Description: This project seeks to provide high-resolution (i.e., daily, 30-m) soil moisture information to guide in-season irrigation decision support for vineyards equipped with variable-rate drip irrigation (VRDI) systems in the Central Valley of California. The primary water resource decision for these systems to when to start irrigation in the late spring/early summer. While the quality of many grape varieties benefits from the introduction of moderate levels of water stress (associated with the delay of irrigation), excessive stress can permanently damage the grape-carrying capacity of vines. The key to balancing these two concerns is the availability of timely, accurate and high-resolution soil moisture products that can only be produced by the assimilation of high-resolution remote sensing products into a soil water balance model.

End Users: The primary end user is from the project E&J Gallo Winery. However, E&J Gallo sources most of their grapes from a very large external grower network that cultivates a significant fraction of the total Californian vineyard acreage. As a result, our system is being designed with the eventual goal of serving this (much larger) secondary end-user community.

Data Sources: Satellite-based retrievals of surface soil moisture, derived from synthetic aperture radar (SAR) observations and surface evaporative fluxes, derived from thermal/infrared land surface temperature (LST), form the backbone of our approach. Thermal-infrared satellite data from the NOAA GOES and VIIRS, NASA MODIS, and USGS Landsat sensors are utilized to retrieve LST at a range of spatial scales. In anticipation of the potential future availability of routine, 200-m surface soil moisture retrievals from the NASA/ISPRO NISAR mission, surface soil moisture fields are acquired from ESA Sentinel-1 SAR imaging of E&J Gallo vineyards.

Major Accomplishments in CY19: This project formally started in early 2019. The major accomplishment during its first year was publication of a proof-of-concept, peer-reviewed journal article (Lei et al., 2020) outlining our novel data assimilation and remote sensing approach. Project personnel also presented updates on the project at the April 2019 GRAPEX workshop in Modesto, CA and the November 2019 National Grape Alliance Workshop on Sensor Technology in Sacramento, CA. Both workshops were attended by key end users and provided important outreach opportunities.

Plans/Expectations for CY20: Planned 2020 activities are focused on operationally implementing the data assimilation system described in Lei et al. (2020). Current plans call for this system to be initialized on May 1, 2020 and provide weekly, 30-m resolution estimates of root-zone (0 to 60-cm) soil moisture estimates for two separate E&J Gallo vineyards located near Ripperdan, CA and Lodi, CA. Data products will be delivered operationally to end users (described above) via the existing “ET dashboard” interface. E&J Gallo has agreed to provide timely feedback on the data quality and format of the product. We will complete weekly data delivery less than one-week behind the real-time acquisition of observations.


Lei, F., Crow, W.T., Kustas, W.P., Dong, J., Yang, Y., Knipper, K.R., Anderson, M.C., Gao, F., Notarnicola, C., Greifeneder, F., McKee, L.M., Alfieri, J.G., Hain, C. and Dokoozlian, N. Data assimilation of high-resolution thermal and radar remote sensing retrievals for soil moisture monitoring in a drip-irrigated vineyard. Remote Sensing of Environment. 239. 111622. 2020.