12/11/2014. Provided by Thomas Harter, UC Davis RAIN. How much groundwater is in an aquifer?

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1 12/11/2014 Drought Effects on Groundwater Management: Understanding Groundwater, Drought, and Streams Overview 1. Differences in aquifer characteristics across California ag areas (capacity, material, water quality, etc)? 2. Consequences of overpumping? 3. Impacts of groundwater extraction on river flows? 4. Thomas Harter University of California Water level status in California s ag regions? 5. Potential impacts of the 2014 Sustainable Groundwater Management Act on ag pumping? RAIN > 50 in Space and Time Disconnect between Water Supply and Water Use ~15 in WATER USERS < 5 in Groundwater = Water completely filling Pores/Fractures Courtesy, Dane Mathis, DWR How much groundwater is in an aquifer? 1

2 California Groundwater Basins 515 groundwater basins 30% 40% of urban and agricultural water supplies From: California Department of Water Resources Sediments => result of erosion, water, wind, lake deposition, ocean bay deposition fractured bedrock of California s mountain ranges Unconfined Aquifer Losing stream 2

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4 12/11/2014 (Semi ) Confined Aquifer A Groundwater Well gravel pack well screen Hydraulic Conductivity from Borehole Logs (Estimated) Cone of Depression near a Well from: U.S. Geological Survey, Ground Water and the Rural Homeowner Courtesy, Claudia Fawn, USGS,

5 Groundwater Use in California: maf/yr The Invisible Storage Reservoir From: DWR California Water Plan 2009 (Bulletin ) From: DWR California Water Plan 2013 Draft (Bulletin ) 5

6 1977 Tule River Basin: Monthly Water Budgets, Oct Sep Courtesy, California Department of Water Resources Ruud, Harter et al., 2003, 2004 Southern Tulare County Water Budget USE SUPPLY 1990 drought 1977 drought Ruud, Harter et al., 2003,

7 Consequences of Groundwater Overdraft Land Subsidence Increased pumping cost: ~ $500 million in 2014 (Howitt et al., 2014) Land subsidence California Department of Water Resources; Drought Response Update Fall

8 Land Subsidence: San Joaquin Valley Consequences of Groundwater Overdraft Increased pumping cost Land subsidence Water quality degradation Seawater intrusion Surface water depletion Impact to groundwater dependent ecosystems California Department of Water Resources; Drought Response Update Fall 2014 Gaining Stream Losing Stream Disconnected Stream Dry Stream 8

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11 Groundwater Dependent Ecosystems And the GW SW Interface Groundwater Dependent Ecosystems: Springs and Seeps Howard and Merrifield, 2010, PlosONE, DOI: /journal.pone Groundwater Dependent Ecosystems: Wetlands Groundwater Dependent Ecosystems: Baseflow Howard and Merrifield, 2010, PlosONE, DOI: /journal.pone Howard and Merrifield, 2010, PlosONE, DOI: /journal.pone

12 12/11/2014 Groundwater Dependent Ecosystems: Flow Contributions Drought History Sacramento River Runoff San Joaquin River Runoff Howard and Merrifield, 2010, PlosONE, DOI: /journal.pone California Department of Water Resources; California Water Plan Update 2013 (Draft) Change in Aquifer Storage Central Valley SR: -0.7 to -1.7 MAF SJR: -1.0 to -2.6 MAF TL: -3.7 to -8.9 MAF CV Total: -5.4 to MAF Change in Groundwater Level, Record Low 20th Century to Drought Current Drought: Worst Groundwater Status In Most Basins California Department of Water Resources; Drought Response Update Fall

13 12/11/ Current Drought: Worst Groundwater Status In Most Basins Northern California Groundwater Level Changes, Spring 2004 Spring 2014 Unmonitored Basins California Department of Water Resources; Drought Response Update Fall 2014 Northern California Groundwater Level Changes, Spring 2004 Spring Central California Groundwater Level Changes, Spring 2004 Spring Central California Groundwater Level Changes, Spring 2004 Spring Southern California Groundwater Level Changes, Spring 2004 Spring

