Northern Cities Management Area 2018 Annual Monitoring Report
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Northern Cities Management Area 2018 Annual Monitoring Report Prepared for The Northern Cities Management Area Technical Group City of Arroyo Grande City of Grover Beach Oceano Community Services District City of Pismo Beach April 24, 2019 Prepared by NCMA 2018 Annual Monitoring Report This page left blank intentionally. - ii - NCMA 2018 Annual Monitoring Report Northern Cities Management Area 2018 Annual Monitoring Report This report was prepared by the staff of GSI Water Solutions, Inc., in collaboration with GEI Consultants, Inc., under the supervision of professionals whose signatures appear below. The findings or professional opinion were prepared in accordance with generally accepted professional engineering and geologic practice. Paul A. Sorensen, PG, CHg Nathan R. Page, PG (Utah) Principal Hydrogeologist Consulting Hydrogeologist Project Manager GEI CONSULTANTS, INC. Samuel W. Schaefer, PE Senior Engineer - iii - NCMA 2018 Annual Monitoring Report This page left blank intentionally. - iv - NCMA 2018 Annual Monitoring Report CONTENTS Page Executive Summary ...................................................................................................................... 1 Groundwater Conditions ................................................................................................... 1 Groundwater Levels ................................................................................................. 1 Change in Groundwater in Storage .......................................................................... 3 Groundwater Quality ................................................................................................ 3 Water Supply and Production/Deliveries ........................................................................... 3 Threats to Water Supply ................................................................................................... 4 1. Introduction ....................................................................................................................... 6 1.1 Description of the NCMA Technical Group............................................................ 3 1.2 Coordination with Management Areas .................................................................. 3 2. Area Description ................................................................................................................ 5 2.1 Setting ................................................................................................................... 5 2.2 Precipitation ........................................................................................................... 5 2.3 Evapotranspiration ................................................................................................ 6 3. Groundwater Conditions ................................................................................................... 7 3.1 Geology and Hydrogeology ................................................................................... 7 3.2 Groundwater Flow ................................................................................................. 7 3.3 Groundwater Monitoring Network .......................................................................... 8 3.4 Groundwater Levels ............................................................................................ 10 3.4.1 Groundwater Level Contour Maps .............................................................. 10 3.4.2 Historical Water Level Trends ..................................................................... 10 3.4.3 Sentry Wells ................................................................................................ 11 3.5 Change in Groundwater in Storage ..................................................................... 13 3.6 Water Quality ....................................................................................................... 13 3.6.1 Quarterly Groundwater Monitoring ............................................................. 14 3.6.2 Analytical Results Summary ....................................................................... 14 4. Water Supply and Production/Delivery ........................................................................... 17 4.1 Water Supply ....................................................................................................... 17 4.1.1 Lopez Lake ................................................................................................. 17 4.1.2 State Water Project ..................................................................................... 20 4.1.3 Groundwater ............................................................................................... 21 4.1.4 Developed Water ........................................................................................ 22 4.1.5 Total Water Supply Availability ................................................................... 23 4.2 Water Use ........................................................................................................... 24 4.2.1 Agricultural Water Supply Requirements .................................................... 24 4.2.2 Rural Use .................................................................................................... 29 4.2.3 Urban Production for Potable Use .............................................................. 30 - v - NCMA 2018 Annual Monitoring Report 4.2.4 2018 Groundwater Pumpage ...................................................................... 31 4.2.5 Changes in Water Production ..................................................................... 33 5. Comparison of Water Supply v. Water Production .......................................................... 35 6. Threats to Water Supply ................................................................................................. 37 6.1 Threats to Local Groundwater Supply ................................................................. 37 6.1.1 Declining Water Levels ............................................................................... 37 6.1.2 Seawater Intrusion ...................................................................................... 38 6.1.3 Measures to Avoid Seawater Intrusion ....................................................... 38 6.2 Threats to State Water Project Supply ................................................................ 39 6.3 Threats to Lopez Lake Water Supply .................................................................. 39 7. Management Activities .................................................................................................... 41 7.1 Management Objectives ...................................................................................... 41 7.1.1 Share Groundwater Resources and Manage Pumping .............................. 44 7.1.2 Enhance Management of NCMA Groundwater .......................................... 46 7.1.3 Monitor Supply and Demand and Share Information .................................. 47 7.1.4 Manage Groundwater Levels and Prevent Seawater Intrusion .................. 48 7.1.5 Protect Groundwater Quality ...................................................................... 50 7.1.6 Manage Cooperatively ................................................................................ 51 7.1.7 Encourage Water Conservation .................................................................. 52 7.1.8 Evaluate Alternative Sources of Supply ...................................................... 57 8. References ...................................................................................................................... 61 Tables Page Table 1. NCMA TG Representatives ............................................................................................ 3 Table 2. Lopez Lake (FCWCD Zone 3 Contractors) 2018 Water Allocation (AFY) .................... 17 Table 3. Lopez Lake Municipal Diversion Reduction Strategy Low Reservoir Response Plan .. 18 Table 4. Lopez Lake Downstream Release Reduction Strategy ................................................ 18 Table 5. 2018 Lopez Lake Deliveries .......................................................................................... 1 9 Table 6. 2018 NCMA SWP Deliveries ........................................................................................ 20 Table 7. NCMA Groundwater Pumpage from Santa Maria Groundwater Basin, 2018 ............... 22 Table 8. Baseline (Full Allotment) Available Urban Water Supplies (AFY) ................................. 23 Table 9. 2018 Available Urban Water Supply, (AF) .................................................................... 24 Table 10. 2018 NCMA Crop Acreages and Calculated Evapotranspiration ............................... 26 Table 11. 2018 IDC Model Results of Monthly Applied Water .................................................... 29 Table 12. Estimated Rural Water Production .............................................................................. 30 Table 13. Urban Water Production for Potable Use (Groundwater and Surface Water, AF) ...... 31 Table 14. NCMA Groundwater Pumpage from Santa Maria Groundwater Basin, 2018 (AF) ..... 32 Table 15. Total Water Use (Groundwater and Surface Water, AF) ............................................ 33 Table 16. 2018 Water Production by Source (AF) ...................................................................... 35 - vi - NCMA 2018 Annual Monitoring Report Figures (all figures are presented at the