University of California

Presentations 2016

Cehrs, David

Presentation Title
Groundwater Management: Past, Present, and Future in the Upper Kings Basin of the Central Valley, California
Institution
Kings River Conservation District
Presentation
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Cehrs5
Abstract
The Upper Kings Basin is located in California’s Central Valley. It resides on the east side of the valley floor between the valley axis and the Sierran foothills of Fresno County. It contains some of the most productive agricultural land within California. This basin experienced no long term, groundwater overdraft until 1950 and recovered from the 1924-1934 drought within four years. Post 1950, the basin has experienced a continual groundwater overdraft averaging about 209.6 million m3 (170,000 acre feet(af)) per year. This has been driven by increasing irrigated agricultural lands, conversion of dryland farmed agriculture to permanent cropped, irrigated agriculture, and increasing urban water demand due to population growth. The greatest water table declines occur below agricultural areas with no surface water delivery, relying on groundwater for irrigation, and metropolitan Fresno/Clovis, which until 2007 relied solely on groundwater. The areas within the basin with the least overdraft are beneath irrigation districts with surface water deliveries and use supplementary groundwater during low delivery years.Four years of drought have stressed the groundwater system as surface water availability has declined. Within the basin, the 2015 groundwater overdraft will approach 2.4 billion m3 (1.9 million af) with the dominant groundwater management mode being a “race to the bottom”. The basin has the potential to achieve future sustainability by the use of cyclic groundwater recharge and storage. This will be driven by capture and recharge of Kings River flood flows. During flood years the basin needs to recharge between 246.6 million m3 and 739.8 million m3 (200,000 af to 600,000 af) of flood flow in 90 to 120 days in dedicated groundwater recharge basins, recharge wells, over irrigation of crops, and dormant flooding of crops. Other management tools will include: fallowing of some agricultural land, mainly land with no access to surface water, limits on groundwater only irrigated agriculture to perhaps 7620 m3/hectare (2.5 af/acre) per year, and urban conservation, specifically the limiting of landscaping irrigation. These future management practices will be driven by California’s 2014 Sustainable Groundwater Management Act through at least five Groundwater Sustainablility Agencies (GSA) within the basin. Critical to achieving groundwater sustainability is the ability of each GSA to individually moderate its groundwater use but for all the GSA’s to work together in recharging wet year flood flows for the benefit of the entire basin.

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