Backers of the proposal to build Utah’s Lake Powell Pipeline appear to have provided conflicting water-use data to state and federal regulators in an apparent attempt to garner support for the project, an advocacy group asserts.

In a 14-page letter released Wednesday, the Utah Rivers Council is asking State Auditor John Dougall to investigate the possibility that officials with the Utah Division of Water Resources and water managers in Washington County have sought to mislead state lawmakers and federal regulators, after the council discovered discrepancies in water-use data provided to both.

The challenge comes as state officials have asked for an extension on their federal application for an operating permit for the southern Utah pipeline. At an estimated cost of between $1.1 billion and $1.8 billion, the proposed project is intended to bring water from Lake Powell to Washington and Kane counties through nearly 140 miles of underground pipe and five pump stations.

In its letter to Dougall, Utah Rivers Council asserts that officials with the state Division of Water Resources and other project proponents have quoted multiple, diverging numbers when discussing Washington County’s water use with state and federal decision makers.

In materials submitted to the Federal Energy Regulatory Commission (FERC), state officials indicated that the Washington County Water Conservancy District’s customers consumed 325 gallons per day per person in 2010. That same filing projects that the per-capita water usage will decrease to 311 gallons per person by 2020. However, state officials also anticipate that the water district’s customer population will increase by more than 50,000, which is likely to cause total water use to rise to 68,450 acre-feet, up from 50,380 acre-feet in 2010.

Yet in an update last August on the pipeline’s progress to the Utah Legislature’s Water Development Commission, Ron Thompson, general manager of the Washington County Water Conservancy District, told lawmakers his county’s water use was in the range of 140 gallons per person per day. And that number went unchallenged by the Division of Water Resources, the Utah Rivers Council notes in its letter.

Eric Millis, director of the Utah Division of Water Resources, said Wednesday in a statement that he had understood the 140 gallon figure to represent residential water use. The figure did not include industrial or other uses, he said, though Millis added that further detail would have to come from the estimate’s source, Washington County Water Conservancy District.

“We believe that any misunderstanding that occurred as a result of the statement was unintentional,” Millis said.

The St. George-based conservancy district is one of two water wholesalers currently slated to receive water from the pipeline project.

In written comments to The Tribune, Thompson said the disputed 140 figure, offered in response to a question after his presentation, represented indoor and outdoor residential use for 2015, not total water usage in Washington County.

“The district is committed to sharing accurate and timely information with lawmakers and the public,” said Thompson.

But according to Utah Rivers Council executive director Zach Frankel, the same Aug. 22 presentation indicated Washington County used 48,599 acre-feet of water in 2015. When divided out across the county’s population, that figure suggests county residents use about 280 gallons of water each day.

The Washington County water district also said it did not calculate per capita water use by dividing total water use by a given area’s population.

Still, such discrepancies — along with the Utah River Council’s long-running concerns about the lack of transparency regarding the plan to pay for the pipeline’s construction — prompted it to call for an investigation, Frankel said.

“Exaggerating future or existing water use is no different than a government representative intentionally exaggerating the number of constituents needing services,” Frankel wrote to Dougall.

Thompson said he welcomed improved data collection on Utah’s water usage.

“Having accurate data is a priority for all water providers throughout the state,” he said. “Utah taxpayers are currently funding a $300,000 state-wide audit of water use data, which includes Washington County’s numbers. We look forward to reviewing that analysis and incorporating any recommendations that may result from that effort.”

This is not the first time the Utah Rivers Council has drawn attention to apparent mismatches in water-use data from Kane and Washington counties. Earlier this year, Frankel succeeded in persuading the State Records Committee to order the release of Utah’s water-use database after arguing that water use reported by the state did not match numbers quoted elsewhere. Water district officials instead put those discrepancies down to various Washington County municipalities being left out of Frankel’s calculations.

Release of the database revealed that the majority of the state’s water-use figures had been modified to correct for errors or fill in missing information.

But state water managers have made progress in improving the accuracy of Utah’s water-use data, officials with the state Division of Water Rights told lawmakers Wednesday.

In the past, some water agencies have refused to provide their water data to the Division of Water Rights. But the agency has hired a new employee and promoted another to form a two-person team dedicated to water-data collection — with new penalties in place to incentivize agencies to report their water use.

A new website is in the works to help collect more accurate data, according to the agency.

State Engineer Kent Jones, who heads of the state Division of Water Rights, said Utah has made great strides over the past year in acquiring better data. And as the accuracy of data has improved, he said, the amount of water use reported by water suppliers has decreased.

Some of the state’s water suppliers may have previously overestimated their usage out of a perceived need to protect their rights to withdraw and store water, Jones said. Others, he said, were reading water meters incorrectly or didn’t have meters at all.

“They were just estimating these numbers,” Jones said. “One water supplier told me they were giving us the numbers that we wanted to see, because they didn‘t want their water rights taken.”

Federal regulators have also questioned water use data provided by the state. In August, FERC asked the Division of Water Resources for more information related to water use, cultural resources, and the state’s ability to finance the Lake Powell Pipeline project.

The water district holds that FERC merely asked for updated water use data, a request it described as a common practice.

State officials are in the process of obtaining an operating permit for the pipeline from FERC, in part because the project also includes hydroelectric generating stations.

But earlier this month, the state told FERC it was unable to provide additional water data because it does not have any water-use numbers from 2011-2014. The 2015 numbers are still under review by a third party, according to an Oct. 10 letter to FERC and will not be available for release until 2018.

The state asked for an extension of the 60-day deadline to allow officials to review information “to provide clarity and accuracy regarding financial considerations of the Lake Powell Pipeline.”