Support for Christy and Norris was provided by the National Science Foundation. We thank Pam Waisanen, USGS National Center for Earth Resources Observation and Science, for assistance with irrigation data displayed in Fig. 1. We thank Nathaniel Stephenson (USGS, Ash Mountain, California) for contributions to the discussion on glacier variations. The staff of NCDC, Tom Ross and Joe Elms in particular, was very helpful in deciphering some confusing station information and in accessing some of the more obscure data files.
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