North Coast

Scott Valley Community Groundwater Study Plan

University of California, Davis (UC Davis) | February 11th, 2008

This Scott Valley Groundwater Study Plan (GW Study Plan) has been requested of Siskiyou County and its Scott Valley stakeholders, as set forth in the Action Plan for the

This Scott Valley Groundwater Study Plan (GW Study Plan) has been requested of Siskiyou County and its Scott Valley stakeholders, as set forth in the Action Plan for the Scott River Temperature Total Maximum Daily Load (TMDL) (adopted Dec. 2005 by the California North Coast Regional Water Board [RWB]). The Action Plan sets forth the elements to be contained in this GW Study Plan; it also sets forth the needs of the RWB for certain information to be developed from the groundwater studies set forth in the GW Study Plan. It has been agreed by Siskiyou County and Regional Water Board staff that the hydrology of the entire valley needs to be understood in order to know the possible array of solutions to any water issues or problems in the Scott Valley. Siskiyou County with its management jurisdiction over groundwater (the RWB has water quality jurisdiction over groundwater under the Porter-Cologne Act) will take a community-based approach to groundwater management planning and to implementing this GW Study Plan. Data, information, and analysis are needed through studies to understand the groundwater hydrology of the Scott River system and its relationship to surface hydrology, especially in areas where groundwater could affect Scott River water temperatures, potential riparian vegetation, and habitat connectivity for anadromous fish. Without knowledge of the overall groundwater hydrology of Scott Valley, solutions to specific issues outlined in the TMDL Action Plan and the Scott River Watershed Council (SRWC) Strategic Action Plan will not be possible. It will be more cost effective to discover and prevent problems before they occur. Baseline data will be needed to determine the best approach in the design and implementation of water projects and water management alternatives and strategies to protect anadromous fish while also protecting the other beneficial uses, including the needs of agricultural operations. Much of this information will need to be developed over a period of time necessary to have a sufficient record from which to discover and test feasible and effective management strategies. This GW Study Plan was developed by the University of California at Davis (UC Davis) with the voluntary assistance of communities, landowners, the SRWC, and the Siskiyou Resource Conservation District (SRCD). The GW Study Plan is intended to be a living blueprint of the hydrologic, ecologic, water resource management, and agricultural management research needs and of the investigative approaches that can be taken to develop management practices that meet the mandate for protection of water, agricultural, and ecological resources in the Scott Valley. The GW Study Plan summarizes the current status of knowledge about the hydro-agro-eco-geography of the Scott Valley and outlines potential approaches to addressing critical current research needs. Individual study projects and tasks are described and scheduled in a way that is most efficient and timely to make the best use of funds to collect the information and data needed.

Scott Valley Integrated Hydrologic Model: Data Collection, Analysis, and Water Budget Final Report

University of California, Davis (UC Davis) | November 14th, 2017

The Scott Valley is an agricultural groundwater basin in Northern California, within the Scott River watershed and part of the much larger Klamath Basin watershed straddl

The Scott Valley is an agricultural groundwater basin in Northern California, within the Scott River watershed and part of the much larger Klamath Basin watershed straddling the California-Oregon border. The Scott River provides important habitat for salmonid fish, including spawning and rearing habitat for coho and fall-run Chinook salmon and steelhead trout. Sufficient flows at adequately low temperatures during summer, for rearing, and fall, for spawning, are critical for healthy fish habitat in the mainstem and tributaries. This report presents the data assembled and the methods used for data analysis and data modeling to prepare the Scott Valley Integrated Hydrologic Model Version 2, which is currently under development. The report includes precipitation data analysis, streamflow data analysis and modeling, geology and groundwater data review and analysis, evapotranspiration and soils data analysis, and preparation of relevant watershed, land use, topography, and irrigation data. The data collection and analysis efforts culminate in the development of a spatio-temporally distributed soil water budget model for the Scott Valley. The soil water budget model is used to determine spatially and temporally varying groundwater pumping rates, surface water diversion rates, and groundwater recharge across the groundwater basin. The spatial resolution of the soil water budget model is by individual fields (land use polygons). Temporal discretization is in daily time steps for the period from October 1, 1990 to September 30, 2011. This period includes several dry years, average years, and wet year periods. Methods and results of the soil water budget model are presented in this report. This report represents the next step toward a better understanding of the interactions between groundwater, surface water, land-use, and agricultural practices with a specific focus on the seasonal impacts of groundwater pumping on streamflow during critical low flow periods. The work presented here relies on an extensive data collection facilitated by the voluntary and active collaboration of communities, landowners, the Scott River Watershed Council (SRWC), the Siskiyou Resource Conservation District (SRCD), and the Scott Valley Groundwater Advisory Committee (GWAC) which has been appointed by the Board of Supervisors in January 2011, meeting monthly since April 2011 and advising UC Davis on its data collection and modeling efforts. In the data analysis and during the model development, numerous assumptions have been made as is common in building a conceptual and numerical integrated hydrologic model. Models cannot represent the complexity of the real system, but are an effort to capture salient hydrologic features with sufficient accuracy to develop modeling results that are useful for a better understanding of the watershed dynamics and water balance.

