Abstract
The Missouri River Basin (MRB) encompasses one of the most important agricultural regions in the world. Three decadal climate variability (DCV) phenomena — the Pacific Decadal Oscillation (PDO), the tropical Atlantic sea surface temperature (SST) gradient variability (TAG), and the West Pacific Warm Pool (WPWP) variability — substantially influence hydro-meteorology and, consequently, spring and winter wheat yields in the MRB as indicated by data from 1961 to 2010. We applied the Soil and Water Assessment Tool (SWAT) to simulate DCV impacts on wheat yields in response to realistic values of the DCV indices in approximately 13,500 hydrologic unit areas covering the MRB. SWAT, driven by scenarios of past hydro-meteorological anomalies associated with positive and negative phases of the PDO and TAG, indicated major impacts on wheat yields, as much as ± 40% of the average in many locations, with smaller impacts of the WPWP variability. SWAT showed much larger wheat yield increases when the positive phase of the PDO and the negative phase of the TAG are superposed, and an equivalent decrease in yields when opposite phases of the two DCV phenomena are superposed. Thus, combined effects of DCV phenomena on wheat yields in the MRB can be dramatic with important consequences for food production and security. The usefulness of this inter-disciplinary study to farmers and other stakeholders for adapting MRB agriculture to DCV, and the applicability of the methodology to other agricultural regions are described. The results’ implications for detection and attribution of climatic change impacts are also described.
Highlights
Multiyear to decadal hydrologic cycles (DHCs) - with dry and wet epochs - affect crop production, urban and rural water systems, pasture and range conditions, livestock production and health, infrastructure including river navigation, electricity generation, recreation, ecological integrity and, regional and national economies (see, for example, Mehta et al (2013a), Mehta (2017))
Building on previous exploratory studies and interactions with stakeholders and policymakers in the Missouri River Basin (MRB), the present study describes results of simulation experiments with high resolution Soil and Water Assessment Tool (SWAT) to estimate impacts of hydro-meteorological scenarios based on decadal climate variability (DCV) phenomena on spring and winter wheat yields in the MRB
All of the six individual DCV scenarios display some influence on the hydro-meteorology of the MRB, with Pacific Decadal Oscillation (PDO) influences being the most substantial
Summary
Multiyear to decadal hydrologic cycles (DHCs) - with dry and wet epochs - affect crop production, urban and rural water systems, pasture and range conditions, livestock production and health, infrastructure including river navigation, electricity generation, recreation, ecological integrity and, regional and national economies (see, for example, Mehta et al (2013a), Mehta (2017)). In addition to the need for information in times of immediate flood and drought emergencies, planning for water, food, energy, and urban infrastructure development would benefit greatly from reliable information, were it available, on prospects for wet and dry epochs extending from a few seasons to a decade or longer. A recent study found that the benefits of a perfect DCV phase forecast one year in advance to the entire U.S agriculture enterprise can be worth $1.1 billion (Rhodes and McCarl 2020). Extrapolated to the worldwide agriculture enterprise, monetary benefits can be many billions of dollars annually if optimized adaptation options, commensurate with likely impacts of the predicted DCV information, are implemented. Skillful forecasts of this kind and adaptation options commensurate with them will require that the causes of DCV phenomena and their impacts be better understood
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