Introduction EXECUTIVE SUMMARY

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PUBLIC DRAFT FINAL

Vina Groundwater Subbasin GSP ES-1 September 10, 2021

EXECUTIVE SUMMARY

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Sustainability Goal:

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to ensure that groundwater is managed to provide a water supply of adequate quantity 3 and quality to support rural areas and communities, the agricultural economic base of 4 the region, and environmental uses now and in the future.

5

Introduction

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In 2014, the California legislature enacted the Sustainable Groundwater Management Act 7 (SGMA) in response to continued overdraft of California’s groundwater resources. SGMA 8 provides for local control of groundwater resources while requiring sustainable management of 9 the state’s groundwater basins. Under the provisions of SGMA, local agencies must establish 10 governance of their subbasins by forming Groundwater Sustainability Agencies (GSAs) within 11 the authority to develop, adopt, and implement a Groundwater Sustainability Plan (GSP or Plan) 12 for the subbasin. Under the GSP, GSAs must adequately define and monitor groundwater

13 conditions in the subbasin and establish criteria to maintain or achieve sustainable groundwater 14 management within 20 years of GSP adoption. Within the framework of SGMA, sustainability is 15 generally defined as long-term reliability of the groundwater supply and the absence of

16 undesirable results.

17

Critical Dates for the Vina Groundwater Subbasin 2022 By January 31, submit GSP to DWR 2027 Evaluate GSP and update, if warranted 2032 Evaluate GSP and update, if warranted 2037 Evaluate GSP and update, if warranted 2042 Achieve sustainability for the Subbasin

18

The Vina Groundwater Subbasin (Vina or Subbasin) is identified by the California Department 19 of Water Resources (DWR) as being in a high priority subbasin. For high priority basins, SGMA 20 requires that preparation of the GSP by January 31, 2022.

21

The Vina Subbasin is managed by two GSAs, the Vina GSA and the Rock Creek Reclamation 22 District (RCRD) GSA. The Vina GSA was formed through the execution of a Joint Powers 23 Agreement (JPA) by three member agencies - the County of Butte, City of Chico, and Durham 24 Irrigation District. The Vina GSA Board of Directors (Board) is composed of 5 seats, each with 25 equal and full voting rights, which consists of an elected official from each member agency, an 26 agricultural groundwater user, and a domestic well user (non-agricultural); the latter two

27 positions being appointed by the Butte County Board of Supervisors. The Vina GSA covers the 28 portions of the Vina subbasin outside of the RCRD GSA jurisdictional boundary. In addition, in 29 2017 Butte College withdrew GSA status and agreed to participate in the development of the 30 GSP by way of a Memorandum of Understanding (MOU) with Vina GSA.

31

The RCRD provides flood control and groundwater sustainability services to approximately 32 4,625 acres of agricultural and single-family residential parcels in northern Butte County. On 33

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October 18, 2016, the RCRD elected to become a GSA and sent notice to DWR of its intent to 34 undertake sustainable groundwater management over its jurisdictional boundaries.

35

The Vina GSA and RCRD haves assumed all SGMA authorities. The GSAs entered into a 36 Coordination Agreement for the purpose of developing and implementing a single GSP for the 37 Vina subbasin.

38

The purpose of the Coordination Agreement was to (a) to develop, adopt, and implement a GSP 39 for the Vina subbasin to implement SGMA requirements and achieve the sustainability goals;

40 and (b) involve the public and subbasin stakeholders through outreach and engagement in 41 developing and implementing the GSP. At the heart of the Coordination Agreement is the focus 42 to maximize local input and decision-making and address the different water demands and 43 sustainability considerations in the municipal and rural areas of the Vina subbasin.

44

The JPA also defines three Management Areas (MAs) within the Vina Subbasin, Vina North, 45 Vina Chico, and Vina South. A Management Area refers to an area within a basin for which a 46 GSP may identify different minimum thresholds, measurable objectives, monitoring, and 47 projects and actions based on unique local conditions or other circumstances as described in the 48 GSP regulations. The interests and vulnerability of stakeholders and groundwater uses in these 49 Management Areas vary based on the nature of the water demand (agricultural, domestic, 50 municipal), numbers and characteristics of wells supplying groundwater, and to some degree the 51 hydrogeology and mix of recharge sources. The RCRD GSA is part of the Vina North

52 Management Area.

53

SGMA requires development of a GSP that achieves groundwater sustainability in the Subbasin 54 by 2042. A pragmatic approach to achieving sustainable groundwater management requires an 55 understanding of (1) historical trends and current groundwater conditions in the subbasin, based 56 on evaluating six sustainability indicators that include groundwater levels, groundwater storage, 57 groundwater quality, land subsidence, depletion of interconnected streams, and seawater

58 intrusion and (2) what must change in the future to ensure sustainability without causing 59 undesirable results (described and defined in Section 3) or negatively impacting beneficial uses 60 and users of groundwater, including groundwater dependent ecosystems.

