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S~ . E~ ARLY IN APRIL, the state and federal governments announced that they had come to an agreement cQnceming river flows through the Black Canyon of the Gunnison National Park. The feds would settle for less than they might have been able to claim under state law, That could mean that water in the upper GunnisQn basin has become available fQr diversion to the Eastern Slope and Front Range. o~ it <:ou!d me:ln nothing of the son. What it does mean is that a big water battle is likely to start heating up almost any day now. Gunnison County has a "not one drop" policy concerning water exports, while Fronr Range interests will argue thatwa- ter in the Gunnison Basin should serve the entire state, not just the Western Slope. As with all matters of Colorado water, it's a compli- cated issue. But we can start with a few facts, One is that Colorado is, on average, a desert. Although some spots are obviously wetter than others, our state overall averages only 17 inches of precipiration a year, and regular agriculture requires at least 20, The Continenral Divide winds through the moun- tains of Colorado. In general, water that lands on the Eastern Slope flows to the Atlantic Ocean, via the Platte, Arkansas, Rio Grande, and their tributaries, Wa- ter on the Western Slope flows into the Pacific Ocean, via the Colorado River and its many tributaries - the Gunnison is the largest tributary in CQIQradQ. On the Eastern Slope, most of the population lives in a belt a few miles east of the Front Range, This strip ex- tends along Interstate 25 from Fort Collins to PueblQ, and it has about 80% of Colorado's population. But it has natural access to only 20% of Colorado's water sup- ply. By contrast, the Western Slope has only 10% of the state's populatiQn, and about BO% of the state's water, Colorado could have tried moving the people to the water, perhaps, but what evolved during the 20th cen- tury, as the Front Range population grew~ w3;s m~ving the water to the people with transmountam dIVersIOns. Collection and stQrage systems were built on the West- ern Slope; the water was conveyed through a tunnel to the Eastern Slope, where it was distributed to farms and cities. There was a logic tQ this, The South Platte valley has some of the most productive agriculture in the United Srates, and providing more water meant that ColQ~ado was better able tQ feed itself. The relauvely unpopulated Western Slope didn't really have a "bene- ficial use" for much of the water that fell on it, and SQ why not move the water to where it would do Colorado the most gQod? So there was the ColoradQ-Big Thompson Project of 1937, taking about 300,000 acre-feet a year from the Colorado River near its headwaters at Grand Lake, and transporting it through the 12,B-mile Alva Adams tun- nel under Rocky Mountain NatiQnal Park to serve irrigators and cities along the South Platte, clear to the Nebraska line, The next drainage to the south, one that sits almQst 18' Colorado Central Magazine. June 2003 A LETTER FROM THE EDITORS Why the Water BuRaloes of Colorado are Starting. to Circle around the Gunnison due west of Denver where the Continenral Divide is a narrow ridge, is the Fraser River. Denver tapped it with the Moffat Tunnel pioneer bore in 1937. Next comes , the Williams Fork, also tapped by Denver. Then the Blue River, which was tapped by Denver with Dillon ReservQir and the Roberts Tunnel in 1962. And then, well, we run out of convenient place~ to tap. The Continental Divide swings. west, m.ean~ng greater transport distances, The east SIde of theDlVl.de is no longer South Plarte drainage, but Arkansas dram- age. The Arkansas valley in Colorado is poorer and less PQPulated, and thus less able to pay for water projects than the SQuth Platte valley. So there are only two major diversions from the Western Slope into the Arkansas: the Boustead 'funnel, part of the Fryingpan-Arkansas project (about 70,000 acre-feet a year), and the Twin Lakes 'funnel, a private development (about 30,000 acre-feet a year), Both of tl1Qse get their water from tributaries of the main stem of the Colorado River in Colorado (which wa's known as the Grand until 1922, and these discus- sions WQuld be simpler if it were still the Grand). That stem is pretty well tapped out now. ON THE WET WESTERN SLOPE, the next basin to the south is the Gunnison. Given what else has happened, the question that comes to mind is "Why hasn't it been tapped before by the Eastern Slope?" For one thing, it sits about 150 miles from the state's population centers. Water that got across the Divide would not arrive on the South Platte that has most of the state's population, but Qn the Arkansas, and getting it to the Platte would mean conveying it across yet an- other mountain range. Just getting it to the Arkansas would be expensive, on account of the economics of tunnels. You want the tunnel's elevation as low as possible, so that you use cheap gravity (as QPPQsed to expensive pumps) to col- lect a lot of water above the tunnel intake. But the lower the tunnel, the longer it is, especially when the mountain range in question is the immense Sawatch Range, rather than the relatively narrow hog-back sec- tion of the Front Range where the Moffat Thnnel was bQred. 001779 ;