2022 Northern Cities Management
Area Annual Report
Agenda Item 12.A
By: Benjamin A. Fine, P.E.
Director of Public Works/City Engineer
Meeting Date: May 16, 2023
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 decreased in the NCMA portion of the SMGB
•Response to below-average rainfall in the last three years •Impacts not greater attributed to ongoing efforts of
NCMA agencies to reduce groundwater pulmping
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 2022 – April elevation ranged 6.7’ – 8.6’
•Spring 2021 7.0’ – 9.0’
•Fall 2022 – Cinega Valley 0’ to 15’ lower than before
irrigation season.
•Production zone ranged from 3.4’ – 7.0 feet above sea level •2021 Production zone ranged from 3.8’ – 7.0 feet above sea level 6 7
Key Point 2 – Groundwater Levels
•Deep Wells 2022
•January – 9.36’
•September 4.4’ (low point)
•December 9.5’
•NCMA/NMMA Boundary
•Monitoring well 32C03
•Below 0’ during the second and third quarters of 2022
•Similar to conditions in 2014 – 2016
8 Key Point 3 – Change in Groundwater Storage
•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) 5,471 AF
•2021 – 6,073 AF
•2007 – 8,982 AF (high)
•2016 – 5,476 AF (previous low)
•Total water use 8,165 AF (8,658 AF 2021)
•Lake Lopez – 2,936 AF
•SWP – 1,704 AF
•Groundwater – 3,523 AF
•Pismo Formation (AG) – 2 AF
11 Key Point 5 – Water Supply and Production
12 Key Point 6 – Threats to Water Supply
•Total pumping = 3,523 AF (2022)
•37% 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) •Levels have increased in 2022 by only 270 AF
•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 2022 there were no indications of seawater intrusion 13
Tree WellsUpdate on Water Supply
Santa Maria Groundwater Basin
•Adjudication = 700 AF
•Deep Well Index Threshold = 7.5 feet
•February 2022 DWI 10.58’
•4.70’ higher than October 2022 (5.88’)
•1.22’ higher than one year ago (9.36’)
15 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
16 State Water
•December 1, 2022 – 5%
•January 26, 2023 – 30%
•February 22, 2023 – 35%
•March 24, 2023 – 75%
•April 20, 2023 – 100%
17 State Water
18 Tree WellsConclusion and Recommendations
Staff Recommendations
•Information only
•City Council receives the NCMA Annual Report
•Discuss the report and ask questions
20 Tree Wells Fiscal Impacts
No Direct Fiscal Impacts
Questions?