Colorado River near Lees Ferry, Arizona, looking downstream.
Photo courtesy of US Geological Survey.
The Colorado River flows 1,450 miles (2,330 km) from the high
peaks of the Rocky Mountains through the desert Southwest, along
the way serving as a vital source of water for municipalities,
agriculture, hydropower, recreation, and fish and wildlife species.
The Colorado is highly variable, with a fivefold difference
in annual flow between the wettest and driest years. The Colorado
is also heavily regulated and strictly apportioned, and in most
years in the past few decades no water has reached its mouth
at the Gulf of California after being doled out so thoroughly.
In recent years, human demands for water supply have approached
the capacity of the Colorado River to provide for them. This
has made it even more critical for water managers to fully understand
and plan for the inevitable swings from periods of wet conditions
to dry conditions and back again. The main source of this understanding
has been the gaged records of streamflow, which are about 100
years long at most. But the recent drought, with unprecedented
low flows at many gages in the Colorado River basin, has called
into question whether the gaged record is an adequate baseline
for water planning.
In this website, Colorado River Streamflow: A Paleo Perspective,
we will assess the gaged record of Colorado River streamflow
in the context of multi-century flow reconstructions from tree
rings. We will describe the Colorado River system and its management,
then the century-long gaged record of flow, and then the use
of tree rings to extend, or reconstruct, the gaged record 400
years or more into the past, providing a more complete picture
of past flow variability. We will take a closer look at the
most recent streamflow reconstructions for Lees Ferry, and how
they compare with previous reconstructions.
to...The Colorado River