Evaluation of the oceanic nino index as a decision support tool for winter wheat cropping systems in the Texas High Plains using SWAT

Authors: Marek, Gary; Baumhardt, Roland - Louis; Brauer, David; Gowda, Prasanna; Mauget, Steven; Moorhead, Jerry

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2018
Publication Date: 6/22/2018
Citation: Marek, G.W., Baumhardt, R.L., Brauer, D.K., Gowda, P., Mauget, S.A., Moorhead, J.E. 2018. Evaluation of the oceanic nino index as a decision support tool for winter wheat cropping systems in the Texas High Plains using SWAT. Computers and Electronics in Agriculture. 151: 331-337. doi.org/10.1016/j.compag.2018.06.030.
DOI: https://doi.org/10.1016/j.compag.2018.06.030

Interpretive Summary: Decades of pumping with minimal recharge has resulted in declining levels of the Ogallala Aquifer in the Texas High Plains. A gradual transition to more dryland management systems including winter wheat cropping rotations is expected. Precipitation forecasting approaches may help producers manage crops accordingly. The Oceanic Nino Index (ONI) was evaluated for predicting relatively wet (El Nino) and dry (La Nina) phases of the El Nino Southern Oscillation (ENSO) using historical measured precipitation data from the USDA-ARS CPRL at Bushland, TX. Results suggested that the sporadic and uncertain nature of precipitation in the Texas High Plains outweighed the ONI signal for the winter wheat growing season. However, analysis of simulated yield values using the Soil and Water Assessment Tool (SWAT) revealed a reduced likelihood of lower yields for El Nino phases.

Technical Abstract: The semi-arid Texas High Plains has experienced decreasing well capacities due to decades of pumping with limited recharge. Improvements in water use efficiency and advances in drought tolerant crop varieties have improved water use efficiency. However, a gradual transition of irrigated lands to dryland management systems is expected for many areas in the region within the coming decades. Producers may elect to allocate more acreage to dryland crops such as winter wheat during this transition. Precipitation forecasting approaches may aid producers when considering planting acreage and additional inputs. Classifications of the El Nino Southern Oscillation (ENSO) periods have been associated with seasonal fluctuations of precipitation in North America. In this study, the Oceanic Nino Index (ONI), used to classify El Nino and La Nina phases of the ENSO, was evaluated for predicting growing season precipitation for winter wheat using measured data from the USDA-ARS Conservation and Production Laboratory (CPRL) for 1950-2015. Although not statistically significant, probability exceedance plots revealed a plausible correlation between precipitation and ONI classifications. Corresponding winter wheat yields were also simulated using the Soil and Water Assessment Tool (SWAT) model using both continuous and single-year scenarios designed to determine the effects of antecedent soil water resulting from inter-seasonal precipitation and residual soil water. The sporadic and uncertain nature of precipitation appears to outweigh the ONI signal for prediction of precipitation for the winter wheat growing season in the Texas High Plains. However, minimum yield values associated with El Nino phase classifications were nearly three times those of La Nina and phase neutral values, suggesting that ONI-based predictions of El Nino conditions have less likelihood of lower yields. This finding provides some support for the ONI as a decision support tool for the planting of increased acreage and/or additional inputs for winter wheat crops in the Texas Panhandle.