Washing the Water
Wetlands at Richland Creek Wildlife Management Area act as a huge water filter, removing pollutants the natural way.
By Wendee Holtcamp
As soon as I step in the shallow wetland, my boot gets stuck in thick mud and I lose my balance. “Oh my gosh! I’m gonna fall!” I say to Darrel Andrews, with the Tarrant Regional Water District (TRWD). I fall backwards, my jacket drenched. I’m cold and wet, but it was my idea to slog through the marsh, so I’m not about to quit before we look around. “Don’t laugh!” I say, as two TPWD biologists — Jeff Gunnels and Hayden Haucke — watch amusedly from the bank.
“Oh, we wouldn’t,” Gunnels says. “At least not while you’re still around!” He hands me a walking stick. “You don’t want to go in without one of these.”
As we trudge through the water, I am entranced by the tiny green duckweed and reddish fernlike azolla floating on the water’s surface, roots dangling into the water. They thrive in the nutrient-rich wetland along with other native vegetation — sedge, bulrush, smartweed, burhead, wild millet. “It’s like a smorgasbord for wildlife,” says Haucke.
This is not your ordinary wetland. The 243-acre “moist soil impoundment” is not a natural wetland, but one imagined by consulting engineer Alan Plummer, planned and paid for by TRWD and formed as a wildlife Shangri-la through the guidance of Gunnels and Haucke, who work on this project at Richland Creek Wildlife Management Area, 80 miles southeast of Dallas/Fort Worth. In the world of constructed wetlands, this represents the first of its kind — a gigantic water recycling project. And 243 acres is just the beginning.
If you didn’t know better, you might think the shallow ponds — or any wetland for that matter — represent wasted land. There is no aquaculture production. No livestock graze on this once-fallow field. Plenty of birds come here: ducks and geese, majestic wading birds, migratory shorebirds and raptors. Frogs lay their eggs and tadpoles metamorphose within the waters. Mammals — raccoons, opossums, bobcat — quench their thirst or seek a crayfish meal. Aquatic invertebrates live, breathe and help decompose vegetation in the wetland. But what does all this mean for humans?
Beyond their role as wildlife habitats, wetlands are also lean, green, water-cleaning machines. Wetlands remove pollutants and suspended sediment — and they do it quickly, cheaply and efficiently. The popularity of constructed wetlands has skyrocketed in tandem with a body of scientific data documenting their effectiveness.
Constructed wetlands have been around for decades. But Texas has dibs on the first water recycling wetland in the nation, the Richland Creek WMA wetland, which will eventually span a whopping 2,000 acres and augment the city of Fort Worth’s drinking water supply via the Richland-Chambers Reservoir.
This award-winning wetland has been heralded as a model for developing public water supply without creating additional reservoirs. I think of it as a giant, shallow impoundment built on a fallow field instead of a river, with a constant input of water from the Trinity River. Water flows through its finely engineered cells — shallow ponds with interior levees that force the water to follow a serpentine path. A thriving native wetland ecosystem maximizes the project’s water-cleaning power.
“We need to make sure that the water coming out of the wetland is at least as good as the water flowing into the reservoir from its tributaries,” says Andrews. “The sampling that has been done … indicates that these wetland systems are capable of meeting that goal.” TRWD tests weekly for suspended solids, pH, dissolved oxygen, phosphorus and nitrogen-based compounds. Annually, they also test for a long list of chemicals in soil, vegetation and water: atrazine, organochlorine and organophosphorus pesticides, PCBs, heavy metals, among others. No law mandates these tests; TRWD conducts them proactively.
“This water entity chose to find an environmentally sensitive solution to water supplies,” says Gunnels.
After more than 10 years of testing, it’s ready to go live. In late 2007, the final step will be made, connecting the “polished” product to Richland-Chambers Reservoir, which provides drinking water for Tarrant County residents. The water will go through additional processing by munici-palities before being delivered to homes.
As effective as wetlands are at cleaning water, they are not miraculous. Toxic chemicals in runoff from agriculture and urban lawns can concentrate in wetland vegetation and sediment. During the past three years, the Richland Creek WMA wetland removed 99 percent of suspended solids, 63 percent of total nitrogen and 54 percent of total phosphorus. However, wetland plants contained mercury, lead and arsenic in the pilot scale project. Studies indicate that biofilms on the vegetation — microorganisms that form a slimy film — likely removed the metals, since water and sediment levels were normal.
To reduce such pollutants in an ecosystem, their use must be reduced. A common misconception is that chemical pollution in this region comes largely from agriculture. “Believe it or not, most pesticides or insecticides are not coming from agricultural lands,” says Gunnels. “Farmers run pretty tight operations. They apply what is absolutely necessary. But homeowners go out and, instead of following the recommended rate for ant poison or herbicide, they think ‘if a little is good, a lot is better.’” TRWD and TPWD will continue to monitor chemical accumulation in the sediment to protect wildlife and ecosystem integrity.
Birdwatchers are catching on to the avian hotspot. In spring, TPWD conducts moist soil drawdowns, which allow vegetation to germinate, creating food for wildlife. Acres of mudflats attract migrating shorebirds, such as yellowlegs, sandpipers, stilts and avocets. In summer, white ibis, herons, egrets and roseate spoonbills frequent the site. More than 5,000 ducks visited last fall — gadwall, shovelers, pintail and teal — and would erupt in great clouds.
Some people criticize the project because the wetlands are artificial, says Gunnels. He retorts, “We know they are artificial wetlands. We want them to simulate natural wetlands as closely as possible. But it is better than the alternative — no wetlands.”
Haucke agrees. This project helps delay — and hopefully prevent — the destruction of some of Texas’ last remaining bottomland hardwood forests, of which about 35 percent of Texas’ original acreage remains. “It’s a win-win situation,” says Haucke. The project pushes the need for additional supply into the future.
There is no simple formula that relates wetland loss to loss of water quality. Constructed wetlands provide exceptional alternatives, but these can’t replace protecting our remaining natural wetlands, particularly with the uncertain future for the Clean Water Act. We need both.
Until the Supreme Court rules again or state laws change, the responsibility for water quality may depend on entities like TRWD willing to bear responsibility for a larger piece of the commons.
Before we started exploring the wetland — where I so elegantly fell in — Andrews topped a bottle with murky Trinity River water. At the last cell, the water’s final destination before it will head towards the reservoir, he fills another bottle with … crystal clear water.
Andrews wows school kids the same way. “When they see water that resembles hot chocolate and is full of floating debris, we hear a lot of ‘ewww’ or ‘nasty’ or ‘gross,’” says Andrews. “It really is satisfying to see those same kids a couple of hours later look on in wonder at a school of fish swimming in crystal clear water as it leaves the system. It’s at that point when you know they really ‘get’ what this project is all about.”