agencies. IRWD was involved in various levels of studies for these plans. For the Tustin MCAS property, IRWD relies on the current land use plans prepared by the City of Tustin. The El Toro MCAS property, formerly within the unincorporated County of Orange, was mostly annexed to the City of Irvine. IRWD has included project water demands based on the City’s and County’s proposed land use plan for the El Toro MCAS property. IRWD’s Lake Forest service area (formerly Los Alisos Water District) is zoned for approximately 2/3 residential and 1/3 commercial development. Existing development is primarily single-family residential with some multi-family residential, office space, commercial industrial and open space. The industrial and commercial developments provide a wide range of services such as manufacturing, assembly, research and development, high technology, aerospace, professional services, biomedical and warehouse operations, among others. The City of Lake Forest is in various stages of developing approximately 950 acres (commercial and residential) of previous vacant land adjacent to the former El Toro MCAS. IRWD coordinates closely with the City of Lake Forest on its ultimate plan for this area and has updated IRWD’s water demand projections accordingly. In late 2001, the Irvine Company (a major landowner within IRWD’s service area) announced the planned dedication of a large area as permanent open space. Most of this land is located in the northwestern portion of IRWD’s service area (City of Orange sphere of influence), with an additional area near Laguna Canyon Road. Based on this change, IRWD made appropriate reductions in its demand projections. Land Use and Water Resource Planning The basis for the preparation of the UWMP is IRWD’s principal water management planning document, the Water Resources Master Plan (WRMP). IRWD’s WRMP describes both the potable and non-potable systems and provides a basis for future IRWD water resource planning. The WRMP is a comprehensive document compiling data and analysis, including current and future land uses, that IRWD considers necessary for its planning needs. The WRMP serves as the basis for the water demand estimates that are used for the District’s other reporting and assessments of future water use. It should be noted that solely for purposes of this UWMP and not for its own planning purposes, IRWD utilized demand projections that were developed by the Municipal Water District of Orange County for its 2025 Regional UWMP, discussed further in Sections 4 and 7. The data within the WRMP are used for hydraulic modeling, the groundwater work plan, assessments of available water supply for specific development projects as required by CWC Section 10910, sub-area master plans and basin pumping projections. The WRMP provides identification of an optimum mix of water resources to meet normal and emergency requirements and prioritizes local supplies versus imported supplies. The foundation for IRWD’s WRMP is the compilation of land use data. This requires interfacing with multiple jurisdictions and developing a GIS based land use database. The computerized GIS linked to the master planning process enables more detailed categorization of land use.
IRWD employs water use factors to assign water demands to various land use types and aggregate the demands. The water use factors are based on average water use and
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IRWD – 2025 Urban Water Management Plan
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