Table 4-2: Minimum Potable Water Budgets at Each Water Shortage Level Shortage Level Target Reduction Messaging and Outreach ET Factor
Outdoor Potable Water Landscape Plant Assumption 40% drought tolerant plants
Indoor Gallons per Capita
No Shortage
0%
Water efficiency programs and outreach Expanded messaging and
.75
50
Level 1 0-10%
10%
40% drought tolerant plants
.75
50
targeted outreach
Level 2 11-20%
20%
Expanded messaging and
No turf; 100% drought tolerant plants
.625
50
targeted outreach
Level 3 21-30%
30%
Expanded messaging and
No turf; 25% drought tolerant plants; 75% native plants; tree health affected
.35
40
targeted outreach
Level 4 21-30%
40%
Expanded messaging and
No turf; 100% native plants; tree health affected
.25
32.5
targeted outreach
Level 5 21-30%
50%
Expanded messaging and
No landscape
0
30
targeted outreach
Level 6 21-30%
60%
Expanded messaging and
No landscape
0
Basic needs only; 20
targeted outreach
b) Water Shortage Contingency Rates: Water Shortage Contingency Rates apply customer water budget reductions at each level of shortage to encourage voluntary customer compliance to decrease water usage as necessary. WSCP rate development uses cost of service methodology. Higher rates for over budget use are linked to purchases of imported water at Metropolitan’s penalty rates, among other things. The tiered rates assume that the lowest cost source of water is used first for each tier. Costs associated with outreach to all customers are allocated to all tiers except the low-volume tier. Costs associated with over-allocation usage, such as targeted outreach and supply reliability programs, are allocated to the inefficient and wasteful tiers. As part of its public notice and rate hearing process under Proposition 218, IRWD adopted Water Shortage Contingency Rates on June 23, 2025, which provides IRWD with the ability to implement rate adjustments in the event of a shortage declaration. IRWD reviews and updates its Water Shortage Contingency Rates based on cost of
WSCP - 37
IRWD – 2025 Water Shortage Contingency Plan
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