between each individual water supply source is then comparable across years with respect to population growth. Weather When conditions are indicative of a dry year or continuous dry years additional adjustments are made by comparing historical dry year customer demands. The customer demands analysis utilizes changes in demands pre- and post- water reduction drought declaration and water use reduction mandates with data going back to 2010 through present. Local California Irrigation Management Information System (CIMIS) data, obtained from station #75 Santa Ana, is also used to track changes in service area weather conditions. Values for evapotranspiration, rainfall, and air temperature are measured at the hourly, daily, and annual scale. CIMIS data is used to track historic trends and allow for additional adjustments and refinement to projected customer demands based on past trends for similar conditions. Capacity Changes Capacity changes related to large-scale supply availability are also considered. These include, but are not limited to, new facility operations, closed facility operations, state mandates, changes to the BPP, and water delivery schedules. For example, knowledge of a scheduled facility closure during the year for project improvements, repairs, replacements or upgrading infrastructure may alter the availability of the supply source for that upcoming year depending on the duration of the work involved. When applicable, the available supply is adjusted for the upcoming year. After the projected demands for the upcoming fiscal year are calculated, adjustments are made to the first-year projected demands based on projected changes to operations by source due to expected weather, growth, and facility capacities. Step 5: Calculate Projected Customer Demands for Year 2 (Single Dry Year) For the purpose of the AWSDA an additional single dry year of projected demands are also calculated for the subsequent year. This provides the projected customer demands for Year 2. The demands for a single dry year are described as follows: Single dry year customer demand projections are based on historic trend analysis under dry year conditions. The analysis uses data for Dry, Wet, and Normal water years is obtained from DWR and cross-checked with the federal drought monitor run by National Integrated Drought Information System (NIDIS) at the state and local level. This information for different year conditions is then applied to the existing percentage change in customer historic water use calculations. Step 6: Compare Total Supply and Demands – Assess Possible Shortage Once demand calculations for Year 1 and Year 2 have been completed, adjustments have been applied, and water supply availability has been confirmed, IRWD staff compares total demands to total supplies. Then, IRWD can ascertain if a supply shortage is anticipated.
WSCP - 19
IRWD – 2025 Water Shortage Contingency Plan
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