Innovations in water management and irrigated agriculture powered water-scarce Middle Eastern economies for millennia. However, as water becomes scarcer because of population growth and economic development, and even more erratic because of climate change, the region’s water security is coming under increasing threat. This report applies an economic model, the Global Trade Analysis Project (GTAP) computable general equilibrium model, to assess the economic impacts of water scarcity for six Middle Eastern countries and also to examine how water-use efficiency improvements and trade can mitigate these impacts. A 20 percent reduction in water supply could decrease GDP by up to 10 percent, compared to 2016 levels. Furthermore, increased water scarcity could reduce labor demand by up to 12 percent and lead to significant land-use changes, including loss of beneficial hydrological services. The report emphasizes how the growing dependence on shared water resources reinforces the need to manage water across boundaries. The message is clear: unless new and transformative policies for sustainable, efficient and cooperative water management are promoted, water scarcity will negatively impact the region’s economic prospects and undermine its human and natural capital.