Sea Level Rise Impacts on Wastewater Treatment Systems Along the U.S. Coasts

American Geophysical Union (AGU) | April 13th, 2018

Wastewater treatment plants are susceptible to flooding resulting from sea level rise. Previous estimates of wastewater exposure have only considered the impacts of mar

Wastewater treatment plants are susceptible to flooding resulting from sea level rise. Previous estimates of wastewater exposure have only considered the impacts of marine flooding at the local or regional scale. In this analysis, we quantify the exposure to marine flooding across the coastal United States and then consider the relative impacts of marine and groundwater flooding at the regional scale in the San Francisco Bay Area. We also estimate the number of people who may lose access to wastewater services if no actions are taken to prevent flooding at wastewater treatment plants. We find that the number of people impacted by sea level rise due to loss of wastewater services could be five times as high as previous predictions of the number of people who experience direct flooding of their homes or property. We also find that groundwater flooding poses a significant threat to wastewater plants in the San Francisco Bay region.

Sea Level Rise in California

Public Policy Institute of California (PPIC) | February 29th, 2024

Sea Level Variations of the United States 1854–2006

National Oceanic and Atmospheric Administration (NOAA) | December 19th, 2009

The United States National Water Level Network (NWLON) was established in the 19th Century to ensure the Nation’s nautical charts, shoreline maps, and elevations relat

The United States National Water Level Network (NWLON) was established in the 19th Century to ensure the Nation’s nautical charts, shoreline maps, and elevations relative to homes, levees, and other coastal infrastructure were accurately referenced to sea level. In support of this mission, NOAA’s Center for Operational Oceanographic Products and Services and its predecessors have determined sea level for the United States since the mid 19th Century. While climate change was not a concern during the mid-1800s, the accurate determination of sea level was critical for navigation and marine boundary determination. To meet these important requirements, technology, procedures, and processes were developed to the highest scientific and engineering standards. At the turn of the 20th Century it was realized that there was a need to account for a rise in sea level and the first National Tidal Datum Epoch was established. Today this Epoch is updated every 20 to 25 years. The Supreme Court recognized these standards and procedures in the landmark 1936 case of Borax, Ltd v. City of Los Angeles when legally defining sea level. Due to those initial efforts and the continued dedication of those charged with the responsibility for monitoring sea level for the United States, we can accurately determine relative (local) mean sea level along the Nation’s coastline today. These observations also play an important role in monitoring change in global sea level. As we monitor change in sea level into the 21st Century, the statement made by Alexander Dallas Bache, the Second Superintendent of the Coast Survey, is as relevant today as when it was stated more than 150 years ago, “It seems a very simple task to make correct tidal observations; but, in all my experience, I have found no observations which require such constant care and attention” (1854). Michael Szabados, Director, Center for Operational Oceanographic Products and Services

Sea-level rise and coastal groundwater inundation and shoaling at select sites in California, USA

Journal of Hydrology: Regional Studies (Elsevier) | January 5th, 2016

Study region: The study region spans coastal California, USA, and focuses on three primary sites: Arcata, Stinson Beach, and Malibu Lagoon. Study focus: 1m and 2m sea-

Study region: The study region spans coastal California, USA, and focuses on three primary sites: Arcata, Stinson Beach, and Malibu Lagoon. Study focus: 1m and 2m sea-level rise (SLR) projections were used to assess vulnerability to SLR-driven groundwater emergence and shoaling at select low-lying, coastal sites in California. Separate and combined inundation scenarios for SLR and groundwater emergence were developed using digital elevation models of study site topography and groundwater surfaces constructed from well data or published groundwater level contours. New hydrological insights for the region: SLR impacts are a serious concern in coastal California which has a long (∼1800km) and populous coastline. Information on the possible importance of SLR-driven groundwater inundation in California is limited. In this study,the potential for SLR-driven groundwater inundation at three sites (Arcata, Stinson Beach,and Malibu Lagoon) was investigated under 1m and 2m SLR scenarios. These sites provide insight into the vulnerability of Northern California coastal plains, coastal developments built on beach sand or sand spits, and developed areas around coastal lagoons associated with seasonal streams and berms. Northern California coastal plains with abundant shallow groundwater likely will see significant and widespread groundwater emergence, while impacts along the much drier central and southern California coast may be less severe due to the absence of shallow groundwater in many areas. Vulnerability analysis is hampered by the lack of data on shallow coastal aquifers, which commonly are not studied because they are not suitable for domestic or agricultural use. Shallow saline aquifers may be present in many areas along coastal California, which would dramatically increase vulnerability to SLR-driven groundwater emergence and shoaling. Improved understanding of the extent and response of California coastal aquifers to SLR will help in preparing for mitigation and adaptation.

Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future

National Academy of Sciences (NAS) | December 13th, 2012

Sea-level rise impacts on seawater intrusion in coastal aquifers: Review and integration

Journal of Hydrology (Elsevier) | February 6th, 2016

Sea-level rise (SLR) influences groundwater hydraulics and in particular seawater intrusion (SWI) in many coastal aquifers. The quantification of the combined and relativ

Sea-level rise (SLR) influences groundwater hydraulics and in particular seawater intrusion (SWI) in many coastal aquifers. The quantification of the combined and relative impacts of influential factors on SWI has not previously been considered in coastal aquifers. In the present study, a systematic review of the available literature on this topic is first provided. Then, the potential remaining challenges are scrutinized. Open questions on the effects of more realistic complexities such as gradual SLR, parameter uncertainties, and the associated influences in decision-making models are issues requiring further investigation. We assess and quantify the seawater toe location under the impacts of SLR in combination with recharge rate variations, land-surface inundation (LSI) due to SLR, aquifer bed slope variation, and changing landward boundary conditions (LWBCs). This is the first study to include all of these factors in a single analysis framework. Both analytical and numerical models are used for these sensitivity assessments. It is demonstrated that (1) LSI caused by SLR has a significant incremental impact on the seawater toe location, especially in the flatter coasts and the flux-controlled (FC) LWBCs, however this impact is less than the reported orders of magnitude differences which were estimated using only analytical solutions; (2) LWBCs significantly influence the SLR impacts under almost all conditions considered in this study; (3) The main controlling factors of seawater toe location are the magnitudes of fresh groundwater discharge to sea and recharge rate. Regional freshwater flux entering from the landward boundary and the groundwater hydraulic gradient are the major contributors of fresh groundwater discharge to sea for both FC and head-controlled (HC) systems, respectively; (4) A larger response of the aquifer and larger seawater toe location changes are demonstrable for a larger ratio of the aquifer thickness to the aquifer length particularly in the HC systems; (5) The lowest sensitivity of seawater toe location is found for the density difference ratio of the seawater and freshwater, and also for the aquifer bed slope; (6) The early-time observations show seawater fingers below the inundated lands due to SLR which are diminished and ultimately extinguished; and (7) A less than 2% reversal effect on the seawater toe location after overshoot mechanism is observed in the transient simulations which suggests that this mechanism is an insignificant and impractical factor compared to other more significant factors.

Seasonal Peak Snow Predictability Derived From Early-Season Snow in North America

American Geophysical Union (AGU) | September 12th, 2023

Early season snow observations show promise in predicting peak snow water equivalent in locations where large-scale ocean-atmosphere patterns similarly influence fall and

Early season snow observations show promise in predicting peak snow water equivalent in locations where large-scale ocean-atmosphere patterns similarly influence fall and winter conditions, and in northern maritime locations where winter temperatures are warm enough that rain on snow and midwinter melt occur.

Seasonal variation in total water storage in California inferred from GPS observations of vertical land motion

American Geophysical Union (AGU) | March 12th, 2014

GPS is accurately recording vertical motion of Earth's surface in elastic response to seasonal changes in surface water storage in California. California's mountains subs

GPS is accurately recording vertical motion of Earth's surface in elastic response to seasonal changes in surface water storage in California. California's mountains subside up to 12 mm in the fall and winter due to the load of snow and rain and then rise an identical amount in the spring and summer when the snow melts, the rain runs off, and soil moisture evaporates. We invert the GPS observations of seasonal vertical motions to infer changes in equivalent water thickness. GPS resolves the distribution of change in total water across California's physiographic provinces at a resolution of 50 km, compared to 200 km resolution from the Gravity Recovery and Climate Experiment. The seasonal surface water thickness change is 0.6 m in the Sierra Nevada, Klamath, and southern Cascade Mountains and decreases sharply to about 0.1 m east into the Great Basin and west toward the Pacific coast. GPS provides an independent inference of change in total surface water, indicating water storage to be on average 50% larger than in the NLDAS‐Noah hydrology model, likely due to larger changes in snow and reservoir water than in the model.