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July 12, 2004
Rains a Welcome Change for Troubled Rio Grande
BROWNSVILLE, Texas — Often cited as one of the most endangered rivers in North America, the Rio Grande is this year gushing with hope. After years of punishing drought, recent rains have refilled reservoirs, flushed out water-sucking non-native plants and sent rejuvenating pulses of freshwater into the river’s coastal estuary.
Texas Parks and Wildlife Department biologists have rushed to take advantage of the situation by stocking more than a million fish in Amistad and Falcon reservoirs this spring and summer, seizing the chance to rebuild drought-plagued fisheries while the lakes are full.
Last June, the surface area of Falcon Lake near Laredo was 22,318 acres, according to the International Boundary and Water Commission office at Falcon Dam. In late June, the lake surface covered 62,822 acres, nearly three times bigger than it was a year ago.
TPWD has so far stocked about 663,000 Florida largemouth bass and 174,000 native northern bass fingerlings at Falcon earlier this year. At Amistad Reservoir this year, TPWD has stocked 552,000 Florida bass and 42,000 northern bass. All of this is designed to take advantage of recent rainfall that has filled up lake arms and creeks that have been dry for years, areas that provide important fish habitat.
Most of the stocked fish are 1.5-inch fingerlings that should grow to legal, catchable size within 1-2 years. However, TPWD has also stocked hundreds of larger broodfish weighing 5-8 pounds each to help jumpstart lake fisheries.
The locals recall the "good old days" at Lake Falcon and back it up with yellowed Polaroids on tackle shop walls. For two years running during the mid-90s, this massive 87,000-acre reservoir was ranked by TPWD as the number one bass tournament lake in Texas; better than Lake Fork or Sam Rayburn or Toledo Bend.
By 1997, in the midst of what turned out to be a 10-year drought, Falcon’s reputation and water level were dropping rapidly. In the summer of 2002 this once mighty impoundment was sitting 54 feet below normal pool level and covered only 13,000 acres. Even if you wanted to go fishing on Falcon, chances were slim you’d be able to access the water at all since most of the boat ramps were high and dry.
The recovery brings new hope from anglers and state fisheries biologists that Falcon could reclaim its glory days.
"While the lake was down we saw all kinds of plant regrowth along the shoreline and when the water increased, that created new habitat," said Jimmy Dean, TPWD’s fisheries biologist for Falcon Lake. "It’s creating in essence a new lake."
In this unusually wet year, the future looks bright for the border reservoirs, but biologists are cautious about long-term predictions. They point out that the lake levels could drop quickly if dry times return and water is released for downstream irrigation and municipal use.
"They should be catching a lot of smaller fish [at Falcon] and in three years will hopefully be back to catching big fish," Dean noted. "We’ll keep our fingers crossed that we continue to get some rain. The need for water can sure come on in a hurry."
Besides Amistad and Falcon, rains have also filled reservoirs on the river’s Mexican side, such as El Cuchillo, which delivers water to the densely populated Lower Rio Grande basin.
In the river itself, swift-moving rainwater has done a great service by flushing out huge, floating mats of exotic (non-native) water weeds such as water hyacinth, which suck up and waste water through evapotranspiration. For miles along some stretches of the lower Rio, these aquatic exotics had become so thick they were actually blocking the flow of river water.
"Everything from the tiny invertebrates and filter feeders all the way up through the water column to the big predators like bass are breeding and increasing their numbers [because of the rainwater]," said Ismael "Smiley" Nava, TPWD’s borderlands biologist, a new position created last year with federal State Wildlife Grants funding.
But Nava also adds a cautionary note: even if water quantity is higher, water quality remains an issue.
"Regarding water pollution, the saying "the solution to pollution is dilution" has some application here—the rains helped," Nava said.
"But there are still border towns in Mexico that don’t have the ability or infrastructure to treat their wastewater or don’t treat it very effectively. Nuevo Laredo has a relatively new water treatment plant that effectively treats about 25 million gallons of wastewater daily and has the capacity to treat more. However, because border cities like Nuevo Laredo are expanding so fast, collection lines to service outlying areas have not kept up with that growth."
"As a result," says Nava, "some untreated water is finding its way into the Rio Grande. The good news is that the river has a natural but limited capacity to treat or stabilize pollutants on its way downstream to the Gulf of Mexico. This cleansing is dependent on the pollution sources, length and flow of the river, microbes in the water and other factors."
And when it comes to having enough water, Nava also remains cautious.
"Even though we’ve had one good year of rain, the last 10 haven’t been that great. It’s an over-appropriated river. If everyone with a water right permit asked for their allotted volume of water, we wouldn’t get a drop past Brownsville."
River water getting "past Brownsville" is important, because it involves the future of the Rio Grande estuary where the river meets the sea.
The good news is "pulses" of floodwater have not only flushed out exotic plants, they’ve also reestablished the river channel to the estuary, which made headlines several years ago when it dried up to the point that the river no longer reached the ocean. But intermittent pulses are not the key to long-term estuarine health.
"When you have more dependable river inflows, you’re going to have good production of commercially important species such as white shrimp and finfish like black drum, red drum and snook," said Randy Blankinship, TPWD coastal fisheries biologist in Brownsville.
"Ecologically speaking, you have production of forage species like striped mullet and croaker, the species the predator fish feed upon. We need to maintain an optimal salinity regime, don’t want too little or too much fresh water. We need sustained, dependable river inflow."
Nava, Blankinship and others stress that now, in a wet year, is the time to make plans for future droughts.
"Even though we’re getting all that [fresh water], this is not a time to put all our planning efforts on the shelf," Blankinship said. "Now’s the time to stick to our guns and continue with planning so that the next time we have a drought, we’re in good shape."
Rio Grande inflow studies are in planning stages, research that should provide numbers about the amount of freshwater needed to keep the estuary functioning.
"The next step is to figure out how to provide those flows and inflows, which will be difficult on the Rio Grande because it’s over-appropriated, so we’re going to have to be innovative," Blankinship said.
"It should be possible to build into water policy provisions various methods of taking into account the effects of drought, such as with the Nueces River, so that you have a variable schedule of water releases where water is provided to the extent that water is available. You’re not only saving water in reservoirs for human health and agriculture, but also providing water for estuaries that provide important commercial and recreational benefits for people. The goal is trying to maintain a balance there."
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