The Nature Conservancy (TNC) and UC research teams presented recent field results from tailwater pump monitoring and multi‑tower eddy‑covariance experiments designed to improve estimates of pump discharge, evapotranspiration (ET) and water budgets on Delta islands.

TNC tailwater monitoring: multiple lines of evidence

Kirk Klausmeier, with TNC, described measuring tailwater pump volumes using pump tests, energy (PG&E) bills, pressure transducers, insertion mag meters and level sensors. He summarized where the lines of evidence aligned and where they did not: some pumps produced consistent timing and magnitudes across instruments, while others showed meter readings that were an order of magnitude too low or spikes an order of magnitude too high. Klausmeier said the discrepancy requires calibration and physical checks: "Good start, but I don't believe the results quite yet," he said, underscoring the value of stacking independent measures and re‑checking meter settings and installations.

Eddy covariance and crop‑scale measurements (UC Davis)

Kosina Suwatadev (UC ANR/UC Davis) presented results from six eddy‑covariance towers, soil moisture profilers and crop management records. She noted energy‑balance closure issues that require quality control and gap‑filling and showed year‑to‑year and site‑to‑site differences in cumulative water use across crop types and management styles. Suwatadev described instances where OpenET matched ground measurements well in some seasons and diverged in senescence or bare‑soil periods, and she emphasized that the results are preliminary pending additional QA/QC and siting review.

Discussion and implications

Participants stressed the need for technical subgroups to address siting, QA/QC and calibration. Several speakers recommended that teams publish calibration notes, include pump float heights and energy‑use comparisons on graphs, and check meter pulse factors and device settings. Presenters committed to continued monitoring through the winter, to run experiments across both wet and dry periods, and to convene follow‑up technical reviews with UC Davis and other partners.

What to watch next

The teams will continue instrument maintenance, calibration checks and cross‑validation across independent measurement lines. Organizers suggested a technical subgroup to reconcile siting and processing methods and to refine how OpenET and eddy‑covariance outputs are harmonized with in‑pipe meter and energy records.