Long-Term Water Prospects in the Western United States*

Based on the changes in the size of closed basin lakes, the author shows that water availability has undergone large fluctuations in response to conditions experienced during full glacial time and during the period of deglaciation. Based on these observations, the author concludes that as the planet warms in response to the buildup of fossil fuel CO2, the distribution of available water will shift. The resulting changes will be particularly noticeable in the world’s drylands. In this paper, the author attempts to invert the response to cold glacial conditions and to interhemispheric temperature differences, which occurred during the interval of deglaciation, to predict how the hydrologic conditions in the western United States might evolve over the next half-century. The tentative conclusion on both scores is that this region will likely undergo a progressive drying. However, because both the glacial and deglacial hydrologic shifts were certainly influenced by the presence of excess ice, as well as by colder temperatures, the author admits that the validity of this inversion is subject to challenge.