Dams on the Side
Off-channel reservoirs can help meet water needs while causing less environmental impact than dams that halt a river’s flow.
By Wendee Holtcamp
I kick off my sparkly flip-flops and slip my feet into the trusty ol’ black rubber boots, pulling them over my jeans. “Every good woman should have a pair of black rubber boots in her trunk,” I say to the trio of Brazos River Authority guys — John Hofmann, John Dickson and David Wheelock. They have brought me out to Allens Creek, the site of a proposed off-channel reservoir, and the ground remains muddy and wet after recent rains.
We head through brush, cedar elm and hackberry trees, on down to the creek. Thick poison ivy vines wind around large trees, and as we get nearer, a couple of turtles plunk into the creek from its banks. Allens Creek flows muddy brown, its water roiling and swirling around submerged tree limbs.
“That is a ginormous oak,” says Hofmann, as we gaze up at its gnarled and thick trunk. Hofmann works as manager of the central and lower basins of the Brazos; and Allens Creek flows into the lower basin of the Brazos, 133 miles upstream from the Gulf of Mexico and west of Houston.
“Will the tree get drowned by the reservoir?” I ask. “I’m worried about the tree.”
They orient me with an aerial map. We stand just a quarter of a mile upstream of the confluence of Allens Creek with the Brazos, and just outside where the levee will get constructed. The earthen levee across Allens Creek will create an off-channel reservoir that will flood roughly 9,500 acres of land — mostly farm fields. Once fully approved, the reservoir will most likely get built around 2018. And the huge oak tree is safe.
Off-channel reservoirs have become a popular option for Texas water planning, and have been lauded as less ecologically harmful alternatives to traditional on-river reservoirs. Not only are most off-channel reservoirs smaller in total size, they should cause fewer impacts to aquatic life in the main river. However, they are not without impact.
“In general, TPWD prefers off-channel reservoirs to new, on-channel reservoirs because the impacts to fish and wildlife are less,” explains Cindy Loeffler, TPWD Water Resources Branch Chief. “Impacts to aquatic ecosystems — rivers, streams, bays and estuaries — are less since not all flow is impounded, as is the case with an on-channel reservoir.”
Traditional reservoirs dam up a river’s main channel. This prevents fish and aquatic critters from migrating downstream and changes a river’s natural dynamics. A dam also keeps much-needed fresh water and sediment from flowing downstream, where they would otherwise reach the estuary at a river’s mouth.
In contrast, an off-channel reservoir requires building a dam or levee on a tributary — a smaller creek, stream, bayou or branch that flows into the larger river. To keep such a reservoir filled to capacity, water must be pumped in from the main river, because tributaries do not typically have enough water volume flowing through them on their own.
Since Senate Bill 1 passed the Texas legislature in 1997, 16 regional groups have started planning for the next 50 years of Texas’ water, and the Allens Creek reservoir is one of the recommended strategies in the 2006 Region H water plan — the region that includes Houston. It will provide future drinking water for the Bayou City, as well as water for agriculture, industry and other uses. Even though Allens Creek is an off-channel reservoir, it will provide approximately two-thirds the yield of the highly controversial proposed Fastrill reservoir in East Texas, and rather than destroying ecologically valuable and rapidly disappearing bottomland hardwood forests, it will mostly inundate old farm fields.
As we walk away from Allens Creek I reach down and pick one of the spring’s early wildflowers. “Are there wetlands that will be destroyed by the reservoir?” I ask. Dickson tells me that the initial reservoir construction plan would have inundated hundreds of acres of high-quality wetlands in a spot called Alligator Hole. A revised plan shifted the reservoir’s location, preserving the wetland. “Can we see it?” I ask.
We drive to Alligator Hole a few miles away. Then only Dickson and I brave the long muddy trudge in our boots to the wetland — a seasonally flooded forest that happens to have about a foot of water at the moment. I laugh at the mud on Dickson’s boot, which looks like a large tree gall. As we walk around, we discuss how few kids get outside on a regular basis to appreciate nature like this — mud, bugs, trees, birds, bees and all of it. He recently took his preteen daughter’s friend fishing; she had never been. I lament how my own daughter does not have a passion for the outdoors like I do. If the renowned Harvard entomologist E.O. Wilson never outgrew his “bug phase,” well then I never outgrew my mud phase. I love to tromp around in my big black boots.
Modifying the original plan to preserve this wetland — ecologically valuable habitat that people once considered nuisance, not splendor — is one way that the Allens Creek project stands as a positive example of collaborative planning. On top of that, the Brazos River Authority has incorporated measures to minimize the reservoir’s impacts on the aquatic ecosystem. Nonetheless, any change in a river system’s structure can alter ecological function.
“[The planned reservoir] still is impacting aquatic habitat on a major tributary in the lower Brazos,” says Kevin Mayes, TPWD aquatic biologist who consulted with the Brazos River Authority in developing the Texas Commission on Environmental Quality water rights permit, “so there could be important functions in that tributary that are lost because the dam proposed is fairly close to the confluence with the Brazos.”
