My recent visits to Canyonlands and Arches National Parks, and the drive to get to Moab, UT along the Colorado River on UT-128, provided plenty of opportunities to see how the power of water can shape landscapes, even those that are currently deserts.
The geology of the region was shaped, at its basis, by water. At one time, the area was an equatorial ocean that precipitated salts, leaving a thick layer of them underlying all the rock that has accumulated since. Layers upon layers of deposition of sand and shale, some volcanic ash, and wind blown material from the young Rocky Mountains created layers of heavier material. When rain became frequent and the rock was infiltrated by water, the salt layers domed up — and were then crushed by the overburden of the layers above. The uplifted areas were then, under desert conditions, eroded by water and wind, leading to the towering pillars and arches seen in Arches National Park.
Meanwhile next door in Canyonlands, the flow of the Green and Colorado rivers exposed layers of rock in canyons which could then be further eroded by infiltrating water and wind as the rivers ground their way deeper through the layers. Unlike the Grand Canyon, which features many layers of harder rock, the rock layers in these areas are softer sedimentary rocks, which allows the elements to play a more dramatic role in shaping delicate and precarious landscapes.
It is hard not to come away from viewing these natural wonders with a sense of awe at the power of water, over very long periods of time, to carve a dramatic landscape even in an area that gets very little rainfall (less than 10” per year). It is highly ironic that two major rivers flow through the area and yet the climate is quite dry.
From a human standpoint, it is also deeply ironic that with all the water of the Green and Colorado rivers, they are not water sources for the local population. Not only are these rivers very silty, and thus hard to manage as sources of drinking water, but the vast majority of the water from the Colorado is spoken for by states downstream — Nevada, Arizona, and especially California. The politics of water makes a strange mess out of a grand flow — and also leaves many communities that sit right next to the river vulnerable to drought in ways that seem paradoxical.
The town of Moab, which historically existed to serve the mining industry and now primarily serves the tourists who visit the magnificent parks, gets its drinking water from small aquifers, many of which come to the surface as springs. Recent estimates indicate that these springs currently have sufficient capacity for the town’s needs, yet one of these aquifers sits under a local golf course — making it vulnerable to contamination from fertilizers.