South Platte water study challenges notion that led to water well ban
March 16, 2011
A study of groundwater in the South Platte River Basin challenges the notion that water well along the river have reduced groundwater supplies.
The study was done to try to maximize the use of water in the South Platte River Basin for everyone in the state, said Bob Longenbaugh, who has been in the water business for 50 years.
He teamed with Halepaska and Associates, a consulting groundwater engineering firm in Littleton, in a study of the South Platte River groundwater for the Weld County Farm Bureau, the Colorado Corn Growers and other organizations.
The study focuses on the importance of groundwater when considering the South Platte as an irrigation source. Logenbaugh said 10.5 million acre-feet of water is in the main stem of the river’s alluvial aquifer – below the surface flow of the river. That’s about eight times the amount that flows down the river annually from snow melt, thunderstorms, return flows, releases from reservoirs and other sources.
The study measured irrigation wells along the river and found some of the highest historic water levels ever recorded in the fall of 2009. Those levels have not receded since then.
Thousands of irrigation wells along the South Platte have been either shut down or limited in the amount of water they are allowed to pump since a Colorado Supreme Court ruling in 2001, which was followed the next year by the worst drought in Colorado history. As a result, some 8,000 wells along the river remain curtailed in the amount of water they can pump each growing season, and 2,000 of those wells have been shut down completely. That was because the state determined the continued pumping of those wells would deplete water supplies downstream and cause harm to senior water right holders who relied on surface water for irrigation.
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Logenbaugh said data collected in the study refutes that notion.
He said the reduction of well pumping not only limits the return of water to the river, but is probably a factor in high water tables along the river from Brighton to Julesburg. In addition, he said, Colorado lost a tremendous amount of water into Nebraska last year, which continues this year. Between Oct. 1, 2009, and Sept. 30, 2010 – the state designated water year – 610,000 acre-feet of water flowed out of Colorado into Nebraska. From Oct. 1, 2010, to Feb. 28 of this year, another 106,000 acre-feet has left the state on the South Platte, he said.
“That’s above what Colorado is required to deliver to Nebraska under the compact. That water belongs to the citizens of Colorado, and Colorado has the right to use that water,” Longenbaugh said. An acre-foot is enough water to provide two families with a year’s supply of water.
Under the compact signed between the two states in 1923, Colorado is required to supply Nebraska with about 240 acre-feet of water per day on the South Platte from April 1-Oct. 15 of each year. Any water above that belongs to Colorado, Longenbaugh said.
Delph Carpenter was born in Greeley in 1877, raised on an irrigated farm, earned a law degree by 1899 and became the first Colorado-born resident elected to the Colorado Senate. As a Greeley attorney, he had a hand in the first seven of the state’s nine river compacts that remain in effect today.
Bob Winter of Windsor is a past president of the Weld County Farm Bureau. Winter said the county farm organization spent $2,500 on the report, but said John Halepaska of the Littleton firm had already started much of the data gathering.
“(The study) verifies what we have expected for years, that (irrigation) wells don’t have a 50-year depletion of water in the river, and in fact, they recycle and refill annually. That’s why the water tables have come up,” Winter said. Much of that data has been around since the 1940s, he said, but it’s never been gathered to be analyzed in one place.
“We finally have a report with facts, and now there are those who question the facts,” Winter said.
Dick Wolfe is the state engineer and director of the Colorado Division of Water Resources. He said he has reviewed the report completed by Longenbaugh and Halepaska and said there is some misinterpretation of the compact between Colorado and Nebraska.
But he agrees with the report that said there is a need for improved management tools. His office has several tools under development and one of those, called a User Supported Data Import tool, will allow registered users to import and store water-level data with the division. It is due to be available in May.
Concerning the excess flow into Nebraska, Wolfe said there may be some misinterpretation regarding the compact.
“There is no set amount. There is a minimum amount Colorado is required to deliver, but there is no requirement to deliver the 240 acre-feet daily (from April 1- Oct. 15). Nebraska, under its claim, which dates back to 1897, has a right to some of the excess flow on a wet year,” Wolfe said. So to say anything that goes into Nebraska above the minimum amount is a misunderstanding of the compact, he said, which indicates a real need for an educational effort.
Many other aspects of the report, Wolfe said, are beyond the authority of his office.
He said groundwater levels are only one of the components in the analysis of the relationship between an alluvial aquifer and the surface water in a river or stream.
“I think the hypothesis that current groundwater levels are an indication that aquifer impacts from past (well) pumping have been abated is an over simplification,” Wolfe said. He said his office would expect the water table throughout the South Platte would show significant recovery following the drought of 2002.
Now retired, Longenbaugh was a Colorado State University Extension irrigation engineer for 19 years and then spent 11 years with the Colorado Division of Water Resources as the assistant state engineer. He retired in 1991, but has remained active in the Colorado water arena.
“The ideas I have are not mine,” Logenbaugh said.
He and the report point out that early settlers on the South Platte quickly realized that once runoff from the mountain snowpack traveled down the river, the flow quickly diminished. But once early farmers began to divert water from the river using ditches to irrigate their fields, the water levels in the aquifer increased and those return flows resulted in the river running at a higher flow rate for a longer period of time.
Then came reservoirs, some as early as the late 1800s, which were used to provide a supplemental water supply when the river flow diminished. Those were followed by the first irrigation wells, in the early 1900s, that were operated by centrifugal pumps that were run by internal combustion or steam engines.
By 1940, there were more than 1,900 wells along the river that pumped 233,000 acre-feet. More wells were added along the river in the 1940s, ’50s and ’60s, until 1965 when the state engineer was required to deny new permits without a water court-approved augmentation – replacement water – plan.
Surface water owners and well operators have been at odds, particularly in dry years, since then.