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Abstract
This paper describes a linked, modular, system of models called IMPACT that includes global economic and water models to explore the impact of different irrigation investment scenarios under changing conditions of water availability (e.g., climate shocks, ground water shortages. The core economic model is a global, partial-equilibrium, multimarket model that focuses on agriculture, solving for production, demand, international trade, and prices that equate supply and demand of agricultural products across the globe. The core economic model is linked to a number of “modules” that include climate models (Earth System Models, ESMs), water models (hydrology, water basin management, and water stress models), crop simulation models (e.g., Decision Support System for Agrotechnology Transfer [DSSAT]), value chain models (e.g., sugar, oils, livestock), and land use (pixel-level land use, cropping patterns by regions). The water models in the IMPACT Modeling System include: (1) the IMPACT global hydrology model (IGHM) that simulates snow accumulation and melt and rainfall-runoff processes, (2) the IMPACT water basin simulation model (IWSM) that simulates optimal management of water storage in river basins to meet demands by economic sectors including irrigated agriculture, and (3) the IMPACT crop water allocation and stress model (ICWASM) that allocates available net irrigated water to crops and estimates the impact of water shortages on crop yields.