Section 2: Watershed Identification

As introduced in Section 1, development of the by the USGS subbasin boundaries (using Hydrologic SWRP boundary started with the Westside IRWM Unit Code Level 8) are Cache Creek (which captures Planning Region, and based on stakeholder interest, the Cache Creek watershed), Putah Creek (which was focused to the drainages within Yolo County. captures the Putah Creek watershed), and the Although there is no formalized analysis of Sacramento River (which captures the Sacramento- countywide water inventories for land use planning, Stone Corral and Lower Sacramento watersheds). The Water Resources Association of Yolo County (Yolo Yolo Bypass is used to manage the much larger WRA) is the primary forum for collaboration among Sacramento River watershed flood flows. water managers in Yolo County. The Yolo WRA, a While the actual Cache and Putah Creek watersheds member of the Westside RWMG, provides a regional account for only a small percentage of the lower land forum to coordinate and facilitate solutions to water area of the SWRP Area, water from Cache Creek and challenges and opportunities in Yolo County, Putah Creek comprise a majority of the water including storm water management. The Yolo WRA entering Yolo County. Direct discharges to the currently has 10 member agencies, which include Sacramento River from Cache and Putah Creeks are agricultural water suppliers, urban water suppliers, limited to larger, more significant flood events, which groundwater managers, and flood protection historically had to overtop the broad natural levees providers (RWMG, 2013). Through focused meetings, adjacent to the river. Currently, water from Cache and these agencies can effectively interact and make key Putah Creek continue to pond during flood events, decisions to facilitate storm water management but the water is also managed through a series of efforts within the Yolo County watersheds. facilities that can convey flows to the Sacramento Yolo County makes up about 1,034 square miles of River during high-runoff events (RWMG, 2013). the Sacramento Hydrologic Region in northern California. It is also underlain completely by the 2.1.1.1 Cache Creek Watershed Sacramento Valley Groundwater Basin. This section The Cache Creek watershed encompasses describes the SWRP Planning Area water resources approximately 1,165 square miles, and about 248 and provides context for watershed management square miles of the watershed is located in Yolo issues that should be addressed through County (approximately 21 percent). Cache Creek implementation of this SWRP, the Westside IRWMP, provides numerous benefits, including habitat and or other county-wide or regional efforts. water supply. YCFCWCD owns the Cache Creek Dam, located on Cache Creek approximately 5 miles 2.1 Surface Water downstream of Clear Lake outlet, and operates both Cache Creek Dam and Clear Lake in accordance with Resources DRAFTthe Solano and Gopcevic Decrees. The North Fork As shown in Figure 2-1, Yolo County is located within Cache Creek subwatershed drains the area north of the Sacramento Hydrologic Region as defined by Clear Lake and includes Long Valley Creek, Wolf DWR and includes the lower portions of both the Creek, and Bartlett Creek. YCFCWCD owns and Putah Creek and Cache Creek watersheds, as well as operates the Indian Valley Dam on the North Fork the surrounding low-lying drainage basins in the Cache Creek, which forms the Indian Valley Reservoir. region, including the Colusa Basin drain (a portion of Indian Valley Reservoir has a total storage capacity of the Sacramento-Stone Corral watershed) and Lower 300,600 AF, of which 40,000 AF is dedicated to flood Sacramento watershed. control. Bear Creek drains the area to the east of the North Fork Cache Creek, and its watershed lies 2.1.1 Hydrologic Boundary entirely within Colusa County. Bear Creek flows into the main stem of Cache Creek at the border of The SWRP watershed delineation is based on the Colusa and Yolo Counties (RWMG, 2013). 12-digit (most detailed) United States Geological Survey (USGS) Watershed Boundary Dataset for subwatersheds. The key water features as indicated

Yolo County Storm Water Resource Plan, May 2017 2-1 Section 2: Watershed Identification

