Submitted to: Proceedings of the World Environmental and Water Resources Congress Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/9/2011
Publication Date: 5/22/2011
Citation: Ha, W., Gowda, P., Oommen, T., Marek, T.H., Porter, D.O., Howell, T.A. 2011. Spatial interpolation of daily reference evapotranspiration in the Texas High Plains. Proceedings of the World Environmental and Water Resources Congress Conference. Paper No. 2796. 2011 CDROM. Interpretive Summary: The Texas High Plains Evapotranspiration (TXHPET) Network collects meteorological data from 18 weather stations and provides daily grass reference evapotranspiration (ET) estimates to producers in the region. Providing accurate daily reference, ET maps helps producers to adopt the reference ET-based irrigation scheduling for the optimized water usage. However, the concern is how to identify a reference weather station that best describes climatic conditions of producers' irrigation fields. This study evaluated two spatial interpolation methods for mapping reference ET in the Texas High Plains. Daily grass reference ET maps were developed for the study period using ordinary kriging and inverse distance weighting (IDW) methods. Results indicated that IDW performs better than ordinary kriging. However, both methods performed poorly during summer growing season when accurate grass reference ET maps are needed for irrigation scheduling.
Technical Abstract: The Texas High Plains Evapotranspiration (ET) Network collects meteorological data from 18 grass reference weather stations at hourly intervals and estimates hourly and daily reference ET using the American Society of Civil Engineers (ASCE) Standardized Reference ET equation. Producers in the Texas High Plains can obtain daily reference ET for any weather station of their interest by subscribing to the fax/email service. However, one concern in using these data is to determine which reference weather station best represents climatic conditions similar to those in their irrigated fields. Availability of accurate daily reference ET maps for the Texas High Plains is expected not only to relieve producers from this concern but also to assist in attracting more producers to adopt the reference ET-based irrigation scheduling. Therefore, the main objective of this study was to evaluate two spatial interpolation methods such as inverse distance weighting (IDW) and ordinary kriging for mapping reference ET in the Texas High Plains. Daily grass reference ET maps were developed for the Texas High Plains using ordinary kriging and IDW methods for the period of 2000-2005, and assessed for mapping accuracy using Root Mean Square Error (RMSE). Comparison of RMSE values between IDW and ordinary kriging methods indicated that IDW outperforms ordinary kriging for approximately 68 % of 2179 days. However, both methods equally performed poorly during summer growing seasons when accurate grass reference ET maps are needed for irrigation scheduling.