Evapotranspiration from a winter wheat field: seasonal patterns and implications for scaling
Abstract
Evapotranspiration (ET) is often considered the most difficult component of the ecosystem water balance to measure, but is critical for accurate assessment. We used the eddy covariance technique to measure ET on a half-hourly time step over the course of the 2013 growing season in a winter wheat field in the Judith Basin, MT. Water tables in the Judith Basin are near the surface (~1-10m depth), presenting a unique opportunity to study hydrological and meteorological variability in a location where plant roots may be able to tap the water table. The regular patterning of the wheat-fallow rotation system simplifies approaches for scaling tower-based flux observations to larger scales in space. We test remote sensing algorithms based on the newly-launched Landsat 8 that offers additional spectral information in the thermal bands over Landsat ETM. Critical to validating remote sensing algorithms is the partitioning of ET into evaporation and transpiration, which are controlled in different ways by environmental drivers. Based on preliminary eddy covariance observations and the ET partitioning approach of Scanlon and Kustas (2010, Agric. For. Met. 150: 89-99), we estimate that evaporation dominates before crop growth but quickly shifts to transpiration dominance as the canopy grows, resulting in rapid summer dry-down of soil moisture. Key Words: Evapotranspiration, Flux Data Analysis, Eddy Covariance, Judith Basin, Wheat, Hydrological and Meteorological Variability
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.H51E1248H
- Keywords:
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- 1818 HYDROLOGY Evapotranspiration;
- 1855 HYDROLOGY Remote sensing;
- 1851 HYDROLOGY Plant ecology;
- 1843 HYDROLOGY Land/atmosphere interactions