The Magnitude of California's Water Challenges

UnIversity of California, Davis (UC Davis) | June 4th, 2024

California will see increasing water scarcity from climate change, the end of overdrafting groundwater and the Colorado River’s massive reservoirs, increased water dedi

California will see increasing water scarcity from climate change, the end of overdrafting groundwater and the Colorado River’s massive reservoirs, increased water dedications for environmental flows, and other factors, such as salination of aquifers and land subsidence reducing canal capacities. Total reduction in average water availability in the coming decades will likely range from 4.6 to 9 million acre-feet per year. For context, this is equivalent to the water use of 1 – 2.8 million acres of irrigated agriculture or most urban water use in California. Perhaps 20-30% of this loss will likely be addressed by ongoing water conservation and supply improvements, being planned and implemented, leaving a 3 – 7.2 million acre-feet/year likely net average difference between statewide water demands and availability.

The Metropolitan Aqueduct: Colorado River Water for Cities in the Metropolitan Water District

Metropolitan Water District of Southern California (MWD) | March 12th, 1931

The Metropolitan Water District of Southern California Annual Report for the Fiscal Year July 1, 2018 to June 30, 2019

Metropolitan Water District of Southern California (MWD) | December 1st, 2019

The Metropolitan Water District of Southern California History and First Annual Report for the Period Ending June 30, 1938

Metropolitan Water District of Southern California (MWD) | January 20th, 1939

The most important issue about water is not supply, but how it is used

Nature Portfolio (Springer Nature) | December 14th, 2023

The Newest Plan of Los Angeles Engineers to Provide More Water for that Enterprising Metropolis

Scientific American | February 1st, 1925

The paradox of irrigation efficiency

American Association for the Advancement of Science (AAAS) | August 24th, 2018

Reconciling higher freshwater demands with finite freshwater resources remains one of the great policy dilemmas. Given that crop irrigation constitutes 70% of global wate

Reconciling higher freshwater demands with finite freshwater resources remains one of the great policy dilemmas. Given that crop irrigation constitutes 70% of global water extractions, which contributes up to 40% of globally available calories (1), governments often support increases in irrigation efficiency (IE), promoting advanced technologies to improve the “crop per drop.” This provides private benefits to irrigators and is justified, in part, on the premise that increases in IE “save” water for reallocation to other sectors, including cities and the environment. Yet substantial scientific evidence (2) has long shown that increased IE rarely delivers the presumed public-good benefits of increased water availability. Decision-makers typically have not known or understood the importance of basin-scale water accounting or of the behavioral responses of irrigators to subsidies to increase IE. We show that to mitigate global water scarcity, increases in IE must be accompanied by robust water accounting and measurements, a cap on extractions, an assessment of uncertainties, the valuation of trade-offs, and a better understanding of the incentives and behavior of irrigators.

The Press and Pulse of Climate Change: Extreme Events in the Colorado River Basin

American Water Resources Association (AWRA) | June 21st, 2022

Extremes in temperature and precipitation are associated with damaging floods, prolonged drought, destructive wildfires, agricultural challenges, compromised human health

Extremes in temperature and precipitation are associated with damaging floods, prolonged drought, destructive wildfires, agricultural challenges, compromised human health, vulnerable infrastructure, and threatened ecosystems and species. Often, the steady and progressive trends (or presses) of rising global temperature are the central focus in how climate impacts are described. However, observations of extreme weather events (or pulses) increasingly show that the intensity, duration and/or frequency of acute events are also changing, resulting in greater impacts on communities and the environment. Describing how the influence of extreme events may shape water management in the Colorado River Basin in clear terms is critical to sound future planning and efforts to manage risk. Three scenario planning workshops in 2019 and 2020 were held as part of a Colorado River Conversations series, identifying potential impacts from multiple intersecting extreme events. Water managers identified climate-related events of concern in the Colorado River Basin that necessitate greater attention and adaptive responses. To support efforts to include consideration of climate-change-driven extremes in water management and planning, we explore the current state of knowledge at the confluence of long-term climate shifts and extreme weather in the Colorado River Basin related to the events of concern that were identified by scenario planning participants.

The Radical Groundwater Storage Test

Scientific American | October 19th, 2017

IN BRIEF California could better survive flood years and drought years by capturing floodwaters and using them to recharge underground aquifers that farmers and muni

IN BRIEF California could better survive flood years and drought years by capturing floodwaters and using them to recharge underground aquifers that farmers and municipalities now pump from when rains are scarce. To do so, water users and managers have to regard surface water and groundwater as one connected resource. A variety of test projects are proving that this approach can work. For example, farm fields can be flooded even when crops are growing so the water can percolate down into aquifers. Revising water rights and paying landowners to allow flooding can help the techniques work across California and the world.

The Relationship between California Rainfall and ENSO Events

American Meteorological Society (AMS) | November 1st, 1989

This paper examines the annual rainfall over California during 11 ENSO events within the period 1950 to 1982. During six of these, unusually wet conditions prevailed thro

This paper examines the annual rainfall over California during 11 ENSO events within the period 1950 to 1982. During six of these, unusually wet conditions prevailed throughout California; conditions were near normal during five events; and in one extreme drought occurred statewide. A comparison with the ENSO classification scheme of Fu et al, based on SST patterns in the Pacific, shows an excellent correspondence. Type 1 years, with large positive temperature anomalies east of the date line and lasting well into winter, are invariably events that enhance California rainfall. Normal years coincide with Type 2 ENSO events (moderate warming over a broad sector); the dry year is the sole Type 3 year, with weak anomalies confined to the eastern Pacific. This study also shows that the response to ENSO is regionally specific. Although throughout the state most years with extremely wet conditions are ENSO years, the tendency for an ENSO event to increase rainfall is greatest in Southern California, where 9 of 11 events produced above-normal rainfall and 8 of the 10 wettest years was an ENSO year. The pattern is more complex in central California; there ENSO years are almost invariably ones with highly abnormal rainfall, but they may be either wet or dry. The areas least influenced by ENSO are the Sierra Nevada and Northern California. The reasons for the geographical pattern of response become apparent when the seasonality and causes of rainfall in the various regions are evaluated.