Survey Shows Areas of Land Subsidence in the Sacramento Valley

Data shows most of the valley has experienced little to no subsidence over the past nine years, with some exceptions

From the Department of Water Resources:

New data released today measure changes in land subsidence in the Sacramento Valley over the past nine years, finding the greatest land surface declines near the city of Arbuckle in Colusa County. According to the Sacramento Valley GPS Subsidence Network Report and accompanying fact sheet, most of the valley has experienced little to no subsidence, however, land in the Arbuckle area has sunk 2.14 feet compared with baseline measurements recorded in the same location in 2008. The report was led by the California Department of Water Resources (DWR), in coordination with 19 state and local agencies.

“We’ve long known that excessive groundwater pumping causes subsidence, which is one of the many reasons we’ve pushed for sustainable groundwater management and pursued innovative tools to better manage and report subsidence throughout the state,” said DWR Director Karla Nemeth. “Data provided by studies like this inform water managers and owners of large infrastructure so they can plan for and prevent against subsidence.”

Land subsidence can damage critical infrastructure, including water delivery systems, levees, roads, and bridges. In 2017, DWR worked with NASA to release a report on San Joaquin Valley subsidence citing areas along the California Aqueduct that have experienced almost two feet of subsidence over three years.

The Sacramento Valley survey results were collected as groundwater levels were recovering from the severe drought of 2012-16, which saw groundwater levels in much of the state reach historic lows. Compared with 2011 pre-drought groundwater levels, the largest decreases were observed in Glenn and Colusa counties at 58 to 43 feet, respectively. Field work indicates that groundwater levels have recovered an average of seven feet, but more frequent and more comprehensive monitoring is needed to more accurately detail the impacts of droughts and high-water years on groundwater levels and subsidence.

The Sacramento Valley GPS Subsidence Monitoring Network, launched by DWR in 2008, surveyed 300 measurement locations in 11 counties from Shasta County in the north to Solano and Sacramento counties in the south. The 2017 resurvey effort was led by DWR’s Division of Integrated Regional Water Management (DIRWM) Northern Region Office (NRO), with the assistance of 19 state, county, and local entities.

“The data provided in this report are an example of the technical assistance we provide and the collaborative effort needed to facilitate successful and sustainable groundwater plans at the local level,” said Taryn Ravazzini, DWR Deputy Director of Special Initiatives.

DWR offers several tools that assist groundwater agencies and the public assess aquifer conditions and plan for sustainable management, including:

  • Land Use Viewer: Allows local agencies and the public to access land use survey datasets for the past 30 years.
  • Well Completion Report Viewer: Provides information about wells collected during the drilling and construction of water wells.
  • SGMA Data Viewer: Compiles many groundwater related datasets that can be used to look at groundwater levels and subsidence.

The Sacramento Valley subsidence report also concludes that areas of Yolo County experienced the most widespread subsidence, in terms of geographic area affected by subsidence, with 31 survey sites measuring a land surface decline between .3 and 1.1 feet. Other statistically significant levels of subsidence were observed at three survey sites in Glenn County (between .44 and .59 feet of subsidence) and five survey sites in Sutter County (between .20 and .36 feet of subsidence).

Vignettes on Local Groundwater Management in the Sacramento Valley

The NorCal Water Association blog writes,

“Local leaders on the Sacramento Valley floor are well organized and coordinated with respect to groundwater management and the efforts to implement the Sustainable Groundwater Management Act (SGMA). Local Groundwater Sustainability Agencies (GSAs) are all working hard to manage groundwater in a sustainable manner with a focus on completing the initial Groundwater Sustainability Plans (GSPs) by January 2022.

With the emphasis on local agency implementation of SGMA, we have asked many of the local leaders to provide their perspective on local groundwater conditions and the management necessary to manage water resources in a sustainable manner. … “

Continue reading at the Northern California Water Association blog here:  Vignettes on Local Groundwater Management in the Sacramento Valley

Butte County: Comment taken on groundwater management area boundaries

From the Chico Enterprise-Record:

“Comment is being taken on proposed boundary changes related to the managing of groundwater beneath Butte County.

The Sustainable Groundwater Management Act requires development of plans to manage groundwater beneath California to avoid undesirable results like land sinking or wells going dry.  The plans are required for defined subbasins of the larger aquifers underground.

The Butte County Department of Water and Resource Conservation has applied to change the subbasin boundaries locally in response to requests by involved agencies, and that’s what the public is being invited to comment upon. …. “

Read more from the Chico Enterprise-Record here:  Comment taken on groundwater management area boundaries

Butte County: Groundwater management agencies before board

From the Chico Enterprise-Record:

“The structure of the agencies being established to manage the groundwater beneath Butte County is made clear by two items before the Butte County Board of Supervisors Tuesday.

The board is being asked to approve agreements to set up the Vina Groundwater Sustainability Agency and the Wyandotte Creek Groundwater Sustainability Agency.

Sustainability agencies are required under the Sustainable Groundwater Management Act, which was approved by the Legislature and signed by Gov. Brown in 2014. … “

Read more from the Chico Enterprise-Record here:  Butte County: Groundwater management agencies before board

Specialty Crop Expansion in the Sacramento Valley- An Exploration of Groundwater Recharge Opportunities

From the Northern California Water Association Blog:

Sacramento Area Council of Government (SACOG)’s Sustainable Water Management Strategies for Specialty Crop Expansion in the Sacramento Valley examined scenarios to consider optimal locations for strategic flooding of cropland to maximize groundwater infiltration and improve water supply reliability for continued specialty crop production and related economic activities.

The work completed has identified attributes in our region’s open space land that facilitate infiltration and those that limit groundwater recharge potential. The project also examined ways these flooding scenarios may provide habitat benefits. The project included a contractual study component to complement RUCS staff work and build upon in-kind services from industry stakeholders, including specialty crop stakeholders, and water resource managers. The contractual work provided technical support and subject-area expertise in groundwater recharge science. This included the collection of environmental data to underpin scenario analysis and enhance the RUCS toolkit; including regional water balances and other factors that impact recharge (e.g. soil type permeability).

Click here to continue reading at the Northern California Water Association blog.

ASU scientists use satellites to measure vital underground water resources

From Arizona State University:

The availability of water from underground aquifers is vital to the basic needs of more than 1.5 billion people worldwide, including those of us who live in the western United States. In recent decades, however, the overpumping of groundwater, combined with drought, has caused some aquifers to permanently lose essential storage capacity.

With the hope of providing water resource managers with better tools to help keep aquifers healthy, a team of scientists from Arizona State University and the Jet Propulsion Laboratory (JPL) are using the latest space technology to look underneath Earth’s surface to measure this precious natural resource.

They’ve focused their efforts on one of the world’s largest aquifer systems, located in California’s Central Valley, measuring both its groundwater volume and its storage capacity. The results of their most recent findings in this groundbreaking study have been recently published in Water Resources Research.

Click here to continue reading from Arizona State University.

The Yuba Accord: A Model for Water Management

From Ellen Hanak at the PPIC Blog:

“Last week a diverse group of stakeholders celebrated the tenth anniversary of the Lower Yuba River Accord—a historic agreement to improve conditions for the river’s endangered fishes, maintain water supplies for cities and farms, and reduce conflict over competing uses for water. Here at the PPIC Water Policy Center we frequently refer to the Yuba Accord as a model for modern water management in California. Here are three reasons why. … “

Continue reading at the PPIC Blog by clicking here.