What would our landscape look like without the rows of cottonwoods marching across the plains?

Look at these three pairs of "Then & Now" photographs. What changes in the natural environment do you see? What do you think caused the changes?

Top: Overlooking Boulder Valley Ranch, 1869 and 2008

The Boulder area was once part of the "Great American Desert." It was a land dominated by vast expanses of short-grass prairie. By 1869, Farmers Ditch was just finished, and ended at the tail-water pond pictured above. From previously unpublished expedition sketches by Henry Elliot with the Preliminary Field Report of the US Geological Survey of Colorado and New Mexico, 1869 (Hayden Expedition), USGS.

Today trees, irrigated pasture, ponds and housing developments fill what used to be xeric grassland. Can you find the irrigation ditch? Hint: Where are the biggest trees?

Middle: Anderson Ditch at 5th, 1900 and 2008

Why aren't there any trees in the photograph taken in 1900? 

Historic photo courtesy of Carnegie Branch Library for Local History, Boulder CO.

Bottom: Goodhue Ditch Headgate, 1909 and 2008

Why is the creek narrower now? Why are there so many more trees now? 

Historic photo courtesy of Carnegie Branch Library for Local History, Boulder CO.