Texas Parks & Wildlife Magazine   


Delta Dawn

The young Colorado River delta is a lush breeding ground for finfish, shrimp, crab — and controversy.

By Wendee Holtcamp

The water’s surface bubbles like a slowly boiling witch’s brew. Each pop and bubble is an oxygen-hungry menhaden breaking the water’s surface, struggling to breathe. Hundreds of them. “This is bad,” TPWD coastal fisheries biologist Bill Balboa says to me, as we motor down the old Colorado River channel on the 22-foot outboard motor boat he takes out weekly to sample fish and other aquatic critters throughout Matagorda Bay. Balboa has led TPWD’s Matagorda Bay ecosystem research for the past eight years. He has a laid-back approach to life, but he takes his job very seriously. And the gurgling water has him seriously concerned.

“This looks like a fish kill.”

I’ve joined Balboa to witness the formation of a 15-year-old delta at the mouth of the Colorado River. River deltas are historically lush fertile lands, floodplains, river valleys — think world history class and the fertile Mesopotamian valley. Our plan is a grand exploration of the cuts and channels, dams and locks of this modified area of the Texas coast where the Colorado enters Matagorda Bay, and to view the newly forming tidal marsh, where elegant shorebirds feed on small delicacies hiding in the cordgrass. We’re here to discuss the history of the region and how an environmental enhancement project — the Colorado River diversion — attempts to return Matagorda Bay to a more natural state. We didn’t expect to witness the precursor to a fish kill.

For the sake of commerce, flood control and fisheries, humankind has wrangled with the mouth of the Colorado for more than 100 years, diverting it here and there, dredging it, dynamiting its logjams, relocating it. The river tells a colorful history, and today’s fish kill can only begin to be understood in light of it.

Before 1900, the Colorado River used to flow into Matagorda Bay, which was not separated into an east and west bay as it is today. In the 1800s, a huge logjam, or log “raft,” formed at the mouth and extended nearly 50 miles upriver. The logjam was so thick that trees grew on it. During those years, heavy rains often flooded the seaside towns of Wharton City and Matagorda. In an attempt to remedy the flooding, a channel was dredged through the logjam. The dredging lasted from 1925 to 1929. Finally, the log raft was dynamited apart in 1929, and a major flood the same year flushed all the remaining log debris downstream.

Clearing the logjam changed the bay. The river started to bring loads of sediment downstream and accelerated the formation of tidal fringe marsh at an astounding rate of 500 acres per year. The marsh quickly spread halfway across the bay.

But the flooding still came. This time, the rapid build-up of sediment in the middle of Matagorda Bay was blamed, so local entities decided they would just divert the river directly into the Gulf, bypassing the bay. In 1934, a channel was dredged and the mud spoil was placed on both sides, forming the present land bridge between East and West Matagorda Bay.

Balboa and I are motoring down this old Colorado River channel, where the menhaden are jumping for air. This would still be the main channel were it not for a 1990 Corps of Engineers project that re-diverted the Colorado yet again — this time into West Matagorda Bay. Scientists had started recognizing the incredibly important role of “freshwater inflow,” or the fresh water coming down a river into a bay, in sustaining its living organisms. In the late 1980s, several interest groups, including biologists, anglers and commercial fisheries, agreed that diverting the river back where it belonged would increase the bay’s biological productivity. Opponents at the time pointed out potential negative impact on seagrasses and oyster reefs.

With the support of TPWD, National Marine Fisheries Service and U.S. Fish & Wildlife Service, the Corps completed the diversion of the Colorado back into West Matagorda Bay by 1992, and an earthen dam plug closed off the old from the new channel. The Corps also plugged off Parker’s Cut (aka Tiger Island) which had previously allowed boat and fish traffic between West Matagorda Bay and the old river channel. Leaving it open would have brought salt water back into the bay and hence be counterproductive to the project’s goals. This tiny earthen plug has led to a mounting controversy over fish kills, water circulation and the state of the bay.

