Climate

Evapotranspiration and climate change water usage estimation of almond and pistachio orchards using the MODIS/ASTER Airborne Simulator (MASTER)

The MODIS/ASTER Airborne Simulator (MASTER) was used to estimate the evapotranspiration (ET) of almond and pistachio orchards in southern California using a variety of remote sensing models including the Vegetation Index Trapezoid (VIT) method, and SEBAL and METRIC ET models.

Additional inputs were acquired using the California Irrigation Management Information System (CIMIS) online weather station data for potential evapotranspiration calculations and hemispherical photography for leaf area index (LAI) data.  Comparisons were made to the CIMIS potential and reference ET, field data of crop water stress, soil moisture, the VIT method, and between the two different ET models SEBAL and METRIC.

Differences in ET between the two models were minimal with a strong linear relationship.

The ET results suggest little water stress in the almond and pistachio crops one to four days since watered.

However, calculations using the measured data with the Thornthwaite potential ET equations and IPCC local climate change models suggest that the same amount of irrigation water would maintain  ~75% of current crop area in future climate scenarios.