61

The GSP is organized as follows and the various components of each Section are summarized 62 further below:

63

1. Section 1: Plan Area. This Section includes agency information, description of the 64 Plan Area, and applicable programs and data sources used to prepare the GSP.

65

2. Section 2: Basin Setting. This Section discusses the Hydrogeologic Conceptual 66 Model (HCM), groundwater conditions and water budget.

67

3. Section 3: Sustainable Management Criteria. This Section discusses undesirable 68 results, identifies the minimum thresholds, and measurable objectives for each of the 69 six sustainability indicators.

70

4. Section 4: Monitoring Network. This Section describes the methods used to monitor 71 the sustainability indicators.

72

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5. Section 5: Project Management Actions. This Section describes projects and 73 management actions that will achieve sustainability within the Subbasin.

74

6. Section 6: Plan Implementation. This Section describes how the GSA will partner 75 with other groundwater users to implement the GSP to achieve groundwater

76 sustainability.

77

The GSP outlines the need to address overdraft and related conditions and has identified 15 78 projects for potential development that either replace groundwater use (offset) or supplement 79 groundwater supplies (recharge) to meet current and future water demands. In addition, the GSP 80 also identifies seven management actions that can be implemented to focus on reduction of 81 groundwater demand. The estimated sustainable yield, or the amount of groundwater that can be 82 withdrawn without causing undesirable results, for the Subbasin is 233,000 acre-feet per year 83 (AFY). This estimate is based on average annual historical groundwater pumping of 243,000 84 AFY and an annual decrease in storage of 10,000 AFY. As such, groundwater pumping offsets 85 and/or recharge on the order of 10,000 AFY may be required to achieve sustainability although 86 additional efforts are needed to confirm the level of pumping offsets and/or recharge required to 87 achieve sustainability. These efforts include collecting additional data and a review of the 88 Subbasin groundwater model, along with other efforts as outlined in the GSP.

89

Groundwater Sustainability Plan Area

90

The Vina Subbasin is in Butte County within the Sacramento Valley as shown in Figure ES-1.

91 The Vina GSA jurisdictional area is defined by the boundaries of the Vina Subbasin in DWR’s 92 2003 Bulletin 118 as updated in 2016 and 2018 except for the area overseen by the RCRD GSA.

93 The RCRD GSA is defined as the jurisdictional boundaries of the RCRD. Figure ES-2 shows the 94 boundaries of the Vina Subbasin, jurisdictional areas for both GSAs, and the three MAs.

95

Outreach Efforts

96

A stakeholder engagement strategy was developed to solicit and discuss the interests of all 97 beneficial users of groundwater in the Subbasin and Plan Area. The strategy included monthly 98 meetings of the Vina GSA and RCRD Board of Directors and the Stakeholder Advisory 99 Committee (SHAC), meetings of the Subbasin Technical Working Group, numerous public 100 workshops and events and a website where all announcements, meeting dates, times, and 101 materials were posted.

102

The Vina GSA also prepared and implemented a Communication and Engagement Plan to 103 encourage involvement from diverse social, cultural, and economic elements of the population of 104 the Vina Subbasin, in addition to meeting SGMA requirements for intrabasin coordination.

105

In addition, various Sections of the GSP were available for preliminary review and comment 106 prior to the final draft version released on September 10, 2021. Comments received on

107 preliminary draft Sections were incorporated as deemed appropriate and helped guide and shape 108 the final draft document.

109 110

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South American Yolo

Corning Red Bluff

Sutter Los Molinos

Colusa

North American

South Yuba Wyandotte Creek Butte

Bend

North Yuba

Solano Antelope

Vina

Figure ES-1

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Project No.: SAC282

20 10 0 20 Miles

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Legend

Sacramento Valley Groundwater Basin Groundwater Subbasins

Vina Subbasin

Other Sacramento Valley Subbasins

Highways

Sacramento Valley Groundwater Basin

Vina GSA

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Rock Creek Reclamation District GSA

Vina GSA

Chico

Durham

Colusa Co.Glenn Co.

