2024 Northern Cities Management
Area Annual Report
Agenda Item 12.B
By: Rosemarie Gaglione, P.E.
Public Works Director
Meeting Date: July 1, 2025
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 Water Elevations
•Water elevation generally increased in the NCMA portion of the SMGB due to:
•Above-average rainfall received during 2023/24 and 2022/23 winter seasons
•Groundwater recharge from a prolonged spill event from Lopez •Ongoing efforts by all NCMA agencies to minimize groundwater extraction, maximize surface water supplies and maintain water conservation practices
6 Water Elevations
You will see four different forms or “datums” of measurement in this report. •Sea Level – The elevation of the ocean at any given point in time •MSL – Mean Sea Level – the average height of the ocean’s surface over a period of 19 years. •AMSL – Above Mean Sea Level – measured from some point above the earth •NAVD 88 – North American Vertical Datum - a vertical datum established in 1988 to replace the previous one in use since 1929. It established what is 0.00 for surveys 7 Ground Water Levels
•Greatest threat to basin = 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
Ground Water Levels
Deep Well Index:
•Spring 2024 – April elevation high 13.8’ ASL
•Spring 2023 – April elevation high 13.5’ ASL
•Fall 2024 – October elevation high 11.5’ ASL
•Fall 2023 October elevation high 12.5’ ASL
10 Groundwater Levels
•Deep Wells 2024 (NAVD 88)
•April 11.3’– 18.1’
•October 10.7’ – 15.9’
•Deep Wells 2023 (NAVD 88)
•January > 9’
•April > 12’
•September > 10’
•December ~ 12’
•NCMA/NMMA Boundary Monitoring Well 32C03 – (AMSL)
•2024 ranged from 12.8’ – 23’
•2023 September > 6’
•Below 0’ during the second and third quarters of 2022 11
Change in Groundwater Storage
•Increased from April 2023 – April 2024 by 530 AF
•Increased from April 2022 – April 2023 by about 3,609 AF •Increased from April 2021 – April 2022 by about 270 AF 12 Groundwater Quality
•Water quality data (chloride, total dissolved solids (TDS) and sodium) are all consistent with historical
concentrations
•No water quality issues
13 Water Supply and Production
•Urban use (NCMA agencies) 5,356 AF
•2023 - 5,240 AF – 25 year low
•2022 – 5,471 AF
•2021 – 6,073 AF
•2016 – 5,476 AF (previous low)
•2007 – 8,982 AF (high)
14 Water Supply and Production
•Total water use 7,783 AF (7,403 AF 2023)
•Lopez Lake – 4,173 AF
•State Water Project – 661 AF
•Groundwater – 2,949 AF
•Pismo Formation (AG) – 0 AF
15 2024 Water Supply and Production - AF
16 Agency Lopez
Lake
State Water
Project
SMGB
Groundwater
Other
Supplies Total
Urban Area
Arroyo Grande 1,965 0 59 0 2,024
Grover Beach 791 0 436 0 1,227
Pismo Beach 1,099 380 15 0 1,494
Oceano CSD 318 281 12 0 611
Urban Water Use Total 4,173 661 522 0 5,356
Non-Urban Area
Agricultural Irrigation Applied
Water 0 0 2,307 0 2,307
Rural Water Users 0 0 80 0 80
Non-potable Irrigation by
Arroyo Grande 0 0 40 0 40
Non-Urban Water Use
Total 0 0 2,163 2,163
Total 4,173 661 2,949 0 7,783
Threats to Water Supply
•Total pumping = 2,949 AF (2024)
•31% of court-accepted 9,500 AF/Y long-term safe yield
•2,697 AF (2023) @ 28%
•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
•Historically we have seen groundwater flow to the ocean, this prevents seawater intrusion
•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 2024 there were no indications of seawater
intrusion
18 Threats to Water Supply
State Water Project (SWP)
•June 2025 - 50%
•2024 – 40%
•2023 – 10%
•2022 – 5%
19 Threats to Water Supply - NEW
Lake Lopez Preliminary Injunction (PI)
•Four Environmental groups filed a lawsuit under the
Endangered Species Act
•Requested more water be released from Lopez Dam to support steelhead
•The County had been releasing 3,200 AF/Y over the last decade •The PI requires release of 5,800 AF/Y plus pulse releases •Safe yield is 4,200 AF/Y
20 Threats to Water Supply - NEW
•Had the PI been in place during the droughts of 2020 – 2023, the lake would have reached
•“Minimum pool” (poor water quality) in late 2020 to early 2021, and •“Dead pool” (no water deliveries) in the latter half of 2021 into the beginning of 2023.
•This would have equated to 27 months of poor water quality, and 15 months without water deliveries from Lake Lopez.
•We would also have reached minimum pool in the 2016/17 drought, with 15 months of poor water quality.
21 Threats to Water Supply - NEW
22 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
23 2024 NCMA Annual Report
Questions?
24 Tree WellsUpdate on Water Supply
Lopez Lake
•January 12, 2022 – 14,942.8 AF
•March 9, 2022 – 14,508.7 AF
•April 8, 2022 – 14,148.1 AF
•May 3, 2022 – 14,051.2 AF
•Sept, 2022 < 10,000 AF
•May 15, 2023 – 49,462.2 AF
•June 17, 2024 – 49,285 (99.6%)
26 State Water
•2022 – 5%
•2023 – 10%
•2024 – 40%
•June 2025– 50%
1,240 AF Table A + 1,240 AF Drought Buffer
@ 40% = 496 AF + 496 AF = 992 AF
27