North Coast

Tule Lake Subbasin Groundwater Sustainability Plan

Tule Lake Subbasin Groundwater Sustainability Agency | December 14th, 2021

On September 16, 2014, Governor Jerry Brown signed into law a three-bill legislative package, composed of Assembly Bill (AB) 1739 (Dickinson), Senate Bill (SB) 1168 (Pav

On September 16, 2014, Governor Jerry Brown signed into law a three-bill legislative package, composed of Assembly Bill (AB) 1739 (Dickinson), Senate Bill (SB) 1168 (Pavley), and SB 1319 (Pavley), collectively known as the Sustainable Groundwater Management Act (SGMA), which is codified in Section 10720 et seq. of the California Water Code. The purpose of this Groundwater Sustainability Plan (GSP or Plan) is to bring the Klamath River Valley – Tule Lake Subbasin (Tule Lake Subbasin or Subbasin), a medium priority basin, into sustainable groundwater management by 2042, which would meet the requirements of SGMA.

Tule Lake* Subbasin Groundwater Sustainability Plan

Tulelake Subbasin Groundwater Sustainability Agency | June 14th, 2024

*Spelled various as one and two words, Tule Lake and Tulelake, across the GSP submissions. From the GSP: "This ... covers the entire Tule Lake Subbasin, which comprises

*Spelled various as one and two words, Tule Lake and Tulelake, across the GSP submissions. From the GSP: "This ... covers the entire Tule Lake Subbasin, which comprises approximately 64,000 acres of irrigated land near the California-Oregon border. The Subbasin is part of the larger Upper Klamath Basin, which extends into Oregon, and is located within the North Coast Hydrologic Region. The Subbasin is within Modoc County and Siskiyou County, which have been respectively identified as "severely disadvantaged” and “disadvantaged” communities. The majority of land in the Subbasin is also in TID [Tulelake Irrigation District], which covers approximately 84% of the Subbasin. As the most prominent public agency within the Subbasin, TID has been the primary GSA responsible for recent planning activities." Due to length, this document has been divided. Part 1, Part 2

Twentieth-century shifts in forest structure in California: Denser forests, smaller trees, and increased dominance of oaks

National Academy of Sciences (NAS) | January 20th, 2015

Twenty-first century hydroclimate: A continually changing baseline, with more frequent extremes

National Academy of Sciences (NAS) | March 14th, 2022

Variability in hydroclimate impacts natural and human systems worldwide. In particular, both decadal variability and extreme precipitation events have substantial effect

Variability in hydroclimate impacts natural and human systems worldwide. In particular, both decadal variability and extreme precipitation events have substantial effects and are anticipated to be strongly influenced by climate change. From a practical perspective, these impacts will be felt relative to the continuously evolving background climate. Removing the underlying forced trend is therefore necessary to assess the relative impacts, but to date, the small size of most climate-model ensembles has made it difficult to do this. Here we use an archive of large ensembles run under a high-emissions scenario to determine how decadal “megadrought” and “megapluvial” events—and shorter-term precipitation extremes—will vary relative to that changing baseline. When the trend is retained, mean state changes dominate: In fact, soil moisture changes are so large in some regions that conditions that would be considered a megadrought or pluvial event today are projected to become average. Time-of-emergence calculations suggest that in some regions including Europe and western North America, this shift may have already taken place and could be imminent elsewhere: Emergence of drought/pluvial conditions occurs over 61% of the global land surface (excluding Antarctica) by 2080. Relative to the changing baseline, megadrought-/megapluvial risk either will not change or is slightly reduced. However, the increased frequency and intensity of both extreme wet and dry precipitation events will likely present adaptation challenges beyond anything currently experienced. In many regions, resilience against future hazards will require adapting to an ever-changing “normal,” characterized by unprecedented aridification/wetting punctuated by more severe extremes.

Ukiah Valley Groundwater Sustainability Plan

Ukiah Valley Groundwater Sustainability Agency (UVGSA) | January 12th, 2022

The Sustainable Groundwater Management Act (SGMA), passed by the California legislature in 2014, requires local entities to jointly assess groundwater conditions in thei