Tehama Co.

Butte Co.

Tehama Co.

Glenn Co.

Butte Co.

Glenn Co.

Figure ES-2

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Project No.: SAC282

5 2½ 0 5 Miles

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Legend

GSA boundaries

Vina Groundwater Subbasin Management Areas

Vina North

Vina Chico

Vina South

Roads

Highways

Other roads Boundaries

County boundaries

Groundwater Sustainability Agencies

Vina GSA

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Basin Setting

111

The Vina Subbasin lies in the eastern central portion of the Sacramento Groundwater Basin. The 112 northern boundary is the Butte-Tehama County line, the western boundary is the Butte-Glenn 113 County line, the southern boundary is a combination of the property boundaries owned by the 114 M&T Ranch, the service area boundaries of RD 2106 and Western Canal Water District, and the 115 eastern boundary is the edge of the alluvium as defined by the DWR Bulletin 118 Update 2003.

116 It is bounded by the following subbasins: Los Molinos to the north, Corning to the west, Butte to 117 the south. The lateral boundaries of the Subbasin are jurisdictional in nature, and it is recognized 118 that groundwater flows across each of the defined boundary lines to some degree.

119

Continental sediments of the Tehama, Tuscan and Laguna Formation compose the major fresh 120 groundwater-bearing formations in the valley with the Tuscan Formation and, to a lesser degree, 121 the Tehama Formation compose the major fresh groundwater-bearing formations in the

122 Subbasin. Figure ES-3 shows a cross section within the Subbasin using data from an Airborne 123 Electromagnetic (AEM) survey conducted in 2018 funded through a grant from DWR. The base 124 of these continentally derived formations is generally accepted as the base of fresh water in the 125 northern Sacramento Valley. Locally, the base of fresh groundwater fluctuates depending on 126 local changes in the subsurface geology and geologic formational structure. In the Vina 127 Subbasin, this is especially the case in the southeastern area of the Subbasin where marine 128 sediments occur at shallower depths on the margins of the valley.

129

Groundwater flows from the north toward the southwestern corner of the Subbasin. While 130 groundwater elevations are lower in the fall than spring, the general direction and gradient of 131 flow are similar during both periods. The Sacramento River borders the Subbasin on its western 132 side and flows from north to south. The larger surface water bodies generally flow from east to 133 west towards the Sacramento River and include Big Chico Creek and Butte Creek. Other smaller 134 or ephemeral streams also generally flow from east to west and include Pine Creek, Rock Creek, 135 Mud Creek, Sycamore Creek, Little Chico Creek, Hamlin Slough, Little Dry Creek, and Clear 136 Creek. The location of the Subbasin along with surface water features is shown in Figure ES-4.

137

Existing Groundwater Conditions

138

Groundwater conditions in the Vina Subbasin are continually monitored and are

139 comprehensively described in reports produced by Butte County since 2001. These documents 140 and other reports portray a subbasin that has adequate groundwater resources to meet demands 141 under most hydrologic conditions. However, comparison of the reports illustrates how in the 142 period between their issuance, groundwater use has increased and as forces ranging from 143 population growth to climate change play out, well-informed water management policies and 144 practices will become necessary. In short, while groundwater conditions in the Subbasin remain 145 stable, maintaining this posture in the future may become less the result of a state of nature and 146 more the reward for thoughtful management.

147

Groundwater levels in the Subbasin indicate that groundwater elevations are relatively stable 148 except for localized cones of depression. Localized depressions have been observed under the 149 City of Chico and in the Durham area. Groundwater quality in the basin is good except in areas 150

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VINA SUBBASIN GSP

AUGUST 2020 DRAFT FIGURE ES-3

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SURFACE WATER FEATURES

AUGUST 2020 DRAFT FIGURE ES-4

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where anthropogenic sources have impacted the groundwater. Figure ES-5 shows the locations 151 of known impacted groundwater from these sources.

