Tuesday, April 21, 2015

Alaska's Wild Rivers


by John Shepard

Like a splash of glacial water to the face, Alaska’s waterways wake you up to the importance of rivers left wild and free. The 49th state has more than 12,000 rivers—so many flowing through so much wild, sparsely inhabited country, that only 9,728 of them have been officially named, according to the US Geological Survey. And on all of these rivers there exist only 167 dams. Alaska’s lack of dams stands out in a world where, according to the International River Network, only one third of the largest 177 rivers flow free and only 21 rivers longer than 1,000 kilometers run unfettered to the sea.

Braided channels of the Teklanika River in Denali National Park.
Braided channels of the Teklanika River in Denali National Park.

I recently had an opportunity to explore several magnificent and wild Alaskan rivers, following them for many miles by train, bus, and small airplane; and observing them up close on foot, and—on the Nenana River just outside Denali National Park—in a one-person raft small enough to fit into a day pack.

What struck me most immediately about these silt-ladened, glacially-fed rivers was the many places where they morphed into multiple, exuberant, wildly braided channels. It was as though the river had split into dozens of clones, each setting off on its own merry adventure, only to merge momentarily with another, and then divide again.  Beneath and among these complex, ever-shifting strands of water were the tons of silt and gravel they carried from mountains that are ever so slowly washing into the sea. These sediments are constantly rearranged by river currents that pulse with variations in flow from rains and melting snows. 

The results of this relentless river-bed sculpting can be surprising. Once when canoeing a heavily braided section of the Coppermine River on its run toward the Arctic Ocean in Canada’s Nunavut Territory, I looked up from the channel I was in to see that the less-eroded channel beside me appeared to have mysteriourly risen several feet higher in elevation, only to dip down to my level again within a few hundred yards. These kinds of living-geology experiences are rarely to be had on rivers that have been tamed and harnessed for human use—rivers constrained by levees and dams, whose reservoirs submerge the braided channels and gradually fill with deposits of water-borne sediments once destined to bring nourishment to biologically rich river deltas and the seas beyond them.

Of course, our civilization has benefitted in multiple ways from the restructuring of waterways. Dams and levees have reduced flooding impacts on human communities; provided hydropower; created water reserves for drinking, agriculture, and industry; and greatly enhanced commercial navigation of rivers like the Mississippi. Southern California would be a sparsely inhabited semi-desert without dams, canals, and reservoirs. Texas, with more reservoirs than Minnesota has lakes, would never be able to support a population projected to grow from 20 million in 2000 to 40 million by 2050 without the extensive damming of its rivers. But in the U.S. and worldwide, such benefits have come with great ecological and human costs. These include major impacts on migratory fish and other aquatic organisms (including species extinctions), loss of farmlands and forests, destruction of wetlands, disruption of groundwater recharge, and lack of sediment to nourish biologically rich and economically vital estuaries and other coastal environments.  

While large dam construction in the U.S. has become historical legacy, and the removal of antiquated, useless dams is a growing trend (see, for example, the recent film DamNation), the building of major dams continues in China, India, Brazil, and elsewhere.  A trip to wild Alaska—or to any place where streams still run free—offers an important reminder of how wonderful an unconstrained river truly is.

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