City of Napa
2025-26
Water Supply and Demand Assessment
Assessment Period July 2025 through June 2026
For Submission to California Department of Water Resources (DWR) by July 1, 2025
ATTACHMENT 1
The City of Napa Water Supply and Demand Assessment for the period July 2025 through June 2026 is defined in the following tables as required by the California Department of Water Resources (DWR). This fourth annual assessment of anticipated demands and available water supplies must be submitted to DWR by July 1, 2025.
Water Demands. The water demand information in Table 2 represents baseline water demands inclusive of the City’s permanent water waste regulations and conservation programs listed in Table 5. Demands reflect a very slight increase above 2024-25 actuals. Residential and commercial demand is expected to remain flat based on established post-drought conditions, while interruptible agricultural demand experiences a 5% increase due to new customers. The demands listed are unconstrained by additional actions that would be taken during an officially declared water shortage (Stage 1-6).
Water Supplies. The water supply information in Table 3 reflects continued improved post- drought scenarios for both local and imported sources. State Water Project supplies are bolstered by significant unused carryover water from previous years, and with a final 2025 North of Delta allocation of 70%, additional carryover supply will become available in 2026. State Water is limited during March due to North Bay Aqueduct annual maintenance. Winter storms filled the two local reservoirs for the third straight year. Lake Hennessey remains above 90% capacity as of June 2025. Due to operational constraints associated with a 36-inch transmission main replacement project, Lake Hennessey will be used more than usual in the second half of 2025. Milliken Reservoir will remain unused for the entire period, as the City replaces and hardens the raw water pipeline damaged in the 2017 Atlas Fire.
As shown in Table 4, the City of Napa projects no water shortages in 2025-26.
The City of Napa declared an end to its most recent water shortage emergency back in April 2023. Subsequently the City adopted permanent water waste regulations that remain in effect even when no water shortage is officially declared. Table 5 is a list of actions that the City continues to implement year-round.
While the current outlook is a welcome respite from the major 2020-2023 and 2013-2016 droughts, the City understands the volatility of California’s climate and is committed to “Making Water Conservation a Way of Life” by meeting its water use targets under SB 606/AB 1668.
Demand on the City water system is projected to remain well below 132 gallons per capita per day as required in its Urban Water Use Objective.
ATTACHMENT 1
Table 1. Annual Assessment Information
Supplier is a Wholesaler
Supplier is a Retailer
If you are both a wholesaler and retailer, will you be submitting two separate reports or a combined report?
Year Covered By This Shortage Report (Required)
Start: July 1, 2025
End: June 30, 2026
Volume Unit for Reported Supply and Demand:
(Must use the same unit throughout) AF
Supplier's Annual Assessment Planning Cycle (Required)
Start Month: JULY
End Month: JUNE
Data Interval: Monthly (12 data points per year)
Water Supplier's Contact Information (Required)
Water Supplier's Name: City of Napa
Contact Name: Patrick Costello
Contact Title: Water Resources Analyst
Street Address: 1700 Second Street, Suite 100
ZIP Code: 94559
Phone Number: (707)257-9309
Email Address: [email protected]
Report Preparer's Contact Information
(if different from above)
Preparer's Organization Name:
Preparer's Contact Name:
Phone Number: (XXX)XXX-XXXX
Email Address:
Supplier's Water Shortage Contingency Plan
WSCP Title City of Napa Water Shortage Contingency Plan WSCP Adoption Date 12/21/2021
Other Annual Assessment Related Activities
Activity Timeline/ Outcomes / Links / Notes
Annual Assessment/ Shortage Report Title: 2025-26 Water Supply and Demand Assessment Annual Assessment / Shortage Report Approval Date: 6/17/2025 Other Annual Assessment Related Activities: Optional
(Add rows as needed)
Type of Supplier (Required to check one or two)
ATTACHMENT 1
Use Type Start Year: 2025 Volumetric Unit Used2: AF Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total by Water Demand Type
All Demands 1460 1460 1380 1260 870 740 710 660 740 880 1170 1400 12730 0 0
0 0
0 0
0 0
0 1460 1460 1380 1260 870 740 710 660 740 880 1170 1400 12730 0 0
0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total
0 0
0 0
Table 2: Water Demands1
Projected Water Demands - Volume3
Total by Month (Non-Potable)
1Projections are based on best available data at time of submitting the report and actual demand volumes could be different due to many factors. 2Units of measure (AF, CCF, MG) must remain consistent. 3When opting to provide other than monthly volumes (bi-monthly, quarterly, or annual), please see directions on entering data for Projected Water Demand in the Table Instructions.