The Sustainable Groundwater Management Act (SGMA), passed by the California legislature in 2014, requires local entities to jointly assess groundwater conditions in their local areas and to develop a Groundwater Sustainability Plan (GSP) by a specified deadline to ensure that sustainable conditions are achieved within 20 years of GSP adoption. An effective and efficient groundwater management plan is critical for the local economy and the health and welfare of the people, the environment, and all other beneficial uses and users of groundwater in a local area. The Ukiah Valley Basin (Basin) is a medium-priority groundwater basin located in Mendocino County. The sole Groundwater Sustainability Agency for the Basin is the Ukiah Valley Groundwater Sustainability Agency (UVBGSA or GSA). The GSA consists of the following local agencies: the County of Mendocino (County), the City of Ukiah (City), the Upper Russian River Water Agency (URRWA), and the Russian River Flood Control and Water Conservation and Improvement District (RRFC). The GSA applied for and was awarded Proposition 1 and Proposition 68 grant funds to develop the GSP and meet the SGMA-mandated schedule for submitting a GSA-approved GSP to the California Department of Water Resources (DWR) by January 31, 2022. GSA will be funded through member agency contributions during the first 5-year implementation period until a fee structure is implemented to support and fund GSA activities. Additional funding opportunities will continue to be explored, including grants. In late-2022, DWR will open round 2 solicitations under the SGMA Grant Program, which will provide approximately $204 million to high and medium priority subbasins to implement the GSP and its projects and management actions. A variety of local interests are represented by the GSA and served on the technical advisory committee (TAC), including municipal-residential water users, agricultural water users, public water systems, local land use planning agencies, environmental users, surface water users, tribal governments, disadvantaged communities, groundwater monitoring and reporting entities, holders of overlying groundwater rights, adjacent Basins, industrial users, commercial users, remediation pumpers, natural ecosystems, and the general public. Many of these local entities have a long history with groundwater and surface water management in the Basin and are well equipped to perform SGMA-required planning functions. The GSA, TAC members, and the public have undertaken a thorough and timely review of past, current, and projected future water resources needs and groundwater conditions to meet SGMA requirements for GSP development. Throughout the development of the GSP, regular communication and engagement activities were conducted to inform and receive input from local stakeholders and the public. The GSP includes a comprehensive groundwater basin description, which was used to develop a regional integrated hydrological model that quantifies current water budgets and projects future conditions of the Basin. The GSP also includes an assessment of the impacts of predicted future groundwater levels on beneficial users, including groundwater-dependent ecosystems, shallow wells, and interconnected surface water using the best available data and science available. Importantly, these assessments are used to develop measurable sustainable management criteria that avoid significant and unreasonable impacts to these beneficial users, and that can be monitored and adjusted throughout plan implementation. The key finding of the GSP, based on a thorough analysis of the best available information, is that the Basin will be sustainable over the next twenty years if planned projects and management actions (PMAs) are implemented as needed with respect to climate change and changes in the water system. These PMAs will help maintain groundwater levels and storage volumes and protect ecosystems, interconnected surface water, and shallow wells. Potential climate change impacts are not fully understood at this stage due to data gaps and the need for additional modeling and data collection. The GSP will implement a more comprehensive data collection that improves modeling capabilities and can provide a better assessment of climate change impacts in the future. The proposed PMAs will promote adaptive management practices and long-term resiliency to varying climatic conditions, such as more frequent, longer-lasting, and more intense droughts and less frequent and wetter winters. As described in Chapter 2, the sustainable yield for the entire Basin is estimated to be at least 6,500 acre-feet, based on historical, average groundwater pumping. The sustainable yield of the Basin is defined based on avoidance of undesirable results. Because the Basin is not overdrafted and the historical pumping average may not represent the actual sustainability yield of the Basin. A groundwater monitoring network comprised of selected wells will be used to track groundwater levels and groundwater quality. Sustainable management criteria set at representative monitoring wells in the network will be implemented to gage these conditions over time and ensure that groundwater levels and quality remain within a range that avoids significant and unreasonable impacts to beneficial uses and users of groundwater. Streamflow measurements are added to the monitoring network to measure surface water depletion due to groundwater pumping in combination with groundwater level measurements and integrated hydrological modeling simulations. Monitoring and data collection efforts will continue through the first five years of GSP implementation to further identify and prioritize project and management actions. Once approved by the GSA, the activities identified throughout the GSP development process will be implemented, including: • Ongoing monitoring and annual reporting on conditions in the Basin; • Ongoing public engagement and outreach; • Coordination within the watershed and with neighboring basins and water management entities; • Development and implementation of a shallow well protection and monitoring program; • Coordination with land use agencies and water supply agencies to promote consistency with the GSP; • Coordination with regional agencies in the development of updated climate change projections; • Implementing PMAs as deemed needed by the GSA to maintain and promote sustainability of the Basin; and, • Preparation of five-year updates to the GSP starting in 2027. Due to file size, the GSP is divided into separate files. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6  

Uncertainty in El Niño-like warming and California precipitation changes linked by the Interdecadal Pacific Oscillation

Nature Portfolio (Springer Nature) | November 10th, 2021

Marked uncertainty in California (CA) precipitation projections challenges their use in adaptation planning in the region already experiencing severe water stress. Under

Marked uncertainty in California (CA) precipitation projections challenges their use in adaptation planning in the region already experiencing severe water stress. Under global warming, a westerly jet extension in the North Pacific analogous to the El Niño-like teleconnection has been suggested as a key mechanism for CA winter precipitation changes. However, this teleconnection has not been reconciled with the well-known El Niño-like warming response or the controversial role of internal variability in the precipitation uncertainty. Here we find that internal variability contributes > 70% and > 50% of uncertainty in the CA precipitation changes and the El Niño-like warming, respectively, based on analysis of 318 climate simulations from several multi-model and large ensembles. The Interdecadal Pacific Oscillation plays a key role in each contribution and in connecting the two via the westerly jet extension. This unifying understanding of the role of internal variability in CA precipitation provides critical guidance for reducing and communicating uncertainty to inform adaptation planning.

