"For us, it gets pretty serious," she said.
Mulroy's sure bet is the $800 million wager she's placed on putting in another drain at elevation 860 feet, which will allow the delivery of water in case Lake Mead reaches dead pool.
"I think it is a matter of time," she said. "I think it is a matter of when, not if," that the No 1 intake is idled by a declining Lake Mead.
The project, scheduled to be complete in 2014, has hundreds of workers conquering rock by burrowing under the bed of Lake Mead for the three-mile-long tunnel to the new No. 3 intake valve. In the staging area at Saddle Island — which was under water in flush years — 15,000 pieces of tunnel segments will be assembled for the completion of the intake tunnel.
The intake itself is like an upside-down concrete funnel made by pouring 10,000 yards of concrete through a 368-foot-long pipe into a big hole in the ground. Workers never touch the water and instead use sonar and a mini submarine to come within an inch of their target in 350-foot-deep water.
Casey Graham, a supervisor on the intake valve project, said this type of cement job has never been tried at that depth under water.
"It's been all about firsts on this project with lots of innovative stuff and six months of planning."
For Mulroy, putting in a third, lower straw is her only option in the high-stakes game of drought, and she's all in.
"I think it is critical for us to begin that construction now, build it today for future generations of Nevadans."
But that drive to secure water in Nevada has rankled Mulroy's neighbors in Utah.
Mulroy is a petite, steely whirlwind in the water world who has earned a reputation for forging an empire that is relentless in its caretaking of southern Nevada water needs.
"Her crowning achievement is her ability to solidify the southern Nevada water voice," said Ron Thompson, manager of the Washington County Water Conservancy District in St. George.
In 1989, when Mulroy became the general manager of the Las Vegas Valley Water District, she was a young woman in an old man's water world.
At one of her first water conferences, she was kindly directed to the spouses' room, not where the business at hand was taking place.
"You've got to assert yourself if you want to be taken seriously," said her spokesman, J.C. Davis.
Assert, she did.
Out of the seven states that share Colorado River water, Nevada is by far the smallest player at the table, with 2 percent of the total allocation. California has nearly 14 times its share at 27 percent. Utah's river allocation is 11 percent, with 1,369,000 acre-feet of water from the Colorado. Nevada? It has 300,000 acre-feet of water.
When the water was divided up in 1922, Las Vegas was just a little railroad town. The water-sharing agreement was negotiated on Nevada's behalf by power brokers in the northern part of the state; southern Nevada was barely a thought.
Mulroy said she won't let that happen again.
By 1991, she had coaxed a coalition of water districts into the umbrella of the Southern Nevada Water Authority. Today, when it comes to issues of the Colorado River and water in general, Mulroy is characterized by friends and foes as a formidable voice.
Nevada's paltry share of Colorado River water sent Mulroy on a mission to snatch up other sources, and she soon began hunting for unclaimed groundwater throughout the state.
Those applications for water in the eastern basins of Nevada have landed Mulroy and her water authority in the crosshairs of angry Utah groups who accuse her of dipping into an unlimited and uncertain resource to feed the "excesses" of Las Vegas. Mulroy contends
Nevada has every right to its groundwater in its state. She says the withdrawals are sustainable and Utah ought to get its own house in order before taking shots at Las Vegas.
"They can't spell conservation in Salt Lake City," she fired back to Utah critics in a 2010 television interview.
The authority's efforts to get the water out of multiple eastern Nevada basins for a pipeline to Las Vegas have been fought in the courts, with Mulroy leading the fight.
One of her combatants is Paul Hejmanowski, an attorney hired by The Church of Jesus Christ of Latter-day Saints to protect water that serves the Cleveland Rogers Ranch from being used for the Vegas pipeline.
"It is not whether but when those springs will go dry if that happens," he said of Nevada's drilling.
In 12 protests heard by the Nevada State water engineer that were specific to the ranch, the church successfully defended four of the applications, but lost on the other eight.
The ranching operation of some 1,750 cattle — in operation since about 1870 — supplies nearly 35 percent of the beef for the church's welfare system.
The church has appealed those water right applications it lost to the water authority, as have scores of other groups such as American Indian tribes, water conservation groups, ranchers, farmers and several Utah counties, setting up another fight in which Mulroy will be at the center.
Those who have done battle with the former soccer mom in a power suit know it will be a war not easily won.
"She is a very capable executive," said Hejmanowski, "somebody you would underestimate at your peril."
Fresh into her job as general manager of the authority, Mulroy suspended issuing any new permits for water for 18 months until she could get a handle on how much water was being used where, and what the available supplies were.
Davis said people still refer to it as the "Valentine's Day Massacre." She's gone head to head with casino operators and instituted new rules that if any potable water is used in water features at a business, it has to be offset by 50 times by yanking out turf or instituting new conservation measures.
"I think we are very rapidly reaching that point where we are going to have to come to grips with urban water use," she said. "We don't have enough water to waste anymore. That is the bottom line."
The attention of the seven states that make up the upper and lower Colorado River basins will be fixed on this summer's release of a two-year federal study probing the availability of water over the next 50 years.
Its findings will provide a framework for the states to find solutions that will produce certainty from a resource that is inherently uncertain: water.
As Barry Wirth, a spokesman for the Bureau of Reclamation puts it: "Everyone is at the table. Everyone has a stake in this."