After Cache Creek flows into Yolo County, it 1940s, the U.S. Army Corps of Engineers constructed continues through the agriculturally intensive Capay levees along the lowermost 9 miles of the South Fork Valley until it reaches the Capay Diversion Dam, channel as part of the Sacramento River Flood where some flows are diverted into YCFCWCD’s Control Project (U.S. Fish and Wildlife Service, 1992). irrigation system. Cache Creek continues downstream of Capay Dam, where it terminates in an area known 2.1.1.3 Sacramento-Stone Corral Watershed as the Cache Creek Settling Basin, just upstream of The Sacramento-Stone Corral watershed the Yolo Bypass. Cache Creek is considered an encompasses 1,884 square miles, most of which is intermittent stream, in that flows in the creek are located outside of Yolo County. Flows in the inconsistent, and there are periods particularly during watershed generally travel from the coastal ranges in the summer when no streamflow is present (RWMG, the west towards the Sacramento River. The majority 2013). of water from the watershed is discharged to the The Cache Creek Settling Basin is a component of the Sacramento River outside the region; however, the Sacramento River Flood Control Project. It was southernmost portion of the watershed flows into the designed to trap sediments carried by Cache Creek county via the Colusa Basin Drain. This drain is a and prevent them from being deposited in the Yolo man-made channel designed to convey irrigation Bypass, thereby maintaining the flood capacity of the drainage and storm runoff from 32 ephemeral Yolo Bypass. The settling basin has an overflow into streams to the Knights Landing outfall gates for the Yolo Bypass, which allows flow to enter the discharge into the Sacramento River. Seven of these Sacramento River upstream of Rio Vista in Solano streams originate in the Dunnigan Hills of Yolo County (RWMG, 2013). County (RWMG, 2013). The Sacramento-Stone Corral watershed comprises nearly 1,884 square miles in the 2.1.1.2 Putah Creek Watershed Sacramento Valley and includes portions of Glenn, Colusa, and Yolo Counties. About 250 square miles of The Putah Creek watershed encompasses the watershed is located in Yolo County approximately 654 square miles and is 50 miles wide, (approximately 13 percent). extending from Cobb Mountain (elevation 4,700 feet) in Lake County to the Yolo Bypass (elevation a few feet above sea level). About 48 square miles of the 2.1.1.4 Lower Sacramento River Watershed watershed is located in Yolo County (approximately The Sacramento River forms the easterly border of 7 percent). Tributaries to Putah Creek within the County. The entire Sacramento River watershed Lake County include Harbin Creek, Big Canyon Creek, covers approximately 27,000 square miles in St. Helena Creek, Dry Creek, Coyote Creek, and Northern California, of which the Lower Sacramento Soda Creek. From Lake County, Putah Creek flows River watershed makes up 1,229 square miles into Napa County and Lake Berryessa. The major (approximately 4.6 percent). Yolo County, which lies tributaries within Napa County include Pope Creek, near the downstream end of the Sacramento River, Chiles Creek, Capell Creek, and EticueraDRAFT Creek. Lake encompasses around 39 percent (approximately 476 Berryessa has a storage capacity of 1,602,000 AF and square miles) of the Lower Sacramento River is regulated by Monticello Dam, which is owned by watershed. Because of its location and relatively small USBR and operated by Solano County Water Agency. drainage area, the portion of the Sacramento River From the outlet of Monticello Dam, Putah Creek located within the county is influenced heavily by the flows into Solano County, where it eventually areas outside it. discharges to the Yolo Bypass (RWMG, 2013).

The South Fork of Putah Creek is an artificial channel constructed over a period of several decades, beginning in the 1870s. It departs from the natural creek channel about 1 mile upstream of Interstate 80 and flows directly east to the Yolo Bypass (Brice, 1998). The creek eventually abandoned its original channel (the North Fork) entirely and was named the South Fork Putah Creek for practical purposes. In the

2-2 Yolo County Storm Water Resource Plan, May 2017 Ca ch e Creek VU16 Cortina Sand Colusa Clarks Ditch- Yuba County Creek Creek Salt Creek County Colusa Basin Sycamore Drainage Canal Rocky Creek- 16 Slough Cache Creek VU Sacramento-Stone Corral Buckeye Creek Dunnigan VU70 Davis Creek-Colusa Creek Basin Drainage Hamilton Creek- South Fork Canal Cache Creek Buckeye Creek Bird VU16 Creek C Lake olusa County B asi n Dr Placer a County Feather River Sutter inag Oat e County VU99 Creek Smith Creek- Can P Willow Spring u Colusa Basin al ta Creek- h Drainage Canal Cre Putah VU16 Colusa Basin ek Drainage Canal Creek Brooks Creek- Cache Creek Cache ¦¨§505 Knights Creek Landing Goodnow Ridge Cut Slough-Cache Creek

