New Water Sources
You could make the argument there’s no such thing as “new” water; it’s not something we can create more of. But an area with a growing population in need of more water has various options for increasing its supply of usable or even potable water. Some, such as the trans-mountain diversions of Colorado, have been in use for decades, but are fraught with controversy. Others, like the groundwater replenishment system in Orange Co., Calif., are relatively new and expensive, but promising. Ocean desalination is so far operating at only one plant in the U.S., and it’s energy-intensive, controversial, and expensive.
In the meantime, growing metropolitan areas are worried about meeting their water supply needs. Here’s a look at some solutions different communities are trying.
Colorado’s Trans-mountain Diversions
Water has been pumped through underground tunnels from the west side of the Continental Divide to the east side for more than a century. New projects are under discussion, and they’re always controversial. On the face of it, the transfer might seem to make sense: Move the water to the area of greater population. What’s the problem?
Regional water questions are never so simple. The largest trans-mountain diversion (also known as a trans-basin diversion) is the Colorado-Big Thompson Project, which moves more than 220,000 acre-feet a year. (One acre-foot provides enough water for an urban family of four for a year.)
That’s a lot of water just for the largest of the trans-mountain projects. And it’s completely consumptive, which means once it’s diverted, the west side won’t see the water again. It’s not recycled and it’s nonrenewable. That matters a lot in an area where recreation and tourism are the economic engines.
Trans-mountain diversions occur at the headwaters, and the headwaters communities make their living from water-based activities such as snow making, fishing, and kayaking. “So the water going to the eastern slope represents foregone economic opportunities,” says Chris Treese of the Colorado River Water Conservation District, on the west slope. And the water being diverted is high-quality mountain water, still free from many of the impurities that are present downstream.
“It’s been a constant battle between east and west,” says Treese. “The tensions are not going to go away.” The question now is, “Does it lead to an escalated fight, or cooperation and mutual agreements?”
Says Drew Peternell, director of Trout Unlimited’s Colorado Water Project, “Many of Colorado’s rivers and streams are depleted to the point that they no longer support robust fisheries or recreational opportunities.”
The headwaters are tapped out, Treese adds, so building new dams or enlarging current ones on the west slope is out of the question. Proposals under discussion now are expensive pumpback projects, which would require pumping water uphill. To develop a new project or squeeze more supply from current ones, water would have to be pumped to more convenient, cost-effective storage or to existing infrastructure.
There have been many lawsuits, but also some cooperative agreements. One such agreement resulted in the construction of Wolford Mountain Reservoir in Grand County in 1996. Both east and west benefit: The West Slope has a 66,000-acre-foot reservoir with extensive recreational facilities, and Denver Water pays for the right to use up to 40 percent of the reservoir’s water.
Western Colorado communities and Denver Water have been working on another mutual agreement that they hope to announce soon, delineating existing and future water rights and detailing how water will be used and shared, Treese says.
Orange County’s Groundwater Replenishment System
The groundwater replenishment system in Orange County, California, has something for everyone: Its water filtration technique will please those who are convinced our water needs can be solved with technological breakthroughs. It has won several environmental awards for its overall recycling and reuse methodology. It’s expensive, costing $481 million to build and $34 million a year to operate--but that’s about half as much as ocean desalination. It also uses about one-third the energy of ocean desalination.
Orange County’s is the largest indirect potable reuse system in the world. “Indirect potable reuse means it treats wastewater to make it potable. It’s indirect because the highly treated wastewater is injected into the ground and withdrawn for drinking water; it’s recycled indirectly.
The water is treated in a three-step process:
- Microfiltration--filters out bacteria and viruses.
- Reverse osmosis--water is forced through plastic membranes under high pressure, removing dissolved chemicals, viruses, and pharmaceuticals. The result is pure water near distilled quality.
- Ultraviolet light exposure--water is exposed to high-intensity UV light with hydrogen peroxide to disinfect and destroy any trace organic compounds.
Half of the water produced is pumped into injection wells, where it serves as a seawater intrusion barrier, safeguarding the fresh water supply from seawater. The other half is used for groundwater recharge, pumped into a 13-mile pipeline to two of Orange County Water District’s recharge basins, in Anaheim. (That groundwater recharge explains why it’s indirect potable reuse, rather than direct.)
The system provides 70 million gallons a day, enough for 600,000 people--about 15 percent of the district’s water supply. It will serve another 250,000 to 300,000 people with an expansion planned to begin at the end of 2011 and take about two years.
