Water Quality and Quantity Focus of Paired Watershed Project
Water Quality and Quantity Focus of Paired Watershed Project
Story by Beverly Moseley
Traveling to Honey Creek out of the Edwards Plateauï¿½s uplands of Honey Creek State Natural Area, the landscape becomes dense with brush and tree canopies that lead down into a riparian bottomland ecosystem.
Sunlight filters through the tree canopies and brush into this unique ecosystem. Plants such as saw palmetto and trees ranging from cypress to Spanish oak are in abundance. Multiple springs erupt, bubble and flow along with the stream bed.
The densely covered landscape leading to Honey Creek is part of a watershed project that assesses benefits from conservation practices, such as brush removal and management, on water quantity and quality.
ï¿½One of the major things is that we can go in and do is selective brush control as part of a total resource management program on private land or public land and see positive benefits to the ecosystem including improved water yield, as well as improved forage production and improved wildlife habitat,ï¿½ said Phillip Wright, a range management specialist with USDA-Natural Resources Conservation Service.
He spoke during a tour highlighting a paired watershed study project in Honey Creek State Natural Area in Comal County, which began in 1999. A watershed is an area of land where water under it or running off it ends up at the same place.
Expanding on previous findings
This watershed project is a follow up to the Seco Creek Water Quality Demonstration project which ran from 1991-1998 in portions of Bandera, Medina and Uvalde counties.
ï¿½This project came into being after we had worked on the Seco Creek project. We came up with some good numbers on improving water yield. We were able to collect data that showed us some pretty positive benefits from doing that type of work [brush management] on water yield from a spring site,ï¿½
Wright was involved with the Seco Creek project and has been involved with the Honey Creek project since its inception. Wright and other agenciesï¿½ personnel began looking for large scale watersheds that shared a border in an effort to validate the Seco Creek project and further evaluate findings.
ï¿½We began working with people in the area trying to find two watersheds side-by-side that we could do instrumentation on, follow-up management on and maintenance on to see how it was going to turn out over time,ï¿½ Wright said.
Honey Creek State Natural Area, managed by Texas Parks and Wildlife, had the paired watersheds that study participants wanted. The studyï¿½s treated watershed, where selective Ashe juniper removal has taken place, totals approximately 350 acres. The untreated watershed where no Ashe juniper removal has been done is approximately 265 acres. The paired watershed project area is part of Honey Creek State Natural Area which is not open to the public. Cattle also are not allowed to graze in the state natural area.
ï¿½To my knowledge this is one the longest ongoing studies of this type on the largest watershed of this type anywhere in the United States,ï¿½ Wright said. ï¿½Weï¿½ve been very lucky to be able to keep this partnership together this long with all the interested parties pushing it and getting it to go and weï¿½re real proud of that fact.ï¿½
Project partners include the USDA-Natural Resources Conservation Service, U.S. Geological Survey, Texas Parks and Wildlife Department, Edwards Region Grazing Lands Conservation Initiative, Edwards Aquifer Authority, Guadalupe-Blanco River Authority, San Antonio River Authority and San Antonio Water System. Some of these partners provided expertise or funding for the project.
Texas Soil and Water Conservation District directors from counties such as Gillespie, Blanco, Kerr, Kendall, Comal and Bandera were in attendance. Some of these directors are working on watershed brush projects in their areas to enhance water yield.
ï¿½The upper Guadalupe project and the Bandera project are clearly new projects and so these directors are just becoming acquainted with the whole. Most know a lot of it, but we just wanted to bring them out to see first-hand why weï¿½re doing what weï¿½re doing on brush projects,ï¿½ said Melissa Grote, program specialist with the Texas State Soil and Water Conservation Board.
Grote added that tour attendees were learning about some of the valuable science and research behind why and how these watershed projects are carried out.
Honey Creek State Natural Area is home to some of Texasï¿½ endangered species, such as the Golden-cheeked Warbler. To ensure nesting sites were not disturbed, Texas Parks and Wildlife mapped out the known nesting areas. A 300 meter buffer was created around these nesting sites. Ashe juniper was removed outside these buffer zones in the treated watershed.
Wright said Texas Parks and Wildlife has worked with local Audubon groups on bird counts in the treated area. Overall the bird numbers and diversity have increased, along with diversity of habitats. Park biologists are working on compiling population data which will be included in the studyï¿½s final findings which should be published in 2011.