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2-4 Yolo County Storm Water Resource Plan, May 2017 Section 2: Watershed Identification

agricultural quality standards but are exceeding or 2.2 Groundwater Resources just below maximum contaminant levels (MCLs) set Groundwater makes up approximately 33 percent of for drinking water. the water supply for users in Yolo County in an average water year, and for many agricultural users and municipalities, groundwater is the only source of 2.3 Land Use Description water supply. Some agricultural areas are fully reliant The County encompasses more than 322,000 acres on groundwater. Municipalities such as the cities of (504 square miles) of land, which is dominated by Woodland and Davis currently obtain their drinking agriculture and open space (with native vegetation). water supplies from well water pumped from the Agriculture makes up approximately 49 percent of deeper Tehama formation. Water from the Tehama the total land area, whereas urban and community formation is of high quality, but water managers are developments represent only 5 percent of the total uncertain about the sustainable yield of the aquifer. land area. Open space (44 percent of the county), Water stored in groundwater aquifers serve as a key provides essential habitat for native species and water supply source in Yolo County. Thousands of broad-ranging opportunities for recreation. Tourists groundwater wells exist within the county, and most and residents are attracted to the region’s lakes, of these groundwater wells are used to supply waterways, and lands for recreational activities like individual domestic demands or small agricultural boating, fishing, hiking, camping, and hunting. These operations. Some of the larger towns and cities also lands are managed by local and private entities as operate municipal wells to meet or help meet urban, well as federal and state agencies such as the Bureau municipal, and industrial demands. Some of the of Land Management (BLM), the U.S. Forest Service communities within the county such as Davis, UC (USFS), and California Department of Fish and Game Davis, and Woodland currently rely on groundwater (CDFG). Table 2-1 summarizes the existing land use as their sole supply source. Maintaining sustainable classifications in the SWRP Area, and Figure 2-3 groundwater aquifers that yield high quality illustrates the distribution of land uses throughout groundwater will be crucial to meet the long-term the county. Figure 2-4 shows the land management water demands within the county. agencies within Yolo County, including municipalities and tribal entities discussed in the following Yolo County primarily encompasses the Yolo subsection. Subbasin of the Sacramento Valley groundwater basin as designated by DWR Bulletin 118 (2016 Table 2-1: Yolo County Land Use Distribution Update) as shown in Figure 2-2. A small portion of Yolo County intersects the Solano Subbasin to the Percent of south. The water bearing formations of this basin Land Use Category Total Acres Total generally have very high storage capacity and are Agricultural 322,224 49.4 essentially contained within two stratigraphic units: Communities 33,074 5.1 (1) the deeper older thick alluvial andDRAFT river sediments Water Surface 10,481 1.6 of the Tehama formation, and (2) the younger Native Riparian/Vegetation 256,920 43.7 shallower sediments, floodplain deposits, and stream Barren/Unclassified 1,218 <1 channel deposits that overlie the Tehama formation Total Acres 623,917 100 (DWR B118, 2016). The sustainable yield of the Yolo Subbasin is not yet fully understood, but the DWR Source: California Department of Water Resources, Bulletin 118 has not identified the subbasin as in an Land Use Survey, Yolo County, 2008. overdraft condition. Groundwater quality concerns in the region relate to drinking water and irrigation uses. Constituents of concern within Yolo County include: arsenic, boron, chromium, salinity, iron, magnesium, nitrate, selenium, and total dissolved solids (TDS). In general, based on the measured levels of these constituents in wells within the county, groundwater quality meets

Yolo County Storm Water Resource Plan, May 2017 2-5 Section 2: Watershed Identification

