2016 Water Inventory and Analysis Report Highlights on Land Use, Water Supply, and Water Budgets Christina Buck, PhD Water Resources Scientist Board of Supervisors August 23, 2016 Water Inventory and Analysis Report 1

Background Update to 2001 Water Inventory and Analysis Report (WI&A) Butte Basin Groundwater Model Refinements to inputs to better represent historical hydrologic conditions Accounting of supplies and demands August 23, 2016 Water Inventory and Analysis Report 2

WI&A Report Highlights I.Land Use: How has it changed since 2000? (Section 3) II. A View of the County Through Differing Water Supplies (Section 4) III. Water Budgets Help Tell a Story (Section 5) August 23, 2016 Water Inventory and Analysis Report 3

Note on Uncertainty Updates to the BBGM and WI&A rely on the best available information All data and estimates are subject to uncertainty Trends and differences are more reliable than absolute numbers August 23, 2016 Water Inventory and Analysis Report 4

Part I. How has land use changed since 2000? A. Total irrigated agricultural acreage has been remarkably stable since 2000 A. Significant land use changes have occurred but mostly related to crop shifts August 23, 2016 Water Inventory and Analysis Report 5

County-Wide Land Use DWR surveys from 1994, 1999, 2004, 2011 Identifies land use, water source, and other attributes High spatial detail Annual changes estimated from ag. commissioner crop reports through 2014 August 23, 2016 Water Inventory and Analysis Report 6

Valley Floor General Land Use August 23, 2016 Water Inventory and Analysis Report 7

Total irrigated agricultural acreage relatively stable since 2000 August 23, 2016 Water Inventory and Analysis Report 8 Valley Floor Irrigated Land Use

Increasing orchard acreage and recent shift to walnuts August 23, 2016 Water Inventory and Analysis Report 9 Valley Floor Orchard Land Use

Orchards Replacing ‘Other Crop’ Acreage August 23, 2016 Water Inventory and Analysis Report 10 Valley Floor ‘Other Crop’ Land Use

August 23, 2016 Water Inventory and Analysis Report 11 VINAWEST BUTTE EAST BUTTENORTH YUBA

Land Use Summary August 23, 2016 Water Inventory and Analysis Report 12 Land use relatively stable since 2000 Valley Floor developed lands increased approximately 7,000 acres between 2000 and 2014 Orchards have shifted from almonds and prunes to walnuts Overall increase in orchards is offset by decreases in other, non-rice crops

Part II. A View of the County Through Differing Water Supplies August 23, 2016 Water Inventory and Analysis Report 13

Water Sources Precipitation (914 TAF) Applied Surface Water (715 TAF) Groundwater Pumping (411 TAF) = 2.04 MAF August 23, 2016 Water Inventory and Analysis Report 14

Large Variations in Streamflow August 23, 2016 Water Inventory and Analysis Report 15

Relatively Stable Surface Water Diversions August 23, 2016 Water Inventory and Analysis Report 16

Groundwater Pumping Variable by Water Year Type August 23, 2016 Water Inventory and Analysis Report 17 Wide range, depending largely on year type. Little correlation with time.

Pumping by Water Demand Type: Valley Floor August 23, 2016 Water Inventory and Analysis Report 18 (374 taf) (31 taf) (5 taf)

Well Infrastructure August 23, 2016 Water Inventory and Analysis Report 19

Well Infrastructure August 23, 2016 Water Inventory and Analysis Report 20

Water Supplies Summary Highly variable precipitation and resulting streamflows from year-to-year Relatively steady surface water supplies due to senior water rights and settlement contracts, despite year-to-year differences in precipitation Variability in precipitation is a driver of year-to-year differences in groundwater pumping August 23, 2016 Water Inventory and Analysis Report 21

Part III. Water Budgets Help Tell a Story - Where does the water come from and where does it go? August 23, 2016 Water Inventory and Analysis Report 22

Land Surface Water Budgets Inflows – Outflows ± Change in Storage = 0 August 23, 2016 Water Inventory and Analysis Report 23 Land Surface (Ag, urban, or native land use) Precipitation Evapotranspiration Deep Percolation Groundwater Pumping Surface Water Deliveries Runoff and Return Flow

Land Surface Water Budgets Valley floor inventory units (and subinventory units) Overall and by general land use Irrigated agriculture and wetlands Developed lands Non-irrigated lands August 23, 2016 Water Inventory and Analysis Report 24

Valley Floor Overall Water Budget August 23, 2016 Water Inventory and Analysis Report 25 Average Annual Inflows and Outflows (thousands of acre-feet)

June 14, 2016 DRAFT Water Inventory and Analysis Report 26 Valley Floor Average Annual Water Budgets Total Inflow/ Outflow 2,040 taf Irrigated Ag./Wetlands (1,587 taf) Developed Lands (140 taf) Non-Irrigated Lands (312 taf)

Annual Budgets Highlight Changes Over Time August 23, 2016 Water Inventory and Analysis Report 27

Valley Floor Inflows/Outflows by Water Year Type August 3, 2016 Water Inventory and Analysis Report 28

Water Budget Summary Irrigated agriculture and wetlands represent the primary use of water and rely mainly on surface water for irrigation Magnitude of inflows/outflows varies widely by inventory unit (and subinventory unit) and land use category Annual pumping influenced by precipitation to meet irrigation demands, particularly for orchard crops Periods of drought result in increased pumping and decreased deep percolation August 23, 2016 Water Inventory and Analysis Report 29

Next Steps Continue to assess the use WI&A information to support development of GSPs under SGMA. Continue process of updating and calibrating the BBGM. Further evaluate results to better understand factors contributing to recent historically low groundwater levels in some areas. Conduct future demands and climate change analysis August 23, 2016 Water Inventory and Analysis Report 30

Water Inventory and Analysis Report August 23, 2016 Water Inventory and Analysis Report 31

2016 WI&A Structure Executive Summary 1.Introduction 2.Inventory and Analysis Methodology 3.Land Use and Cropping Patterns 4.Climate and Hydrology Climate Surface Water Hydrology Groundwater Hydrology 5.Historical Water Demands and Supplies 6.Future Water Demands and Supplies 7.Conclusions and Recommendations 8.References August 23, 2016 Water Inventory and Analysis Report 32

2016 WI&A Structure (continued) APPENDICES: A.Water Suppliers and Managers B.Butte County Stream Gages and Monitoring Wells C.Subinventory Unit Land Use and Water Budgets D.Assessment of Butte County Drought Impacts, August 23, 2016 Water Inventory and Analysis Report 33

Acknowledgements Butte County Board of Supervisors Davids Engineering, Inc. Butte County Water Commission and Project Advisory Committee Local Water Suppliers and Managers, U.C. Cooperative Extension, California Department of Water Resources August 23, 2016 Water Inventory and Analysis Report 34

Questions/Discussion August 23, 2016 Water Inventory and Analysis Report 35