HomeMy WebLinkAboutCC 2026-03-24_09d Water Supply and Demand UpdateItem 9.d.
MEMORANDUM
TO: City Council
FROM: Bill Robeson, Assistant City Manager/Public Works Director
BY: Shane Taylor, Utilities Manager
SUBJECT: Monthly Water Supply and Demand Update
DATE: March 24, 2026
RECOMMENDATION:
Receive and file the Monthly Water Supply and Demand Update.
IMPACT ON FINANCIAL AND PERSONNEL RESOURCES:
Approximately two (2) hours of staff time are required to prepare the report.
BACKGROUND:
The City of Arroyo Grande’s water entitlements are calculated on a water year that began
April 1, 2025. The current water supply 2025 -26 includes:
2,290 Acre Feet (AF) from Lopez Lake Reservoir/Lopez contract entitlement.
The current modeled safe yield is 35 7 AF of groundwater from the Santa Maria
River Santa Maria River Groundwater Basin, with an entitlement of 1,323 AF.
An additional 160 AF of groundwater is available from the Pismo formation from
the existing City well system.
In addition to the annual Lopez Lake Reservoir contract entitlement, the City will have
689.69 AF of stored Lopez water, which is unused entitlement from water year 2024 -25.
The City also previously accepted an offer to purchase 470.33 AF of surplus Lopez water.
The surplus water cost is $55,146.74 or $117.14 per AF.
The total supply from Lopez Lake Reservoir for this water year is 3,450 AF. The predicted
water use for the 2025-26 water year is 2,100 AF.
In February 2026, the City’s water use was 149.8 AF. The overall per capita use was 97
gallons per day. The residential per capita use was 75 gallons per day. There has been
a total of 15.6 inches of rain since July 2025 at the Corp Yard gauge.
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Item 9.d.
City Council
Monthly Water Supply and Demand Update
March 24, 2026
Page 2
ANALYSIS OF ISSUES:
As of March 12, 2026, the USDA Drought Monitor reports San Luis Obispo County as
normal. Lopez Lake is at 87.5% (43,269.2). The deep well index for the First quarter of
2026 was completed on February 24, 2026. The index level was 12.28 feet above sea
level, which is 4.78 feet above the threshold value. The current deep well index is 1.74
feet higher than October 2025, and 0.04 feet higher than January 2025.
In the current water year, the City took delivery of all stored and surplus water totaling
1,160 AF. The use of this water prevented it from possibly spilling and being lost. It is
estimated that 1,600 AF of unused entitlement will be available for storage at the end of
the current water year (March 31, 2026)
On January 15, 2025, in response to a preliminary injunction issued by the United States
District Court to the County of San Luis Obispo, Lopez Lake downstream releases were
increased from 2.0 million gallons per day to 5.1 million gallons per day. This release rate
was in place until December 29, 2025.
The 9th District Court of Appeals overturned the preliminary injunction and returned the
water releases to the interim downstream release schedule. The current release rate on
January 14, 2026, was 4.8 cubic feet per second (cfs) or 3.1 million gallons per day. A
gradual decrease in the release process to former rates is necessary to monitor creek
conditions. The current rate as of March 12, 2026, is 3.6 cfs or 2.3 million gallons per day.
The City and all other Zone 3 contractors will continue to work with the County to assess
and report on the impact on our water supply from Lopez Lake until the litigation is
resolved. However, the significant costs of the ongoing litigation and future improvements
will be shared by the ratepayers of the City and other Zone 3 member agencies.
To keep the community informed of the current status of the litigation and the City’s water
system, staff have developed a webpage where updates will be published. The webpage
can be accessed at www.arroyogrande.org/lopezlakelitigation.
Council Goals Workplan
In the current Council Goals workplan for Fiscal Year 2025 -27, under the Council Goal of
“Achieve Water Resilience”, the Council has directed staff to Pursue 2026 State Water
Ballot Measure, with the specific subtask to Seek Council approval placing a November
Ballot Measure. On March 10, 2026, the Council provided direction to bring back final
ballot language for consideration to place the item on the ballot for the November 2026
General Election.
ALTERNATIVES:
The following alternatives are provided for the Council’s consideration:
1. Receive and file the report, or
2. Provide other directions to staff.
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Item 9.d.
City Council
Monthly Water Supply and Demand Update
March 24, 2026
Page 3
ADVANTAGES:
The report provides the City Council and the public with the current and projected water
supply and demand conditions.
ENVIRONMENTAL REVIEW:
No environmental review is required for this item.
PUBLIC NOTIFICATION AND COMMENTS:
The Agenda was posted at City Hall and on the City’s website in accordance with
Government Code Section 54954.2.
ATTACHMENTS:
1. Monthly Operations Report for February 2026
2. Lopez Lake Reservoir Storage Projections
3. Previous Use Comparison
4. Deep Well Index Levels for 1st Quarter
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HISTORICAL FIRST QUARTER DEEP WELL INDEX LEVELS
Northern Cities Management Area
San Luis Obispo County, California
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Deep Well Index
Threshold: 7.5 feet
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Deep Well Index is the synoptic average of groundwater elevations
in the deep wells of Sentry Well clusters 24B,30F, and 30N.
"Approximate" Deep Well Index elevations are based on
non-synoptic measurments, made during the same quarter.
ATTACHMENT 4
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