152

Groundwater storage in Subbasin is relatively stable except in the areas noted above with

153 depressions. The Sacramento River and streams that cross the Subbasin stabilize storage volumes 154 by providing recharge to the Subbasin. The total fresh groundwater in storage was estimated at 155 over 16 million-acre-feet (MAF). The amount of groundwater in storage has decreased by 156 approximately 0.07 percent per year between 2000 and 2018. As such, it is highly unlikely the 157 Subbasin will experience conditions under which the volume of stored groundwater poses a 158 concern. However, the depth to access that groundwater across the Subbasin does pose a 159 concern.

160

Land subsidence has not historically been an area of concern in the Subbasin and there are no 161 records of land subsidence caused by groundwater pumping. Seawater intrusion is not applicable 162 to the Vina Subbasin due to distance from the Delta and Pacific Ocean.

163

Surface waters can be hydraulically interconnected with the groundwater system, where the 164 stream baseflow is either derived from the aquifer (gaining stream) or recharged to the aquifer 165 (losing stream). If the water table beneath the stream lowers as a result of groundwater pumping, 166 the stream may disconnect entirely from the underlying aquifer. Both situations exist in the Vina 167 Subbasin. Within the floodplain of the Sacramento River, there is a continuous saturated zone 168 that connects the shallowest aquifer to the river. The connectivity between shallow and deeper 169 aquifer zones will dictate the overall connectivity to the River. In the upland areas outside of the 170 Sacramento River floodplain, there are creeks that flow seasonally and often dry up in late 171 summer or are dry for an entire year during dry conditions. In this case, the upland creeks may 172 not be influenced by “high groundwater connectivity” and the presence of an undesirable result 173 is not clear cut with respect to surface water depletion. The streams dry up regardless of the 174 groundwater condition, and streams that are already dry are not considered interconnected

175 surface water. However, the upland streams are an important source of recharge to the aquifer, so 176 the health of these stream channels and their adjacent riparian zones is important to groundwater 177 sustainability.

178

Potential impacts of the depletion of interconnected surface water were discussed by

179 stakeholders during technical discussions covering the fundamentals of groundwater-surface 180 water interactions and mapping analysis of groundwater dependent ecosystems (GDEs) prepared 181 by Butte County Department of Water Resources. Potential impacts identified by stakeholders 182 were:

183

• Disruption to GDEs 184

• Reduced flows in rivers and streams supporting aquatic ecosystems and water right

185 holders

186

• Degradation of “Urban Forest” habitat in the City of Chico 187

• Streamflow changes in upper watershed areas outside of the Vina GSA’s boundary 188

• Water table depth dropping below the maximum rooting depth of Valley Oak (Quercus 189 lobata) or other deep-rooted tree species

190

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• Cumulative groundwater flow moving toward the Sacramento River from both the Vina 191 Subbasin and surrounding GSAs on both the east and west side of the river

192

The Vina Subbasin acknowledges that overall function of the riparian zone and floodplain is 193 dependent on multiple components of the hydrologic cycle that may or may not have

194 relationships to groundwater levels in the principal aquifer. For example, hydrologic impacts 195 outside of the Vina Subbasin, such as upper watershed development or fire-related changes in 196 run-off, could result in impacts to streamflow, riparian areas, or GDEs that are completely 197 independent of any connection to groundwater use or conditions within the Vina Subbasin.

198

Sustainable Management Criteria

199

SGMA introduces several terms to measure sustainability. The sustainability goal is the 200 culmination of conditions resulting in a sustainable condition (absence of undesirable results) 201 within 20 years. The sustainability goal for the Vina Subbasin is:

202

to ensure that groundwater is managed to provide a water supply of adequate quantity 203 and quality to support rural areas and communities, the agricultural economic base of 204 the region, and environmental uses now and in the future.

205

Sustainability indicators (SIs) refer to any of the effects caused by groundwater conditions 206 occurring throughout the Subbasin that, when significant and unreasonable, cause undesirable 207 results. The six sustainability indicators identified by DWR are:

208

1. Chronic lowering of groundwater levels indicating a significant and unreasonable 209 depletion of supply if continued over the planning and implementation horizon 210

2. Significant and unreasonable reduction of groundwater storage 211

3. Significant and unreasonable degraded water quality 212

4. Significant and unreasonable land subsidence that substantially interferes with surface

213 land uses

214

5. Depletions of interconnected surface water that have significant and unreasonable 215 adverse impacts on beneficial uses of the surface water

216

6. Significant and unreasonable seawater intrusion 217

Undesirable results are the significant and unreasonable occurrence of conditions that adversely 218 affect groundwater use in the Subbasin, including reduction in the long-term viability of

219 domestic, agricultural, municipal, or environmental uses of the Subbasin’s groundwater.

