2023 Northern Cities Management
Area Annual Report
Agenda Item 12.B
By: Benjamin A. Fine, P.E.
Director of Public Works/City Engineer
Meeting Date: June 18, 2024
Santa Maria Ground Water Basin Adjudication
•Subject to ongoing litigation
since 1997
•Division of the basin into three
separate management areas
•Monitoring Program and Annual
Report
•Formalized the division of the
NCMA safe yield from the
“Gentleman’s Agreement”
2 Northern Cities Management Area (NCMA)
•Arroyo Grande
•Pismo Beach
•Grover Beach
•Oceano Community
Services District (OCSD)
•Private Users
3 NCMA Annual Report
Groundwater monitoring and data
collection sufficient to characterize:
•Land and water uses in the basin
•Sources of supply to meet those uses
•Groundwater conditions (including
water levels and water quality)
•Amount and disposition of other
sources of water in the NCMA
4 Key Point 1 – Water Elevations
•Water elevation generally increased in the NCMA portion of the SMGB
•Response to above-average rainfall received during 2022/23 winter season
•Also attributed to ongoing efforts by all NCMA agencies to minimize groundwater extraction and maximize surface water supplies and maintaining water conservation practices
5 Key Point 2 – Ground Water Levels
•Greatest threat to basin = saltwater intrusion
•Deep Well Index
•Average of 3 sentry wells (24B03, 30F03 and 30N02)
•DWI < 7.5’ = conditions favorable to saltwater intrusion •Spring 2023 – April elevation ranged 7.5’ – 13.5’
•Spring 2022 6.7’ – 8.6’
•Fall 2023 – Production zone ranged from 8.2’ – 12.5 feet above sea level
•2022 Production zone ranged from 3.4’ – 7.0 feet above sea level 6 7
Key Point 2 – Groundwater Levels
•Deep Wells 2023
•January > 9’
•April > 12’
•September > 10’
•December ~ 12’
•Deep Wells 2022
•January – 9.36’
•September 4.4’ (low point)
•December 9.5’
•NCMA/NMMA Boundary
•Monitoring well 32C03
•September > 6’
•Below 0’ during the second and third quarters of 2022
8 Key Point 3 – Change in Groundwater Storage
•Groundwater storage increased from April 2022 – April
2023 by about 3,610 AF
•Groundwater storage increased from April 2021 – April 2022 by about 270 AF
9 Key Point 4 – Groundwater Quality
•Quality data (chloride, total dissolved solids (TDS) and sodium) all consistent with historical concentrations
•No water quality issues
10 Key Point 5 – Water Supply and Production
•Urban use (NCMA agencies) 5,240 AF – 25 year low
•2022 – 5,471 AF
•2021 – 6,073 AF
•2007 – 8,982 AF (high)
•2016 – 5,476 AF (previous low)
•Total water use 7,403 AF (8,165 AF 2022)
•Lake Lopez – 3,493 AF
•SWP – 1,213 AF
•Groundwater – 2,697 AF
•Pismo Formation (AG) – 0 AF
11 Key Point 5 – Water Supply and Production
12 Key Point 6 – Threats to Water Supply
•Total pumping = 2,697 AF (2023)
•3,523 AF (2022)
•28% of court-accepted 9,500 AFY long-term safe yield
•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 •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 2023 there were no indications of seawater intrusion 13
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%)
15 State Water
•December 1, 2023 – 10%
•March 22, 2024 – 30%
•April 23, 2024 – 40%
1,240 AF Table A + 1,240 AF Drought Buffer
@ 40% = 496 AF + 496 AF = 992 AF
16 State Water
17 Staff Recommendations
•Information only
•City Council receives the NCMA Annual Report
•Discuss the report and ask questions
18