California Agriculture
California Agriculture
California Agriculture
University of California
California Agriculture

Current issue and featured articles

CAv072n01
Special Issue
The Sustainable Groundwater Management Act
January-March 2018
Volume 72, Number 1
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INTRODUCTION
Special Issue: The Sustainable Groundwater Management Act
by Jim Downing
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This special issue of California Agriculture focuses on the implications of the Sustainable Groundwater Management Act, or SGMA, the package of bills signed into law by California Gov. Jerry Brown in September 2014.
EDITORIAL
Supporting sustainable groundwater management
by Faith Kearns, Doug Parker
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UC Agriculture and Natural Resources (UC ANR) is working to develop one of the most promising groundwater recharge approaches — replenishing aquifers by spreading wintertime river flood flows onto farm lands and other open spaces.
RESEARCH NEWS
UC groundwater research: A survey
by Jim Downing
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As California implements the Sustainable Groundwater Management Act (SGMA), UC research is building knowledge and supporting innovation in groundwater recharge, groundwater accounting, groundwater quality, groundwater governance and more. Here's a sample of work from across the UC system.
CONVERSATION
Four decades of sustainable groundwater management
by Jim Downing
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An interview with Peter Kavounas, General Manager, Chino Basin Watermaster
CONVERSATION
Enforcing the Sustainable Groundwater Management Act
by Jim Downing
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An interview with Sam Boland-Brien, Groundwater Management Program Chief, California State Water Resources Control Board
CONVERSATION
A seat at the table for rural drinking water
by Jim Downing
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An interview with Adriana Renteria, Regional Water Management Coordinator, Community Water Center
CONVERSATION
Advocating for growers as SGMA moves forward
by Jim Downing
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An interview with Christina Beckstead, Executive Director, Madera County Farm Bureau
OUTLOOK
Can we speed this up?
by Ronald C. Griffin
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A perspective on SGMA from outside California

