BOISE • Scientists say climate change is making it tougher for Idaho reservoir managers to forecast weather, control floods and manage water for farming, recreation and fisheries.
Future challenges were foreshadowed recently, when two days of record high temperatures, accompanied by record rainfall in the same week, pushed a surge of water in the Boise River.
That forced dam managers with the Bureau of Reclamation to boost water they were sending out of Lucky Peak Dam upstream from Boise to levels not seen since 1998.
Dam managers say that if the reservoir behind the dam had been full, there could have been problems managing the water. Ron Abramovich, of the Natural Resources Conservation Service, says this phenomenon — a warm spring, heavier rains and more unpredictability — is all something to expect more of as the climate changes.
“A lot of people think global warming is going to be a gradual increase in temperatures,” said Abramovich, a water specialist. “It may be a roller coaster, kind of like the stock market.”
Idaho water managers have about a hundred years of data to base their conclusions on. That information shows that runoff used to begin in early April.
But now, it’s starting in late March.
Droughts and wet years have come and gone over the past century on the Boise River, said U.S. Geological Survey hydrologist Greg Clark. But the past 30 years have generally been drier. With the snowpack melting earlier, that leaves flows lower in the late summer and fall in the tributaries above reservoirs and in rivers without dams.
That affects things besides farmers’ irrigation water. It affects fish, for instance, especially since the water is getting warmer and potentially less hospitable for native species, said Clark, associate director for the Idaho Water Science Center in Boise.
And recreationalists could start to notice, too.
On the Boise River, longer periods of high spring flows through town to prevent flooding delays floating season. On rivers such as the Middle Fork of the Salmon, low late-season flows late limit the number of days for whitewater rafting.
The Bureau of Reclamation wants new forecasting models to help it manage water.
But with money tight and the federal government cutting back on research spending, maintaining even the status quo is going to be a challenge. Case in point: Money for the 100-year-old Boise Middle Fork streamflow gauge is in doubt, Clark said. But these long-term stations do provide data that might otherwise be missed, he said.
The agency is sponsoring research by Boise State University hydrologist Mel Kunkel, whose new modeling technique looks at all of the cyclical “signals” scientists have discovered in the Pacific, include El Ni0x241o and La Ni0x241a weather patterns and annual temperature shifts.
This year, when others were predicting a drier year, Kunkel’s model for the Boise River predicted significantly higher precipitation.
At least so far, it turns out he’s right: Between 110 percent and 150 percent of average amounts fell in the Weiser, Payette, Boise, Clearwater, Panhandle and Henrys Fork, according to the Natural Resources Conservation Service in Idaho’s most recent water supply report.
Information from: Idaho Statesman, http://www.idahostatesman.com