Divergent effects of climate change on future groundwater availability in key mid-latitude aquifers

Nature Portfolio (Springer Nature) | July 24th, 2020

Groundwater provides critical freshwater supply, particularly in dry regions where surface water availability is limited. Climate change impacts on GWS (groundwater stora

Groundwater provides critical freshwater supply, particularly in dry regions where surface water availability is limited. Climate change impacts on GWS (groundwater storage) could affect the sustainability of freshwater resources. Here, we used a fully-coupled climate model to investigate GWS changes over seven critical aquifers identified as significantly distressed by satellite observations. We assessed the potential climate-driven impacts on GWS changes throughout the 21st century under the business-as-usual scenario (RCP8.5). Results show that the climate-driven impacts on GWS changes do not necessarily reflect the long-term trend in precipitation; instead, the trend may result from enhancement of evapotranspiration, and reduction in snowmelt, which collectively lead to divergent responses of GWS changes across different aquifers. Finally, we compare the climate-driven and anthropogenic pumping impacts. The reduction in GWS is mainly due to the combined impacts of over-pumping and climate effects; however, the contribution of pumping could easily far exceed the natural replenishment.

Diverse stakeholders create collaborative, multilevel basin governance for groundwater sustainability

California Agriculture (UCANR) | March 13th, 2018

The Sustainable Groundwater Management Act (SGMA) is introducing significant changes in the way groundwater is governed for agricultural use. It requires the format

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.

Documentation of a Groundwater Flow Model (SJRRPGW) for the San Joaquin River Restoration Program Study Area, California

U.S. Geological Survey (USGS) | September 23rd, 2014

To better understand the potential effects of restoration flows on existing drainage problems, anticipated as a result of the San Joaquin River Restoration Program (SJRRP

To better understand the potential effects of restoration flows on existing drainage problems, anticipated as a result of the San Joaquin River Restoration Program (SJRRP), the U.S. Geological Survey (USGS), in cooperation with the U.S. Bureau of Reclamation (Reclamation), developed a groundwater flow model (SJRRPGW) of the SJRRP study area that is within 5 miles of the San Joaquin River and adjacent bypass system from Friant Dam to the Merced River. The primary goal of the SJRRP is to reestablish the natural ecology of the river to a degree that restores salmon and other fish populations. Increased flows in the river, particularly during the spring salmon run, are a key component of the restoration effort. A potential consequence of these increased river flows is the exacerbation of existing irrigation drainage problems along a section of the river between Mendota and the confluence with the Merced River. Historically, this reach typically was underlain by a water table within 10 feet of the land surface, thus requiring careful irrigation management and (or) artificial drainage to maintain crop health. The SJRRPGW is designed to meet the short-term needs of the SJRRP; future versions of the model may incorporate potential enhancements, several of which are identified in this report. The SJRRPGW was constructed using the USGS groundwater flow model MODFLOW and was built on the framework of the USGS Central Valley Hydrologic Model (CVHM) within which the SJRRPGW model domain is embedded. The Farm Process (FMP2) was used to simulate the supply and demand components of irrigated agriculture. The Streamflow-Routing Package (SFR2) was used to simulate the streams and bypasses and their interaction with the aquifer system. The 1,300-square mile study area was subdivided into 0.25-mile by 0.25-mile cells. The sediment texture of the aquifer system, which was used to distribute hydraulic properties by model cell, was refined from that used in the CVHM to better represent the natural heterogeneity of aquifer-system materials within the model domain. In addition, the stream properties were updated from the CVHM to better simulate stream-aquifer interactions, and water-budget subregions were refined to better simulate agricultural water supply and demand. External boundary conditions were derived from the CVHM. The SJRRPGW was calibrated for April 1961 to September 2003 by using groundwater-level observations from 133 wells and streamflow observations from 19 streamgages. The model was calibrated using public-domain parameter estimation software (PEST) in a semi-automated manner. The simulated groundwater-level elevations and trends (including seasonal fluctuations) and surface-water flow magnitudes and trends reasonably matched observed data. The calibrated model is planned to be used to assess the potential effects of restoration flows on agricultural lands and the relative capabilities of proposed SJRRP actions to reduce these effects.

