Sweetwater taps $2.58m in reserves for imported water to combat severe reservoir algae blooms

Sweetwater taps $2.58m in reserves for imported water to combat severe reservoir algae bloomsThe California utility is shifting to 100% imported raw water to bypass severe taste and odor issues, while advancing an aeration project and alternative algaecides for long-term reservoir management.

The Governing Board unanimously approved $2,588,800 to purchase up to 1,600 acre-feet of raw water from the San Diego County Water Authority.

Geosmin levels in Sweetwater Reservoir exceeded 200 nanograms per liter, forcing a shift away from local surface water.

Funds will be drawn from the Authority's $18.89 million Rate Stabilization Fund, which is designed to absorb unexpected imported water costs.

Long-term mitigation includes a planned aeration and destratification system and potential future granular activated carbon (GAC) treatment.

Sweetwater Authority's Governing Board unanimously approved the transfer of nearly $2.6 million from its Rate Stabilization Fund on May 20, 2026, to purchase additional imported water. The emergency procurement of up to 1,600 acre-feet of raw water from the San Diego County Water Authority (SDCWA) is an immediate response to severe taste and odor (T&O) issues stemming from intense spring algae blooms in the Sweetwater Reservoir. Director of Water Quality Justin Brazil reported that the reservoir has experienced multiple severe algal events this fiscal year. A winter bloom of a potentially new strain of Euglena caused filter clogging and a fishy odor, while an ongoing spring bloom of Anabaena circinalis drove geosmin levels above 200 nanograms per liter. Because these concentrations are more than an order of magnitude above typical human detection thresholds, the utility was forced to abandon source water blending and transition the Perdue Water Treatment Plant to 100% imported aqueduct water on May 1. To fund the $2,588,800 purchase without impacting the current operating budget, the Authority is drawing from its Rate Stabilization Fund, which currently holds $18.89 million. The financial mechanism is specifically designed to absorb the costs of unplanned imported water purchases when local surface water becomes untreatable or unavailable, mitigating rate shocks for customers. To manage the immediate bloom, the Authority applied copper sulfate to the reservoir on May 6 and is planning subsequent applications. However, to avoid breeding copper-resistant algae strains like Leptolyngbya—which severely impaired filtration earlier in the fiscal year—staff is updating the utility's Aquatic Pesticide Application Plan to include hydrogen peroxide-based algaecides, which degrade into water and oxygen rather than accumulating in sediments. Long-term infrastructure solutions are also advancing to reduce reliance on emergency water purchases. An aeration and destratification project for the Sweetwater Reservoir is currently under contract and expected to be completed next calendar year. The system aims to maintain an oxygenated water column, preventing the release of nutrient-rich sediments that feed the blooms. Additionally, the utility is evaluating granular activated carbon (GAC) as part of a future PFAS mitigation project, which would offer the secondary benefit of absorbing T&O compounds.