Some of you may have heard talk about the challenges facing Colorado River supplies in the long term.   The recently released Fourth National Climate Assessment has a chapter dedicated to water issues in the Southwest and this image below is of a set of charts from the report.   What this shows is that while precipitation over the last 120 years has held about flat on average, temperatures have been increasing steadily and river flows have been decreasing steadily.  

As the temperature goes up, more water is taken up by plants and the soil and less runs off into the river systems.   Once water gets to the storage reservoirs (Mead and Powell), warmer temperatures increase evaporation.

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