AUSTIN (KXAN) – Austin Water Utility pipes leaked more water in 2020 than in any of the previous 12 years, but utility officials said the city’s water losses are still within an acceptable range.

Austin Water Utility’s pipes lost more than 7.34 billion gallons of water – that’s gallons of physical water leaked from the distribution system. That total doesn’t include an additional 1.51 billion gallons of “apparent losses,” which are accounting losses taken on paper, according to Austin Water Utility’s water loss audit submitted to the Texas Water Development Board.

For perspective, 7.34 billion gallons is more than 22,555-acre feet of water. Lady Bird Lake has a volume of about 7,151 acre-feet of water. Austin’s water system leaks 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 trended upward over the past decade, but Austin water officials said the city is still within a normal operating limit. In 2019, KXAN investigated the city’s water losses, finding the system had lost more than 6 billion gallons.

Leakage Index

According to one measurement, called the infrastructure leakage index or ILI, Austin’s water loss is still “appropriate,” the utility said.

Austin’s leakage index last year was a 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 remain within the normal range.”

A 4.22 leakage index is the nearest the city has come in the past decade to a 5, which is the upper limit for an acceptable range, according to the city.

A lower leakage index means a utility has less avoidable water losses.

The leakage index is calculated with a formula that incorporates the length of city’s water mains, the pressure in the system and the number of connections. The leakage index is independent and not affected by the amount of water demand and the city’s population, according to Austin Water.

Austin Water said it is putting programs and tools in place to improve its ILI, including a program to replace deteriorating cast iron water mains that are prone to leaking. The city also expects its “advanced metering infrastructure” to be complete in the next four years. That will help with pressure management and leak detection and should help lower the leakage index as well, according to Austin Water.

John Sutton, manager of the TWDB’s water conservation program, said leaks are inevitable.

“No matter how tight your system is, you’re always going to have some leakage,” Sutton said. “And so that’s kind of what’s called allowable leakage.”

Public water systems are required to submit water loss audits to TWDB, said Sutton.

“It gives them an idea of what happened over the last year within their system,” he said. “The data that’s asked within the audit kind of helps identify areas where water loss may be happening, where a utility may consider mitigation.”

Sutton said two more important measurements to check in the audits are real and apparent water losses “normalized.” Those measurements show the number of gallons lost per connection per day.

Austin’s audits shows both numbers are at their highest points in the past eight years. Austin lost an equivalent of 82.37 gallons of real 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. Also, if a utility comes to TWDB for financial assistance for a water supply program, TWDB can examine their water loss audits. Certain water loss thresholds should be met. If they aren’t, TWDB can require the utility to include funds to address that issue or seek a waiver if they are already addressing that problem, Sutton said.

February’s devastating winter storm caused leaks across the city, but Austin Water officials do not expect that event to have a major effect on water loss totals. That’s because most of the water leaked was lost on the customer side of water meters, so those customer losses would not show up as water losses in the utility’s audit.