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.Salinization is starting to appear in some of those areaswhere the irrigation water contains salt.Another form arises > from anindustrial method to extract methane for natural gas from coal beds bydrilling into the coal and pumping in water to carry the methane up to thesurface.Unfortunately, water dissolves not only methane but also salt.Since1988, the adjacent state of Wyoming, which is almost as poor as Montana, hasbeen seeking to boost its economy by embarking on a big program ofmethane extraction by this method, yielding salty water that drains fromWyoming into southeastern Montana's Powder River Basin.To start to understand the apparently intractable water problems that be-devil Montana along with other dry areas of the American West, think ofthe Bitterroot Valley as having two largely separate water supplies: irrigationfrom ditches fed by mountain streams, lakes, or the Bitterroot River itself, towater fields for agriculture; and wells drilled into underground aquifers,which provide most of the water for domestic use.The valley's larger townsprovide municipal water supplies, but houses outside those few towns allget their water from individual private wells.Both the irrigation water sup-ply and the well water supply are facing the same fundamental dilemma: anincreasing number of users for decreasing amounts of water.As the Bitter-root's water commissioner, Vern Woolsey, explained it succinctly to me,Whenever you have a source of water and more than two people using it,there will be a problem.But why fight about water? Fighting won't makemore water!"The ultimate reason for decreasing amounts of water is climate change:Montana is becoming warmer and drier.While global warming will pro-duce winners as well as losers in different places around the world, Montanawill be among the big losers because its rainfall was already marginally ade-quate for agriculture.Drought has now forced abandonment of large areasof farmland in eastern Montana, as well as in adjacent areas of Alberta andSaskatchewan.Visible effects of global warming in my summering areas inwestern Montana are that snow in the mountains is becoming confined tohigher altitudes and often now no longer remains throughout the summeron the mountains surrounding the Big Hole Basin, as it did when I first vis-ited in 1953.The most visible effect of global warming in Montana, and perhaps any-where in the world, is in Glacier National Park.While glaciers all over theworld are in retreat on Mt.Kilimanjaro, in the Andes and Alps, on themountains of New Guinea, and around Mt.Everest the phenomenon hasbeen especially well studied in Montana because its glaciers are so accessibleto climatologists and tourists.When the area of Glacier National Park wasfirst visited by naturalists in the late 1800s, it contained over 150 glaciers;now, there are only about 35 left, mostly at just a small fraction of their first-reported size.At present rates of melting, Glacier National Park will have noglaciers at all by the year 2030.Such declines in the mountain snowpack arebad for irrigation systems, whose summer water comes from melting of thesnow that remains up in the mountains.It's also bad for well systems tap-ping the Bitterroot River's aquifer, whose volume has decreased because ofrecent drought.As in other dry areas of the American West, agriculture would be impos-sible in the Bittterroot Valley without irrigation, because annual rainfall inthe valley bottom is only about 13 inches per year.Without irrigation, thevalley's vegetation would be sagebrush, which is what Lewis and Clark re-ported on their visit in 1805-1806, and which one still sees today as soon asone crosses the last irrigation ditch on the valley's eastern side.Construc-tion of irrigation systems fed by snowmelt water from the high mountainsforming the valley's western side began already in the late 1800s and peakedin 1908-1910 [ Pobierz całość w formacie PDF ]