Documentation of Model Input and Output Values for the Geohydrology and Mathematical Simulation of the Pajaro Valley Aquifer System, Santa Cruz and Monterey Counties, California

U.S. Geological Survey (USGS) | July 14th, 1990

As part of a study of the geology and hydrology of the Pajaro Valley aquifer system, Santa Cruz and Monterey Counties, California, a three-layer mathematical mode

As part of a study of the geology and hydrology of the Pajaro Valley aquifer system, Santa Cruz and Monterey Counties, California, a three-layer mathematical model was developed, using the computational algorithm of McDonald and Harbaugh (1984). The results of the Pajaro Valley study are given by Johnson and others (1988).

Domestic well vulnerability to drought duration and unsustainable groundwater management in California's Central Valley

Environmental Research Letters (IOP) | March 18th, 2020

Millions of Californians access drinking water via domestic wells, which are vulnerable to drought and unsustainable groundwater management. Groundwater overdraft and th

Millions of Californians access drinking water via domestic wells, which are vulnerable to drought and unsustainable groundwater management. Groundwater overdraft and the possibility of longer drought duration under climate change threatens domestic well reliability, yet we lack tools to assess the impact of such events. Here, we leverage 943,469 well completion reports and 20 years of groundwater elevation data to develop a spatially-explicit domestic well failure model covering California’s Central Valley. Our model successfully reproduces the spatial distribution of observed domestic well failures during the severe 2012–2016 drought (n=2027). Next, the impact of longer drought duration (5–8years) on domestic well failure is evaluated, indicating that if the 2012–2016 drought would have continued into a 6 to 8 year long drought, a total of 4037–5460 to 6538–8056 wells would fail. The same drought duration scenarios with an intervening wet winter in 2017 lead to an average of 498 and 738 fewer well failures. Additionally, we map vulnerable wells at high failure risk and find that they align with clusters of predicted well failures. Lastly, we evaluate how the timing and implementation of different projected groundwater management regimes impact groundwater levels and thus domestic well failure. When historic overdraft persists until 2040, domestic well failures range from 5966 to 10 466 (depending on the historic period considered). When sustainability is achieved progressively between 2020 and 2040, well failures range from 3677 to 6943, and from 1516 to 2513 when groundwater is not allowed to decline after 2020.

Draft EIR Monterey Amendment to the State Water Project Contracts (Including Kern Water Bank Transfer) and Associated Actions as Part of a Settlement Agreement (Monterey Plus)

California Department of Water Resources (DWR) | April 1st, 2015

The California Department of Water Resources (Department), as the lead agency under the California Environmental Quality Act (CEQA), prepared the environmental impact rep

The California Department of Water Resources (Department), as the lead agency under the California Environmental Quality Act (CEQA), prepared the environmental impact report (EIR) for the Monterey Amendment to the State Water Project Contracts (Including Kern Water Bank Transfer) and Associated Actions as Part of a Settlement Agreement (Monterey Plus) (Monterey Plus EIR). The Department certified the Monterey Plus EIR on February 1, 2010. Several parties challenged the adequacy of the Monterey Plus EIR under CEQA. In 2014, the Monterey Plus EIR was found by the Sacramento County Superior Court (Court) to comply with CEQA in all aspects except with respect to the development, use, and operation of the Kern Water Bank (KWB). The Court specified that the Department is to correct the deficiencies and recertify the EIR without reopening the non-defective portions of the EIR. Upon recertification, only those portions of the Revised EIR (REIR) that are new or changed shall be subject to challenge under CEQA by petitioners or other interested parties. For these reasons, the Department has developed this three-volume Monterey Plus Draft Revised EIR. Document A1 presents all the changes to the Monterey Plus EIR made as a result of the Department’s reanalysis of the Kern Fan Element (KFE) property transfer and new analysis of the KWB development and continued use and operation.  Since DWR decertified the Monterey Plus EIR, pursuant to the Court’s order, the Revised EIR also includes, without modification, the 2007 Draft EIR (Document B, including Volumes I and II) and the 2010 Final EIR (Document C, including Volumes I and II). Together, the three documents constitute the Monterey Plus Draft Revised EIR (Figure P-1). The Draft Revised EIR focuses on the development and continued use and operations of the KWB near Bakersfield. Potentially significant impacts before mitigation were related to groundwater levels and quality, Kern River water quality, the Cross Valley Canal, terrestrial biological resources, erosion, hazardous materials, waterborne disease, cultural and paleontological resources, greenhouse gas emissions, and cumulative impacts.  Potentially significant and unavoidable impacts were related to cumulative growth-related impacts. The Draft Revised EIR identifies hazardous sites on or near KWB Lands that have been remediated.