2.3.1 Communities Of the 23 county agencies that currently deliver water, 11 pump groundwater, 7 divert surface water, The major communities and tribal areas within the and 5 supply a combination of groundwater, surface county are shown in Figure 2-4. The Yooha Dehe water, and other water supply. Wintun tribal area is located at the western side of the county. The four incorporated cities within the There are also 80 minor water systems within the county are Davis, West Sacramento, Winters, and county, of which 75 use groundwater as their sole Woodland. Other unincorporated communities source of water supply, and the remaining using scattered throughout the county include Esparto, either surface water or non-potable water. Knights Landing, Dunnigan, Monument Hills, Clarksburg, Madison, Yolo, Zamora. 2.3.3 Other Land Use Agencies Of the above communities, 12 include areas that are Local, state, and federal land management agencies considered Disadvantaged Community (DAC) or in the county are shown in Figure 2-4 and include the Economically Distressed Area (EDA) according to following: DWR’s definitions:  Yolo County  DAC: census geographies “with an annual  median household income (MHI) that is less U.S. Bureau of Land Management than 80 percent of the Statewide annual MHI  U.S. Bureau of Reclamation (PRC Section 75005(g))).”  U.S. Fish and Wildlife (http://www.water.ca.gov/irwm/grants/resou rces_dac.cfm)  U.S. Forest Service  EDA: census geographies with “a population  California Department of Fish and Wildlife that is ≤20,000 people; and less than 85% of  State Lands the State's MHI.” (https://gis.water.ca.gov/app/edas/) Figure 2-5 shows the DACs and EDAs within Yolo 2.4 Watershed Management County. Issues The SWRP presents an opportunity to address the 2.3.2 Water and Wastewater Service issues identified in the Westside IRWMP specific to Providers storm water resource management in Yolo County. The county includes 45 major municipalities, special Challenges identified in the IRWMP related to storm districts, and agencies with water supply, wastewater water management include: Habitat and Invasive management, flood control, and other water or Species, Infrastructure Protection, Flood Management resource management responsibilities. It includes 14 and Other Natural Disasters, Climate Change, Water agencies that are strictly wholesale orDRAFT retail water Quality, Sustaining Groundwater Resources, and Land suppliers and 5 agencies providing both water and Use. wastewater services. There are 2 agencies that provide only flood control services and 11 2.4.1 Habitat and Invasive Species reclamation districts that provide flood control and The lakes, creeks, wetlands, sloughs, and other water storm drain maintenance services. There are 5 features throughout the region provide key habitat agencies that provide other water resource for many of California’s well-known fish and wildlife coordination, and the remaining 8 agencies provide species (see Figure 2-7). Anadromous fish migrate some combination of the above services. Figure 2-6 into the region and use its waterways for spawning. identifies the service areas and agency boundaries for Resident and migratory waterfowl rely on the lakes the municipalities and agencies where data are and wetlands for food and nesting habitat. Changes available. See Appendix B for a listing of the water to the landscape from agriculture, development, and and wastewater service agencies within Yolo County, flood control projects have diminished aquatic and as well as brief overviews for each system. riparian habitat over the last 150 years (RWMG, 2013).

2-6 Yolo County Storm Water Resource Plan, May 2017 Section 2: Watershed Identification

Regional conservation areas, such as the Yolo Bypass Wildlife Area and Cache Creek Natural Area/Cache Creek Wilderness Area have been established to protect important habitats and species. Cache Creek is designated as a California Wild and Scenic River. This designation for more than 31 miles of the creek is aimed at maintaining free-flowing conditions and preserving its aquatic and riparian environment (RWMG, 2013).

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Yolo County Storm Water Resource Plan, May 2017 2-7 Section 2: Watershed Identification

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2-8 Yolo County Storm Water Resource Plan, May 2017 k ree C C e a h ch c e C Colusa reek 16 Yuba County a VU County C VU16

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2-10 Yolo County Storm Water Resource Plan, May 2017 Ca ch e Creek 16 Colusa Yuba County VU County VU16

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2-12 Yolo County Storm Water Resource Plan, May 2017 Ca ch e Creek 16 Colusa Yuba County VU County VU16

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2-14 Yolo County Storm Water Resource Plan, May 2017 DAC:Disadva n tagedCom m uniden ity tified aacen s susgeography “with an an n ua l m edianhousehold incom lessistha e(MHI) t Dun n igan thapercen n80 theofStatewide t an n uaMHI l (PRCSection(http://www.wa ter.75005(g))).” ca .gov/irwm /gran ts/resources_da c.cfm )

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2-16 Yolo County Storm Water Resource Plan, May 2017 COLUSA COUNTY W.D. RECLAMATION Colusa DISTRICT 108 Yuba County County

