Understanding the food-energy-water nexus through hydroeconomic modeling under near-term climate change and regional development portfolios

Abstract:

Understanding the nexus between food, energy and water (FEW) systems is critical for basins with intensive agricultural water use as they face significant challenges under changing climate and regional development. We consider Flint River basin, GA, to understand the FEW nexus as agricultural water use accounts for a third of total water withdrawals. Potential changes in climate indicate drier summer months and also increased competition between public utility and agricultural water use due to regional development. We investigate the associated FEW nexus in the Flint River basin based on potential changes in regional agricultural profit through a hydroeconomic modeling framework that considers groundwater pumping under various climate and deficit irrigation scenarios. Using a crop simulation model, AquaCropOS, calibrated for six major field crops for the area, we estimate the yield under rainfed, fully irrigated, and deficit (lack of irrigation controlled by the frequency and rate) irrigation scenarios. A Bayesian hierarchical model has been developed to estimate the deficit yield and NASS-reported yield based on rainfed yield and fully irrigated yield through deficit irrigation parameters. Finally, a regional hydroeconomic optimization (RHEO) model using Positive Mathematical Programming is developed with acreage under rainfed, full irrigation, deficit irrigation, and deficit irrigation parameters being the decision variables. The RHEO model considers the total fixed costs, total variable costs, pumping costs, price received, and water withdrawal permits. Interestingly, analyses show that optimal deficit irrigation is economically better than full irrigation because the increase in yield decreases with each additional unit of water supplied. As expected, wet years have higher total regional profits compared to dry years indicating the critical role of changing climate. RHEO model will also be used to explore the changes associated with near-term future scenarios such as increased irrigation costs, reduced summer precipitation, higher growing degree days in the growing season, reduced water availability and the portfolio management strategies to under the regional FEW nexus.