Farm waters run deep: a coupled positive multi-attribute utility programming and computable general equilibrium model to assess the economy-wide impacts of water buyback

Little is known about the economy-wide repercussions of water buyback, which may include relevant feedbacks on the output of economic sectors at a regional and supra-regional scale. Limited studies available rely on standalone Computable General Equilibrium (CGE) models that represent competition for water explicitly, but this approach presents significant data and methodological challenges in areas where mature water markets are not in place -the case of most regions worldwide. To bridge this gap, this paper couples a microeconomic Positive Multi-Attribute Utility Programming (PMAUP) model that elicits the value and price share to water with a macroeconomic, regionally-calibrated CGE model for Spain. Methods are illustrated with a case study in the Murcia Region in southeastern Spain. Economy-wide feedbacks amplify income losses in Murcia's agriculture from - 20.5% in the PMAUP model up to - 33% in the coupled PMAUP-CGE model. Compensations paid to irrigators enhance demand in the region, but supply contraction in agriculture and related sectors lead to overall GDP losses (up to - 2.1%) in most scenarios. The supply gap is partially filled in by other Spanish regions, which experience a GDP gain through a substitution effect (up to + .034%). In all scenarios, aggregate GDP for Spain decreases (up to - .023%).