Monday, May 13, 2013

Ain't it Grand

My stomach rose into my throat as the Bell helicopter dropped over the lower rim of the inner gorge, into the most intimate depths of the Grand Canyon.  As the river, our tiny boat and our crew came into view, I heard the words of its first explorer, John Wesley Powell.  He described the Grand Canyon as “the great unknown” when he entered it on August 12, 1869 from the relative gentle beauty, soft rock and smooth water of Glen and Marble Canyons.  The cool ribbon of green flowed quietly, agelessly through the inferno of the ancient lava rock, the lifeblood plumbing of the American west, looking like a beard on a beauty queen. 

The Indians say that you never see the same river twice but the river we were seeing was a far different river than the one John Wesley Powell saw for the first time more than 100 years ago.  With the installation of Glen Canyon dam and the ignominiously named Lake Powell, the river has been tamed, harnessed and controlled.  Without the dam, the river would be flowing at almost 120,000 cubic feet per second (cfs) because of the healthy winter snow pack still melting in the Colorado Rockies, the Wind River range of Wyoming and the Uinta mountains of Utah.  Even with some extra flood control releases at the dam, the current river was flowing at a nominal 27,000 cfs.  The river would, historically, be blood red with sediment and close to 60 degrees, but now, 200 miles below the dam, it was still flowing emerald green, hungry for sediment and barely 49 degrees. 

Why drown a canyon to tame a river, we asked, for fountains and light shows in the mid day Mojave heat of Las Vegas, to grow rice in the Imperial valley or irrigate cow pastures at 7500 feet in northern Utah?  The token Bureau of Reclamation flushing flows of 45,000 cfs released for one week a few years ago may have helped scour the channel and rebuild some beaches but it is apparent that to mimic the natural system they will have to release more sediment filled, warm water for a longer period of time to match the natural range of variability.  It’s at least a philosophical step, in the right direction, towards considering the rivers ecology as well as its economics. 

In the morning I awoke early and hiked to a ledge overlooking the river and the camp.  From my perch the hydraulics of the river and the canyon became evident.  The side canyon had spewed a tremendous amount of rock and debris during countless flash flood events, creating a large alluvial fan that extended halfway into the river channel and made our perfect beach campsite.  The alluvial fan also created a small rapid by filling the channel with debris, creating a calming ‘sub-critical’ backwater effect upstream and a constricted, steepened channel downstream.  The river poured over the elevated rock control section like calm, deep water pours over a water fall.  At the constriction of the river the water depth got thinner and the velocity faster as the profile approached a transitional ‘critical depth’, as hydrologists call it.  The water flowed through the rapid waves very thin and fast in a ‘super-critical’ state and at the end of the rough steepened constricted section, the river flattened and returned to a slower and deeper, more energy efficient flow regime called sub-critical flow.  This trans-critical sequence is called an energy dissipating ‘hydraulic jump’, where the water surface exits the rapid actually higher than the middle of the rapid, allowing it to flow back upstream along the side of the rapid creating a shear flow zone and the back-water eddy.  The water then returned to the rapid again as the lateral flow that is so tricky for kayakers and canoeists.

The fast moving, hungry water of the rapid can carry more sediment as it back cuts into the deposition from the side canyon, but drops it quickly after it slows down in the eddy creating beaches and point bars.   This particular eddy swirled behind the shelter of the alluvial fan that served as our camp and created a beautiful bay of deep, relatively calm water.  Other famous big rapids on the river were formed this way: Lava Rapid by a lava flow into the river, Crystal Rapid and Separation Rapid by two large side washes entering the river at the same spot.  I returned to camp, after this personal revelation, but could find no one who shared my hydraulic fascination.  We all appreciate the river for something different.  Therein lies the problem.

They tell me that the rock formations of the Grand Canyon, some as old as 3 billion years, were pushed up 50 million years ago and the canyon was cut in a paltry 6 million years.  In geological times there could have been hundreds of Grand Canyons.  They say there are distinctive rock layers mysteriously missing in places and parts of the river used to flow the other way.  You can not travel this canyon without thinking of the greatness of God, and the insignificance of man, but you also can not forget about the huge power dam above you and the bigger, controlling one below.  There have been several plans for dams in the canyons, the last as recently as Ronald Regan.  Congress has passed a law that forbids dams in the Grand Canyon, until they pass another law.  Only God can make such a place for the ages but only man can muck it up in a matter of years.

On the way home we fly over the big dam that sits like a plug in a puddle.  Hoover Dam tamed the lower river in the 1930s and created the relatively sterile looking Lake Mead without much opposition or loss of unique beauty.  It was, and still is, an Art Deco engineering marvel that set the stage for development of the West.  Power generation revenue from this cash register dam was enough to fund most of the Bureaus subsidized water development projects in the forties, fifties and sixties and is still going strong. The lower canyon is stark and dark with lava flows and ancient silt and sand stones in a Mojave vegetation complex full of Barrel cactus and Fire Sticks.  Glen Canyon Dam was built in the 60s as a trade off with environmentalists for not building a dam in Dinosaur Monument.  The sole purpose of Glen Canyon Dam is to give the upper states water use flexibility and guarantee a ten year 75 million acre feet water supply to the lower basin states.  It is a very expensive insurance policy assuring us we will not have to change our wasteful ways. The 500 million dollars per year power generation revenue is just icing on the cake. 

David Brower, then president of the Sierra Club, made the deal with the Bureau of Reclamation before he and the environmental movement knew that Glen Canyon was an irreplaceable national treasure. The upper canyon was shady, lush and airy with vertical faces of polished red sandstones and side canyons as thin as a man or as cavernous as a cathedral.  As a regretful older man, Brower, along with the Sierra Club and ex Bureau Chief Dan Beard, proposed the removal of the dam because of the waste of water from infiltration and evaporation, enough annually for the city of Chicago, and the lack of a real need for the storage.  They were fighting the power companies, the water users and more than 3 million recreationists that enjoy Lake Powell annually.  To Brower, flooding Glen Canyon for recreation was like flooding the Sistine Chapel to get a closer look at the ceiling.  Perhaps the proposal was the last desperate act of a remorseful eco-warrior, or perhaps it was an extreme bargaining position for better environmental operation of the dams and the river.  With both Lake Powell and Lake Mead half empty and perhaps a slim chance of ever filling again, maybe it is an idea so outrageous that it might be worth re-considering. 

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