220 Categories of undesirable results are defined through the sustainability indicators.

221

Minimum thresholds (MT) are numeric values for each sustainability indicator and are used to 222 define when undesirable results occur. Undesirable results occur if minimum thresholds are 223 exceeded in an established percentage of sites in the Subbasin’s representative monitoring 224 network. Measurable objectives (MO) are a specific set of quantifiable goals for the maintenance 225 or improvement of groundwater conditions. The margin of operational flexibility is the range of 226 active management between the MT and the MO. Interim milestones (IM) are targets set in 5- 227

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year increments over the implementation period of the GSP offering a path to sustainability.

228 Figure ES-6 illustrates these terms using the groundwater level sustainability indicator.

229 230

231

Figure ES-6: Illustration of Terms Used for Describing Sustainable Management Criteria 232 Using the Groundwater Level Sustainability Indicator

233

A total of 17 representative wells were identified for measurement of groundwater levels in the 234 Subbasin, and 8 representative wells were identified for groundwater quality monitoring. The 235 GSP uses groundwater quality data as a basis for evaluating conditions from saline water below 236 the fresh water and uses groundwater level data as the basis for evaluating conditions for

237 groundwater levels, groundwater storage, and subsidence. The GSP has identified a data gap for 238 development of sustainable management criteria (SMC) for depletion of interconnected surface 239 waters and has provided a framework for evaluation of this Sustainability Indicator (SI).

240 However, for this GSP, the SMC developed for groundwater levels are used as a proxy for 241 interconnected surface water in an interim manner until data gaps are addressed. As such, the 242 representative monitoring sites (RMS) described above provide the basis for measuring the five 243 relevant sustainability indicators across the Subbasin.

244

Minimum thresholds and measurable objectives were developed for each of the representative 245 wells. Figure ES-7 shows a typical relationship of the minimum thresholds, measurable

246 objectives, and historical groundwater level data for a sample groundwater level representative 247 monitoring well.

248

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249

Figure ES-7: Representative Monitoring Site For Groundwater Levels With Relationship 250 Of Measurable Objectives, Minimum Thresholds and Operational Range

251 252

Minimum thresholds for groundwater levels were developed with reference to domestic well 253 depths. For the Vina North and South, the Management Areas were divided into polygons that 254 represent proximate areas to each representative monitoring site well. The size of each polygon 255 depends on the density of the RMS network. For example, the higher the density of RMS wells 256 in a Management Area, the smaller the polygons. Each polygon is a different shape and size, 257 determined by the distribution of the RMS wells in the Management Area. The result is a more 258 refined dataset that more proximately reflects the relationship of domestic wells with each RMS 259 well. In addition, rather than just looking at a percentage of domestic wells to protect, the

260 elevation levels were examined in comparison to what would be considered sustainable domestic 261 wells for the area. For the Vina Chico MA, due the area, the MT for all RMS wells was based on 262 the 15 percentile of total well depth for wells completed after 1980. The DWR database used for 263 information on total depths of the domestic wells is not always accurate or precise, nor is it 264 known which of the wells in the database are in use or have been abandoned or replaced. As 265 such, the GSP has identified these data as a data gap that will be further investigated.

266

To establish the MO, the water-level hydrograph of observed groundwater levels at each RMS 267 was evaluated. The historical record at these locations shows cyclical fluctuations of

268 groundwater level over a four- to seven-year cycle. The MO for groundwater levels at each RMS 269 well was set at the trend line for the dry periods (since 2000) of observed short-term climatic 270 cycles extended to 2030. Figure ES-8 shows an example of this trend line for an RMS well.

271 Table ES-1 shows the MTs and MOs for groundwater levels at each of the RMS wells.

272

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Figure ES-8: Illustration of Long-Term Trend Using Historical Water Levels Extended to 273 2030 for Development of Measurable Objectives

274

Table ES-1: Groundwater Levels Sustainable Management Criteria by Representative 275 Monitoring System in Feet Above Mean Sea Level

276

RMS Well ID MT MO IM

2027 2032 2037 Vina Subbasin – North Management Area

25C001M 50 130 131 130 130

10E001M 80 136 139 136 136

07H001Ma 72 136 145 136 136

05M001M 31 115 116 115 115

36P001M 45 108 110 108 108

33A001M 72 125 126 125 125

Vina Subbasin – Chico Management Area CWSCH01b

85

106 108 106 106

28J001M 110 111 110 110

CWSCH03 108 110 108 108

CWSCH02 105 108 105 105

CWSCH07 108 109 108 108

Vina Subbasin – South Management Area

21C001M 44 64 66 64 64

18C003M 65 130 134 130 130

10C002M 20 92 95 92 92

24C001M 18 77 82 77 77

09L001M 30 91 94 91 91

26E005M 36 95 96 95 95

Note:

a MO is associated with GSP Well ID 18A001M.