Dunnigan Water Colusa Drain District Mutual Water Tenhunfeld, Company Fred, Wallace Dunnigan Sutter Jack, Et Al County Water River Garden Giovannetti, Lake Works Farms Company Driver, B. E. County William A. Et Al Yolo RD 787 Placer Feather River Heidrick, County Mildred (1616) County Edson, Wallace Yolo - L. And Heidrick, Zamora Water Mary O. Mildred RD District (8322) Knights Landing 730 Community RD 1600 Yocha Service District DESERET Dehe Cacheville Hershey Land Wintun FARMS OF Service Company CALIFORNIA Esparto District Community Knaggs Service District Walnut Yolo Ranches Mesquite Investors, LLC Wilson Ranch Land Madison Service Wild Wings Woodland And Family Real Property Golf Partnership Trust District Yolo County Flood Limited Partnership Community Control And Water RD 827 RD 527 Conservation District RD 2035 RD 537 RD Lake Rolling Acres Riverby 785 Legend Berryessa Lake Mutual Water Limited Yolo County SWRP Boundary Berryessa Company Conaway Westside Region Preservation Yolo County Group West County Boundaries Housing Sacramento City Boundaries Authority Davis RD 900 Streams Napa UC Davis Water Bodies County Winters Sacramento ^ To be Transferred to Yolo County County Source: Land Status, Bureau of Land Management, 2011; ^ California Department of Fish and Game (DFG) Owned and Operated Lands, CA Dept. of Fish and Game, 2011. RD 765

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2-18 Yolo County Storm Water Resource Plan, May 2017 Ca ch e Creek 16 Colusa Yuba County VU County VU16 Legend

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These conservation areas and designation, however, infrastructure due to the unmanaged growth of do not cover the entire county, and additional work is invasive plant communities necessary to improve special status and endangered  Flooding risks as a result of alterations to the species habitat including the following objectives stream channel conveyance capacity and raised (RWMG, 2013): water levels during high flows

 Increased erosion as a result of decreased bank  Increase productive floodplain connectivity, stability due to weaker root structures of invasive  Improve overall fish passage, plant species, causing undercutting and bank collapse. Erosion also results from changes in flow  Expand contiguous extent of riparian canopy, patterns due to invasive plant obstructions within  Establish and manage additional reserves and waterways, which can cause constrictions, higher preserves, and flow velocities in certain areas, and potentially  Protect vernal pools and migratory bird wintering increased erosion. areas.  Increased fire hazards resulting from the dense Invasive plants present a significant challenge to the growth patterns of some invasive plants, which management of the county’s water resources. Hence, present a significant fuel source in upland areas addressing the spread of invasive species is an and decrease the ability of riparian areas to serve important component of maintaining the natural as natural firebreaks. Native riparian areas tend to diversity of the region and helping to protect water be open networks of plants and steep and lightly (RWMG, 2013). vegetated banks that are poor fire fuel.  From the late 19th century to today, development of Displacement of native habitats and associated urban communities, agriculture conducted across wildlife due to water quality changes from invasive large areas, and disturbance of the stream channels species and as a result of the species’ ability to as a result of mining and construction of outcompete native plants, leading to the loss of infrastructure has altered riparian habitat throughout food and habitat for native wildlife the region. This disturbance has led to increased  Hindered navigation for recreational activities as a intrusion of invasive species in both terrestrial and result of invasive species obstructions to waterways aquatic areas, which can cause widespread impacts and upland areas. through the watershed. A number of invasive plants and animal species either already occur in or threaten 2.4.2 Infrastructure Protection to invade the region (RWMG, 2013). Invasive plant species of concern in the county include, distaff One of the ongoing challenges facing water suppliers thistle (Carthamus lanatus), purple loosestrife and wastewater management agencies is aging and (Lythrum salicaria), ravenna grass (Saccharum inadequate infrastructure. Much of the water storage ravennae) and yellow flag iris (Iris pseudacorus).DRAFT and conveyance infrastructure, including the dams, canals, pipelines, and pump stations throughout the The major risks to the watersheds from the spread of county, was built in the 1960s or earlier and could be invasive aquatic and terrestrial plant species include nearing the end of its useful life. Some of the water (RWMG, 2013): supply systems may also require technological  Water quality impacts resulting from temperature updates to keep pace with modern regulatory changes due to alterations in river shading and requirements and other drivers. Production chemical processes (increased nutrient loading, groundwater wells also have a limited useful life, and increased pH, and decreased dissolved-oxygen groundwater producers must periodically drill content) replacement wells. Further, increasingly stringent water treatment requirements have required many  Water supply impacts, including reduced local existing and new wells to be retrofitted with availability of surface water and groundwater due groundwater treatment systems to remove to excessive evapotranspiration needs of invasive contaminants and undesirable constituents such as species and obstructions to water supply arsenic, iron, and manganese. Many communities in the county are facing similar needs for investment in

