U.S. Water Resource Systems under Climate Change

Water availability is a growing concern globally (UN, 2012). Many countries are affected by water scarcity and quality issues (Postel, 2000). The United States (U.S.) is no exception, with the Colorado and the Rio Grande rivers so severely exploited that they often do not reach the oceans. The exploitation of U.S. water resources is the consequence of growing population and economic activity, and lack of conservation measures. Under the threat of climate change and consequently a change in water resources, water issues are even more pressing. To investigate the issue of water allocation and scarcity for the U.S., we use a computable general equilibrium (CGE) model to drive water requirements in an integrated assessment framework. Specifically, we apply a specially tailored version of the Integrated Global System Model – Water Resource System (IGSM-WRS) model (Strzepek et al., 2012), which draws on the water system module (WSM) developed by the International Food Policy Research Institute (Rosegrant et al. 2008). WRS allows the linkage of WSM with the IGSM (Sokolov et al. 2005). This integrated assessment framework facilitates evaluation of both the direct (via a geophysical model) and indirect (thanks to a CGE model) impacts of climate policy on water scarcity. Taking advantage of data available for the U.S., we model water at a 99-basin level (instead of the 14 regions in the global WRS model). Detailed economic inputs are supplied by the 11-region U.S. Regional Economic Policy (USREP) model (Rausch et al. 2009). This CGE model also provides detailed energy demand which allows a better estimation of water requirements for mining and thermoelectric power generation.