Pajaro Valley Basin Management Plan Groundwater Sustainability Update 2022

Pajaro Valley Water Management Agency (PVWMA) | November 17th, 2021

Pajaro Valley Water Management Agency Basin Management Plan Update

Pajaro Valley Water Management Agency (PVWMA) | February 14th, 2014

Pajaro Valley Water Management Agency Revised Management Plan

Pajaro Valley Water Management Agency (PVWMA) | February 14th, 2002

Preliminary Evaluation of Impacts of Potential Groundwater Sustainability Indicators on Future Groundwater Extraction Rates – Oxnard Plain and Pleasant Valley Groundwater Basins

United Water Conservation District (UWCD) | April 4th, 2017

This evaluation was performed to estimate the combined sustainable yield of the Oxnard Plain (including the Forebay) and Pleasant Valley groundwater basins (the study are

This evaluation was performed to estimate the combined sustainable yield of the Oxnard Plain (including the Forebay) and Pleasant Valley groundwater basins (the study area). The purpose is to provide supporting information to United Water Conservation District’s (United) management and Board of Directors in establishing groundwater management policies that are consistent with the mission of the agency. United recognizes that the compliance actions associated with the Sustainable Groundwater Management Act (SGMA), the formation of a Groundwater Sustainability Agency (GSA), and the creation and implementation of Groundwater Sustainability Plans (GSPs) have the potential to change how groundwater resources are managed in Ventura County. This report was prepared for the benefit of United’s Board of Directors and senior management, and is not intended to serve as a GSP, define how the sustainable yield should be determined by the GSA, or specify what value or range of values should be used as the sustainable yield. The analyses and results are meant to be used as a starting point in evaluating potential impacts to United’s operations as a result of sustainability planning already underway by the Fox Canyon Groundwater Management Agency (FCGMA) for the study area. Note: an addendum to this was published on November 7, 2017

Projected responses of the coastal water table for California using present-day and future sea-level rise scenarios

U.S. Geological Survey (USGS) | August 11th, 2020

Coastal groundwater levels (heads) can increase with sea level rise (SLR) where shallow groundwater floats on underlying seawater. In some areas coastal groundwater could

Coastal groundwater levels (heads) can increase with sea level rise (SLR) where shallow groundwater floats on underlying seawater. In some areas coastal groundwater could rise almost as much as SLR, but where rising groundwater intersects surface drainage features, the increase will be less. Numerical modeling can provide insight into coastal areas that may be more or less vulnerable to hazards associated with SLR-driven groundwater shoaling (moving closer to the ground surface) and emergence (flooding the ground surface), providing coastal planners with critical information that can be used to increase public safety, mitigate physical damages, and more effectively manage and allocate resources in complex coastal settings. Seamless unconfined groundwater heads for coastal California groundwater systems were modeled with homogeneous, steady-state MODFLOW simulations. The geographic extent examined was limited primarily to low-elevation (land surface less than approximately 10 m above mean sea level) areas. In areas where coastal elevations increase rapidly (e.g., bluff stretches), the model boundary was set approximately 1 kilometer inland of the present-day shoreline. Steady-state MODFLOW groundwater flow models were used to obtain detailed (10-meter-scale) predictions over large geographic scales (100s of kilometers) of groundwater heads for both current and future sea-level rise (SLR) scenarios (0 to 2 meters (m) in 0.25 m increments, 2.5 m, 3 m, and 5 m) using a range of horizontal hydraulic conductivity (Kh) scenarios (0.1, 1, and 10 m/day). For each SLR/Kh combination, results are provided for two marine boundary conditions; local mean sea level (LMSL) and mean higher-high water (MHHW), and for two model versions. In the first model version, groundwater reaching the land surface is removed from the model, simulating loss via natural drainage. In the second model version, SLR impacts are modeled by simply raising the present-day (SLR 0m) modeled groundwater head by the amount of sea-level rise, simulating the worst-case "linear" response to sea-level rise. Modeled groundwater heads were then subtracted from high-resolution topographic digital elevation model (DEM) data to obtain water table depths. Groundwater head and water table depths are presented in raster GeoTIFF format. Polygon shapefiles also present water table depths by depth range (emergent, 0 to 1, 1 to 2, 2 to 5, and greater than 5 meters depth). All results are presented by County.

