Program. Water banking is a highly reliable and cost-efficient practice of recharging low-cost water to underground storage aquifers during wet periods and recovering this water for later use. IRWD’s Water Bank and the development of additional banking through the Kern Fan Project provide an important water management tool to improve imported water reliability and protect IRWD customers from imported water shortages. The 2025 Study concluded that no supply shortage gaps were identified in the scenarios modeled with use of water banking, as an emergency supply option, and increased conservation. A major earthquake and catastrophic Delta levee failure would create significant disruptions in SWP supplies to Southern California and could result in at least a Level 3 shortage. Depending on the extent of the damage it could result in shortages that are beyond currently forecasted events, with shortages ranging from Level 4 to Level 6. IRWD would rely on its water banking emergency supplies for 18,100 AFY or more, in addition to increased conservation in the case of such a catastrophic event. Table 3-3 illustrates the projected use of the IRWD water banking program under the six levels of shortage. Table 3 ‑ 3: IRWD Shortage Levels and Projected Use of Water Banking Supplies IRWD WSCP Shortage Level
Anticipated Water Bank Usage (AFY)
Access may be limited
No Shortage Identified
Level One
Shortage Warning (up to 10%)
300 to 3,000
Level Two
7,300 to 11,500
Significant Shortage (up to 20%)
Level Three
14,800 to 18,100
Severe Shortage (up to 30%)
Level Four
Severe Shortage (up to 40%) Level Five Crisis Shortage (up to 50%) Level Six Crisis Shortage (exceeding 50%)
18,100+
An additional water supply available to IRWD during shortage conditions would be to pump above the Basin Production Percentage (BPP) set by the Orange County Water District (OCWD). This would be a feasible and available source of water, should IRWD’s Water Banking Program not have available supplies in the amounts listed in Table 3-3 . However, pumping additional groundwater could be subject to surcharges and limitations imposed by OCWD. The Water Banking Program would be used in combination with other response actions under the implementation of IRWD’s WSCP.
WSCP - 28
IRWD – 2025 Water Shortage Contingency Plan
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