Notes: Monthly demands are estimated to be just slightly above 2024-25 actuals and include contracted volumes delivered to St. Helena. Residential and CII demand is projected to remain flat, while interruptible agricultural demand increases 5%. These baseline demands are inclusive of the City's permanent water waste regulations and conservation programs listed in Table 5. They are unconstrained by additional actions that would be taken during a declared shortage (Stage 1-6).
Total by Month (Potable)
Additional
Description
(as needed)
Level of
Treatment
for Non-
Potable
Supplies
Drop-down
list
Drop-down list
May select each use multiple times
These are the only Use Types that will
be recognized by the WUEdata online
submittal tool
(Add additional rows as needed)
Demands Served by Potable Supplies
Demands Served by Non-Potable Supplies
Three years ago total demand
Four years ago total demand
Optional (for comparison purposes)
Last year's total demand
Two years ago total demand
ATTACHMENT 1
Water Supply Start Year: 2025 Volumetric Unit Used2: AF Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Total by
Water
Supply Type
Supply from Storage Lake Hennessey 1100 1100 1100 1100 250 250 100 100 1000 700 700 750 8250 Supply from Storage Milliken Reservoir 0 0 0 0 0 0 0 0 0 0 0 0 0 Purchased/Imported Water State Water Project 1050 1150 1050 1400 1250 1250 1050 1050 500 1050 1050 1150 13000 0 0
0 0
0 0
0 2150 2250 2150 2500 1500 1500 1150 1150 1500 1750 1750 1900 21250 0 0 0
0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total
0 Table 3: Water Supplies1
Projected Water Supplies - Volume3
Water
Quality
Drop-down
List
Total Right
or Safe
Yield*
(optional)
Additional Detail on
Water Supply
Drop-down List
May use each category multiple
times.These are the only water
supply categories that will be
recognized by the WUEdata online
submittal tool
(Add additional rows as needed)
Potable Supplies
Non-Potable Supplies
eAR Reported Total Water Supplies
Optional (for comparison purposes)
1Projections are based on best available data at time of submitting the report and actual supply volumes could be different due to many factors. 2Units of measure (AF, CCF, MG) must remain consistent. 3When opting to provide other than monthly volumes (bi-monthly, quarterly, or annual), please see directions on entering data for Projected Water Supplies in the Table Instructions.
Notes: Lake Hennessey supplies reflect a reservoir at >90% capacity as of June 2025. State Water Project supplies reflect significant carryover supplies from previous years and a 2025 70% Table A North of Delta allocation. The Milliken Treatment Plant will remain offline, awaiting FEMA approval of the City's plans to replace and harden the raw water pipeline damaged in the 2017 Atlas Fire.
Total by Month (Potable)
Total by Month (Non-Potable)
ATTACHMENT 1
Table 4(P): Potable Water Shortage Assessment1
Start Year: 2025 Volumetric Unit Used2: AF
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun3 Total
Anticipated Unconstrained Demand 1460.0 1460.0 1380.0 1260.0 870.0 740.0 710.0 660.0 740.0 880.0 1170.0 1400.0 12730.00 Anticipated Total Water Supply 2150.0 2250.0 2150.0 2500.0 1500.0 1500.0 1150.0 1150.0 1500.0 1750.0 1750.0 1900.0 21250.00 Surplus/Shortage w/o WSCP Action 690.0 790.0 770.0 1,240.0 630.0 760.0 440.0 490.0 760.0 870.0 580.0 500.0 8,520.0 % Surplus/Shortage w/o WSCP Action 47% 54% 56% 98% 72% 103% 62% 74% 103% 99% 50% 36% 67% State Standard Shortage Level 0 0 0 0 0 0 0 0 0 0 0 0 0 Benefit from WSCP: Supply Augmentation 0.0
Benefit from WSCP: Demand Reduction 0.0
Revised Surplus/Shortage with WSCP 690.0 790.0 770.0 1240.0 630.0 760.0 440.0 490.0 760.0 870.0 580.0 500.0 8520.0 % Revised Surplus/Shortage with WSCP 47% 54% 56% 98% 72% 103% 62% 74% 103% 99% 50% 36% 67% = Auto calculated
= For manual input
Table 4(NP): Non-Potable Water Shortage Assessment 1
Start Year: 2025 Volumetric Unit Used2: AF
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun3 Total
Anticipated Unconstrained Demand: Non-Potable 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00 Anticipated Total Water Supply: Non-Potable 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Surplus/Shortage w/o WSCP Action: Non-Potable 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 % Surplus/Shortage w/o WSCP Action: Non-Potable