We head back up the river channel, past the closed Parker’s Cut to the Gulf Intracoastal Waterway, where the Corps of Engineers regulates barge traffic through a series of locks. These massive gates open and close off flow from the Colorado River to let barges pass. The lockmaster gives us a go-ahead. We negotiate past a pungent-smelling barge carrying toxic benzene, then head around the bend and down the new diversion channel, making our way to the mouth of the actively forming delta.

In addition to bringing fresh water, the river carries soil and debris scoured from land it runs through, particularly during flood flows, and dumps this sediment at its mouth. Dead trees make the delta treacherous for boat traffic, but they trap sediment to provide structure where marsh grass can grow. Clumps of smooth cordgrass grow in the mucky marsh mud, extending into the horizon, their stiff green blades emerging from the salty water.

Roseate spoonbills sift crustaceans from the water with their flattened spoon-like bills, their elegant pink feathers like jewels against the pale blue sky. White ibises stand scattered throughout the delta. These estuaries are renowned nursery habitat for young finfish, shrimp and crabs.

Many people do not realize that the muddy sediment a river carries downstream contains nutrients, including nitrogen and silica, which tiny phytoplankton (plant-like animals) that form the base of the entire bay food web, need to survive. Diatoms are an abundant silica-shelled phytoplankton that shrimp, crabs, and juvenile fish feed upon. A sandpiper runs to and fro, picking critters out of the mud. “This is probably one of the most dynamic areas on the Texas coast,” says Balboa. “It has created acres and acres of marsh habitat.” A U.S. Fish & Wildlife Service study documented that more than 300 acres of marsh have formed since the delta’s inception.

Some locals love the diversion project, while others think it’s caused harm, and there’s nothing like a fish kill to get people riled up. Al Garrison has been a fishing guide for 25 years, serves as Executive Director of the Matagorda Bay Found-ation, and recently retained attorney Jim Blackburn to convince the Corps of Engineers to open Parker’s Cut, or another channel, to increase circulation to the east end of West Matagorda Bay. Garrison says he is totally opposed to the diversion project. “I’ve seen absolutely no benefit for the environment, fisheries or production of the bay,” says Garrison. “The last meeting I attended with LCRA [Lower Colorado River Authority], they showed that the productivity of [the] bay has gone way down — oysters, shrimp, crabs and fish.” Garrison would not acknowledge that any new marsh has been created or its role in the production of finfish, crabs, or shrimp, but he said there are certain times of year when this end of the bay is good for fishing. “They can present a situation that’s good for fish and bad for shrimp, or if it’s good for fish, it’s bad for crabs or oysters,” says Garrison. “They’re trying to play God and they can’t do it.”

LCRA’s job is to carve up the fresh water allocation pie that must nourish bays, people, agriculture, cities and industry. Every week, Balboa and his crew drag trawl nets, bag seines and gill nets throughout the bay to analyze species presence and abundance. LCRA used this data to examine productivity of nine species — redfish, flounder, oysters, blue crab, white and brown shrimp, black drum, menhaden and mullet. Over a 20-year period, redfish and oysters have shown increases, while the others have shown gradual declines. However, as LCRA’s John Wedig points out, “We’ve had an exceptionally wet 10 to 12 years,” and rainy conditions decrease salinity. “It’s really too early to tell the long-term trends.”

The water quantity coming down all Texas rivers is threatened as future reservoirs are constructed and companies and river authorities sell water to water-poor cities like San Antonio. State agencies, nonprofits and politicians are currently wrangling to determine how much water people, cities, agriculture, fish and wildlife need to survive in a state where the population keeps increasing. Bays need a certain amount of freshwater inflow to maintain healthy commercial and recreational fisheries. The problem lies in determining exactly how much freshwater estuaries need, and how reduced flow in rivers will affect that equation.

