Less salinity = more life, freshwater inflow management structure completed
by Jennifer Lewis
Aug 15, 2014 | 1537 views | 0 0 comments | 3 3 recommendations | email to a friend | print
Lester Contracting installing the last of the box culverts with sluice gates for the structure.
Lester Contracting installing the last of the box culverts with sluice gates for the structure.
The completed freshwater inflow managment structure on the Rincon Bayou at the Nueces Delta Preserve.
The completed freshwater inflow managment structure on the Rincon Bayou at the Nueces Delta Preserve.
ODEM - One of the main ideas for ensuring healthy bays and estuaries is to have “a good sound management practice,” and a key factor is in maintaining a healthy system freshwater inflows. “Our purpose is maintaining the health of bays and estuaries within the 12 county region known as Coastal Bend, from the southern end of San Antonio Bay to the Land Cut,” said Jake Herring, Director of Land Conservation at the Coastal Bend Bays & Estuaries Program (CBBEP).

A 5,800-acre nature preserve, located off Highway 77 near Odem, is home to birds and various wildlife and has been at the top of the list of the many priorities for the Coastal Bend Bays and Estuaries Program. The installation of a freshwater inflow management structure was completed in July 2014.

The inflow management structure was designed to redirect water from the City of Corpus Christi’s freshwater diversion pipeline discharge point to the Rincon Bayou and Nueces River Delta. It is located in the Rincon Bayou diversion channel, between the Corpus Christi pipeline and Nueces River. Choke Canyon and Lake Corpus Christi reservoirs reduced the amount of freshwater inflow to the Nueces Estuary since their construction and has thus caused the channelization bypassing the delta and flowing directly into Nueces Bay. And with water flowing into the bay, there is a greater need for flow to the Nueces Bay delta (southern end of San Patricio County, the bluff edge just south of Odem, to the outskirts of Portland).

About 10 years ago, private land owners of approximately 20,000 acres were asked to get involved, and since then, they bought the 5,800 acres and are currently in the process of purchasing an additional 4,700 acres. In the end, CBBEP hope to have the 10,500 acres of contiguous estuarian habitat in San Patricio County because when the property is owned by CBBEP-they will be managing it for its habitat value and thus manage healthy wetlands and grasslands.

Nursery Grounds

The delta is a “nursery ground” for shrimp, crabs, and fish. Small organisms need shelter from bigger fish so they go where there is structure and plants, where they can hide and feed within them. Both Herring and Jace Tunnell, Director of Research and Planning said, almost in unison, “It’s our job to protect it.” Lower salt content means stimulus for the organisms and the cycle of life can continue.

Freshwater needs to be pumped due to the fact that there are often many droughts, and the watersheds do not have enough freshwater. Inspiration also stemmed from the City of Corpus Christi to need for the inflows, which led to the construction of the Rincon Bayou.

The two-mile long pipeline, which was completed in 2008, pumps freshwater above the saltwater barrier dam and around and into Nueces Delta, and the Rincon Bayou at the headwaters. The pipeline is where the drinking water comes from Lake Corpus Christi, down the Nueces River, who then takes the water and treats the water at treatment plants. The Calallen Dam, prevents saltwater from the bay from intruding upon the freshwater from the reservoirs. If the dam wasn’t there, then the salt water, which is very dense, could go all the way up to 25 miles, such is the case in the Aransas River. And also because, as Herring said, “being able to treat for saltwater is very expensive.”

Salinity Effects

Herring explained that without pumping it is a “salt pan; like an accumulation of salt build over years and the salt stays until it gets flushed out which would take years.” With their help, life in the bays and estuaries can go on without the risk of high amounts of salinity.

The Gulf is fresher than the delta. When there is no pumping, the salinity count is so high that vegetation and all possibilities of life is slim to next to impossible. Seventy parts per thousand (ppt) is an average for some areas of the delta (without pumping) and vegetation starts dying when salinity is at about 50 ppt. “We have seen vegetation since 2009, when the pipeline started being used and since then we have placed monitors throughout this whole system,” Tunnel said.

