–cool east tropical Pacific SST pattern. All models contain a mode of variability linking such tropical Pacific SST anomalies to a wave train with a ridge off the North American west coast. This mode explains less variance than ENSO and Pacific decadal variability, and its importance in 2012/13 and 2013/14 was unusual. The models from phase 5 of CMIP (CMIP5) project rising greenhouse gases to cause changes in California all-winter precipitation that are very small compared to recent drought anomalies. However, a long-term warming trend likely contributed to surface moisture deficits during the drought. As such, the precipitation deficit during the drought was dominated by natural variability, a conclusion framed by discussion of differences between observed and modeled tropical SST trends.

Causes of the Extreme Dry Conditions over California During Early 2013

American Meteorological Society (AMS) | September 30th, 2014

The state of California experienced extreme dry conditions during early 2013. In particular, January and February received 28% and 15%, respectively, of their nor

The state of California experienced extreme dry conditions during early 2013. In particular, January and February received 28% and 15%, respectively, of their normal monthly rainfall. When January and February are combined, January/ February 2013 is ranked as the driest of the period 1895–2014. Such large precipitation deficits exerted enormous stress on water resources in an already high water-demand region. Thus, it is of practical importance to investigate the causes of this extreme climate event so as to assess its predictability. *Chapter 3, Explaining Extreme Events of 2013 from a Climate Perspective, Bull. Amer. Meteor. Soc., 95 (9)

Central Valley Project and State Water Project Drought Operations Plan and Operational Forecast April 1, 2014 through November 15, 2014

Delta Stewardship Council (Delta Council) | April 8th, 2014

Central Valley Project Municipal and Industrial Water Shortage Policy Guidelines and Procedures

U.S. Bureau of Reclamation (USBR) | February 2nd, 2017

The Bureau of Reclamation (Reclamation) prepared the Central Valley Project (CVP) Municipal and Industrial (M&I) Water Shortage Policy (WSP) Environmental Impact Stat

The Bureau of Reclamation (Reclamation) prepared the Central Valley Project (CVP) Municipal and Industrial (M&I) Water Shortage Policy (WSP) Environmental Impact Statement (EIS) to evaluate the potential impacts of CVP M&I WSP alternatives. A Record of Decision was signed on November 13, 2015, to implement Alternative 4 (Appendix A), Updated M&I WSP (preferred alternative). The purposes of the M&I WSP are to: Define water shortage terms and conditions for applicable CVP Contractors. Determine the quantity of water made available to CVP Contractors from the CVP that; together with the M&I Contractors’ drought water conservation measures and other Non-CVP water supplies, would assist the M&I Contractors in their efforts to protect public health and safety (PHS) during severe or continuing droughts. Provide information to Contractors for their use in water supply planning and development of drought contingency plans.