277

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MTs and MOs for water quality were defined by considering two primary beneficial uses, 278 drinking water and agricultural uses, that would be at risk of undesirable results as it relates to 279 specific conductance, a measure of the water’s saltiness. Minimum thresholds are 1,600 micro- 280 siemens per centimeter (µS/cm) for each representative monitoring well, consistent with the 281 upper limit of the California Secondary Maximum Contaminant Level (SMCL) for electrical 282 conductivity. Measurable objectives are 900 µS/cm for each representative monitoring well, 283 consistent with the California SMCL for electrical conductivity.

284

Data needed to develop the Secondary MCs for interconnected surface waters includes definition 285 of stream reaches and associated priority habitat, streamflow measurements to develop profiles at 286 multiple time periods, and measurements of groundwater levels directly adjacent to stream 287 channels, first water bearing aquifer zone, and deeper aquifer zones. These data are not available 288 and are a data gap for the GSP. The GSAs in the Vina Subbasin intend to further evaluate this 289 SMC to avoid undesirable results to aquatic ecosystems and GDEs. To that at end, an

290 Interconnected Surface Water SMC framework has been developed for the GSP. As such, for 291 this GSP the groundwater levels SMC are used by proxy and the MT and MO for interconnected 292 surface water is the same as for groundwater levels.

293

The MTs and MOs for groundwater levels are also used for the land subsidence and groundwater 294 storage sustainability indicators, as both are strongly linked to groundwater levels. The

295 groundwater levels MTs are found to be protective of land subsidence and groundwater storage.

296

Water Budgets

297

The groundwater evaluations conducted as a part of GSP development have provided estimates 298 of the historical, current, and projected groundwater budget conditions. The current analysis was 299 prepared using the best available information and through use of the Butte Basin Groundwater 300 Model (BBGM). The BBGM was initially developed in 1992 and has been updated over time to 301 simulate historical conditions through 2018. To prepare water budgets for this GSP, historical 302 BBGM results for water years 2000 to 2018 have been relied upon and four additional baseline 303 scenarios have been developed to represent current and projected conditions utilizing 50 years of 304 hydrology. It is anticipated that as additional information becomes available, the model will be 305 updated, and more refined estimates of annual pumping and overdraft can be developed.

306

Based on these analyses and an evaluation of declining water levels, the long-term groundwater 307 pumping offset and/or recharge required for the Subbasin to achieve sustainability is

308 approximately 10,000 AFY. The estimated sustainable yield for the subbasin is 233,000 AFY 309 Groundwater levels are expected to continue to decline based on projections of current land and 310 water uses. Projects, identified in Section 5, that offset groundwater pumping and/or increase 311 recharge will help the Subbasin reach sustainability.

312

The projected Subbasin water budget was also evaluated under climate change conditions, which 313 simulate higher demand requiring increased groundwater pumping despite more precipitation 314 and streamflows. The climate change scenario used for the analysis was based on the 2030 and 315 2070 central tendency climate change datasets provided by DWR to support GSP development.

316 Figure ES-9 illustrates the cumulative change in groundwater storage for current and future 317 conditions.

318

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319

Figure ES-9: Cumulative Change in Groundwater Storage for Current and Future

320 Conditions Baseline Scenarios

321 322

Monitoring Networks

323

The GSP outlines the monitoring networks for the six sustainability indicators. The objective of 324 these monitoring networks is to monitor conditions across the Subbasin and to detect trends 325 toward undesirable results. Specifically, the monitoring network was developed to do the 326 following:

327

• Monitor impacts to the beneficial uses or users of groundwater 328

• Monitor changes in groundwater conditions relative to measurable objectives and 329 minimum thresholds

330

• Demonstrate progress toward achieving measurable objectives described in the GSP 331