Pure Water Soquel Groundwater Model Simulation Results

Soquel Creek Water District | June 22nd, 2018

This technical memorandum discusses model simulation groundwater levels, groundwater budget, and particle tracking results to support the Environmental Impact Rep

This technical memorandum discusses model simulation groundwater levels, groundwater budget, and particle tracking results to support the Environmental Impact Report of the Pure Water Soquel project involving replenishment of advanced purified recycled water within Soquel Creek Water District’s (SqCWD’s) service area. Six model simulations have been run using the calibrated GSFLOW model for the Santa Cruz Mid- County Basin (the Basin) where SqCWD’s service area is located. These simulations have different pumping and active replenishment distributions, as follows: Two Projected Existing Conditions (No Project) simulations with SqCWD’spumping distribution reflecting future demand without additional replenishment at proposed recharge wells. Two Project simulations with SqCWD’s pumping distribution reflecting future demand and pumping re-distribution with the addition of replenishment at the Monterey and Cabrillo College Dr. sites (referred to as the Cabrillo-Monterey simulations). These simulations also represent potential replenishment at the Twin Lakes Church site instead of one of the two Cabrillo College Dr. sites. The Twin Lakes Church site is approximately 500-750 feet to the west of the Cabrillo College Dr. sites. Two Project simulations with the same pumping distribution as the Cabrillo- Monterey simulations, but with replenishment at the Monterey and Willowbrook sites (referred to as the Monterey-Willowbrook simulations).Simulation groundwater levels are evaluated for the following effects: Comparison of groundwater levels at coastal monitoring wells to protective elevations estimated to prevent seawater intrusion from further occurring in groundwater supply aquifers. Groundwater levels in the recharge wells to assess whether model results are consistent with estimated capacities for the well, recognizing that site specific testing will be needed to confirm recharge well capacities. Groundwater levels at nearby wells to evaluate effects on operation of those municipal, private, and institutional wells.Simulation groundwater budgets are evaluated for following effects: • Flows entering and leaving the Basin, including flows to and from groundwater in storage and flows offshore to prevent seawater intrusion. • Flows between groundwater and surface water. This memo does not include results for a Cumulative simulation. Information from the City of Santa Cruz to define its Aquifer Storage and Recovery project to be cumulative with Pure Water Soquel is not available or developed at this time. This memo includes results from particle tracking based on the above simulations performed to support the Salt and Nutrient Anti-degradation Study and permitting of the recharge wells. This involves particle tracking of simulated purified, replenishment water to evaluate the fate of the water as it travels in subsurface aquifers. Particle tracking is also used to evaluate travel times of purified, replenishment water, which requires refined analysis near the recharge wells. A scope to superimpose analytic element solutions for recharge and nearby extraction wells onto GSFLOW results to facilitate travel time calculations was approved by SqCWD Board December 18, 2017 and results should be forthcoming in July 2018.

Recommendations to Address the Expansion of Seawater Intrusion in the Salinas Valley Groundwater Basin

Monterey County Water Resources Agency (MCWRA) | October 12th, 2017

This report provides a discussion of the current knowledge and related background information surrounding seawater intrusion pathways and potential impacts ther

This report provides a discussion of the current knowledge and related background information surrounding seawater intrusion pathways and potential impacts thereof on the Salinas Valley Groundwater Basin. This document also serves as a body of evidence to catalogue the findings used to support the recommendations presented herein. Staff is making six recommendations, with each focused on a component that influences, or could be impacted by, the advancement of seawater intrusion. The recommendations are being presented in an order that builds upon the foundational knowledge laid out in the background section of this report, rather than in an order of priority. Each recommendation can be implemented on its own or in concert with the others, and the relative importance of each will be discussed individually in this report. However, the recommendations have been conceptualized as a comprehensive solution that, along with continued operation of projects that have been constructed for the same purpose, have the strongest potential to ensure success in slowing or halting further seawater intrusion when implemented simultaneously.

Resistivity imaging reveals complex pattern of saltwater intrusion along Monterey coast

Journal of Hydrology (Elsevier) | February 22nd, 2017

A coastal region represents a dynamic zone where fresh groundwater in the coastal aquifers interacts with saline ocean water. The location of the freshwater-saltwater int

