AUSTIN (KXAN) – Austin Water Utility’s pipelines lost more water in 2020 than in the previous 12 years, but utility officials said the city’s water losses were still within an acceptable range.
Austin Water Utility’s pipelines lost more than 7.34 billion gallons of water – that is, gallons of physical water that leaked from the distribution system. That total does not include an additional 1.51 billion gallons of “face loss,” which are accounting losses taken on paper, according to Austin Water Services water loss audit subject to Texas Water Development Council.
To perspective, 7.34 billion gallons is over 22,555 acres of feet of water. Lady Bird Lake has volume of approximately 7,151 acre-feet of water. The leaked Austin water system could have filled the downtown lake three times, according to TWDB measurements and records. An acre-foot of water can cover an acre in a foot of water.
Austin’s water loss totals have tended to increase over the past decade, but Austin water officials have said the city is still within a normal operating limit. In 2019, KXAN investigated the city’s water losses, finding that the system had lost more than 6 billion gallons.
According to one measure, called the Infrastructure Leakage Index or ILI, Austin’s water loss is still “appropriate,” the utility said.
Austin’s leak rating last year was 4.22, according to the audit.
“For a utility like Austin Water, an ILI of between 3 and 5 is considered appropriate,” Austin Water said in an email. “However, with an increase in our ILI from 2019, Austin Water is taking an aggressive approach to water loss so that we stay within the normal range.”
A leakage rating of 4.22 is the closest to the city over the past decade to 5, which is the upper limit of an acceptable range, according to the city.
A lower leakage rating means that a utility has less preventable water loss.
The leakage index is calculated with a formula that integrates the length of the city’s water pipes, the pressure in the system and the number of connections. The leak index is independent and is unaffected by the amount of water demand and the city’s population, according to Austin Water.
Austin Water said it was putting in place programs and tools to improve its ILI, including a program to replace deteriorating cast iron water pipes that tend to leak. The city also expects its “advanced metering infrastructure” to be completed within the next four years. This will help with pressure management and leak detection and should also help reduce the leak index, according to Austin Water.
John Sutton, director of TWDB’s water conservation program, said the leaks were inevitable.
“No matter how tight your system is, you will always have leaks,” Sutton said. “And so that’s kind of called allowable leaks.”
Public water supply systems are required to submit water loss audits to TWDB, Sutton said.
“It gives them an idea of what’s been going on in the last year within their system,” he said. “The data requested as part of the audit helps identify areas where water loss may occur, where a utility can consider mitigation measures. “
Sutton said two other important metrics to check in audits are actual and apparent “normalized” water loss. These measurements show the number of gallons lost per connection per day.
Austin audits show both numbers are at their highest in the past eight years. Austin lost the equivalent of 82.37 gallons of actual water per connection per day last year, according to the audit.
TWDB provides the audits to regional water planning groups to help them strategize for future water needs. In addition, if a utility asks TWDB for financial assistance for a water supply program, TWDB can review its water loss audits. Certain water loss thresholds must be respected. If not, TWDB may require the utility to include funds to address this issue or request a waiver if it is already addressing the issue, Sutton said.
February’s devastating winter storm caused leaks throughout the city, but Austin Water officials don’t expect this event to have a major effect on total water loss. This is because most of the water leaks were lost on the customer side of the water meters, so these customer losses would not show up as water losses in the utility audit.