ARS | Publication request: Satellite mapping of crop water demand in California

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 15, 2010
Publication Date: April 12, 2011
Citation: Johnson, L., Trout, T.J., Wang, D., Melton, F. 2011. Satellite mapping of crop water demand in California. Meeting Abstract. Assoc. Amer. Geog Annual Meeting April 12-16,2011, Seattle Washington.

Technical Abstract: Surface delivery of irrigation water in the San Joaquin Valley is becoming increasingly restricted due to urbanization and environmental regulation, and the strain is projected to worsen under most climate change scenarios. Remote sensing technology offers the potential to monitor crop evapotranspiration regionally, while potentially making farm-based irrigation scheduling more convenient and efficient. Landsat imagery was used in this study to estimate basal crop evapotranspiration (ETcb), which is primarily related to plant transpiration, for several San Joaquin Valley fields throughout the 2008 growing season. Fractional cover was measured in study fields planted to several crop types (row crops, grains, orchard, and vineyard) of varying maturity on satellite overpass days. Landsat images were atmospherically corrected and converted to normalized difference vegetation index, fractional cover and basal crop coefficient (Kcb). Measurements of grass reference ET from the California Irrigation Management Information System were used to retrieve ETcb (mm/day) on each overpass date. Temporal profiles of Kcb and ETcb were developed for several individual study fields, while spatially contiguous maps were generated for the San Joaquin Valley for each overpass. The satellite-based approach, as implemented in regions with an available reference ET network, potentially enables timely estimation of crop water use for resource monitoring and irrigation scheduling. Additional results will be shown from a prototype monitoring system currently under development.