A drive into Curecanti National Recreation Area around Blue Mesa Reservoir, at first glance, may appear barren, a vast expanse of sagebrush covered mesas. A closer look, however, will reveal a fascinating variety of life zones throughout the recreation area.
A SEMI-ARID SHRUBLAND
RIPARIAN ZONES AND DRAINAGES
Even the smallest stream can provide enough water to support narrowleaf cottonwoods and willows. A gulch where water is often not visible during most of the year can be a drainage for rainfall and snow melt. These drainages provide enough water to support drought resistant trees like juniper and gamble oak and large shrubs including serviceberry and wild rose. Often a clump of trees and large shrubs inconspicuously placed in the middle of an expanse of sagebrush is the sign of a drainage gully.
PONDEROSA PINE AND DOUGLAS FIR FOREST
Heading north from the recreation area towards the West Elk Mountains the vegetation thickens and the trees grow taller as the elevation changes. Just a seven mile drive north along the Soap Creek arm of Blue Mesa Reservoir to Curecanti's Ponderosa Campground will demonstrate this variation. Ponderosa Campground is scattered with ponderosa pine, Douglas fir, and spruce trees. Although requiring more precipitation than sagebrush, a ponderosa pine forest signifies a dry environment, since they usually grow in places that receive less than 25 inches of precipitation per year.
THE CANYON WALLS
The geologic masterpiece called the Black Canyon of the Gunnison begins in Curecanti below Blue Mesa Dam. You can peer into the canyon from above, at one of the overlooks on Highway 92. Take a trail into the canyon or ride through the canyon on the Morrow Point Boat Tour. No matter how you decide to view the canyon, you will probably notice a difference in the two walls of the canyon. The south-facing wall of the canyon is extremely steep and is sparsely vegetated with sagebrush and juniper trees. The north-facing wall is not as steep and often thick with Douglas fir, mountain maple, serviceberry, and a dense undergrowth.
The striking difference between the canyon walls is due to the amount of sunlight hitting these walls, which in turn determines the amount of freeze-thaw erosion occurring on each wall. The continuous cycle of freezing and thawing water, expanding and contracting within the canyon walls, weaken the rocks, causing them to break off or erode. Since the south-facing wall receives more direct sunlight throughout the day, any moisture that falls there quickly evaporates. Without any moisture, freeze-thaw erosion is less likely to take place. The north-facing wall is in shadow much of the day. Water evaporates much slower in the cool shade. The water that remains on the north-facing wall freezes and thaws throughout the winter, which increases the erosion that takes place. So, water in all of its stages, continues to erode the Black Canyon and has caused more erosion on the north-facing wall than on the south-facing wall. The combination of increased freeze-thaw erosion and the amount of soil created by it has created a more hospitable environment for plant life on the north-facing wall than the south-facing wall.
Did You Know?
Morrow Point Dam, found within the silent walls of the Black Canyon, was the first thin-arch, double curvature concrete dam built in the United States (completed in 1968).