Peer-reviewed research and review articles

How are Western water districts managing groundwater basins?
by Claire Newman, Richard Howitt, Duncan MacEwan
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A study of 18 districts finds that common groundwater management approaches that minimize economic impacts to agricultural users include low-cost monitoring and a flexible combination of supply augmentation and demand management.
Making the transition from open-access groundwater rights to sustainable groundwater management is a formidable task for newly formed groundwater sustainability agencies in California. As agencies begin to decide how to make equitable water allocations, how to monitor groundwater use and what mix of supply- and demand-side mechanisms to adopt to satisfy sustainability criteria, the groundwater management strategies in place across other basins in the western United States are worth studying. We surveyed 18 groundwater districts in California and other Western states to identify the management approaches and practices they have instituted. The conclusions we draw suggest a correlative rights framework of water allocation with phase-ins for heavy users; metered pumping; flexible arrangements for trading and carrying over allocations for multiple years; and incentivizing groundwater recharge, including recharge from deep percolation from crops. Rigid formulas for significantly reducing groundwater use in medium- and high-priority basins are likely to have significant negative effects on the regional economy.
Farmers share their perspectives on California water management and the Sustainable Groundwater Management Act
by Meredith T. Niles, Courtney Hammond Wagner
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Focus groups with Yolo County farmers demonstrate that farmers' perceptions of and responses to the regulation are important to its success.
Agriculture is the largest human use of water in California, which gives farmers a critical role in managing water to meet the goals of the Sustainable Groundwater Management Act (SGMA). To explore farmers' perspectives on SGMA, we held focus groups with 20 farmers in Yolo County, where the groundwater basin has been given a high/medium priority under SGMA. The farmers had varying perspectives about the factors that led to SGMA and varying responses to the regulation. They suggested that drought, competing agricultural and urban uses, and an increase in perennial crops were factors in recent water use, resulting in changes to water quality and quantity. Impacts of those changes included variable well levels, increased infrastructure costs, and ecosystem impacts, which farmers had responded to by implementing multiple management strategies. Additional research in other regions is imperative to provide farmers' viewpoints and strategies to policymakers, irrigation districts, farmer cooperatives, and the agricultural industry and give farmers a voice at the table.
Diverse stakeholders create collaborative, multilevel basin governance for groundwater sustainability
by Esther Conrad, Tara Moran, Marcelle E. DuPraw, David Ceppos, Janet Martinez, William Blomquist
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Groundwater sustainability agencies recently formed in three large groundwater basins in the Central Valley have developed innovative ways to incorporate farmers' voices and respect local autonomy.
The Sustainable Groundwater Management Act (SGMA) is introducing significant changes in the way groundwater is governed for agricultural use. It requires the formation of groundwater sustainability agencies (GSAs) to manage groundwater basins for sustainability with the engagement of all users. That presents opportunities for collaboration, as well as challenges, particularly in basins with large numbers of agricultural water users who have longstanding private pumping rights. The GSA formation process has resulted in the creation of multiple GSAs in many such basins, particularly in the Central Valley. In case studies of three basins, we examine agricultural stakeholders' concerns about SGMA, and how these are being addressed in collaborative approaches to groundwater basin governance. We find that many water districts and private pumpers share a strong interest in maintaining local autonomy, but they have distinct concerns and different options for forming and participating in GSAs. Multilevel collaborative governance structures may help meet SGMA's requirements for broad stakeholder engagement, our studies suggest, while also addressing concerns about autonomy and including agricultural water users in decision-making.
How can we support the development of robust groundwater sustainability plans?
by Vishal K. Mehta, Charles Young, Susan R. Bresney, Daniel S. Spivak, Jonathan M. Winter
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A decision support process helped stakeholders in Yolo County understand the vulnerabilities of their groundwater situation and evaluate strategies to overcome them.
Three years after California passed the Sustainable Groundwater Management Act (SMGA), groundwater sustainability agencies (GSAs) are now preparing to develop their groundwater sustainability plans (GSPs), the blueprints that will outline each basin's road to sustainability. Successful GSPs will require an effective participatory decision-making process. We tested a participatory process with the Yolo County Flood Control and Water Conservation District, a water-limited irrigation district in the Central Valley. First, we worked with district stakeholders to outline the parts of the plan and set measureable objectives for sustainability. The district defined seven management strategies, which the research team evaluated against climate, land use and regulatory uncertainties using a water resources model. Together, we explored model results using customized interactive graphics. We found that the business-as-usual strategy was the most unlikely to meet sustainability objectives; and that a conjunctive use strategy, with winter groundwater recharge and periphery ponds storage, achieved acceptable measures of sustainability under multiple uncertainties, including a hypothetical pumping curtailment. The process developed a shared understanding of the vulnerabilities of the local groundwater situation and proved valuable in evaluating strategies to overcome them.
Managed winter flooding of alfalfa recharges groundwater with minimal crop damage
by Helen E. Dahlke, Andrew G. Brown, Steve Orloff, Daniel Putnam, Toby O'Geen
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Over 90% of the water applied to sites in Davis and Scott Valley percolated to recharge groundwater, making this a viable practice on highly permeable soils.
It is well known that California experiences dramatic swings in precipitation that are difficult to predict and challenging to agriculture. In times of drought, groundwater serves as a crucial savings account that is heavily relied upon. However, few tools exist to proactively refill this crucial reserve in wet years. We explored the idea of intentional winter flooding of agricultural land to promote on-farm recharge of the underlying groundwater. Field experiments were conducted on two established alfalfa stands to determine the feasibility of groundwater recharge and test realistic water application amounts and timings and potential crop damage. We studied soils with relatively high percolation rates and found that most of the applied water percolated to the groundwater table, resulting in short-lived saturated conditions in the root zone and minimal yield loss. While caution is appropriate to prevent crop injury, winter recharge in alfalfa fields with highly permeable soils appears to be a viable practice.
Paso Robles vineyard irrigation study provides benchmark data to assist future area groundwater management
by Mark C. Battany, Gwen Tindula
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Researchers have identified baseline irrigation application data that can help groundwater sustainability agencies estimate regional irrigation usage for wine grape crops.
Accurate information on irrigation water usage does not exist in many areas where groundwater is the primary water source. This lack of information will hinder efforts to manage these groundwater basins sustainably according to current and future water regulations and policies. Using a low-cost methodology of irrigation-line pressure sensors connected to data loggers, we estimated irrigation applications at 84 vineyard sites in the Paso Robles Groundwater Basin over 4 years (2010–2013). We compared irrigation amounts with the preceding winter's rainfall and with the growing season reference evapotranspiration (ETo). Over the study period, the average annual irrigation application was 11.46 inches (291 millimeters). The average annual application correlated inversely to the preceding winter's rainfall, while the irrigation over the growing season (April–October) correlated directly with the ETo over this same period. This study provides an initial data framework that can be used by groundwater sustainability agencies to help manage groundwater in the Paso Robles area. The methodology also could be utilized in other regions to estimate regional irrigation usage while maintaining anonymity for participants.
Modeling guides groundwater management in a basin with river–aquifer interactions
by Laura Foglia, Jakob Neumann, Douglas G. Tolley, Steve Orloff, Richard L. Snyder, Thomas Harter
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A Scott Valley study shows gains in understanding seasonal dynamics of groundwater–surface water fluxes as model tools address more complex natural phenomena.
The Sustainable Groundwater Management Act (SGMA) of 2014 seeks to maintain groundwater discharge to streams to support environmental goals. In Scott Valley, in Siskiyou County, the Scott River and its tributaries are an important salmonid spawning habitat, and about 10% of average annual Scott River stream flow comes from groundwater. The local groundwater advisory committee is developing groundwater management alternatives that would increase summer and early fall stream flows. We developed a model to provide a framework to evaluate those alternatives. We first created a water budget for the Scott Valley groundwater basin and integrated the detailed, spatiotemporally distributed water budget results into a computer model of the basin that simultaneously accounted for groundwater flow, stream flow and landscape water fluxes. Different conceptual representations (using the MODFLOW RIV package and MODFLOW SFR package) of the stream–aquifer boundary provided significantly different results in the seasonal dynamics of groundwater–surface water fluxes. As groundwater sustainability agencies draw up plans to meet SGMA requirements, they must choose and test simulation tools carefully.

