Climate and discharge trends in Mississippi River Basin LTAR watersheds

Authors: Baffaut, Claire; Moriasi, Daniel; Witthaus, Lindsey; Malone, Robert - Rob; Wacha, Kenneth - Ken; Metz, Megan

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/8/2023
Publication Date: 10/29/2023
Citation: Baffaut, C., Moriasi, D.N., Witthaus, L.M., Malone, R.W., Wacha, K.M., Metz, M.E. 2023. Climate and discharge trends in Mississippi River Basin LTAR watersheds [abstract]. ASA-CSSA-SSSA Annual Meeting Abstracts, October 30, 2023, St. Louis, MO. Available: https://scisoc.confex.com/scisoc/2023am/meetingapp.cgi/Paper/151181

Interpretive Summary:

Technical Abstract: The sustainability of future agriculture cannot be assessed without considering the expected changes in climate. Global Climate Models (GCM) predict increases in temperatures and precipitation in the Mississippi River Basin. Based on existing literature, eco-hydrologic models driven by these GCM products predict increases in annual discharge, peak flow, but also the frequency of low flow periods. Early GCM models predicted these outcomes for periods starting as early as 2025 and one would expect that long-term precipitation, temperature, and discharge records would start showing these trends. However, few studies have compared observed trends to GCM predicted trends in the United States. The objective of this study is to determine whether future climate and associated discharge trends predicted by GCM are already detectable. The study focuses on watersheds located within the regions represented by four Long-Term Agroecosystem Research sites in Iowa, Missouri, Oklahoma, and Mississippi, all within the Mississippi River Basin. We analyzed potential trends in long-term records (>50 years) of precipitation, temperature, and discharge at annual, and seasonal scales. We considered multiple climate indicators that characterize extreme and average temperature, rainfall amount, discharge, peak discharge, and drought periods. Preliminary results based on measured data in USDA engaged in experimental watersheds engaged in the Long-Term AgroEcosystem Research network in Iowa, Missouri, and Oklahoma show that trends in many temperature, precipitation, and discharge indicators confirm the trends predicted by the GCM. However, stream base flow, number of zero flow days, or drought flow (minimum discharge that occurs for a week once in 10 years) have increased at multiple gauges in Missouri and Iowa, and at some in Oklahoma, which contradicts the increasing risk of drought predicted by the GCM and eco-hydrologic models. We will speculate on possible interpretations of this contradictory result.