Satellite imagery can support water planning in the Central Valley

Most agricultural systems in Califor- nia's Central Valley are purposely flexible and intentionally designed to meet the demands of dynamic markets such as corn, tomatoes and cotton. As a result, crops change annually and semiannually, which makes estimating agricultural water use difficult, especially given the ex- isting method by which agricultural land use is identified and mapped. A minor portion of agricultural land is surveyed annually for land-use type, and every 5 to 8 years the entire valley is completely evaluated. We explore the potential of satellite im- agery to map agricultural land cover and estimate water usage in Merced County. We evaluated several data types and determined that images from the Moderate Resolution Imag- ing Spectrometer (MODIS) onboard NASA satellites were feasible for clas- sifying land cover. A technique called "supervised maximum likelihood classification" was used to identify land-cover classes, with an overall ac- curacy of 75% achievable early in the growing season.