Seco Creek Project Shows Brush
Control Improves Water Yields

KERRVILLE — The Seco Creek Water Quality Demonstration Project, initiated in April 1990, is a cooperative project involving, state, federal and local agencies. Lead agencies on the project are USDA's Natural Resources Conservation Service, Texas Cooperative Extension Service, USDA Farm Services Agency and the Texas State Soil and Water Conservation Board.

Those attending the recent Holistic Resource Management of Texas annual meeting here heard an overview of the project from Phillip Wright, one of the project coordinators with the Natural Resource Conservation Service.

Seco Creek Watershed, Wright said, comprises an area of 267 square miles (170,670 acres) in South Central Texas. The watershed overlies the Edwards Aquifer, which is the sole drinking and industrial water source for more than 1.5 million people in and around the San Antonio area. It is also the primary irrigation source for 103,000 acres of cropland.

The primary purpose of the project, Wright said, was to study water quality and quantity impacts on a smallscale watershed where selective brush management was implemented.

Researchers now have eight years of data collected from the site, two years pre-treatment and six years post-treatment. Water quality was collected on a monthly basis, while water quantity data and cumulative rainfall totals were collected on a weekly basis.

On this eight-acre watershed, 85 percent of the ashe juniper canopy was removed. Six years after the treatment, with 35 percent less rainfall, researchers recorded a 25 percent increase in spring flow.

"That amounts to approximately 40,000 acres of water per year from the treated area within the eight acre watershed," Wright told listeners.

Water quality on that site, he added, never exceeded EPA drinking water standards over that eight year period.

"With good management, and by that I mean proper grazing management and proper selective brush control management, we can maintain or improve water quality and we can in certain areas significantly increase water yield," he told listeners.

He showed a picture of a cedar break. On such a site, a rainfall event is essentially ineffective because the closed canopy prevents the raindrops from reaching the soil surface. It's one of the reasons there is little, if any, understory vegetation in cedar breaks.

Removing juniper cover to manageable levels not only improves the vegetation, it also greatly enhances wildlife habitat. The two go hand in hand, he explained, because there is now a more diverse food supply, which means that a greater diversity of animals can now live there.

Chaining and dozing can be used to open up a cedar break if one can afford it. However, if not properly done, erosion can be a problem, Wright said. He recommended reseeding the site with a good range seeding mix.

To maintain wildlife habitat, he recommended doing brush control work in irregular patterns or in strips.

Wright told listeners that any time brush control work is done, NRCS is bound by National Environmental Policy Act requirements.

"We cannot do anything that will adversely impact endangered species," he said in response to one listener’s question. "When we identify potential habitat, we bring that to the landowner's attention. As long as that landowner is not spending federal dollars on his land, he still has the right and the privilege to do whatever he wants to do.

"We have no regulatory authority," Wright added, "and don't want it. We (NRCS) are providing information and assistance."

Most important, he said, brush control can only have a positive impact on water yield if proper grazing management is applied and if proper follow-up maintenance treatments are used.

"If you don’t do these two things, then don’t bother. You’ll do more damage than good," he insisted.

Wright discussed several other tools studied on the Seco Creek Project and he offered them to listeners as viable methods for conserving water.

Irrigation, Wright noted, is a visible water use, but a very important water use.

"Farmers are producing food and fiber for livestock and human consumption. We need to use water for irrigation, but we need to use it wisely. There are new technologies out there that are allowing landowners to do that very effectively."

One such tool that has been around for several years now is Low Energy Precision Application used with center pivots. Designed by the Texas Agricultural Experiment Station, LEPA is one of the most efficient irrigation methods available, Wright said. Researchers discovered that shifting from a high pressure drop to a LEPA system improved application efficiency by 35 percent from 65 to 95 percent.

LEPA is an effective tool, not only in conserving water and getting water on the crop where it needs to go, but also in conserving energy. A high pressure system requires 80 pounds of energy while LEPA only requires 14 pounds of pressure.

Water conservation, Wright pointed out, should not just be a concern of the agriculture community. Urban and suburban areas must do their part as well, and soil moisture monitoring is another effective and simple tool that can be used by everyone to conserve water. It can be used not only to measure soil moisture in croplands, but also soil moisture in a landscape.

"Statistics indicate that about half the water used in urban homes goes to landscape use. If we could improve efficiency by just 25 percent we would conserve a lot of water.

"Many who water their lawns with a timing mechanism have no idea how much water needs to be applied," Wright pointed out. "By measuring the soil moisture, applications can be timed so that watering only occurs when the landscape needs it."

Wildscaping or xeriscaping is another worthy water conserving tool, the speaker said.

Wright discussed concerns he has with some household septic systems, primarily those that are old or that were not installed properly, and the possible negative impact they could have on water quality of a recharge zone. As a solution, he suggested developing an artificial wetland as a holding area for waste water. The plants in the wetland, he explained, help accumulate nutrients and provide time for decomposition of organic matter that could potentially pollute the soil and seep into ground water. He pointed out, however, that the design must be approved by local authorities.

"We can conserve water by using the effluent," Wright said, "and at the same time improve water quality."

Another conservation tool that not only improves water use efficiency but also wildlife habitat is a rainwater catchment. A catchment can be something as simple as an inverted tin roof, the speaker said. A 16X16 inverted tin roof, for example, yields approximately 160 gallons of water for every one-inch of rainfall. Again, this kind of tool can be used by homeowners to capture and save rainwater.

He concluded with a message on nutrient management. Nutrient management, Wright said, is another critical aspect to maintaining optimum water quality. Wright stressed the importance of obtaining soil samples to test for nutrient levels so proper fertilizer rates are used.

"It scares me to think about how much fertilizer is applied to these Coastal bermuda pastures that may not be necessary. You should not apply fertilizer on anything until a proper soil analysis is done to determine nutrient requirements for the crops growing on that soil," he reiterated. "That's not only for pastureland, cropland, orchards, it's for urban situations as well — your yard."