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.

Screening of Pharmaceuticals in San Francisco Bay Wastewater

San Francisco Estuary Institute (SFEI) | October 1st, 2018

Previous studies have shown that pharmaceuticals are widely detected in San Francisco Bay, and some compounds occasionally approach levels of concern for wildlife. In 20

Previous studies have shown that pharmaceuticals are widely detected in San Francisco Bay, and some compounds occasionally approach levels of concern for wildlife. In 2016 and 2017, seven wastewater treatment facilities located throughout the Bay Area voluntarily collected wastewater samples and funded analyses for 104 pharmaceutical compounds. This dataset represents the most comprehensive analysis of pharmaceuticals in wastewater to date in this region. On behalf of the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP), the complete dataset was reviewed utilizing RMP quality assurance methods. An analysis of influent and effluent information is summarized in this report, and is intended to inform future monitoring recommendations for the Bay.

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.

Sensitivity of Mountain Hydroclimate Simulations in Variable-Resolution CESM to Microphysics and Horizontal Resolution

American Geophysical Union (AGU) | July 31st, 2018

Severe sustained drought revisited managing the Colorado River system in times of water shortage 25 years later—Part II

American Water Resources Association (AWRA) | December 4th, 2022

SGMA Best Management Practice: Hydrogeologic Conceptual Model

California Department of Water Resources (DWR) | December 23rd, 2016

The objective of this Best Management Practice (BMP) is to assist in the use and development of hydrogeologic conceptual models (HCM). The California Department of Water

The objective of this Best Management Practice (BMP) is to assist in the use and development of hydrogeologic conceptual models (HCM). The California Department of Water Resources (the Department or DWR) has developed this document as part of the obligation in the Technical Assistance Chapter (Chapter 7) of the Sustainable Groundwater Management Act (SGMA) to support the long-term sustainability of California’s groundwater basins. Information provided in this BMP is meant to provide support to Groundwater Sustainability Agencies (GSAs) when developing a HCM in accordance with the Groundwater Sustainability Plan (GSP) Emergency Regulations (GSP Regulations). This BMP identifies available resources to support development of HCMs. This BMP includes the following sections: Objective. The objective and brief description of the contents of this BMP. Use and Limitations. A brief description of the use and limitations of this BMP. HCM Fundamentals. A description of HCM fundamental concepts. Relationship of HCM to other BMPs. A description of how the HCM relates to other BMPs and is the basis for development of other GSP requirements. Technical Assistance. A description of technical assistance to support the development of a HCM and potential sources of information and relevant datasets that can be used to further define each component. Key Definitions. Definitions relevant for this BMP as provided in the GSP and Basin Boundary Regulations and in SGMA. Related Materials. References and other materials that provide supporting information related to the development of HCMs.

SGMA Best Management Practice: Modeling

California Department of Water Resources (DWR) | December 23rd, 2016

The objective of this Best Management Practice (BMP) is to assist with the use and development of groundwater and surface water models. The California Department of Water

The objective of this Best Management Practice (BMP) is to assist with the use and development of groundwater and surface water models. The California Department of Water Resources (the Department or DWR) has developed this document as part of the obligation in the Technical Assistance chapter (Chapter 7) of the Sustainable Groundwater Management Act (SGMA) to support the long-term sustainability of California’s groundwater basins. Information in this BMP provides technical assistance to Groundwater Sustainability Agencies (GSAs) and other stakeholders on how to address modeling requirements outlined in the Groundwater Sustainability Plan (GSP) Emergency Regulations (GSP Regulations). This BMP identifies available resources to support the development of groundwater and surface water models. This BMP includes the following sections: 1. Objective. The objective and outline of the contents of this BMP. 2. Use and Limitations. A description of the use and limitation of this BMP. 3. Modeling Fundamentals. A description of fundamental modeling concepts. 4. Relationship of modeling to other BMPs. A description of how modeling relates to other BMPs and is a tool used to develop other GSP requirements. 5. Technical Assistance. A description of technical assistance for the development of a model, potential sources of information, and relevant datasets that can be used to further define model components. 6. Key Definitions. Definitions relevant for this BMP as provided in the GSP Regulations, Basin Boundary Regulations, and SGMA. 7. Related Materials. References and other materials related to the development of models.