Tributaries provide refuges for fish and other aquatic organisms when conditions in the main river are not favorable, Mayes explains. “Aquatic organisms can use tributaries to avoid those harsh conditions due to flooding or low water or poor water quality. So that’s one thing that might be lost if they were to impound Allens Creek.”
The permit granted by TCEQ for the Allens Creek reservoir specifies values for low and normal river flows needed for the Brazos River to maintain its natural state of affairs. Rivers, after all, wax and wane as drought and flood cycle through the years. The Brazos River Authority will only be able to pump water from the Brazos if enough remains in the river to meet the water needs both for a healthy aquatic ecosystem and for downstream water users. “It’s a significant step forward,” says Hofmann, adding that it’s one of the first reservoir permits to pass through TCEQ since the 1980s.
Although the Allens Creek off-channel reservoir is not yet a surefire thing — public meetings have to take place and some permits need to be secured — the collaborative effort should pay off. Because “everybody’s at the table,” says Mayes, “maybe, just maybe, there won’t be any surprises at the end.”
The Allens Creek reservoir history stands in stark contrast to the heated controversy over proposed reservoirs in East Texas, particularly Marvin Nichols and Fastrill. The reservoirs would provide water for Region C — which includes Dallas and Fort Worth — but in the process will dam up rivers and submerge thousands of acres of bottomland hardwood forest.
Region C has some of the highest per capita water use, which it projects on into the future rather than reducing water waste with effective conservation planning. A National Wildlife Federation study entitled “Save Water, Save Rivers, Save Money: The Potential of Municipal Water Conservation in Texas” found that if the City of Dallas alone decreased its per-person water use by 1 percent per year over 60 years, the city could save roughly twice as much as the Fastrill reservoir would provide — conserving more than 200,000 acre-feet of water per year. The achievement is not far-fetched. Water conservation efforts enabled both San Antonio and El Paso to decrease water use by 30 percent in less than 20 years.
On the other hand, Region H, which includes Houston, has embraced tactics such as advanced water conservation, drought planning, brush management, naming ecologically unique streams, and off-channel rather than new on-channel reservoirs.
Although intensive water conservation has yet to begin here, it will include improving the efficiency of agricultural irrigation, conservation in private residences and businesses, and brush control for private land.
Within and outside Region H, Allens Creek is not the only off-channel reservoir being considered. In the second phase of water planning, Region H substituted an off-channel for an originally planned on-channel Little River reservoir as an alternative water supply tactic. And in Region G, in north Texas, the Wheeler’s Branch off-channel reservoir southwest of Fort Worth nears completion. Sixty miles southwest of Fort Worth, I’ve donned my black rubber boots again, ready to see another off-channel reservoir site — Wheeler’s Branch, a tributary of the Paluxy River.
As we drive through this Cross Timbers region of Texas, with its rolling hills and scattered live oaks, I tell my two kids that the singer Jewel lives around here, on a ranch in Stephenville with her boyfriend, rodeo champ Ty Murray. I put in her latest CD and listen to the song Stephenville: “I’m trying to listen to the leaves speak/ Trying to steal secrets from fishes in the creek/ Trying to figure out who I am.” I bet she’s a woman not averse to tromping through mud in a pair of black rubber boots.
The Paluxy River flows into the Brazos, and the Brazos River Authority transferred a 2,000 acre-feet per year water rights permit to Somervell County Water District in 2000. The off-channel Wheeler’s Branch reservoir was designed as an alternative to the originally planned on-channel Paluxy Reservoir, after a state court overturned its construction permit.
Kevin Taylor, SCWD general manager, drives me out to see this off-channel reservoir, which is still under construction. We walk through some mud and overlook the basin, which nears completion. Before long this will be filled with water pumped from the Paluxy as well as natural flow from its tributary, Wheeler’s Branch. The reservoir will provide water for irrigation, industry and drinking in Somervell County and the towns within. At only 169 acres of surface area, the impoundment will be 100-fold smaller than the proposed Allens Creek reservoir, but the water will provide the county enough water for the foreseeable future.
The Wheeler’s Branch and the larger Allens Creek off-channel reservoirs were planned with TPWD’s input, and that of other stakeholders. They stand as examples of collaborative efforts providing more environmentally friendly solutions. However, off-channel or on, each reservoir is unique, and its benefits should be weighed against costs.
Janice Bezanson with the Texas Conservation Alliance (formerly the Texas Committee on Natural Resources) says, “We are opposed to all unneeded reservoirs or reservoirs for which there is an economically feasible lower-impact alternative.” “Off-channels aren’t magic bullets to solving our water problems,” says Mayes. They do provide water supply while causing less environmental damage than a larger on-channel reservoir. Combined with water conservation, water reuse and other low-cost water supply options, off-channel reservoirs provide a step in the right direction — a direction that helps meet the needs of people while minimizing impacts on the environment. And that, after all, is a step toward sustainability.
