For additional information about the datasets, please see the section on "Data Access and Metadata" included in the following report available from this project: "2015 Assessment of Conditions in the California Central Valley".

https://nex.nasa.gov/nex/projects/1372/

Excerpt from Executive Summary: 

Scientists at NASA Ames Research Center working with the California Department of Water Resources (CDWR), U.S. Geological Survey, U.S. Department of Agriculture, and California State University, Monterey Bay have demonstrated the feasibility of using satellite imagery to track the extent of fallowed land in the Central Valley of California on a monthly basis.

During the summer of 2015, the project documented more than 1.91 million fallow (uncultivated) acres in the California Central Valley, an increase of 522,000 acres relative to 2011, the last year that followed a winter with above average precipitation across the state. The estimates released by NASA confirm the model-based estimates included in a report on economic impacts of the drought released by UC Davis in August, which estimated 540,000 acres were fallowed in 2015 due to the drought.

Of the 1.91 million acres in the Central Valley that were fallow throughout the summer, NASA and USDA estimated that at least 1.03 million acres were also fallow during the winter season. This represents an increase in 2015 in annually fallow agricultural land of 626,000 acres relative to 2011.