Friday, May 23, 2003 | 11:44 a.m.
Four years of drought are threatening the amount of water available to Las Vegans and others who are dependent on Lake Mead. The drought is also threatening the quality of that water.
As the water levels continue to drop, staff members of water agencies in Southern Nevada are increasingly concerned that the quality of the region's drinking water is becoming affected.
The problem is that as contaminants, including perchlorate and the detritus of the urban community, flow into the Las Vegas Wash and ultimately into the lake, there is less and less water to dilute that contamination.
"It's obviously a huge concern to us," said Pat Mulroy, general manager of the Southern Nevada Water Authority, the regional agency that delivers wholesale water to distributors in Las Vegas, the urban areas of unincorporated Clark County, Henderson, North Las Vegas and Boulder City.
Mulroy and her staff are looking at two contaminants in particular: perchlorate, an ingredient in rocket fuel entering the wash from an industrial site in Henderson, and cryptosporidium, a microscopic organism found in untreated surface water. Both can be found in water from the wash entering Lake Mead.
Perchlorate has been the target of research, but scientists disagree on how dangerous it is. Environmentalists would like virtually all of the chemical out of water used for drinking and for crop irrigation in California -- which Lake Mead water also goes to.
Federal and state agencies have not set a hard standard for the amount that is acceptable to humans, but the water authority uses the suggested Nevada level, which is 18 parts per billion -- a small handful in an Olympic-sized swimming pool. The chemical has been linked to hormone problems in humans.
The level in water reaching the taps of customers in the Las Vegas area has been 10 to 13 parts per billion.
Cryptosporidium can cause severe diarrhea in healthy people, and can be fatal to people with compromised immune systems.
Problems with both contaminants are potentially growing because there is simply less water in the lake to dilute the water from the wash. If the lake, as expected, drops to about 50 percent capacity by the middle of next year, the concentration of contaminants flowing into the lake will be doubled.
But another issue comes into play through the complex hydrodynamics of the lake, the largest man-made reservoir in the world. Mulroy said during the summer months, water from the wash is more or less trapped within a thermal layer, called a thermocline.
The thermocline usually is about 50 feet below the surface. At the present time, that puts it just 50 feet above the first intake, bringing water to consumers throughout Southern Nevada.
As the surface of the lake continues to drop, the thermocline with the highest concentrations of contaminants gets closer to the intake and potentially into the water supply.
Mulroy said the scientists and technicians working with the water authority are not sure if or when the thermocline will be a problem.
"How bad is it? That's the thing we're trying to figure out," she said. "I'm really concerned about those who are immune-impaired. They really need to take extra caution when we get there, but we're not there yet."
Mulroy said the authority probably will not start taking water from the thermocline for at least a year, possibly more. In the meantime, the agency's researchers are engaged in a continuing battle to find and apply fixes to water quality problems.
Mulroy said the authority probably will not start taking water from the thermocline for at least a year, possibly more. In the meantime, the agency's researchers are engaged in a continuing effort to monitor and improve water quality, she said.
"This is a never-ending challenge," she said. "We are able to detect compounds at smaller and smaller concentrations. ... We are going to do our level best to protect the water quality.
"You do everything humanly possible with the tools you have available."
Linda Blish, water authority laboratory manager, is one of dozens of staff members working on that effort. She said people now should not fear the water from the tap.
Her agency is performing 300,000 analyses from 30,000 water samples a year, Blish said.
She said the water authority has some good news on the water quality front. One piece of it, ironically, has to do with the thermocline that her colleagues are worried about.
Because the water from the wash forms a layer within the lake, much of the contamination is kept away from the intake, at least as long as the thermocline is away from the intake, Blish said.
"The thermocline helps us now," she said. "(But) within a couple of years we could be pulling directly from the thermocline."
But the water authority already has one big tool to deal with any water quality problems from the thermocline -- a second intake, completed in 2000, means that the agency can "blend" water from upper and lower water levels, effectively diluting the concentration of contamination.