Before the water district and the Orange County Sanitation District finished the treatment plant in 2008, the sanitation district was considering building a second ocean outfall that would dump wastewater five miles out at sea. “There would be a huge battle with the environmental community, and it would probably cost $200 million,” says Gina DePinto of the Orange County Water District.
Instead, the two agencies raised more than $90 million in loans and grants and built the groundwater replenishment system. The result addresses both water supply and disposal needs. The system decreases Southern California’s dependence on water from Northern California (the Sacramento-San Joaquin River Delta) and the Colorado River. As we have seen, the Colorado River has battles of its own. And water from Northern California costs almost $700 per acre/foot, says DePinto, and is likely to rise to $800 by 2012. Transportation only adds to the cost. (The movement of water from Northern to Southern California is the biggest user of energy in the state.)
How Feasible is Desalination?
Ocean desalination uses reverse osmosis to remove the impurities from seawater to make it a source of potable water through the water utility. Only one seawater desalination plant is currently operating in the United States, the Tampa Bay Seawater Desalination facility.
The Florida plant has been plagued by financial and technological problems from the start. It first opened in 2003, then had to shut down for a series of repairs. When it finally opened again in 2008, its water supply was well below capacity for more than a year. The capital costs for the plant and the 15-mile pipeline that connects it to the water system were $158 million, $40 million over budget.
In fiscal year 2010 the plant produced an average 11 million gallons a day (mgd), less than half its 25 mgd capacity. Operating costs were nearly $13 million. Spokesman Brandon Moore says the low figure simply means that’s all that was needed in a fairly wet year. Tampa Bay Water, the utility that operates the plant, uses the desalinated water to supplement its groundwater and river water supply. The three water sources are blended and sent to six local governments, to be distributed to their water utilities.
When the plant is working at full capacity, it uses about 44 mgd of seawater to produce 25 mgd of fresh water, leaving 19 mgd of concentrated seawater, or brine. The brine is directed back to Tampa Electric’s Big Bend power plant, mixed with up to 1.4 billion gallons of cooling water and returned to Tampa Bay.
Three counties in northeast Florida are working with the St. Johns River Water Management District on building another desalination plant, to be called Coquina Coast. The plant would have the same planned capacity of 25 mgd initially and is projected to cost more than $530 million, according to media reports. Final construction costs, as production reaches 80 mgd, are projected to top $1.3 billion.
And in Carlsbad, Calif., Connecticut-based Poseidon Resources--which worked on the Tampa Bay plant until the public utility bought it out--has been trying to build a desalination plant for more than ten years. The cost for the San Diego County plant is estimated at $650 million, financed largely through tax-exempt bonds.
The developer has successfully fought off ten lawsuits over the project. Poseidon projects that the plant would provide 10 percent of the region’s drinking water, enough for 300,000 residents--half as many as the Orange County groundwater replenishment system, at substantially higher cost.
Treating the highly concentrated saltwater brine makes desalination an energy-intensive process. “The future cost of desalinated water will be more sensitive to changes in energy prices than will other sources of water,” says the report Desalination, With a Grain of Salt -- A California Perspective, by the Pacific Institute, a nonpartisan research institute with a focus on water.
The report notes that there are also environmental concerns about desalination. The treatment process may introduce biological or chemical contaminants into the water supply. The machinery kills small fish and plankton. The concentrated saltwater produced by reverse osmosis may contain chemical pollutants. Safely disposing of the salty effluent can be a problem.
Then there’s the high cost. “Desalination is currently too expensive,” says Heather Cooley, co-director of the water program at the Pacific Institute. “As water availability becomes increasingly constrained, that can change over time. For California, it will very likely be part of our water resource portfolio ten to twenty years out, when we will have maxed out other available sources.”
At that point, Cooley says, “we will need to decide how we build desalination plants.” Australia, after a multi-year drought, started a very aggressive conservation program and built desalination plants connected to wind power. Initial construction cost more, but the plants will be more sustainable over the long term.
The San Antonio Water System is looking at an alternative to ocean desalination: brackish water desalination. Like ocean desalination, the system would use reverse osmosis, and there would still be potential problems with brine disposal and electrical costs, says spokeswoman Anne Hayden. But brackish water is more readily available in landlocked San Antonio. And it’s not as saline as seawater, so the brine would be less intensive. The plant, the first phase of which would be completed in 2016, would produce about 10 mgd.