Draft Final Groundwater Sustainability Plan for the Borrego Springs Groundwater Subbasin

Borrego Water District (BWD) | August 30th, 2019

The Borrego Valley Groundwater Sustainability Agency (GSA, Agency), which comprises the Borrego Water District (BWD) and the County of San Diego (County), developed a Gro

The Borrego Valley Groundwater Sustainability Agency (GSA, Agency), which comprises the Borrego Water District (BWD) and the County of San Diego (County), developed a Groundwater Sustainability Plan (GSP, Plan) to provide a structure to enable local government, groundwater users and the local community to work together to achieve sustainable use of groundwater resources in the Borrego Springs Groundwater Subbasin (Subbasin) (California Department of Water Resources (DWR) Basin No. 7.024.01) of the Borrego Valley Groundwater Basin. The GSP was subsequently repurposed as a Groundwater Management Plan (GMP), an integral part of a Physical Solution in a groundwater rights adjudication consistent with the requirements of the Sustainable Groundwater Management Act (SGMA). The purpose of this GMP is to refine and expedite implementation of the Physical Solution and to avoid litigation over the GSP and its associated Project and Management Actions (PMAs). The GSP and this resulting GMP was developed through a process of stakeholder negotiation among major water users, landowners and government agencies. Specifically, this GMP is adopted as part of the Physical Solution by means of a Judgment. The Judgment was agreed to by Stipulating Parties accounting for more than 75% of groundwater production and more than 50% of non-minimal producer well owners as an alternative to the GSA/GSP process for the Borrego Springs Subbasin under SGMA (California Water Code Sections 10733.6 and 10737.4). This GMP includes and is to be interpreted and implemented consistent with and subject to the provisions of the Judgment. The provisions of the Judgment control over and supersede any contrary provisions contained in this GMP. Due to size, this file has been divided. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6

Drawdown ‘‘Triggers’’: A Misguided Strategy for Protecting Groundwater-Fed Streams and Springs

National Groundwater Association (NGWA) | October 31st, 2016

There is increasing recognition of the importanceof groundwater to the survival and function of terrestrial ecosystems (e.g., Ribeiro et al. 2013), which has grown from

There is increasing recognition of the importanceof groundwater to the survival and function of terrestrial ecosystems (e.g., Ribeiro et al. 2013), which has grown from understanding of the intimate connections between groundwater and surface water (Winter et al.1998). In this context, management strategies that can protect groundwater-dependent ecosystems (GDEs) such as springs and groundwater-fed streams are of critical importance. One strategy being adopted in some casesis the use of “drawdown triggers.” This involves specifying an amount of acceptable drawdown relative to baseline at a particular monitoring point, which if exceeded, triggers a management response. This technical commentary examines this strategy, highlighting potential pit-falls. There are important aspects of the response of groundwater and connected springs and streams which may be overlooked if drawdown triggers are adopted as the primary strategy for GDE protection. A case study of a recently approved mining project is discussed and some additional and/or alternative approaches proposed.

Drift of Earth's Pole Confirms Groundwater Depletion as a Significant Contributor to Global Sea Level Rise 1993–2010

American Geophysical Union (AGU) | June 15th, 2023

Drinking Water and Exclusion: A Case Study from California's Central Valley

California Law Review | February 1st, 2012

The American West is notorious for its water wars, and California's complex water allocation and governance challenges serve as a bellwether for contemporary water gove

The American West is notorious for its water wars, and California's complex water allocation and governance challenges serve as a bellwether for contemporary water governance across western states, Policy makers and environmental advocates typically represent California's water woes as a regulatory problem - a failure to balance the needs of growing urban populations with ecological preservation and agricultural irrigation. These debates, however, often elide the issue of water deprivation, and they do not adequately address the concerns of an important constituency: low-income, rural communities. This Comment argues that a focus on regulation misses a fundamental feature of water inequality: the structure and design of local water districts. Utilizing a case study of California's Central Valley to illustrate how these structural barriers operate, I argue that Calfornia's complex system of local water districts fractures governance, limits electoral participation, and undermines the State's stated environmental, equity, and utilitarian water goals. I offer suggestions for alternative local water district organization in order to address the constraints of Calfornia's current water governance regime.