IRWD’s water supplies include groundwater, imported water from the Metropolitan Water District of Southern California (Metropolitan) purchased through MWDOC, recycled water and local surface water. Since the 1990’s, IRWD has made major investments to diversify its water supply portfolio by increasing local groundwater and recycled water supplies to reduce its reliance on imported water. Imported water is more susceptible to shortage due to long term drought so development of local supplies helps to improve IRWD’s supply reliability. In addition, IRWD has invested in water banking as an emergency storage project that further improves IRWD’s water supply reliability in times of extended drought or supply interruptions.
Hydrologic Conditions and Reporting Period
IRWD’s 2025 UWMP presents the findings of its 2025 water reliability assessment evaluated over a planning horizon from 2030-2045. In addition, IRWD presents the findings of its Drought Risk Assessment over the period 2030 to 2045 under the conditions associated with a normal year, single-dry year and a drought lasting at least five consecutive years. Projections are made in five-year increments. IRWD conducted an assessment of trends in IRWD’s customer water use between 2010-2025 to determine the impact of a single dry year and five consecutive dry years on customer demands. IRWD’s Plan assumes the following: • Normal Year. The year 2012 most closely represents the water supply conditions that IRWD considers available during a normal water year.
• Single Dry Year. IRWD’s potable demands in a single dry year increase by 5 percent, and non-potable demands increase by 10 percent.
• Five-Consecutive-Year Drought. IRWD’s potable demands in the first year of a five-year drought would increase the same as a single dry year, or 5 percent. In year two and three potable demands would increase by an additional 1 percent each year. These increases are primarily due to greater irrigation demands. As the drought progresses and in response to increased conservation outreach, demands would decrease by 1 percent in year four and decrease by another 5 percent in year five. Non-potable demands would increase initially by five percent in the first and second years and by an additional one percent in year three. As the drought progresses, non-potable demands would decrease by two percent in year four and by five percent in year five.
Findings of the 2025 UWMP
The 2025 UWMP provides an assessment and summary of IRWD’s water service reliability through 2045 under the assumptions and sources of information described above. As a reporting document, the UWMP will be updated every five years to reflect changes in water demand and supply projections. The 2025 UWMP satisfies all the content and process requirements mandated by the UWMP Act. Key findings of the 2025 UWMP are as follows: • The total water supplies available to IRWD will meet the projected water demands of existing and planned uses through 2045 under a single dry-year condition and over five
ES - 2 IRWD – 2025 Urban Water Management Plan – Executive Summary and Lay Description
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