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Moving Forward with Imperfect Information 459Case Study 4: Transmission Planning in the Western StatesBox 19.5Resource management decisions must be basedWestern governors have long identified clean,diverse, and reliable energy as a regional and nationalpriority. But access to transmission lines isa significant impediment to increasing renewableresources as a portion of the overall energy portfolio.There is also a broad recognition of the needto consider water, land use, and wildlife whenplanning and developing energy supplies in theWest. To address these issues, the Western Governors’Association and the Western States WaterCouncil are collaborating with the Department ofEnergy and the National Laboratories on the RegionalTransmission Expansion Project (RTEP).A major focus of the project is to seek generationand transmission options that are compatiblewith reliable water supplies and healthy wildlifecommunities in the West (Iseman and Schroder2012).Electricity generation and reliability of thegrid are dependent on availability of water resources.Most of the power generated in the Westrequires water, and in order to move electricity topopulation centers, transmission lines need to besited near these power plants. Even low-carbonelectricity portfolios require additional watersupplies. Consequently, the reliability of the gridand electricity supplies depends on the availabilityof water.To make better decisions on energy and water,risks associated with a variable water supplymust be considered. Drought has always beena fact of life in the arid West. Thus, consideringdrought in this planning effort is prudent in orderto minimize risks to both the grid and watersupplies. However, projections of drought in theshort term (less than fifty years) are uncertain.Long-term climate projections indicate there willpotentially be more severe drought events; but inthe short term, natural variability trumps climatechange.To address risks posed by drought, the RTEPteam is using past droughts to test the vulnerabilityto dry conditions of proposed transmissionsystems. These droughts are not necessarily thoserecorded in the observation records, but ratherpaleodroughts that occurred up to 1,000 yearsago, as evidenced by tree rings in the region.ReferencesBoykoff, M. 2011. Who speaks for the climate? Making sense of media reporting on climate change. PortMelbourne, Australia: Cambridge University Press.Crosbie, R. S., J. L. McCallum, and G. R. Walker. 2011. The impact of climate change on drylanddiffuse groundwater recharge in the Murray-Darling Basin. Waterlines Report No. 40. Canberra,Australia: National Water Commission.Fowler, H. J., S. Blenkinsop, and C. Tebaldi. 2007. Linking climate change modelling to impactsstudies: Recent advances in downscaling techniques for hydrological modelling. InternationalJournal of Climatology 27:1547–1578.Hawkins, E., and R. Sutton. 2009. The potential to narrow uncertainty in regionalclimate predictions. Bulletin of the American Meteorological Society 90:1095–1107, doi:10.1175/2009BAMS2607.1.