2020-2021 ENGINEER’S REPORT ON WATER SUPPLY AND REPLENISHMENT ASSESSMENT Prepared for: Coachella Valley Water District Prepared by: Wildermuth Environmental, Inc. April 2020 Table of Contents Executive Summary ...................................................................................................................................... 1 Mission Creek Subbasin Area of Benefit ........................................................................................ 1 West Whitewater River Subbasin Area of Benefit .......................................................................... 2 East Whitewater River Subbasin Area of Benefit ........................................................................... 2 – Introduction ........................................................................................................................... 1-1 1.1 Purpose of the Engineer’s Report ................................................................................... 1-1 1.2 Basin Description and Setting ......................................................................................... 1-1 1.3 The Sustainable Groundwater Management Act ............................................................ 1-4 1.4 Organization of Report ..................................................................................................... 1-5 – Overview and History of Groundwater Replenishment and Assessment .......................... 2-1 2.1 Definition and General History of Overdraft Leading to the Groundwater Replenishment Program (GRP) .................................................................................................................. 2-1 2.1.1 Definition of Overdraft .............................................................................................................. 2-1 2.1.2 General History of Overdraft in the Basin ................................................................................ 2-2 2.1.3 History of Water Management by CVWD .................................................................................. 2-2 2.2 Management Areas and Areas of Benefit ....................................................................... 2-4 2.2.1 Mission Creek Subbasin Management Area and Area of Benefit .......................................... 2-4 2.2.2 West Whitewater River Subbasin Management Area and Area of Benefit ............................ 2-5 2.2.3 East Whitewater River Subbasin Area of Benefit .................................................................... 2-5 2.3 Replenishment Water Sources ........................................................................................ 2-5 2.3.1 Colorado River Water ................................................................................................................ 2-5 2.3.1.1 Coachella Canal ....................................................................................................................................... 2-5 2.3.1.2 Colorado River Water Allocations ........................................................................................................... 2-6 2.3.1.3 QSA Transfer ............................................................................................................................................ 2-7 2.3.1.4 Drought Contingency Plan ....................................................................................................................... 2-7 2.3.2 State Water Project ................................................................................................................... 2-7 2.3.2.1 Table A Allocations ................................................................................................................................... 2-7 2.3.2.2 SWP Supplemental Water ....................................................................................................................... 2-8 2.3.2.3 SWP Exchange to MWD ........................................................................................................................... 2-8 2.3.2.4 Advance Delivery Agreement .................................................................................................................. 2-9 2.3.2.5 Apportionment of State Water Project Exchange Water ....................................................................... 2-9 2.3.2.6 SWP Reliability ....................................................................................................................................... 2-10 2.3.2.7 Delta Conveyance .................................................................................................................................. 2-10 2.3.2.8 Sites Reservoir Project .......................................................................................................................... 2-11 2.3.3 Other Non-SWP Supplemental Water ................................................................................... 2-11 2.3.4 Recycled Water ...................................................................................................................... 2-12 2.4 Direct and In-Lieu Replenishment ................................................................................. 2-12 2.4.1 Mission Creek Subbasin Management Area and Area of Benefit ....................................... 2-12 2.4.2 West Whitewater River Subbasin Management Area and Area of Benefit ......................... 2-13 2.4.3 East Whitewater River Subbasin Area of Benefit ................................................................. 2-13 2.5 Groundwater Replenishment Program Assessment .................................................... 2-14 2.5.1 Authority to Assess ................................................................................................................. 2-14 2.5.2 Funding Mechanisms ............................................................................................................. 2-14 2.5.2.1 Replenishment Assessment Charge .................................................................................................... 2-14 2.5.2.2 Coachella Valley Water District State Water Project Tax .................................................................... 2-15 2.5.3 Methods for Determining Groundwater Production ............................................................. 2-15 2.5.4 2016 Cost of Service Study ................................................................................................... 2-16 April 2020 i 126-006-003 2020-2021 Engineer’s Report… Table of Contents 2.5.5 Effects of Conservation .......................................................................................................... 2-16 – Mission Creek Subbasin Area of Benefit ............................................................................ 3-1 3.1 Definition of Area of Benefit ............................................................................................ 3-1 3.2 Groundwater Conditions .................................................................................................. 3-1 3.3 Groundwater Production .................................................................................................. 3-5 3.4 Direct and In-Lieu Replenishment ................................................................................... 3-6 3.4.1 Replenishment Facilities .......................................................................................................... 3-6 3.4.2 Direct Replenishment ............................................................................................................... 3-7 3.4.3 In-Lieu Replenishment .............................................................................................................. 3-8 3.5 Future Projects ................................................................................................................. 3-8 3.6 Need for Continued Replenishment ................................................................................ 3-8 3.7 Replenishment Assessment ............................................................................................ 3-8 3.7.1 Groundwater Replenishment Program Costs .......................................................................... 3-8 3.7.2 Methods for Determining Groundwater Production ................................................................ 3-9 3.7.3 Income Statement .................................................................................................................... 3-9 3.7.4 Recommended RAC for Fiscal Year 2020-2021 .................................................................. 3-11 – West Whitewater River Subbasin Area of Benefit .............................................................. 4-1 4.1 Definition of Area of Benefit ............................................................................................ 4-1 4.2 Groundwater Conditions .................................................................................................. 4-1 4.3 Groundwater Production .................................................................................................. 4-5 4.4 Direct and In-Lieu Replenishment ................................................................................... 4-7 4.4.1 Replenishment Facilities .......................................................................................................... 4-7 4.4.2 Direct Replenishment ..............................................................................................................