Simplified 1-D Hydrodynamic and Salinity Transport Modeling of the Sacramento–San Joaquin Delta: Sea Level Rise and Water Diversion Effects

University of California, Davis (UC Davis) | December 11th, 2013

Simulated Effects of Ground-Water Management Alternatives for the Salinas Valley, California

U.S. Geological Survey (USGS) | December 15th, 1988

A two-dimensional digital ground-water flow model was developed to analyze the geohydrology of the ground-water basin in the Salinas Valley. The ground-water model was ca

A two-dimensional digital ground-water flow model was developed to analyze the geohydrology of the ground-water basin in the Salinas Valley. The ground-water model was calibrated for steady-state and transient simulations by comparing simulated with measured or estimated inflows, outflows, and water levels for 1970-81. Preliminary estimates of hydraulic properties and some inflows and outflows were adjusted during model calibration. The simulated mean annual water budget for the basin was 559,500 acre-feet per year each of outflow and inflow. Inflow components consisted of Salinas River recharge (38.3 percent), percolation of irrigation water (34.0 percent), small stream and Arroyo Seco recharge (20.9 percent), seawater intrusion (3.4 percent), and other sources (3.4 percent). Outflow components consisted of agricultural pumpage (91.5 percent), municipal pumpage (4.0 percent), and riparian phreatophyte evapotranspiration (4.5 percent). For the steady-state calibration, 70 percent of the simulated water levels were within 9 feet of measured water levels for 1970-81. A sensitivity analysis determined the overall stability of the model results. The model input variable that probably contributes most to the uncertainty of the results is the quantity of ground-water recharge contributed by irrigation return flow to the unconfined aquifer. A 15-percent change in the estimate of this variable causes an 11-percent change in the simulated river-seepage rate and a 6-percent change in the simulated seawater-intrusion rate. The calibrated model was used to investigate several water-resources management alternatives. Projected pumpage increase at a rate of 1 percent per year for 20 years caused declines in mean annual water levels of 10 to 20 feet in some areas and an increase in seawater intrusion from 18,900 to 23,600 acre-feet per year. Pumpage decreases in the coastal area decreased seawater intrusion more effectively than pumpage decreases farther inland. When pumpage was decreased near the coast, seawater intrusion decreased oneseventh as much. When pumpage was decreased uniformly throughout the valley, the decrease in seawater intrusion was only one-fourteenth the decrease in pumpage. Simulations indicated that replacement of ground-water pumpage with imported surface water in a 9,000-acre service area near the coast would result in a decrease in seawater intrusion equaling nearly onehalf the quantity of imported water. This further confirmed that the rate of seawater intrusion is most sensitive to pumpage near the coast.

Simulating and Evaluating Atmospheric River-Induced Precipitation Extremes along the U.S. Pacific Coast: Case Studies from 1980-2017

American Geophysical Union (AGU) | January 29th, 2020

Atmospheric rivers (ARs) are responsible for a majority of extreme precipitation and flood events along the U.S. West Coast. To better understand the present‐day charac

Atmospheric rivers (ARs) are responsible for a majority of extreme precipitation and flood events along the U.S. West Coast. To better understand the present‐day characteristics of AR‐related precipitation extremes, a selection of nine most intense historical AR events during 1980–2017 is simulated using a dynamical downscaling modeling framework based on the Weather Research and Forecasting Model. We find that the chosen framework and Weather Research and Forecasting Model configuration reproduces both large‐scale atmospheric features—including parent synoptic‐scale cyclones—as well as the filamentary corridors of integrated vapor transport associated with the ARs themselves. The accuracy of simulated extreme precipitation maxima, relative to in situ and interpolated gridded observations, improves notably with increasing model resolution, with improvements as large as 40–60% for fine scale (3 km) relative to coarse‐scale (27 km) simulations. A separate set of simulations using smoothed topography suggests that much of these gains stem from the improved representation of complex terrain. Additionally, using the 12 December 1995 storm in Northern California as an example, we demonstrate that only the highest‐resolution simulations resolve important fine‐scale features—such as localized orographically forced vertical motion and powerful near hurricane‐force boundary layer winds. Given the demonstrated ability of a targeted dynamical downscaling framework to capture both local extreme precipitation and key fine‐scale characteristics of the most intense ARs in the historical record, we argue that such a configuration may be highly conducive to understanding AR‐related extremes and associated changes in a warming climate.