2 – PLAN AREA AND BASIN SETTING CHAPTER 2 PLAN AREA AND BASIN SETTING This Chapter of the Ojai Valley Groundwater Basin (OVGB)1 Groundwater Sustainability Plan (GSP) is organized into four major parts. Section 2.1, Description of the plan area, covers administrative, statutory, and policy issues, as well as aspects of the built environment related to water supply and demand. Specifically, Section 2.1 describes administrative boundaries, land use and population characteristics, and identifies existing water resources monitoring and management plans and programs. Section 2.2, Basin Setting, covers the general geographic and climatic setting of the OVGB. Section 2.3, Hydrogeologic Conceptual Model, describes the geologic and hydrogeologic setting, as well as the historical and current groundwater conditions in the OVGB. Finally, Section 2.4, Water Budget, covers the groundwater budget including groundwater flux, alternative water supplies, and quantification of historical, current, and future water budget conditions. A list of references cited, as well as all figures, are provided at the end of the chapter. 2.1 DESCRIPTION OF THE PLAN AREA As described in Chapter 1, Introduction, the Groundwater Sustainability Agency (GSA) boundary includes all but 143.7 acres of the OVGB as defined by the California Department of Water Resources (DWR). The OBGMA was granted a basin boundary modification to more closely align basin delineation with geology and hydrogeologic conditions in 2016, resulting in the current Bulletin 118 delineation. The OBGMA jurisdiction, as defined in the original enabling legislation, Senate Bill (SB) 534, known as the Ojai Basin Groundwater Management Agency (OBGMA) Act, differs slightly from the DWR defined extent of the OVGB. Areas outside the OBGMA boundary include narrow, shallow alluvial filled stream channels along the southern flank of the Topatopa Mountains (northern boundary of the OVGB) and a strip of land along the western margin of the OVGB. There is no known groundwater extraction in these areas of the OVGB. Therefore, the areas outside the OBGMA boundary but within the OVGB are effectively managed under this GSP. The boundary of the OVGB as defined by the DWR is used as the boundary of the plan area in this GSP. The GSA consists solely of the OBGMA. This GSP therefore consists of a “single plan covering the entire basin developed and implemented by one groundwater sustainability agency,” per California Water Code Section 10727(b)(1) and applies to the 5,913.4 acres within the OVGB. 1 The Ojai Valley Groundwater Basin is abbreviated as the “Ojai Valley Basin” or OVGB in this document. DRAFT Groundwater Sustainability Plan for the Ojai Valley Groundwater Basin 2021 2-1 2 – PLAN AREA AND BASIN SETTING The Ojai Valley Basin is designated by the DWR as one of California’s 46 high priority2 alluvial basins (DWR 2020a). The Ojai Valley Basin (DWR Basin No. 4-002) has a surface area of approximately 5,913.4 acres, or 9.2 square miles, and underlies the City of Ojai in the central part of Ventura County (County). The OVGB’s boundaries are formed by Tertiary age3 consolidated rocks associated with the Topatopa Mountains of California’s Transverse Ranges to the north and east, the Upper Ojai Valley Groundwater Basin (DWR Basin No. 4-001) to the east, the Santa Ana Fault and Black Mountain to the south, and the Upper Ventura River Groundwater Subbasin (DWR Basin No. 4-003.01) to the west (Figure 2-1, Plan Area and Contributing Watershed; DWR 2004). The eastern and western boundaries of the OVGB correspond to recognized bedrock highs that limit groundwater exchange flow between the OVGB and adjacent basins (DWR 2004; Kear 2005). Although the plan area is defined as the OVGB, information applicable to the Upper Ojai Valley Basin and Upper Ventura River Subbasin, as well as the hydrologic characteristics of the watersheds contributing to the Ojai Valley Basin, is also provided in this chapter. DWR has designated the Upper Ojai Valley Basin as having a very low priority, because there is less than 2,000 acre-feet4 per year (AFY) of extraction from the basin (DWR 2020a). DWR has designated the Upper Ventura River Subbasin as having a medium priority, because total groundwater extraction is greater than 2,000 AFY and adverse impacts to streamflow and habitat have been identified (DWR 2020a; Hopkins 2013; NMFS 2005; LARWQCB 1998). Study is ongoing to determine instream flow recommendations for the Ventura River (CDFW 2021). Natural recharge to the OVGB occurs through percolation of surface waters through alluvial channels, infiltration of precipitation that falls directly on the valley floor, water diverted into the San Antonio Creek spreading grounds, subsurface flow, and irrigation return flow (DWR 2004). The San Antonio Creek watershed upstream of the OVGB is the major contributing watershed to the OVGB, which is a subwatershed of the Ventura River watershed. The San Antonio Creek watershed is approximately 32,743.1 acres, or 51.2 square miles and completely encompasses the OVGB (Figure 2-1). The portion of the San Antonio Creek watershed that contributes recharge to the OVGB is approximately 20,340.8 acres, or 31.8 square miles (Figure 2-1). A summary of the groundwater basins, contributing watershed, and DWR designations is provided in Table 2-1. 