Location: Hydrology and Remote Sensing LaboratoryTitle: Evaluation of evapotranspiration estimates derived using satellite remote sensing for irrigation management in California vineyards Author
|Kustas, William - Bill|
Submitted to: Beltsville Agricultural Research Center Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 4/3/2017
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: Water management is a critical aspect of successful grape production in California’s Central Valley, which represents nearly 1 million acres of grape production valued at approximately 6 billion dollars. Despite competing water use interest and a reduction in water availability over much of California due to recent long-term droughts, vineyard acreage and production continues to increase. As such, there is significant interest in developing efficient water management strategies for these viticulture production systems. In the current study, we investigate the utility of satellite-derived maps of evapotranspiration (ET) based on remotely sensed land surface temperature (LST) imagery as a useful tool to determine crop water use and stress. These mapping products are being evaluated collaboratively with viticultural researchers from E&J Gallo Winery in California for operational use in irrigation scheduling and vineyard water management. As a first step in this study, we evaluate ET derived from two operational remote sensing-based ET modeling approaches. The first is a model currently used by Gallo for irrigation decision-making, known as the Mapping Evapotranspiration with Internalized Calibration (METRIC) modeling approach. We compare this with a new scheme developed by ARS researchers known as the Disaggregated Atmosphere Land EXchange Inverse (ALEXI/DisALEXI) modeling system. ALEXI/DisALEXI provides ET estimates with both high spatial resolution (30-m) and temporal resolution (daily timesteps) by fusing LST data from multiple satellite platforms. This new approach is being modified to further separate total ET into transpiration by the vines and evaporation from the inter-row region – information critical for improving water management in highly structured canopies such as vineyards. Both models are evaluated over two vineyard study sites being monitored as part of the Grape Remote sensing Atmospheric Profile and Evapotranspiration eXperiment (GRAPEX) near Lodi, California between years 2013 and 2016. Surface energy balance/ET and biophysical data collected from each site are used to evaluate the performance of both models. Spatial and temporal patterns in ET produced by the two models are also compared to identify biases that might be related to landcover type and seasonal variability. These findings will be used to develop improved inputs to operational management toolkits used by Gallo for irrigation scheduling and vineyard water management.