Benefit from WSCP: Supply Augmentation 0.0
Benefit from WSCP: Demand Reduction 0.0
Revised Surplus/Shortage with WSCP 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 % Revised Surplus/Shortage with WSCP
1Assessments are based on best available data at time of submitting the report and actual volumes could be different due to many factors. 2Units of measure (AF, CCF, MG) must remain consistent. 3When optional monthly volumes aren't provided, verify Tables 2 and 3 use the same columns for data entry and are reflected properly in Table 4 and make sure to use those same columns to enter the benefits from Planned WSCP Actions. Please see directions on the shortage balancing exercise in the Table Instructions. If a shortage is projected, the supplier is highly recommended to perform a monthly analysis to more accurately identify the time of shortage. 4If you enter any WSCP Benefits, then you must enter the corresponding planned Actions into Table 5.
Planned WSCP Actions4
1Assessments are based on best available data at time of submitting the report and actual volumes could be different due to many factors. 2Units of measure (AF, CCF, MG) must remain consistent. 3When optional monthly volumes aren't provided, verify Tables 2 and 3 use the same columns for data entry and are reflected properly in Table 4 and make sure to use those same columns to enter the benefits from Planned WSCP Actions. Please see directions on the shortage balancing exercise in the Table Instructions. If a shortage is projected, the supplier is highly recommended to perform a monthly analysis to more accurately identify the time of shortage. 4If you enter any WSCP Benefits, then you must enter the corresponding planned Actions into Table 5. = From prior tables
Planned WSCP Actions4
ATTACHMENT 1
July 1, 2025 to June 30, 2026
Enter Amount
(Drop-down
List)
Select % or
Volume Unit
Start Month End Month
0 (No Shortage)
Landscape - Limit landscape irrigation to
specific times Yes July June
0 (No Shortage) Landscape - Restrict or prohibit runoff from landscape irrigation Yes July June
0 (No Shortage) Other - Prohibit use of potable water for washing hard surfaces Yes July June
0 (No Shortage) Other - Require automatic shut of hoses Yes July June 0 (No Shortage)
Other - Customers must repair leaks,
breaks, and malfunctions in a timely
manner
Yes July June
0 (No Shortage) Offer Water Use Surveys Yes July June
0 (No Shortage) Provide Rebates for Turf Replacement Yes July June 0 (No Shortage) Provide Rebates for Landscape Irrigation Efficiency Yes July June
0 (No Shortage) Provide Rebates on Plumbing Fixtures and Devices Yes July June
NOTES:
Notes Section to be used only
for clarifying details, and not
for listing specific actions.
Actions must be entred into
table rows above.
1If you plan Supply Augmentation Actions then you must enter WSCP Benefits from Supply Augmentation Actions into Table 4. If you plan Demand Reduction Actions then you must enter WSCP Benefits from Demand Reduction Actions into Table 4. 2If an Action is planned to be implemented in multiple non-contiguous periods of the year, please make separate entries on multiple rows for the same action spanning the different implementation periods.
Table 5: Planned Water Shortage Response Actions
Add additional rows as needed
How much is action going to
reduce the shortage gap?
(Optional)
When is shortage response
action anticipated to be
implemented2?Is action
already being
implemented?
(Y/N)
ACTIONS1: Demand Reduction, Supply
Augmentation, and Other Actions.
(Drop-down List)
These are the only categories that will be
accepted by the WUEdata online submittal
tool. Select those that apply.
Anticipated Shortage
Level
Drop-down List of
State Standard Levels (1 -
6) and Level 0 (No
Shortage)
Demand Reduction Actions listed above are permanent water waste regulations and conservation program offerings for the City of Napa. They remain in effect at all times, even when no water shortage is declared.
ATTACHMENT 1