High salinity content in the upper delta happens if pumping does not occur. Before 2009, when the pipeline began to be used, the salinity station, which was instituted in May, showed 120 ppt for the salinity count in the upper delta. In October, the salinity count dropped immediately. Only two times has the number reached back up to 70 ppt, but only for a very limited time since they had water available. It depends on tidal flow as well. For example, 500 acre-feet is needed during winter months. But, if the tide is high, like in October, 1,500-2,000 ppt goes all the way down to the bay within 24 hours.

The first time they turned it on, half of the freshwater when back up to Nueces River, and half went down stream. Herring reiterated the importance of funding in addition to everything else.

“If you look at the outfall, it went straight back into the river,” Herring said. “And, when looking at cost of pumping, it’s expensive to pump water because of electricity and we want 100 percent going downstream.”

Salinity loves the shallow environment in the area. In some spots, the river is only as high as waste deep. In many spots, it’s as low as 6 inches deep. Freshwater evaporates, and salt concentrates, so it’s imperative to keep salinity down by pushing the water out.

How does the structure work?

The box culverts have gates. Whenever they start pumping water, the valve is cranked, which moves the gates up and down. The fish can go back and forth when the water is not pumping and the gate stays open and when the gates are closed, the water can go downstream and push out the salinity.

Legal Agreements

When the Choke Canyon reservoir was completed in 1982, Corpus Christi began to look at the importance of having provisions passing through a certain amount of water to the bays and estuaries. In 1987, it took five years to fill and some was needed to pass water through to Bay. In the 1990s, the Coastal Bend Bays foundation which was established (1992) and sought to help the environment and manage the water inflow, 151,000 acre-feet was passed in 1992.

“Agreed orders began to be enforced in 1995, “ Tunnell said, “which is when they came up with the “pass-through requirement.”

It is a monthly requirement which varies month -to-month, but the annual requirement overall is 151,000 acre-feet. How much they use each month depends upon the weather conditions. For example, in June, approximately 14,000 acre feet went into reservoirs and so even though the target was 23,000 acre feet, they passed through the 14,000 acre feet.

If it rains in reservoirs, they monitor the gauges in the watershed, so they know how much water is going in. Anything that comes in above that, they can keep in reservoir. The latest agreed order was in 2001, when they added modifications for the drought contingency plan and the pipeline.

“The orders are really important,” Tunnell said. “If you look at reservoirs, 55 percent of water does not reach the bay.”

With all the water being used to bathe and send to treatment plants, and other places, that’s over 550,000 people using water from different watersheds.

Continuing Projects and Education

The Harte Research Institute and Texas A&M Corpus Christi are checking to see what pumping is doing for the organisms. They are testing and looking at how the pumping has affected benthic organisms such as worms and bugs.

“They are looking at the impact of inflows because they already know pumping is beneficial so they are looking at how long it takes [life] to recover upon decreasing salinity, etc,” Tunnell said. The University of Texas is also doing a visual model of the representation of all the testing and how it affects the different areas in question.

Tunnell is excited about the project for many reasons.

“The constant water pumping is doing wonders for this area,” Tunnell said. “It’s cool to see solar panels as the primary energy source and to be able to maintain that flow with the new technology.” And after almost three years of hard work, and efforts from various organizations to get this project finished, it’s clear that it takes a team to do it, as Jake Herring pointed out, “we definitely do not do all of this on our own, we rely heavily on partnerships, we are all working on this for the benefit of the environment and the Nueces Delta.

Herring continued, “so many people from many different organizations may have their own specific missions and goals, but we are all working together as different parts to implement it all- to benefit the whole.”The moving parts needed to complete this structure included organizations such as Corpus Christi, National Oceanic and Atmospheric Administration (NOAA), the Texas General Land Office Coastal Management Program and the Coastal Conservation Association-Texas (CCA).

Herring also loves the idea of benefiting the environment and being able to enjoy the benefits of their work.

“Doing good work for the benefit of environment and community is rewarding and I myself like to spend a lot of time outdoors,” Herring said. “When you can mix work and recreation in one job, it feels good to do what we are doing and it makes for a happy work place.”

Beyond the environment and peaceful work space, these gentlemen are family men who think of their kids’ future often.

“Being able to take our kids outside and do the same activities with them that we did when we are growing up, it’s important,” Tunnell said. “It’s really important that they have those same experiences, like to see certain birds or go fishing. It’s generational protection.”

To learn more about upcoming projects or watch some of their educational videos, go to
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