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wastewater treatment facilities, and several are  Need to evaluate development in the floodplain seeking to upgrade their flood protection (the more development, the greater the risk to infrastructure (RWMG, 2013). public safety) As a result of the combination of aging infrastructure  Inadequate compensation to Yolo County for and rising expectations, water managers within the providing the City of Sacramento with flood county must determine how they can make the protection. Failure of the federal and state significant investments required to replace and governments to equitably address the Sacramento modernize aging infrastructure (RWMG, 2013). River Flood Control Project induced flood risks within and adjacent to the Yolo Bypass. 2.4.3 Flood Management and Other  Inadequate flood protection from existing Cache Natural Disasters Creek levees. Much of Yolo County is a natural floodplain. Three  Erosion of existing Cache Creek levees geographic regions with flooding issues include:  Inadequate vegetation removal on Cache Creek Cache Creek basin/Woodland, Sacramento River (impedes capacity) corridor, Western Yolo floodplain (Madison, Esparto, Airport Slough, etc.) and Yolo County land west of  Insufficient understanding of the risk of Cache the un-leveed part of the Yolo Bypass south of Putah Creek flooding Creek. The unincorporated area of Yolo County near  Inadequate levees to protect Madison and Esparto Cache Creek, as well as parts of the City of Woodland, from Lamb Valley Slough flooding have only 10-year flood protection according to the Federal Emergency Management Agency (FEMA;  Inadequate flood protection at the airport. Yolo WRA, 2007). Future land use changes in the Yolo Bypass must be Yolo County contains 2015 miles of levees as part of closely monitored to help ensure that impediments the Sacramento River Flood Control Project, including to flow do not occur that would further minimize the Yolo Bypass. The Yolo Bypass does not, and has capacity. All current and future land uses in the not, functioned at design flow capacity for many Bypass must be consistent with flow capacity years. This poses a threat to the citizens of Yolo, requirements and subject to consistent State Solano, and Sacramento Counties if future flood Reclamation Board enforcement. There should be no events exceed the capacity of the Bypass. redirected hydraulic impacts as a result of the project Geotechnical studies are necessary to determine operations, upstream development, or in-bypass whether some of the Yolo County’s Sacramento River projects. levees are subject to under-seepage or other potential causes of levee failure (Yolo WRA, 2007). 2.4.4 Climate Change Some of the issues surrounding flood management Climate change could significantly impact Yolo and storm drainage within Yolo CountyDRAFT include: County, impacting the ecological, environmental, and  Through seepage and under-seepage threats to economic conditions. The potential impact of climate Sacramento River levees change should be studied and considered in planning for resource management and economic  Erosion threats to Sacramento River levees development. The following areas of concern are  Inadequate funding for geotechnical studies to particularly relevant to the region (RWMG, 2013): determine erosion, stability, and seepage threats to  Increases in peak storm water runoff flows and Sacramento River levees and subsequent repair flood risk projects  Increased evapotranspiration  Inadequate public outreach (need for flood insurance, understanding of evacuation plans, etc.)  Decreased agricultural production due to changes in temperature and carbon dioxide levels  Inadequate emergency preparedness plans for levee failures  Reductions in the habitat of riparian and aquatic species

