Droughts on the San Francisco Regional Water
System (RWS) are governed by two plans:
The Tier 1 Plan allocates RWS water between San Francisco retail customers and the Wholesale Customers collectively.
The Tier 2 Plan is the method for allocating the Wholesale Customers’ share of RWS supply among the 26 Wholesale
Customers.
Ti
er 1 and 2 Plan Implementation
Following declaration of a water shortage emergency by the San Francisco Public Utilities Commission (SFPUC), the SFPUC calculates the Tier 1 allocations. Then BAWSCA calculates each Wholesale Customer’s individual allocation by applying the methodology in the Tier 2 Plan.
For the duration of the water shortage emergency, the SFPUC provides monthly reports to Wholesale Customers and
BAWSCA, tracking actual water usage against drought
allocations and detailing any transfers of shortage allocations or banked water among agencies.
The Tier 1 and Tier 2 Plans were implemented for the first time ever during the 2021-23 drought.
Tier 1 and Tier 2
Drought Allocation
Plans
December 2024
SF Retail
Share
Wholesale
Customer
Share
Application and Adoption of the
Tier 1 and Tier 2 Plans
The Tier 1 and Tier 2 Plans only apply during
system-wide water shortages caused by
drought of 20% or less.
T
he Tier 1 Plan is contained in the Water
Supply Agreement between San Francisco
and the Wholesale Customers (WSA).
Changes to the Tier 1 Plan require an
amendment to the WSA.
T
he existing Tier 2 Plan was adopted in
2011 and set to expire in 2018. Since 2018,
the BAWSCA Board has annually extended
the existing Tier 2 Plan while the Wholesale
Customers developed a revised Tier 2 Plan.
T
he Tier 2 Plan must be unanimously
adopted by the 26 Wholesale
Customers. Under the WSA, San
Francisco must provide allocations of
water unanimously agreed to by all
Wholesale Customers or adopted by the
BAWSCA Board. (WSA Section 3.11.C) If a
Tier 2 Plan is not adopted by the BAWSCA
Board, San Francisco may make a final
allocation decision.
Tier 1 Plan Tier 2 Plan
21335941.6
Tier 1 Shortage Allocation Plan Update
The Tier 1 Shortage Allocation Plan (Tier 1 Plan)
allocates RWS supplies between San Francisco
retail customers and the Wholesale Customers
collectively and outlines the administrative
process for drought allocations, including
timelines, transfers of shortage allocations, and
excess use charges.
San Francisco and the Wholesale Customers
agreed to amend the Tier 1 Plan to include a new
Tier 1 Excess Use Charge Family Plan (described
below).
Updated Tier 2 Drought Response and Implementation Plan In early 2022, BAWSCA and Wholesale Customers began negotiating a Tier 2 Drought Response Implementation Plan (Tier 2 Plan) update. Lead negotiators appointed by each agency established four policy principles (listed below). Through mid-2024, the lead negotiators assessed various methods for allocating RWS drought supplies to align with these policy principles until they agreed on a final methodology.
Policy Principles
#1: Provide sufficient water for the basic health
and safety needs of customers.
#2: Minimize economic and other adverse
impacts of water shortages on customers and
the BAWSCA region.
#3: Provide predictability of drought allocations
through consistent and predetermined rules for
calculation, while allowing for flexibility to
respond to unforeseen circumstances.
#4: Recognize benefits of, and avoid
disincentives for, water use efficiency and
development of alternative water supply
projects.
Ti
er 2 Plan Term
The Tier 2 Plan term is coordinated with the term
of the WSA to avoid simultaneous renegotiation
of these related agreements.
Neg
otiated Tier 2 Plan Allocation Formula
Allocations are determined using multiple
factors:
- Minimum and Maximum Cutbacks:
Establishes the upper and lower bounds of
each Wholesale Customer’s final allocation.
- Residential Per Capita Basis: Allocates
water on a residential per capita basis, based
on the portion of each agency’s potable
water demand met by the RWS.
- Non-Residential Base Use: Allocates water
based on each agency’s estimated non-
residential indoor (base) use.
- Seasonal Purchases: Allocates water based
on estimated seasonal use from the RWS.
- Base Purchases/Individual Supply
Guarantee (ISG) Weighted Share:
Remaining water is allocated based on a
weighted share of 2/3 of RWS purchases and
1/3 of ISG.
Tier 1 Excess Use Charge Family Plan
Excess use charges are only applied when the collective Wholesale Customer usage exceeds the Tier 1 allocation. If this occurs, excess use charges will be proportionally applied to agencies that exceeded their individual Tier 2 allocations. 21335941.6