Metropolitan Water District (MWD) staff reported progress on a water‑balance pilot on Bolden/Bridal Island designed to improve estimates of net channel depletion and agricultural net use in the Delta.

Pilot goals and instrumentation

Russ Ryan, program manager at MWD, said the project’s first phase uses low‑density sensors at five locations and will add discharge meters on major pump stations to provide direct flow measurements. He described the program as a way to assemble the inputs and outputs that feed a water‑balance model — siphons, seepage, pump discharges, ET and rainfall — to answer the question of whether channels experience net depletion at study sites.

Costs, installation and maintenance

Ryan outlined anticipated installation and maintenance work: an initial count of meters and planned procurement is underway, with capital costs varying widely by meter size (he cited a range “from 10,000 to $2,025,000 per meter depending on the size”) and referenced an earlier consultant estimate of roughly $170,000–$200,000 per year to maintain multiple island meter installations.

Why return flows matter

Participants, including attorney George Hartman and other DMEC members, emphasized the need to measure return flows (drainage pumping and seepage) to compute net agricultural usage properly. Hartman said that without measuring water pumped back to the system, “you really don't know the net usage of agricultural lands in the Delta.” Presenters discussed using energy records, discharge meters and modeled seepage to account for these return flows.

Modeling and next steps

MWD plans to incorporate prior studies and models (Hydrofocus, Tetra Tech) and coordinate model inputs with state staff and consultants. Ryan said instrumentation deliveries are complete and that field installs and a monthly modeling coordination cadence are planned into the winter and next spring. The group agreed to continue technical coordination and share historic documents and project webpages as they are finalized.

What remains unresolved

Participants requested clearer comparisons between pump float settings and meter data, calibration checks for meter pulse factors, and standardized reporting methods. Ryan and other presenters committed to follow‑up on meter links, installation timelines, and calibration details.