The magnitude and spatial patterns of historical and future hydrologic change in California’s watersheds

Ecological Society of America (ESA) | February 12th, 2015

Process-based models that link climate and hydrology permit improved assessments of climate change impacts among watersheds. We used the Basin Characterization Model (BCM

Process-based models that link climate and hydrology permit improved assessments of climate change impacts among watersheds. We used the Basin Characterization Model (BCM), a regional water balance model to (1) ask what is the magnitude of historical and projected future change in the hydrology of California’s watersheds; (2) test the spatial congruence of watersheds with the most historical and future hydrologic change; and (3) identify watersheds with high levels of hydrologic change under drier and wetter future climates. We assessed change for 5135 watersheds over a 60-year historical period and compared it to 90-year future projections. Watershed change was analyzed for climatic water deficit, April 1st snowpack, recharge, and runoff. Watersheds were ranked by change for the historical and twofuture scenarios. We developed a normalized index of hydrologic change that combined the four variables, and identified which watersheds show the most spatial congruence of large historical change and continued change under the two futures. Of the top 20%of all watersheds (1028), 591 in the Sierra Nevada Mountains and Northwestern eco-regions have high spatial congruence across all time periods. Among watersheds where change accelerates in the future, but not historically, a majority are congruent between both climate models, predominantly in the Sierra Nevada, Cascade Ranges and the Northwestern eco-regions. This congruence of impacts in watersheds under drier or wetter scenarios is driven by snowpack, but in areas with low snowpack, hydrologic change varied spatially depending on projected precipitation and temperature, with 151 watersheds in Northwestern California showing high levels of drying under the drier scenario, while 103 watersheds in Central western and Southwestern California show increasing hydrologic activity under the wetter scenario. In some regions, the loss of snowpack allows the cycle of runoff and recharge to function without delay represented by springtime snow melt, causing these watersheds to become more immediately hydrologically responsive to changing climate. The study also found watersheds with low rainfall that have already passed through their highest response to changing climate, and show less future change. The methods used here can also be used to identify watersheds resilient to changing climate.

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 Mohave Desert region, California--a geographic, geologic, and hydrologic reconnaissance

U.S. Geological Survey (USGS) | July 15th, 1929

The Monterey Amendments to State Water Project Contracts: A History

California Water Impact Network (C-WIN) | February 28th, 2010

Policy statement: C-WIN works to overturn the Monterey Plus amendments to the State Water Project contracts. To return the state mandated "Urban Preference"; to require t

Policy statement: C-WIN works to overturn the Monterey Plus amendments to the State Water Project contracts. To return the state mandated "Urban Preference"; to require the contracts to reflect water that is really there; to stop the abusive pumping of water that is not surplus; and to return the Kern Water Bank to the public to firm up the urban preference for the 22 million urban water users south of the Delta in times of drought. Drought from 1987 to 1992, and again in 1994, financial crisis among state water contractors, and the prospect of tighter regulation of Delta exports by the State Water Project (SWP) by the state and federal government provoked the project’s most serious crisis. In 1994 four of the SWP contractors, including the Metropolitan Water District of Southern California (MWD) and the Kern County Water Agency which together control about 75 percent of State Water Project allocations, and representatives from Paramount Farming (a private company), met secretly in Monterey to attempt to resolve their water shortage dilemma. The result was the Monterey Amendments to the State Water Project water service contracts.

The Monterey Plus Amendments to State Contracts: “Paper Water” and the Kern Water Bank Giveaway: A C-WIN Policy Brief

California Water Impact Network (C-WIN) | January 1st, 2012

Changes secretly made to the State Water Project by water contractors and the California Department of Water Resources in the 1990s, known as the Monterey Plus Amendments

Changes secretly made to the State Water Project by water contractors and the California Department of Water Resources in the 1990s, known as the Monterey Plus Amendments, caused ecological destruction in the Delta and made water supplies for State Water Project customers much more expensive and less reliable.

The Monterey Plus Amendments to State Water Contracts: It’s Chinatown, Jake

California Water Impact Network (C-WIN) | February 1st, 2014

In the 1990s, ,ive of the extant 29 State Water Project contractors secretly colluded with the California Department of Water Resources (DWR) to change SWP policy, a move

In the 1990s, ,ive of the extant 29 State Water Project contractors secretly colluded with the California Department of Water Resources (DWR) to change SWP policy, a move subsequently known as the Monterey Plus Amendments. These changes caused major disruptions in Delta ecosystems and made water less accessible and much more expensive for most State Water Project customers, especially during droughts. Urban ratepayers bore the brunt of the burden, as they found out to their profound dismay in the drought that beleaguered the state from 2007 to 2009. The Monterey Plus Amendments were concluded 17 years ago, but they are not established law, and are under current court challenge.

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

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