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 Decreased availability of water supplies. concern for irrigators in the valley who could be affected by the negative plant growth impacts 2.4.5 Water Quality (RWMG, 2013). High priorities for water quality include complying Pesticides are another major concern related to water with discharge requirements and Basin Plan quality impairment for the Westside Region. Surface Objectives and providing water of suitable quality for waters in the Yolo County are 303(d) listed for a host the intended beneficial use (RWMG, 2013). Water of pesticides that impair freshwater habitat and quality objectives are prescribed by the Regional commercial and sport fishing beneficial uses. The Water Quality Control Board in the Water Quality source of pesticides is runoff from agricultural Control Plan for the Sacramento River and San applications (RWMG, 2013). Joaquin River Basins (Basin Plan) to protect the many Compliance with state and federal water quality beneficial uses of the region’s waters, including programs is discussed in further detail in Section 3: municipal and domestic supply, agricultural supply, Water Quality Compliance. industrial supply, recreation, fishing, freshwater and wildlife habitat, and migration and spawning corridors. The Basin Plan includes narrative and 2.4.6 Sustaining Groundwater numeric water quality objectives. Waste load Resources allocations have been, and will continue to be, Groundwater is a key component of the county’s adopted as part of the development of total conjunctive water supply portfolio. Urban areas, maximum daily loads (TMDLs) for 303(d) listed agriculture, and the environment in Yolo County waterways within Yolo County (RWMG, 2013). depend upon a reliable water supply, a combination Cache Creek, Colusa Basin Drain, and the Sacramento of both groundwater and surface water. In a normal River within Yolo County all have TMDLs, and year, nearly all urban water users in the county, additional TMDLs are anticipated in the future for the except the City of West Sacramento, rely on Colusa Basin Drain, Davis Creek and Reservoir, groundwater as their primary source of water supply. Putah Creek, and Sacramento River. Surface water Farmers rely on groundwater for approximately 40 quality constituents of primary concern in Yolo percent of their supply in a normal year but rely more County include mercury, boron, pesticides, nutrients, heavily on groundwater during drought years. In the and fecal coliform (RWMG, 2013). future, urban population growth will result in an increase in water supply needs and demands from The Upper Cache Creek carries mercury-laden flows cities, unincorporated communities, and UC Davis through Cache Creek to the settling basin that drains (Yolo WRA, 2007). into the Yolo Bypass, which ultimately drains into the Bay Delta. Through this conveyance pathway, Cache It is unknown if the deep aquifers in the area are able Creek is a major contributor of mercury to the Bay to sustain current and future demands. Although Delta. Putah Creek has also been identified as a major agencies have tried to improve the understanding of contributor of mercury; however, theDRAFT construction of groundwater resources through preparation of Lake Berryessa has greatly reduced this contribution groundwater management plans and monitoring (RWMG, 2013). programs, much work remains to quantify the reliable, sustainable groundwater supplies available Boron is another common source of water quality (RWMG, 2013). impairment for the county. Boron, a naturally occurring element in the soils of the region, dissolves Sustaining groundwater resources is also important in water and is carried into surface water bodies. because heavy reliance on groundwater and While necessary for plant growth at low groundwater pumping has resulted in subsidence concentrations, boron in high concentrations is toxic (consolidation of the aquifer causing decreased to plants and can stunt their growth. Portions of ground levels). Lower land surfaces resulting from Cache Creek, Putah Creek, Willow Slough, Willow subsidence of peat soils behind levees, some of Slough Bypass and the Tule Canal have been 303(d) which can be attributed to groundwater pumping, listed for elevated boron concentrations that may be also contribute to flood risk because of the reduced impairing agricultural water quality. From an end use effectiveness of the levees. Subsidence due to perspective, boron in surface water is mainly a groundwater pumping has been detected in the

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northern Yolo-Zamora area of Yolo County between  Removal of natural vegetation and wildlife habitat, Zamora and Knights Landing, where subsidence is including destruction of wetlands, waterways, and reported to be on the order of 5 feet, and the vicinity shoreline ecologies of Davis and Woodland, where subsidence is  Improper livestock husbandry and other poorly estimated at 2 or 3 feet (RWMG, 2013). implemented agriculture, industry, and commercial BMPs 2.4.7 Land Use  Potential conflict between land and water use for: The following land uses and human activities can (a) recreation and tourism, (b) agriculture, and contribute to the degradation of soils, waterbodies, (c) opportunities to restore and preserve the and habitat and can make watershed management environment. more difficult. Some of the listed activities have been described under several earlier topics but are In addition, urban development (parking lots, roads, additionally emphasized here because of their and other impervious areas) contributes to increased importance to the stakeholders (RWMG, 2013): runoff and pollution and decreased infiltration and natural creek and river flows. Methods to address  Alteration of the natural landscape for any these land use impacts include increasing urban purpose, creating disturbed soils susceptible to greenspace, low impact development techniques erosion, and requiring installation of minimum such as reduced impervious area and vegetated control measures prescribed for NPDES facilities and infiltration basins for storm water runoff stormwater management permit compliance; capture, and conversion of impervious pavement to  Application or accidental release of potentially pervious materials. contaminating substances or prohibited waste

discharges to water supplies, including wastewater system overflows, septic system failures, water treatment byproducts, pest abatement, improper disposal of litter or refuse, and lack of stormwater management

DRAFT

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