|Chavez Eguez, Jose|
Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 3/26/2007
Publication Date: 6/17/2007
Citation: Chavez Eguez, J.L., Gowda, P., Howell, T.A., Marek, T.H., New, L.L. 2007. Evapotranspiration mapping using METRIC for a region with highly advective conditions. [abstract]. In: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE). Paper No. 072146. June 17-20, 2007, Minneapolis, Minnesota. Interpretive Summary: The Texas High Plains agriculture is supplied with groundwater almost entirely by the Ogallala Aquifer. Therefore, the future economy of the Texas High Plains depends heavily on the sustainability of the Ogallala Aquifer. In this regard, accurately mapping regional crop water use or evapotranspiration (ET) would provide valuable information for efficient agricultural water management. In this paper, ET was estimated using a model based on satellite imagery and weather station data. The ET model estimates were compared with the ground measurements from four irrigated fields at different irrigation levels. Two fields each were planted to corn and cotton. Results indicated that the satellite based ET model performed better for low evapotranspiration rates than for very high evapotranspiration rates. Further evaluation of this model is needed under a range of agroclimatological conditions and/or using a large number of satellite images acquired through the crops growing season.
Technical Abstract: Agriculture in the Texas High Plains accounts for approximately 92% of groundwater withdrawals. Because, groundwater levels are declining in the region, efficient agricultural water use is imperative for sustainability and regional economic viability. Accurate regional evapotranspiration (ET) maps would provide valuable information on crop water demand and usage. In this study, a regional ET map was produced for an 11-county area in the Texas High Plains, using METRIC (Mapping Evapotranspiration at High Resolution using Internalized Calibration), a remote sensing based ET algorithm, and meteorological data measured at four ET weather stations maintained by the Texas High Plains Evapotranspiration Network (TXHPET). For this purpose, a Landsat 5 Thematic Mapper image acquired on 27 June 2005 was used. Performance of the ET model was evaluated by comparing predicted daily ET with values derived from a soil water budget at four different commercial irrigated fields. Good agreement was found between the remote sensing based ET and soil water budget ET for low to moderate ET rates. Less agreement resulted for higher ET rates. Use of METRIC for advective conditions of the Texas High Plains is promising; however, further evaluation is needed using lysimeter or Scintillometer derived ET measurements for different agroclimatological conditions and/or a larger number of image scenes.