Seminar speaker: Moriah Bostian, Professor of Economics and Chair of Economics in the Economics Department at Lewis & Clark

Title: Irrigation Productivity in the San Salvador Basin, Uruguay

Abstract: Agricultural enterprises are often detrimental to water quality in terms of nitrogen and phosphorus  nutrient pollution. Supplemental irrigation, while economically beneficial, could augment these  environmental impacts due to increased nutrient runoff and percolation. In this study we evaluate the environmentally adjusted productivity of irrigated farming areas in the San Salvador Basin in Uruguay. We use the Soil and Water Assessment Tool (SWAT), a biophysical model calibrated for this basin, to simulate crop production yields and nutrient runoff levels for a variety of fertilization and irrigation scenarios. We consider production inputs (fertilizer, irrigation), desirable outputs (crop yields), and undesirable outputs (nitrogen and phosphorous loading in streams). Areas with higher levels of crop yield output and lower levels of nutrient loading, for a given level of fertilization and irrigation, are considered more productive than their lower-yield and higher polluting counterparts. We map the spatial distribution of productivity levels over the basin to identify areas where irrigation is more productive and to also identify the most productive crop fertilization scenarios for a given area. These findings could be used to construct a relative ranking system to target irrigation and fertilization policy incentives for both economic and environmental objectives.