2025 Northern Cities Management
Area Annual Report
Agenda Item 12.B
By: Rosemarie Gaglione, P.E.
Public Works Director
Meeting Date: June 16, 2026
Santa Maria Ground Water Basin Adjudication
•1983 Gentlemen’s Agreement – collaborative
management of the basin
•2002 Groundwater Management Agreement –
formalized the “safe yield”
•2005 Stipulation for the Santa Maria River Valley
Groundwater Basin Adjudication – requires that this
annual report be produced
•2008 Judgement After Trial – divided the basin into 3
separate management areas
2 Santa Maria Ground Water Basin Adjudication
•NCMA – Northern Cities
Management Area
•NMMA – Nipomo Mesa
Management Area
•SMVMA – Santa Maria Valley
Management Area
3 Northern Cities Management Area (NCMA)
•Arroyo Grande
•Pismo Beach
•Grover Beach
•Oceano Community
Services District (OCSD)
•Private Users (Agriculture)
4 NCMA Annual Report
Groundwater monitoring and data
collection are done to characterize:
•Land and water uses in the basin
•Sources of supply for those uses
•Groundwater conditions (including
water levels and water quality)
•Amount and disposition of other
sources of water in the NCMA
5 Groundwater Elevations
•The groundwater elevation generally decreased in the
NCMA portion of the SMGB due to:
•Slightly below-average rainfall received during the 2024/25 winter season (as compared to 2023/24)
•Increased groundwater pumping (as compared to 2023/24) 6 Groundwater Levels
•Greatest threat to basin is saltwater intrusion
•Deep Well Index (DWI)
•Used to determine whether aquifer conditions indicate
potential to promote seawater intrusion
•Based on an average of 3 sentry wells (24B03, 30F03 and 30N02)
•If the Deep Well Index < 7.5 feet (NAVD 88), conditions are favorable to saltwater intrusion
8 9
Deep Well Index – NAVD 88
•Deep Wells 2025
•January 12.2 ft
•July 9.5 ft
•October 10.5 ft
•Deep Wells 2024
•January 12.3 ft
•April 13.8 ft
•October 11.51 ft
10 NCMA / NMMA Boundary Well – NAVD 88
•2025
•January 17.0 ft
•July 9.9 ft
•2024
•2024 ranged from 12.8 ft – 23 ft
11 Change in Groundwater Storage
•Decreased from April 2024 – April 2025 by 1,149 AF
•Increased from April 2023 – April 2024 by 530 AF
12 Groundwater Quality
•Water quality data (chloride, total dissolved solids (TDS) and sodium) are all consistent with historical
concentrations
•No water quality issues
•No evidence of current seawater intrusion
13 Water Supply and Production
•Urban use (NCMA agencies) 5,477 AF
•2024 – 5,356 AF
•2023 - 5,240 AF – 25 year low
•2016 – 5,476 AF (previous low)
•2007 – 8,982 AF (high)
14 2025 Water Production - AF
16 Agency Lopez
Lake
State Water
Project
SMGB
Groundwater
Other
Supplies Total
Urban Area
Arroyo Grande 1,891 0 179 0 2,070
Grover Beach 708 0 519 0 1,226
Pismo Beach 1,022 486 36 0 1,545
Oceano CSD 473 95 67 0 636
Urban Water Use Total 4,095 581 801 0 5,477
Non-Urban Area
Agricultural Irrigation Applied
Water 0 0 2,447 0 2,447
Rural Water Users 0 0 80 0 80
Non-potable Irrigation by
Arroyo Grande 0 0 49 0 49
Non-Urban Water Use
Total 0 0 2,163 2,163
Total 4,095 581 3,377 0 8,053
Threats to Water Supply – Groundwater
•Total pumping = 3,377 AF (2025)
•36% of court-accepted 9,500 AF/Y long-term safe yield
•2,949 AF (2024) @ 31%
•Storage should increase with consecutive years at 30 – 40% of safe yield (this has been the case for the past decade) •The aquifer is still in a tenuous position with respect to seawater intrusion
17 Threats to Water Supply - Groundwater
•Historically we have seen groundwater flow to the ocean, this prevents seawater intrusion
•1,300 AF historically flowed from the NMMA to the NCMA •Pumping depression near Black Lake Canyon within the NMMA appears to have reversed the groundwater gradient
•Creates conditions more likely to result in seawater intrusion •During 2025 there were no indications of seawater
intrusion
18 Threats to Water Supply - SWP
State Water Project (SWP) – Table A Allocations
•June 2026 – 45%
•2025 - 50%
•2024 - 40%
•2023 - 100%
•2022 - 5%
•2021 - 5%
19 Threats to Water Supply - SWP
•SWP deliveries have been reduced due to
•Climate change, including long term drought
•Reduction in snowpack
•SWP reliability rate over the last 12 years is 45.6%
•Drought buffers can replace lost water in a drought for up to two years
•Subsidence in the San Joaquin Valley
•Groundwater over-pumping has lowered the ground surface •The ground surface dropped 10 – 30 feet over the last century •The ground surface dropped several feet in the last decade 20 Threats to Water Supply - SWP
•The concrete canal rests on the ground surface
•The canal has dropped enough in a few places to reduce conveyance capacity
•DWR expects to deliver 3% less water due to subsidence •Operational changes have been made
•Without improvements, DWR expects that this could cause further delivery reductions of from 18% - 87% by 2043
21 Threats to Water Supply - NEW
25 NCMA Technical Group Mission Statement
Preserve and enhance the sustainability of water supplies for the Northern Cities Management Area by:
•Enhancing supply reliability
•Protecting water quality
•Maintaining cost-effective water supplies
•Advancing the legacy of cooperative water resources management •Promoting conjunctive use
26 2024 NCMA Annual Report
Questions?
27