Blish noted that the concentration of perchlorate at a higher lake elevation can be double the concentration lower in the lake.
"Even if we see some increases, we would plan to blend from the lower intake," she said. "We have that capacity and that capacity will improve over the next couple of years."
Blish has another weapon in her arsenal to fight water contamination -- $110 million in advanced ozonation processes at the new River Mountains and older Alfred Merritt Smith water treatment plants, the two key facilities that water for daily use passes through.
Ozonation is an advanced technology that in large part replaces chlorination to kill bacteria and other organisms. Essentially, it blasts oxygen into the water, and produces fewer nasty by-products than the older technology.
The ozonation process is still coming on line, but later this summer all of Las Vegas' water should get the treatment, Blish said.
Another tactic the authority is using to try to keep contamination out of the drinking water is trying to keep it out of the wash in the first place. It is a tough job.
Fertilizer from lawns, pet waste, motor-vehicles products -- anything that goes onto the lawns, roads and driveways in the Las Vegas Valley ultimately can be flushed into the wash, then the lake.
"The Las Vegas Wash is the drainage point for all the water that is in Las Vegas," said Peggy Roefer, water authority regional water quality supervisor. "It's like a big bowl. When we don't have rain, it gets dirty. Then when it does rain, all those things can cause problems.
"Anything that anybody puts in those tributaries ends up in the lake."
Roefer said it is not just the used motor oil that causes concern. It also is the nutrients that pet waste or lawn fertilizer pump into the system. Those nutrients can help spark algae blooms and the growth of microorganisms that can cause problems.
Algae last year clogged the system's treatment facilities, cutting about 20 percent of the system's capacity because of the need to replace filters.
The Las Vegas Wash Coordination Committee is starting an aggressive effort to let people know that what they put down the sewer can affect the drinking water, Roefer said.
Blish said one common tool used to treat water at home is not much of an option for huge volumes of water. Reverse osmosis and similar membrane-based technologies are not practical when dealing with the millions of gallons that pass through the treatment plants daily, she said.
But new technologies and tools to protect water quality will come, Blish and Mulroy pledged. Mulroy said if necessary, the agency can devise short-term technological fixes such as flexible water pumps to suck in lake water from better sources.
The agency, especially if it has a successful conservation plan in place, can negotiate with the other six states of the Colorado River Compact to keep Lake Mead levels high enough to avoid concentrated contamination problems, Mulroy said.
Mulroy said her agency will spend whatever is possible to protect the water quality, but she warned the problem and the fixes could demand millions of dollars in infrastructure investment.
And despite the tools to protect water quality, Mulroy and her staff said there are still unknowns about what will happen to the lake and the water system in the coming years.
The agency is "looking at what-ifs" because of the drought, Blish said.
"We have never treated water at this level before," Blish said. "It's a very dynamic situation. We want to make sure we are prepared for what can happen."
Blish said there is one thing that could provide a real solution, but it is not an option within the control of the water authority.
Just as natural processes helped create the water-quality problem by concentrating contaminants through a drought, nature has the ultimate solution to the problem
An end to the drought -- a lot of snow in the Rocky Mountains, the source of the Colorado River feeding Lake Mead -- would flush out the system, something that the river has not been able to do for years.
"Pray for snow along the Colorado and make sure there's lots of it in the Rockies," Blish advised.
Craig Westenburg, a hydrologist with the federal U.S. Geological Survey, is studying contamination in the lake and the effect of the drought. He said the research is ongoing, but clearly as the water level gets lower, the inflow of the wash gets closer to the intakes for the water system.
He said four years of drought has been rough, but it could get worse. Ten-year droughts along the Colorado River have been found through study of the historical and geological record. Those who have come to depend on deep lake water held back by the 70-year-old Hoover Dam may have to radically adjust their lifestyles.
"We have not had a 10-year drought since the dam was built."
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