A coastal region represents a dynamic zone where fresh groundwater in the coastal aquifers interacts with saline ocean water. The location of the freshwater-saltwater interface is governed by the density and pressure differences on the two sides of the interface and the subsurface hydrologic properties that control fluid movement. Saltwater intrusion is the process in which this interface moves landward, with saltwater then occupying parts of the aquifer that were once fresh. While this process has been observed and documented throughout the world for over a century (Bear et al., 1999), climate change, growing water demands, and manipulation of natural hydrologic systems have led to saltwater intrusion being considered a significant threat to future freshwater resources globally (Kinzelbach et al., 2003; Barlow and Reichard, 2009; Werner et al., 2013). Saltwater intrusion can have a number of significant economic and environmental impacts, including diminished freshwater storage capacity, contamination of freshwater production wells, soil salinization, and decreased nutrient laden freshwater discharge to marine ecosystems (Johannes, 1980; Taniguchi et al., 2002; Werner et al., 2013). A number of steps can be taken to attempt to slow the rate of saltwater intrusion, including spatial and temporal changes in the extent of groundwater pumping, in landuse, in surface water diversions, and in artificial recharge (Abarca et al., 2006). What is needed however is a way to prioritize these actions, or combinations of actions, so as to optimize the impact on saltwater intrusion. This requires an accurate understanding of the current distribution of freshwater and saltwater, that can be used to predict future locations in response to these, and other, actions (Sanford and Pope, 2009). Saltwater intrusion is traditionally mapped and monitored using measurements made in wells and predictive flow models (Werner et al., 2013). There are a number of limitations with these methods. Measurements made in wells provide point data, which may fail to capture the spatial complexity in subsurface conditions. Improving spatial coverage with additional wells can be cost prohibitive (Ogilvy et al., 2009). Additionally, salinity measurements from wells can be flux-averaged concentrations, and head measurements in wells are affected by the density of the water column so can be misinterpreted in the presence of unknown salt water, and are susceptible to measurement, instrument, and time lag errors (Carrera et al., 2009; Post and Von Asmuth, 2013). Models are generally calibrated by matching historic head values in wells and/or matching salinity values from well samples (Carrera et al., 2009), thus all the limitations of well data are carried over into the model calibration. Given these limitations there is significant opportunity for additional methods of mapping and monitoring the distribution of saltwater in the subsurface for improved management of coastal aquifers.

Salinas River Watershed Area Salt Modeling

California Central Coast Regional Water Quality Control Board (CCRWQCB) | November 13th, 2015

Tetra Tech supported EPA Region 9 and the Central Coast Regional Water Quality Control Board (CCRWQCB) for an assessment of salt impairments and development of a

Tetra Tech supported EPA Region 9 and the Central Coast Regional Water Quality Control Board (CCRWQCB) for an assessment of salt impairments and development of a salt mass balance in the Lower Salinas River and Reclamation Canal watersheds. This effort can inform development of salt-related TMDLs by the CCRWQCB and a salt and nutrient management plan for the Salinas Valley aquifers. Three reaches have reported 2010 303(d) listings for salt-related impairments in these watersheds including impairments due to chloride, sodium, electrical conductivity, and total dissolved solids – Lower Salinas River, Santa Rita Creek, and Alisal Creek. This report provides data analysis and a literature review (Sections 1 through 5), development of a water and salt mass balance tool (Sections 6 through 8), and salt source assessment (Section 9). The results of the analysis provide a strong foundation for assessing salt sources and understanding salt mass balance in the study area, but can be improved with refined representation of cropland locations, rotations, and irrigation practices.

Salinity distribution in heterogeneous coastal aquifers mapped by airborne electromagnetics

Soil Science Society of America (SSSA) | February 8th, 2011

Understanding the hydrologic setting of any given area is a challenging task, especially considering that the amount of available informaon is ofen very sparse re

Understanding the hydrologic setting of any given area is a challenging task, especially considering that the amount of available informaon is ofen very sparse relative to the size of the area and the complexity of the problem. We used geophysical transient electromagnetic (TEM) data from an airborne SkyTEM instrument to investigate discharge of freshwater from a river catchment into a coastal lagoon area, in support of large-scale hydrologic mapping of the HOBE hydrology research center. Existing hydrologic data indicate possible outflow from the catchment underneath the survey area, a hypothesis that was indeed backed up by our geophysical results. The results revealed a stratified geologic setting frequently incised by buried valleys beneath the lagoon. They also showed that the valleys are saturated with sea water, unlike the layers at the same depth that are probably saturated with brackish water. The salinity decreases with depth in large parts of the lagoon. The salinity distribution in the setting indicates the presence of intricate flow systems beneath the coastal area and the lagoon, and we propose that it is governed by the heterogeneity in the geologic setting. We also demonstrated how water depth as well as salinity can be accurately mapped using SkyTEM in combination with a robust and flexible inversion scheme.