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Scott Valley

2023 SVIHM Materials:

2021 Groundwater Sustainability Plans:

Journal Articles:

  • Tolley, D., L. Foglia, T. Harter, 2019. Sensitivity Analysis and Calibration of an Integrated Hydrologic Model in an Irrigated Agricultural Basin With a Groundwater-Dependent Ecosystem. Water Resour. Res., doi:10.1029/2018WR024209 (open access)
    • NOTE: The above article includes a full update to the 2018 version of the Scott Valley Integrated Hydrologic Model, SVIHM, with embedded links to data and software sources.
  • Cantor, A., D. Owen, T. Harter, N. G. Nylen, and M. Kiparsky, 2018. Navigating Groundwater-Surface Water Interactions under the Sustainable Groundwater Management Act, Center for Law, Energy & the Environment, UC Berkeley School of Law, Berkeley, CA. 50 pp., https://doi.org/10.15779/J23P87

  • Owen, D., A. Cantor, N. Green Nylen, T. Harter, and M. Kiparsky, 2019. California groundwater management, science-policy interfaces, and the legacies of artificial legal distinctions. Env. Res. Lett. 14(4). https://doi.org/10.1088/1748-9326/ab0751
  • Foglia, L., J. Neuman, D.G. Tolley, S.B. Orloff, R.L. Snyder, and T. Harter, 2018. Modeling guides groundwater management in a basin with river-aquifer interactions. California Agriculture 72(1):84-95.

  • Foglia, L., A. McNally, and T. Harter, 2013. Coupling a spatio-temporally distributed soil water budget with stream-depletion functions to inform stakeholder-driven management of groundwater-dependent ecosystems. Water Resour. Res. 49:7292-7310, doi:10.1002/wrcr.20555 (open access).

Reports and Online Webinars:

  • Summary of the Scott Valley private water level monitoring program, 2006-2018.

Water Level Hydrograph 2023-10

Figure:  Water level hydrographs for currently and recently active wells in the Scott Valley water level monitoring program, 2006 through 2023.

Stream v WL Comparison 2023-10

Figure:  2020/21 (green), 2021/22 (red), 2022/23 (dark blue), and 2023/24 (light blue) monthly average depth to groundwater (ft) in "Valley Floor" wells of the Scott Valley monitoring network (all shown as dashed lines).  Solid lines (same color scheme) show the streamflow reading at the USGS Ft. Jones gage on the day of well water level sampling (usually sometime in the second half of the month). Note: May 2023 stream flow was above 1,000 cfs throughout the month (between 1,100 cfs and 3,100 cfs).

Overall. groundwater levels follow the seasonal variations of streamflow and - very generally speaking - in years with higher flows, groundwater levels are higher. There are exceptions that are also relevant to the design of the Scott Valley GSP, for example: At the end of October 2021, four days after an unusual atmospheric river provided enough rain to connect the entire length of the Scott River and generated a peak flow of over 800 cfs, the average depth to water level in Valley Floor wells was 15.9 ft.  In contrast, late November 2020 featured more shallow average depth to water level of 15.5 ft (the first major 2020 rain occurred just before Thanksgiving).  Despite the higher aquifer water levels at the end of November 2020 (when compared to late October 2021), the Scott River would not connect until more storms occurred in mid-December. This shows that water levels are difficult to interpret with respect to inferring instream flows.




Principal Investigator:
Thomas Harter [contact for technical comments/questions]

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.

Over the past four years, we have been working with the Groundwater Sustainability Agency for Scott Valley, the Siskiyou County Flood Control District, and its Technical Advisory Council, to develop a Groundwater Sustainability Plan under the regulations of the Sustainable Groundwater Management Act, passed by the California legislature in 2014. These efforts are following significant prior technical development by UC Cooperative Extension and its groundwater program in the Scott Valley:

The April 2013 Scott Valley Integrated Hydrologic Model data 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, landuse, and agricultural practices with a specific focus on the seasonal impacts

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 Groundwater Management and Enhancement 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.

The GW Study Plan and the Integrated Hydrologic Model are developed by the University of California at Davis (UC Davis) with the voluntary assistance of communities, landowners, the SRWC, the Groundwater Advisory Committee, 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 2008 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.