The San Pedro River in the United States has lost more than half of its historical perennial surface water. Most of this reduction appears to be caused by groundwater pumping, though other factors may have had some influence. Flow on many tributaries appears to be closer to historical lengths, but historical data are lacking for many streams, especially in Mexico. The remaining perennial reaches have become increasingly important for migratory birds and other wildlife.
This map is one of four downloadable San Pedro River Watershed Maps.
Added March 30, 2010
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