during “dry” periods to offset reduced water supplies under periods of severe drought or during periods of supply interruptions. Water banking, recharge, storage, and recovery programs provide a cost effective and reliable supplemental source of water that can be relied upon during major droughts and periods of supply interruptions. IRWD has secured water supplies for its water banking projects through unbalanced exchange partnerships with other agencies. These partnerships allow agencies with surplus water to store water in IRWD’s water banking projects in return for transferring half or more of the water to IRWD. In addition, as previously stated, wheeling and exchange agreements including a long-term Coordinated Operating Agreement with MWDOC and Metropolitan allows the delivery of SWP supplies from IRWD’s Water Banking Program to the IRWD service area (see “Emergency Supplies – Water Banking” below for quantification of supplies made available). Step 3: Calculate Projected Customer Demands for Year 1 Once the historic customer demand data is obtained, IRWD updates existing customer type information and monthly water use by customer and water type. To calculate the unconstrained demand for IRWD customers, an average is taken across the past three fiscal years, by all customer and water types to determine the upcoming customer demand projections. This is the projected unconstrained customer demands for Year 1. The unconstrained demand includes all customer types (i.e. residential, landscape, CII, data centers etc.) and water types (potable and non-potable). Step 4: Apply Adjustments for Expected Weather, Growth, and Capacity Changes Once the base customer unconstrained demands are projected, then adjustments are made for local weather conditions, population growth and any expected capacity changes for that year. These projections are used as a comparison to validate the three-year average, to track changing demands across all fiscal years and to identify wet, normal, and dry year trends in customer demands. Water supply and demand conditions are prone to fluctuation each year. IRWD’s historic planning methods and diverse portfolio of water supplies allow for accommodating these annual fluctuations relatively easily, with additional built-in measures for significant changes when necessary. The AWSDA specifically takes into account population growth when comparing customer demand changes from year to year. Population Growth In addition to the fiscal year average, calculations are performed comparing customer demand changes, by customer type, across all fiscal years, normalized for population growth each year. Population growth data, as calculated by the CDR at California State Fullerton, is supplied each January by MWDOC for the IRWD service area. The ongoing customer water use calculations are based on fiscal year use data for total water sources, total potable sources, and total recycled sources. Using the data obtained from CDR, these total values are then normalized across fiscal years by taking the ratios of AF per customer. The percentage change calculated
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IRWD – 2025 Water Shortage Contingency Plan
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