Water short years show strong correlation between west and east slopes

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From The Pueblo Chieftain (Chris Woodka):

Western Water is studying future water projections for the Colorado Water Conservation Board. “It has always been thought that if you are bringing in water from both sides of the Continental Divide, you have protection. That is not the case,” said Jeff Lukas, of Western Water. “While they vary from year to year, the dry years and wet years in both basins show a strong correlation.” The two driest years on record in both basins were 1977 and 2002, and the record of imports into the Arkansas River basin bears out Lukas’ depiction of drought protection — or the lack of it. Other than 1987, when little water was brought over in the Fryingpan-Arkansas Project simply because there was no place to put it, 1977 and 2002 produced the least imported water for the Arkansas Valley. In other words, there wasn’t much water available on the other side of the mountains either.

In 1977, the Fry-Ark Project was just getting ramped up, and Lake Pueblo was still filling. Imports, however, dropped to just 11,400 acre-feet, or less than one-third of the typical year at the time because 1977 was the driest on record for the Western Slope.

In 2002, Fry-Ark flows through Boustead Tunnel totalled just 13,200 acre-feet, or about one-fourth of the long-term average. Basinwide, in 2002, imports totalled just half of the long-term average at 67,224 acre-feet, with projects like Twin Lakes, Homestake and Board of Water Works diversions pulling in every drop available. The year 2002 was the driest on record for the Arkansas River basin, and second-driest on the Colorado River.

In the past 500 years, the period of record for tree rings in both basins, there have been about eight annual droughts as severe as 1977 and 2002. All show both basins were equally affected. “They’re showing the same extreme low-flow years,” Lukas said. More ominous are long-term drought periods in Colorado, some lasting up to 60 years.

In the Arkansas River basin, the longest period of prolonged drought in recorded years was from the 1950s through the ’70s. While there were wet years and even drier years in the 1930s, the average was far below normal. By comparison, the 1980s and ’90s were the wettest years since the 1910s and ’20s, and the past decade has been relatively average. The Colorado River basin as a whole — it stretches over seven states — saw its lowest recorded flow period in a century in the first decade of this century. However, its performance in Colorado has essentially mirrored the Arkansas River basin. While there is much more water available every year in the Colorado River basin, its wet and dry years come at the same time as the Arkansas River basin.

More Colorado water coverage here.

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