2 Basin prioritization classifies the California’s 515 basins and subbasins into priorities based on components identified in the California Water Code. The priority process consists of applying datasets and information in a consistent, statewide manner in accordance with the provisions in California Water Code, Section 10933(b). Further information on DWR’s basin prioritization process can be found on the following website: https://water.ca.gov/Programs/Groundwater-Management/Basin-Prioritization. 3 Geologic period from 66 million to 2.6 million years ago. The geologic timescale classifies this time period as the Cenozoic Era that includes the Paleogene and Neogene Periods. 4 The volume of water required to cover 1 acre of land (43,560 square feet) to a depth of 1 foot; equal to 325,851 gallons or 1,233 cubic meters. DRAFT Groundwater Sustainability Plan for the Ojai Valley Groundwater Basin 2021 2-2 2 – PLAN AREA AND BASIN SETTING Table 2-1 Summary of the OVGB, Adjacent Basins, and Contributing Watershed Area Area DWR Designations Previous Basin/Watershed Square Basin Critically Basin Groundwater GSP Required Name Acres Miles Number Overdrafted Priority Management Plan per SGMA Ojai Valley 5,913.4 9.2 4-002 No High Yes Yes Groundwater Basin Adjacent Basins Upper Ojai Valley 3,806.3 5.9 4-001 No Very low No No Groundwater Basin Upper Ventura River 5,278.1 8.2 4-003.01 No Medium No Yes Groundwater Subbasin Watershed Contributing to the Ojai Valley Groundwater Basin San Antonio Creek 32,743.1 51.2 Watershed Not applicable, but relevant for recharge to the OVGB and the water budget. Area Contributing to 20,340.8 31.8 OVGB Source: DWR 2020a. Notes: DWR = Department of Water Resources; GSP = Groundwater Sustainability Plan; SGMA = Sustainable Groundwater Management Act. 2.1.1 Summary of Jurisdictional Areas and Other Features 2.1.1.1 Land Use Jurisdictions within the OVGB The OVGB consists primarily of private land under County jurisdiction, the City of Ojai, and public land owned and managed by the U.S. Forest Service. The developed land uses in the OVGB include in general residential, agricultural, recreational, and commercial. Approximately 67% of the OVGB consists of private land under County jurisdiction, 31% of the OVGB consists of the City of Ojai, and 2% of the OVGB consists of a portion of the Los Padres National Forest. The Los Padres National Forest intersects the OVGB on the northern border and occupies the mountain regions above the Ojai Valley. The land uses in the contributing watershed include primarily open space and recreation, and some agriculture (Figure 2-2, Jurisdictional Boundaries). Table 2-2 summarizes the land ownership and jurisdiction in the OVGB. Table 2-2 Summary of Land Ownership in the OVGB Ownership Type Agency Description Acres / % of Total Private Private Mixed land use including primarily residential, 3,963.5 / 67% agriculture, and undevelopable or protected land under Ventura County jurisdiction City City of Ojai Mixed land use including primarily residential, 1,847.2 / 31% commercial/industrial, and open space and recreation within Ojai City limits DRAFT Groundwater Sustainability Plan for the Ojai Valley Groundwater Basin 2021 2-3 2 – PLAN AREA AND BASIN SETTING Table 2-2 Summary of Land Ownership in the OVGB Ownership Type Agency Description Acres / % of Total Federal U.S. Forest Service Los Padres National Forest public land 102.7 / 2% Grand Total 5,913.4 Source: Geographic information system analysis of jurisdictional boundaries. 2.1.1.2 Water Agencies Relevant to the Plan Area The primary water agency serving the OVGB is the Casitas Municipal Water District (CMWD). In addition to CMWD, there are multiple small private water companies that provide water service within the OVGB, including the Siete Robles Mutual Water Company, Senior Canyon Mutual Water Company, Hermitage Mutual Water Company, Gridley Road Water Group, and Ventura County Property Administrator. Additional water agencies relevant to the OVGB include the Ojai Valley Sanitary District (OVSD), which provides sewer service, and the Ojai Water Conservation District (OWCD), which is a water reclamation district. Each water agency relevant to the OVGB is described below and shown on Figure 2-3, Water Purveyors. Casitas Municipal Water District The public water district serving the OVGB is the CMWD, which provides water service to upwards of 70,000 people in western Ventura County including the developed portions of the Ojai Valley within its service area.