Stealing rivers ... and less to steal

By Noel Gollehon

Two scientific studies published this month captured some pretty dramatic details of how climate change is affecting our rivers, lakes and streams. A recent article in Nature Geoscience described the first known case of river piracy due to climate change. In this case, the climate change pirate stole the flow of a whole river contributing to the Bering Sea via the Yukon River, and gave it to the Gulf of Alaska via the Alsek River. This occurred when record temperatures in early 2016 caused a complete re-routing of meltwaters as the Kaskawulsh Glacier retreated. Using models of glacial retreat, the scientists estimate a 1 in 200 chance of this occurring without anthropological effects. The change in course will increase the flow in the Alsek, a commercial salmon fishery, and deprive the flow to Kluane Lake in Kluane National Park. Kluane Lake was a 158-square-mile lake that now experiences dust storms on its drying floodplain and will certainly become smaller due to the loss of its primary water flow. The river capture occurred over the span of just four days, a veritable geologic instant—sometimes a climate effect is very fast.

Another article in Nature Communications describes a 10-20 percent loss in the snow water content of western mountain snowpack between the 1980s and 2000s. The study examined the reasons for this decline and concluded that there is an anthropological component to the decline. The researchers then used climate models to project the changes in snow water levels into the future. They predicted up to a 60 percent decline in snowpack runoff in the future depending on how hard they pushed the buttons regarding climate change. In this case the change in snowpack water supply was observed over decades: perhaps not fast by our standards, but really fast in hydrologic terms.

To me, both of these stories illustrate the potential range of timing in the hydrologic impacts of anthropologic climate change that is often masked in the year to year variability of streamflow and runoff. Whether occurring virtually overnight or over decades, these studies emphasize that we, and trout and salmon, are already observing impacts of climate change in ways that affect us all.

Noel Gollehon is the chair of the Trout Unlimited National Leadership Council's Climate Change Working Group.