OCWD Groundwater Basin Storage Evaluation Joint Planning Committee July 25, 2018
Current Basin Management Policies 0 AF Increase BPP; Reduce or stop purchases of imported water - 100,000 No BPP change; Purchase enough imported water to help Target balance recharge with expected pumping - 150,000 Accumulated No BPP change; Purchase enough imported water Overdraft with goal of reducing overdraft based on expected Range pumping - 300,000 Purchase additional imported water and/or Reduce BPP to reduce overdraft - 350,000 Purchase additional imported water and Reduce BPP to reduce overdraft MWD CUP 66,000 AF SARCCUP 36,000 AF - 500,000
Questions to Answer How much storage do we need for a drought? Is there storage space remaining for other programs?
2011 to 2016 Drought • Driest or second driest period in SoCal since 1400s • Significant reduction in rainfall – 55% of average • Captured SAR storm flows reduced • Less Natural Incidental recharge • Year 5 of drought cycle • MWD deliveries were reduced • Governor required 25% conservation
During 2011-16, basin storage decreased 161,000 af (or 145,000 af without MWD CUP) 218,000 Acre-feet 379,000 (16,000 is CUP)
Three Drought Scenario Projections # Description 1 Repeat 2011 to 2016 drought w/current demands & supplies 2 Repeat 2011 to 2016 drought; State does not reduce water demands by 25% in Year 5; MWD deliveries cut in years 4 & 5 3 Scenario #2 plus MWD delivery reductions in years 6 & 7 6
Accumulated Overdraft Projections 0 Drought Base Case -50,000 Scenario 1 ends -100,000 Scenario 2 -150,000 Scenario 3 -200,000 -250,000 -300,000 287,000 -350,000 180,000 af -400,000 -450,000 -500,000 2018 2019 2020 2021 2022 2023 2024 2025 7
Findings 1. Lower total water demands over last 10 years have reduced impacts from drought cycles 2. GWRS Final Expansion will increase base supplies improving drought resiliency
Recommendations 1. Accumulated overdraft target and basin storage triggers can be lowered 50,000 af without jeopardizing drought preparedness. 2. Maximum accumulated overdraft should remain at 500,000 af. 3. Storage agreements should be contained within SARCCUP storage, at least until MWD CUP terminates in 2028.
Proposed Basin Management Policy Revisions 0 AF Increase BPP; Reduce or stop purchases of imported water - 100,000 - 150,000 No BPP change; Purchase enough imported water to help balance recharge with expected pumping - 200,000 - 150,000 No BPP change; Purchase enough imported water with goal of reducing overdraft based on expected pumping - 300,000 - 350,000 Purchase additional imported water and/or Reduce BPP to reduce overdraft - 350,000 - 400,000 Purchase additional imported water and Reduce BPP to reduce overdraft MWD CUP 66,000 AF SARCCUP 36,000 AF - 500,000
End of Presentation 11
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