Integrating a Novel Method to Estimate Grapevine Water Use and Stress into Multi-Tiered Precision Irrigation Management. AVF Project #2025-2796.

Summary of Progress:

We continued our efforts on this project to test and refine the use of IRT wavelet method as a method to track vine water use and stress across a variety of field sites and vineyard settings.  In year 2, we repeated a second year of study in experimental vineyard located in Davis with variable rate irrigation system, where we conducted a drought experiment with heavily instrumented and measured vines.  Physiological measurements were also taken on days when a drone was flown to capture aerial thermal and spectral imagery for comparison with the ground-based measures.  Data from these image collection dates is still being processed and should be completed before the beginning of the 2026 growing season.  Measurements were made in upper and lower leaves within the canopy as we will be comparing the effectiveness of the TSEB and 3SEB ET models to partition canopy water use vs middle water use and is being compared against the various viewing angles of the IRTs.  We also installed a new wavelet IRT station at the Oakville South Station.  This station includes additional sensors to test what is needed for effective pairing of the ground-based remote sensing approaches.  Working with a computer science technician the team developed a web-based dashboard that will be used for the ingestion of wavelet IRT, OpenET and other relevant irrigation management.  It allows the user to enter data on irrigation amounts and timing.  We will test and refine the dashboard for operational irrigation management in 2026 (see images below).  We are still analyzing data from the previous year of effort and will submit multiple manuscripts in the next year related to this work.

IRT wavelet analysis was performed on various sites during the 2025 field season.  An array of 10 IRT sensors was installed on vines in an experimental vineyard in Davis where a variable rate irrigation system was used to deliver varying amounts of water.  Measurements at this site were paired with regular diurnal physiological measurements and other instrumentation for comparison.  An additional station was established in UC Davis Oakville Station on the south property in a Cabernet Sauvignon commercial production block.  We continue to maintain eddy covariance flux towers at GRAPEX sites in Barelli, Sierra Loma and Ripperdan ranches, at sites where 1 Hz IRT data is available it is being compared against eddy covariance flux tower measurements.  We will install additional IRTs at these sites in the summer of 2026 with various sensor orientation within the flux footprint to determine the spatial range of inference for each IRT sensor.  This will also include sensors pointing solely at the vine canopy as well as the soil/cover mix in the middles to be able to run the TSEB model locally from this tower data.  This output will be compared against the wavelet method, OpenET and flux data at each site.