There are five monitoring networks in the Vina Subbasin: a representative network for water 332 levels; a broad network for water levels; a representative network for water quality; a broad 333 network for water quality; and a broad network for land subsidence. Representative networks are 334 used to determine compliance with the minimum thresholds, while the broad networks collect 335 data for informational purposes to identify trends and fill data gaps. The two monitoring 336

-400 -300 -200 -100 0 100 200 300 400

year 1… year 3… year 5… year 7… year 9… year 11… year 13… year 15… year 17… year 19… year 21… year 23… year 25… year 27… year 29… year 31… year 33… year 35… year 37… year 39… year 41… year 43… year 45… year 47… year 49…

Acre-Feet (thousands)

Current Future Conditions, No Climate Change

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networks for water quality will additionally be used to develop an electrical conductivity 337 isocontour to monitor for potential intrusion for underlying saline waters and water levels data 338 will inform depletions of interconnected surface water.

339

The monitoring networks were designed by evaluating data from Butte County’s existing BMO 340 program, the United States Geological Survey (USGS), and participating GSAs. The monitoring 341 network consists largely of wells that are already being used for monitoring in the Subbasin.

342 Figure ES-10 shows the location of groundwater monitoring wells for the representative 343 monitoring network.

344

Wells in the monitoring networks will be measured on a semi-annual schedule. Historical 345 measurements have been entered into the Vina Subbasin Data Management System (DMS), and 346 future data will also be stored in the DMS. A summary of the wells in the monitoring networks is 347 shown in the table below.

348

Summary of Monitoring Network Wells

Representative Networks Well Count

Groundwater Level 17

Groundwater Quality 8

Broad Network

Groundwater Levels 78

Groundwater Quality 7

Subsidence 191

349

Data Management System

350

The DMS that will be used is a geographical relational database that will include information on 351 water levels, land elevation measurements, and water quality testing. The DMS will allow the 352 GSAs to share data and store the necessary information for annual reporting.

353

The DMS will be on local servers and data will be transmitted annually to form a single

354 repository for data analysis for the Subbasin’s groundwater, as well as to allow for preparation of 355 annual reports. GSA representatives have access to data and will be able to ask for a copy of the 356 regional DMS. The DMS currently includes the necessary elements required by the regulations, 357 including:

358

• Well location and construction information for the representative monitoring points 359 (where available)

360

• Water level readings and hydrographs including water year type 361

• Land based measurements 362

• Water quality testing results 363

• Estimate of groundwater storage change, including map and tables of estimation 364

• Graph with Water Year type, Groundwater Use, Annual Cumulative Storage Change 365

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A City of

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Rock Creek Reclamation District GSA

Vina GSA

23N02W25C001M

23N01W10E001M 23N01E07H001M

22N01W05M001M

23N01W36P001M

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Figure ES-10

P:\GIS\SAC282 - Butte County\Project\202010_GSP_Maps\20210420\RMS_GWE_Vina.mxd 5/6/2021 5:03:35 PM (Author: SMitchell)

Project No.: SAC282

4 2 0 4 Miles

³

May 2021

Groundwater Level RMS Wells

Vina GSP

DRAFT

Groundwater Sustainability Agency (GSA)

Vina GSA

Rock Creek Reclamation District GSA

Vina Subbasin Management Areas North

Chico

South

Legend

RMS GWE Monitoring Wells

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Highways

County boundaries

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Additional items may be added to the DMS in the future as required. Data will be entered into 366 the DMS by each GSA. The majority of the data will then be aggregated to the entity that is 367 responsible for the regional DMS and summarized for reporting to DWR.

368

Plan Implementation

369

Implementing the Vina Subbasin GSP will require numerous management activities that will be 370 undertaken by the GSAs, including:

371

• Monitoring conditions relative to applicable sustainability indicators at specified 372 frequency and timing

373

• Entering updated monitoring data into the Subbasin DMS 374

• Refining the Subbasin model and water budget planning estimates 375

• Preparing annual reports summarizing the conditions of the Subbasin and progress 376 towards sustainability and submitting them to DWR

377

• Updating the GSP once every five years 378

• Overseeing and monitoring projects, management actions, and collection of data 379 identified as “data gaps” within the GSP.

380

• Coordinating with neighboring subbasins 381

The GSP also presents a schedule of implementation of the items discussed above as described in 382 Section 6.

383 384 385 386 387