Understanding End-of-Century Snowpack Changes Over California’s Sierra Nevada

American Geophysical Union (AGU) | January 29th, 2019

Updated Study Reporting Levels (SRLs) for Trace-Element Data Collected for the California Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project, October 2009–October 2018

U.S. Geological Survey (USGS) | April 16th, 2020

Groundwater samples have been collected in California as part of statewide investigations of groundwater quality conducted by the U.S. Geological Survey for the Groundwat

Groundwater samples have been collected in California as part of statewide investigations of groundwater quality conducted by the U.S. Geological Survey for the Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project (PBP) since 2004. The GAMA-PBP is being conducted in cooperation with the California State Water Resources Control Board to assess and monitor the quality of groundwater resources used for public and domestic drinking-water supply and to improve public knowledge of groundwater quality in California. Quality-control samples (including but not limited to field, equipment, and source-solution blanks) were collected to evaluate and quantify the quality of the groundwater sample results. The GAMA-PBP previously determined study reporting levels (SRLs) for trace-element results based primarily on field blanks collected in California from May 2004 through March 2013. SRLs are raised reporting levels used to reduce the likelihood of reporting false detections attributable to contamination bias. The purpose of this report is to identify any changes in the pattern or magnitude of concentrations or detections in field blanks since the last evaluation that would require changing or ending the use of SRLs implemented in October 2009. Constituents analyzed were aluminum, antimony, arsenic, barium, beryllium, boron, cadmium, chromium, hexavalent chromium, cobalt, copper, iron, lead, lithium, manganese, molybdenum, nickel, selenium, silver, strontium, thallium, uranium, vanadium, and zinc. For this review, data from 167 field blanks collected from October 2009 through October 2018 by the GAMA-PBP for trace elements were compiled. Based on a consistent pattern of decreasing cobalt and manganese concentrations in field blanks from 2009 to 2013, the GAMA-PBP decided to reevaluate all trace-element SRLs, effectively setting an end date for previously defined SRLs. Beginning October 2013, SRLs would be determined from field-blank data collected through October 2018. The detection frequency and upper limit of potential contamination bias (BD-90/90) were determined from field blanks for each trace element. The BD-90/90, that is, the upper 90-percent confidence limit of the 90th percentile concentration of potential extrinsic contamination, was calculated by assuming the binomial probability distribution. These results were compared to each constituent’s detection limit to determine whether an SRL was necessary to minimize the potential for detections in the groundwater samples, attributed principally to contamination bias. Results of the evaluation were used to set SRLs for trace-element data collected by the GAMA-PBP between October 2013 and October 2018. Trace elements prescribed an SRL based on this review were hexavalent chromium, cobalt, copper, lead, and zinc. This review also resulted in the removal of SRLs from iron, manganese, molybdenum, and nickel. Although an SRL for hexavalent chromium could not be evaluated in the earlier reviews because the data were not collected regularly until 2015, one was established herein as 0.34 micrograms per liter (μg/L). The SRL for cobalt, as previously implemented, had been to reject all results; it was changed to 0.16 μg/L following a reduction in cobalt field-blank detection frequency resulting from mitigation steps, starting in 2014, aimed at reducing contamination bias introduced by high-capacity capsule filters used during sample collection. The SRL for copper did not change, and the SRL for lead changed very little based on this review. Lastly, the SRL for zinc was lowered from 6.2 μg/L to 3.9 μg/L.

Updating and recalibrating the integrated Santa Rosa Plain Hydrologic Model to assess stream depletion and to simulate future climate and management scenarios in Santa Rosa, Sonoma County, California

U.S. Geological Survey (USGS) | March 10th, 2025

The Santa Rosa Plain Hydrologic Model (SRPHM) was developed and published in 2014 through a collaboration between the U.S. Geological Survey (USGS) and Sonoma Water to an

The Santa Rosa Plain Hydrologic Model (SRPHM) was developed and published in 2014 through a collaboration between the U.S. Geological Survey (USGS) and Sonoma Water to analyze the hydrologic system in the Santa Rosa Plain watershed, help meet the increasing demand for fresh water, and prepare for future uncertainties in water resources. The original model simulated hydrological conditions and water use from water years 1975 to 2010. Recently (2023), the USGS, in cooperation with the California State Water Resources Control Board and Sonoma Water, updated the SRPHM model to extend its simulation period to the end of the 2018 calendar year, incorporate new estimates of rural and agricultural water use, and use an efficient input format for climate variables. The updated model was recalibrated, and evaluation of the new model calibration is included in this report. This report presents the results of comparing the hydraulic heads, streamflow, and groundwater budget simulated by the updated model with those generated by the original model and observed data. The main difference in the simulated budget between the original and updated SRPHM is the estimates of agricultural pumping, rural domestic pumping, and return flow generated from rural water use that was not simulated in the original model.

Updating California Water Laws to Address Drought and Climate Change

California Planning & Conservation League Foundation | February 3rd, 2022