14 California Groundwater Rights: Background Sustainable Groundwater Management Act of 2014 Correlative Rights Doctrine California constitutional mandate for beneficial use Special districts (20 different types, about 2,300 districts) o Water districts, irrigation districts, private water companies, reclamation districts, water conservation districts, water replenishment districts, water storage districts, etc. County police power controls groundwater exports o Baldwin vs. Tehama County, 1994 Basin adjudication / physical solution controls extraction o City of Barstow vs. Mojave Water Agency, 2000: Right of water users to negotiate physical equitable, practical solution, regardless of water rights Individual water rights holders cannot be forced into a voluntary agreement Sustainable Groundwater Management Act of 2014: Local/Regional Control => if local/regional control fails: State Water Resources Control Board The Courts SEC. 2. Section 113 is added to the Water Code, to read: 113. It is the policy of the state that groundwater resources be managed sustainably for long term reliability and multiple economic, social, and environmental benefits for current and future beneficial uses. Sustainable groundwater management is best achieved locally through the development, implementation, and updating of plans and programs based on the best available science. Sustainable Groundwater Management Act of 2014 SEC. 3. Part 2.74 (commencing with Section 10720) is added to Division 6 of the Water Code, to read: PART Sustainable Groundwater Management CHAPTER 1. General Provisions This part shall be known, and may be cited, as the Sustainable Groundwater Management Act In enacting this part, it is the intent of the Legislature to do all of the following: (a) To provide for the sustainable management of groundwater basins. (b) To enhance local management of groundwater consistent with rights to use or store groundwater and Section 2 of Article X of the California Constitution. It is the intent of the Legislature to preserve the security of water rights in the state to the greatest extent possible consistent with the sustainable management of groundwater. (c) To establish minimum standards for sustainable groundwater management. (d) To provide local groundwater agencies with the authority and the technical and financial assistance necessary to sustainably manage groundwater. (e) To avoid or minimize subsidence. (f) To improve data collection and understanding about groundwater. (g) To increase groundwater storage and remove impediments to recharge. (h) To manage groundwater basins through the actions of local governmental agencies to the greatest extent feasible, while minimizing state intervention to only when necessary to ensure that local agencies manage groundwater in a sustainable manner. [all emphasis added by TH] Sustainable Groundwater Management Act of Unless the context otherwise requires, the following definitions govern the construction of this part: (u) Sustainable groundwater management means the management and use of groundwater in a manner that can be maintained during the planning and implementation horizon without causing undesirable results. (w) Undesirable result means one or more of the following effects caused by groundwater conditions occurring throughout the basin (Section (w)): (1) Chronic lowering of groundwater levels indicating a significant and unreasonable depletion of supply if continued over the planning and implementation horizon. Overdraft during a period of drought is not sufficient to establish a chronic lowering of groundwater levels if extractions and recharge are managed as necessary to ensure that reductions in groundwater levels or storage during a period of drought are offset by increases in groundwater levels or storage during other periods. (2) Significant and unreasonable reduction of groundwater storage. (3) Significant and unreasonable seawater intrusion. (4) Significant and unreasonable degraded water quality, including the migration of contaminant plumes that impair water supplies. (5) Significant and unreasonable land subsidence that substantially interferes with surface land uses. (6) Surface water depletions that have significant and unreasonable adverse impacts on beneficial uses of the surface water. [all emphasis added by TH] Medium and High Priority Groundwater Basins (CASGEM) Medium and High Priority Groundwater Basins (CASGEM) 14

15 Groundwater Management Plans: Inventory and Assessment Sustainable Groundwater Management Act Groundwater Sustainability Agencies (GSAs) & Groundwater Sustainability Plans (GSPs) 20 years after AB 3030 sustainable groundwater management planning still poses a challenge Online Resources (California DWR groundwater level monitoring program (California DWR drought information) (scroll to Drought Info ) (shallow groundwater depth and salinity) (California DWR drought workshop 1/2014) 15