Early view articles

OUTLOOK
The race in the fields: Imports, machines and migrants
by Philip Martin
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The slowdown in unauthorized Mexico–U.S. migration has set off a race in U.S. agriculture between rising imports, more machines, and foreign guest workers. Trade policy, including North American Free Trade Agreement (NAFTA) re-negotiations, and immigration policy, including more enforcement and new or revised guest worker programs, will determine the winner.
PEER-REVIEWED
Employment and earnings of California farmworkers in 2015
by Philip Martin, Brandon Hooker, Marc Stockton
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A review of wage data from agricultural employers suggests that most California farmworkers were employed for less than a full year in 2015.
The average employment of hired workers in California agriculture (NAICS 11) rose over 10% between 2005 and 2015, when some 16,400 agricultural establishments hired an average 421,300 workers who were paid a total of $12.8 billion, which was 27% of the state's $47 billion in farm sales. This means that a full-time equivalent (FTE) employee would earn $30,300, implying an hourly wage of $14.55 for 2,080 hours of work. We extracted all Social Security numbers reported by California agricultural establishments and found that the average annual pay received by the 848,000 workers who had at least one job on California farms was $20,500 in 2015, two-thirds of the average annual wage of an FTE worker, reflecting some combination of lower wages and less than full-year work.
PEER-REVIEWED
Automated lettuce thinners reduce labor requirements and increase speed of thinning
by Elizabeth Mosqueda, Richard Smith, Dave Goorahoo, Anil Shrestha
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Automated thinners were as accurate in thinning lettuce as manual thinning, produced comparable yields, and were more than three times faster than thinning crews.
Salinas Valley lettuce growers are adopting automated lettuce thinners to improve labor efficiency. We conducted field studies in 2014 and 2015 to compare the time involved in automated and manual thinning of direct-seeded lettuce and any differences in lettuce quality and yield. We recorded the number of doubles (two closely spaced plants) left behind after thinning, time taken to remove the doubles, final crop stand, efficiency in weed removal, crop yield and disease incidence. Using an automated thinner in place of manual hoeing reduced the thinning labor requirement from 7.31 ± 0.5 person-hours per acre to 2.03 ± 0.5 person-hours per acre. Automated thinning left more doubles than manual thinning, resulting in additional time to remove them, but was overall more labor-efficient and had no impact on yield or disease incidence.
Editor Jim Downing talks about the special issue of California Agriculture on the Sustainable Groundwater Management Act.

 

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