|Hunsaker, Douglas - Doug|
|Pinter jr, Paul|
Submitted to: Proceedings of the World Water and Environmental Resources Congress
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2005
Publication Date: 7/14/2005
Citation: French, A.N., Fitzgerald, G.J., Hunsaker, D.J., Barnes, E., Clarke, T.R., Lesch, S., Roth, R., Pinter Jr, P.J. 2005. Estimating spatially distributed cotton water use from thermal aerial imagery. Proceedings of the World Water and Environmental Resources Congress, May 15-19, 2005, Anchorage, Alaska, USA. p. 526 (pdf 11 pgs). Interpretive Summary: Productive growth of cotton requires large quantities of irrigation water in arid lands. Considering increased water resource scarcity, maintaining this productivity in future years will require much more precise irrigation scheduling than needed previously. The only way to achieve higher precision is to learn how the main water use process--evapotranspiration--is spatially distributed. This study shows first results from a cotton experiment in 2003 where spatial estimates of evapotranspiration were resolved at 1 meter resolutions using aerial thermal infrared imagery. The daily evapotranspiration values show good agreement with soil moisture data. Extension of these results to include most of the crop growth cycle will be an important component of future irrigation scheduling technologies.
Technical Abstract: High resolution thermal infrared (TIR) observations of irrigated lands have the potential to retrieve spatially distributed estimates of evapotranspiration (ET) and thereby assess crop stress and refine water scheduling. To assess this possibility we use a remote sensing data set from a 2003 central Arizona cotton experiment in combination with ground-based observations to estimate instantaneous ET. The spatially distributed estimates are compared with those derived from soil neutron probe water observations. We retrieve ET from TIR observations using a two source energy balance (TSEB) approach, which models surface energy fluxes from distinct soil and vegetation sources. This distinction of energy sources is important for heterogeneous and sparsely vegetated surfaces since soil and plant ET processes are significantly different. TSEB requires radiometric surface temperatures, vegetation densities from Normalized Difference Vegetation Index (NDVI) and near surface meteorological observations. Incorporation of TIR observations into other remote sensing surveys could help realize near-real-time water use monitoring at local and regional scales.