Location: Soil and Water Management ResearchTitle: Identifiying and evaluating a suitable index for agricultural drought monitoring in the Texas High Plains Author
|Moorhead, Jerry - Jed|
|Singh, Vijay - Texas A&M University|
|Porter, Dana - Texas Agrilife Extension|
|Marek, Thomas - Texas Agrilife Research|
|Stewart, B.a - West Texas A & M University|
Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2014
Publication Date: 6/11/2015
Citation: Moorhead, J.E., Gowda, P., Singh, V.P., Porter, D.O., Marek, T.H., Howell, T.A., Stewart, B. 2015. Identifiying and evaluating a suitable index for agricultural drought monitoring in the Texas High Plains. Journal of the American Water Resources Association. DOI: 10.1111/jawr.12275.
Interpretive Summary: Drought is a natural event that can have adverse impacts on agriculture. Numerous drought monitoring methods are available for use; however, their suitability for use in monitoring agricultural drought is unknown. In this study, a comprehensive literature review was conducted to identify a suitable method for monitoring agricultural drought. The selected method was tested for its application in the Texas High Plains. An evapotranspiration (ET) based drought monitoring method "Standardized Precipitation-Evapotranspiration Index (SPEI)" was found to be the best method for agricultural drought monitoring. Application of the SPEI to the Texas High Plains indicated that it is limited to monitoring agricultural drought during summer growing seasons, as it does not account for the large amounts of water that may be stored in the root zone during the summer fallow period, and be available for winter wheat.
Technical Abstract: Drought is a highly destructive natural phenomenon that affects portions of the United States almost every year. Severe water deficiencies can become catastrophic for agriculture and crop yields, especially in the Texas High Plains where generally inadequate rainfall is augmented by irrigation for crop production. Evapotranspiration (ET) or crop water demand is an important component in the agricultural water budget; thus, it is strongly desired to include ET in agricultural drought monitoring. The main objectives of this study were to: (1) conduct a literature review of drought indices to identify a simple but adequate drought index for monitoring agricultural drought; and (2) using the identified drought index method, develop, and evaluate drought indices for the Texas High Plains. Based on the literature review, the Standardized Precipitation-Evapotranspiration Index (SPEI) was found to be the best method for assessing agricultural drought. However, the SPEI needs to be revised by replacing potential ET of a reference crop, with potential ET of an individual crop to develop crop-specific SPEIs to better understand the impact of drought and facilitate estimation of regional irrigation demand. Crop-specific SPEI for major crops in the Texas High Plains were calculated using climatic data from Texas High Plains Evapotranspiration (TXHPET) Network weather stations. Analysis of trends, and magnitudes of crop-specific SPEIs at a monthly time-step indicated that they follow crop water demand patterns for summer crops. This suggests that a crop-specific SPEI is an appropriate index to monitor agricultural drought and estimate irrigation demand. However, its application was limited to summer crops, as it does not account for the water stored in the root zone during the summer fallow period for winter wheat (Triticum Aestivum L.).