Water fountains in front of San Diego County building

Flaws in Forecasting San Diego’s Water Demand

For the last 40 years, state and local water agencies have preached water conservation to Californians. They created drought-tolerant demonstration gardens, funded low-flow toilet replacements, subsidized artificial turf installations, supported high-efficiency plumbing fixtures and appliance requirements, ran school education and public information campaigns, and much more.

Unsurprisingly, these tactics worked – and continue to work – leading to a significant decline in per capita water usage. Yet somehow our region’s water management plans continue to predict otherwise, leading us to question where our water and our tax dollars are going.

The Urban Water Management Plan

Every five years, the San Diego County Water Authority, the public agency responsible for providing our region’s water supply, is tasked with updating the Urban Water Management Plan (UWMP). The UWMP is used to forecast San Diego’s future water use and how the Water Authority will meet those needs.

SDCWA Projected Service Area Demand
Source: SDCWA Urban Water Management Plans 1995-2015; SDCWA Draft Forecast Nov. 2020

The graph above shows that every management plan from the last 25 years has incorrectly predicted demand would continue to increase. Instead, we have seen both overall demand and per capita demand decrease in San Diego due to water conservation measures. It’s important that UWMPs accurately forecast future water demand because if demand forecasts are too high, the Water Authority could risk wasting significant taxpayer and ratepayer dollars on infrastructure and water contracts that we don’t need.

Unfortunately, once again the newly adopted 2020 management plan seems to dramatically undervalue the effectiveness of water efficiency and conservation measures leading to artificially high demand forecast models. It also fails to consider the impact the ongoing historic drought and new statewide water efficiency requirements will have on even greater conservation efforts in the years ahead.

As shown in the graph below, this year’s plan instead shows an increase in expected use, despite the continuing trend of conservation over the past 20-plus years.

Regional Historical and Projected Normal Water Demands
Source: 2020 Urban Water Management Plan, San Diego County Water Authority

The Future of San Diego’s Water Supply

With California in the grips of yet another historic drought, predicting future water demand is vital to water affordability and the environment. By over-predicting future water demand, the Water Authority could potentially use inflated water demand forecasts to justify wasting significant public funds on irrelevant infrastructure and construction projects, like additional energy-intense and environmentally destructive desalination plants, or the proposed regional conveyance system pipeline.

Supporting common-sense water supply solutions, ensuring affordability, and eliminating taxpayer waste is top of mind for San Diego Coastkeeper. Our advocacy team continues to monitor the future of San Diego’s water supply. Coastkeeper promotes holistic water management practices that provide a multitude of benefits at a fraction of the cost. We advocate and support measures – like conservation, wastewater recycling, and stormwater capture – that build climate resilience and protect our communities.

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