“There are so many factors that make bays what they are. It’s very difficult to show cause and effect,” says Balboa. LCRA is using catch rates for productivity and correlating freshwater inflow to these data, but Balboa explains, “No one can say that a gallon of water equals this much in terms of estuarine productivity.” He also stresses that the data can only assess overall bay production rather than pinpoint a particular area, such as at the new delta.

“I agree with Bill’s statement that bay productivity/ecology is a very complex issue,” says Wedig. “That's just one of the reasons LCRA is currently conducting what we believe is the most thorough study to date of the bay’s health. This study measures not just critter abundance, but also includes habitat, nutrients, primary productivity and macro-benthics.”

Species in bay ecosystems have evolved to deal with pulses in salinity, and no salinity level is optimal for all species. “People say extremes are bad, or the salinity should be maintained at a certain level, but bays evolved around chaotic events including flood and drought,” says Balboa. One needs only look at adaptations of the organisms to understand that the bay has long been a place where chaos and change rule. According to the classic text, Shore Ecology of the Gulf of Mexico, the best-adapted bay fauna are mobile: swimmers, crawlers and burrowers.

The irony of how people react to changing bay conditions does not escape Balboa, “If we get a flood and it kills the reef, automatically it’s a bad thing. But when the reefs are producing market-sized oysters it’s because of the fresh water.’” Oysters are highly sensitive to salinity, and when fresh water floods in, they die. But even if an entire reef is wiped out, free-swimming larvae recolonize the oyster shell substrate when salinities increase. It’s all part of the dynamic cycle of estuary life.

Blackburn differs from his client, Garrison, on the overall benefit of the new delta, applauding it as an environmentally beneficial project, but says something needs to be done to restore circulation to the old Colorado River channel to prevent fish kills. The fish kills did not occur before, but five have occurred since its completion. “If you open up Parker’s Cut, I don’t know if you’ll solve the circulation problem, but you’ll provide a pathway for fish to get out of the channel,” says Blackburn. “I don’t think Parker’s Cut is the only fix that would be appropriate, but some channel needs to be cut.”

In the 15 years since the diversion, the area has seen two major floods and two major droughts. “Because of the boom or bust nature of our inflows, it’s going to change where people fish,” says Balboa. “A lot of people are not happy about the diversion because they used Parker’s Cut for access. They’re angry because they lost business.”

Some locals love what the diversion project has done for Matagorda Bay. “I’ve fished that thing all my life. It’s the greatest thing that happened to that bay,” says Raymond Cox, a veteran fishing guide. “You’ve got a river bringing silt down that’s replenishing that bay. It’s making more wetlands for the plankton that feed everything in the bay. It made the greatest fishing hole I’ve seen anywhere in the world. If you open it [Parker’s Cut] up, you’re going to kill what you built.”

We head out into the open bay and drag a trawl net behind the boat to see what we can catch. We haul up various and sundry creatures, including cabbagehead jellyfish, gafftopsail catfish, lookdown (a Gulf fish), moon fish, white shrimp, brown shrimp, bay anchovy, spotted sea trout, a smooth pufferfish and sauerkraut grass — a colonial bryozoan. The mix of creatures in our catch indicates a fairly high salinity — normal for this bay. Most of these organisms breed in the Gulf, and their eggs or juveniles drift back into the bay, where they feed and grow, many seeking shelter in the coastal marsh. We dump the creatures overboard and head back.

The day after our grand Matagorda Bay river delta exploration, thousands of dead menhaden wash ashore at the mouth of the old river channel. These commercially important fish enter the channel in mass aggregations seeking deep, still water. Balboa agrees the closing of Parker’s Cut and the diversion channel have caused increased fish kills, but thinks that if a channel should be opened, it should be in East Bay, not around the new delta. A lot of money and effort went into the project, and no one really knows what any modification would do. “This isn’t a project that will yield results overnight,” Balboa concludes, “it was supposed to yield results over a long time.”

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