Testing the waters
The study watersheds are fully implemented with monitoring devices such as weirs or water measuring devices that are used on streams or springs. Real time rainfall gauges and Bowen energy ratio stations which monitor evapotranspiration rates, also are being utilized. Data collection and monitoring began on both watersheds in 2000. Selective Ashe juniper removal and management began in 2003 on the 350 acre treated watershed and continued through 2005. About 80 percent of Ashe juniper has been removed.
ï¿½We tried to take it back to what it originally was, which was oak, juniper woodlands and oak-savannah,ï¿½ Wright said.
No reseeding of grasses has been done.
ï¿½TPW does have some very restrictive regulations on reseeding. It has to be native seed from within a very close area reintroduced back. We didnï¿½t have a good seed source and wanted to see what it would do with natural revegetation. Since we started monitoring following the brush control, weï¿½ve seen little bluestem, big bluestem, Indian grass and switch grass all come back in on this site with no reseeding,ï¿½ Wright said.
Richard Slattery from the U.S. Geological Survey, a water resource project partner, monitors and measures the components of the watersheds hydrologic budget to better understand how brush management affects the water cycle. This includes measurements of rainfall, stream flow and evapotranspiration rates which are used to make estimates of groundwater inflow that may be made available for aquifer recharge.
ï¿½We want to see how much rain is coming down, how much bounces back [evaporates], how much is running off. When we measure all those components as a residual, we can assume so much infiltrated or even goes deeper down and percolates and gets into the ground water system,ï¿½ said George Ozuna, deputy director of the Texas Water Science Center for U.S. Geological Survey.
He added that prior to selective brush removal collected data revealed 60 percent of the moisture coming in was going back out through evapotranspiration.
ï¿½Thatï¿½s not available to runoff, not available for spring flow, not available for deep infiltration or percolation to the aquifer,ï¿½ Ozuna said.
Wright stressed to attendees that they should think total resource management not just brush control. In other words, for livestock producers brush control should be followed up with conservation practices such as proper grazing and stocking rates.
Ozuna agreed: ï¿½Itï¿½s the package. The range is improved. The endangered species, the songbirds and habitat have improved.ï¿½
Finding more answers
Honey Creek is a spring fed creek. Its primary source of water is a single spring coming from one of the longest caves in Texas.
ï¿½Thatï¿½s the headwaters where it flows out of that spring,ï¿½ Wright said.
Water is reaching Honey Creek from the treated watershed through the soil profile, he said. But determining whether itï¿½s new water from rainfall or old water that has been in the ground for some time is more difficult.
Wright said questions still remain such as: Where does the water go once you do something that improves water yield?
ï¿½We canï¿½t answer that question. We know it either goes into the ground and is available for deep recharge, or it goes in the ground into a shallow system ï¿½ and it comes out in spring flow,ï¿½ Wright said. ï¿½But to track it all the way down as to where exactly that drop of water goes - itï¿½s not feasible. Itï¿½s not doable. You just donï¿½t have the technology to do it.ï¿½
Studies are being done using isotopes to help determine whether spring flow to Honey Creek is from rainfall or old ground water.
ï¿½The radioactive isotopes that occur in the atmosphere can give us that type of information and USGS is looking at those types of studies on this area,ï¿½ Wright said.
In the treated watershed, an energy balance Bowen ratio station is used to obtain evapotranspiration data for the paired watershed project. Data on properties such as net solar radiation, soil heat flux, soil temperature, soil moisture and differences in air and vapor pressures are collected. The instruments are mounted on a 30 ft tower which allows the station to monitor a larger representative site area. The area one tower station is so tall (30 feet), because it was installed above the existing tree canopy, before selective Ashe juniper removal was performed on the treated watershed site.
Richard Slattery from the U.S. Geological Survey, a water resource project partner, monitors and measures the hydrologic components of the paired watersheds. This information will be used to help better understand how brush management effects the water cycle of the watersheds. At the untreated watershed, which totals approximately 265 acres, Slattery shared with attendees during a recent tour how a crest stage gage is used to record peak water levels.
Honey Creek is a spring fed creek which flows through Honey Creek State Natural Area in Comal County. Multiple springs erupt and flow along the creek bed and into the waters. Studies conducted by the Natural Resources Conservation Services and partners have shown that Honey Creek is benefiting from an upland paired watershed research project that assesses benefits from conservation practices, such as brush removal and management on water quantity and quality.
Attendees at the Honey Creek Paired Watershed Project tour travel through the dense landscape of the untreated watershed in the paired watershed study. No Ashe juniper removal has been done on this approximately 265 acre site.