|Small preserve lake||Karst formation|
|Small creek||Karst formation|
Concordia University Texas is located on a 386-acre tract in northwest Austin, four miles east of Lake Travis. The university dedicated approximately 250 acres of its campus as a nature and wildlife preserve as part of a conservation easement with Travis County. The campus is a “living classroom” for the study of responsible urban environmentalism and offers a unique opportunity to investigate and manage endangered species, native plants, hydrology, forestry, geology along with archeology in a spectacular setting crafted by God’s divine hand.
The Concordia Preserve is part of the regional Balcones Canyonlands Preserve (BCP) created in 1996 to protect eight federally listed endangered species, including two songbirds (Golden-cheeked Warbler and Black-capped Vireo – both found on the Concordia preserve) and six invertebrates. The BCP is managed under a regional permit issued under section 10(a) of the Endangered Species Act by the U.S. Fish & Wildlife Services and jointly held by Travis County and The City of Austin. The Concordia preserve was created by permit TE-827597-2 from U.S. Fish & Wildlife. The BCP currently incorporates approximately 27,000 acres and will ultimately include 30,000 acres of prime habitat, making it one of the nation’s largest urban preserves (current BCP map).
The campus sits along the eastern edge of the Jollyville Plateau (part of the larger Edwards Plateau) where five tributaries merge to form Bull Creek. The university is located above the central valley in the Bull Creek Watershed, a 25 square mile region that drains to the Colorado River at Lady Bird Lake (Town Lake). The area passes through the environmentally sensitive Edwards Aquifer Recharge Zone. As a result, hydrology and the flow of water through the area (both quantity and quality), is extremely important.
Within the Concordia Preserve there are 28 archeological sites, 13 of which have been included within the National Register of Historic Places. These sites include 10 rockshelters, two open terrace sites and one Central Texas burned rock midden.
ROCKSHELTER – projecting limestone rock ledges weathered over time and forming a cavity which continues to increase in size. As the cavity grows portions of the ceiling can flake and fall to the floor of the cavity. It is not unusual for these rockshelters to have been inhabited, with the archeological layer subsequently covered by falling rock.
OPEN TERRACE – sites containing natural stair-steps to the top of a canyon or upland area. These areas are often found close to reliable water supplies and can contain cooking areas (hearths) and work areas for the manufacture of tools.
BURNED ROCK MIDDEN – a low, donut-shaped mound of heat-fractured rock, ash, carbonized plant and animal remains and artifacts used by prehistoric people for outdoor cooking and baking.
For generations Native Americans living on the headwaters of Bull Creek took advantage of the geological and hydrological systems supporting the biology of this valley. Intact archeological sites, when investigated, reveal the prehistory of these peoples in the places where they lived, ate and worked. As a group, these archeological sites tell the story of the people who once lived in this valley.
The Concordia Preserve exists to “preserve” a variety of special features in an essentially pristine and undisturbed setting, including: precious archeological remains, endangered wildlife and native plants and monitor/maintain appropriate hydrology. The 250-acre tract is held in trust by Concordia for the benefit of community research and will not be developed. The preserve is closed to the public.
Click to view the site contraint map of the nature preserve (PDF)
Importance of Watersheds
A watershed is an area of land that drains to a particular creek, lake or aquifer. Water travels from the highest hill to the lowest area where it forms some body of water. Austin has 66 creek watersheds, most of which enter the Colorado River at Lady Bird Lake (Town Lake) before flowing to the Gulf of Mexico.
In “old Austin” most rain water runs off the land, down streets to a storm drain, picking up pollutants as it travels. It then flows through underground pipes which lead directly to creeks. New developments are required to install water treatment ponds to capture some runoff and remove a portion of the pollutants before reaching creeks.
How Development Can Impact a Watershed
In an undeveloped watershed, about 50% of rainfall is absorbed by the land. Vegetation and soil filter pollutants from the water as it moves slowly down into groundwater. Traveling below the surface, groundwater re-emerges at the seeps and springs that feed various creeks. This process provides baseflow, the constant source of fresh water that supports aquatic life and creates flowing streams to sustain humans.
In developed watersheds, roadways, parking lots and rooftops cover much of the land. Rainwater that previously infiltrated to groundwater quickly runs off these hard surfaces. Baseflow in the creeks is reduced while the chances of flooding and stream bank erosion are increased. In “old Austin” many creeks have excessive flow during heavy rains and dry up shortly afterwards. New developments are required to build water detention ponds to reduce flooding and erosion.
Karst is the English word for Kras, a Slovenian region in Eastern Europe resting on a limestone plateau. Limestone is a sedimentary rock composed of mineral calcite (calcium carbonate). The primary source of calcite is usually shells of marine organisms. Secondary calcite can also be deposited by groundwater that precipitates the material in caves. Karst topography is a unique landscape formed when soluble bedrock, such as limestone, dolomite or gypsum, dissolves over time by groundwater. Rainwater, made acidic by carbon dioxide from the atmosphere and soil, slowly infiltrates rock cracks, dissolving the rock and enlarging openings. The dissolution process produces fissures, sinkholes, underground streams and caverns. Karst openings often support unique ecosystems that include plants, bacteria, crickets, spiders, fish, amphibians (such as salamanders) and small mammals.
The Golden-cheeked Warbler (Dendroica chrysoparia) is a true Texas native. The species is known to nest only in Central Texas. Warblers migrate to the region from Central America and southern Mexico in mid-March to nest and raise their young. They return to their southern home in late July or early August for the winter months. Warblers frequent closed-canopy woodlands of mature Ashe juniper (often called cedar), live oak, Spanish oak and shin oak. This type of habitat is typically found in relatively moist areas with steep-sided canyons and slopes. Feeding on insects and spiders, Warblers use long strips of cedar bark and spider webs to build their nests. Females lay 3-4 eggs during nesting season with an adult reaching a length of 4.5 inches. The Golden-cheeked Warbler has been on the endangered species list since May 4, 1990.
The Black-capped Vireo (Vireo atricapilla) migrates to Texas from the western coast of Mexico to nest from April through July. They prefer rangelands with scattered clumps of shrubs separated by open grassland. The Vireo builds a cup-shaped nest in the fork of a branch 2-4 feet above ground. Nests are normally constructed in shrubs, such as shin oak or sumac. Females lay 3-4 eggs hatching in 14-17 days. Both parents incubate the eggs and feed the chicks with a diet of insects. Adults reach a length of 4.5 inches and have a lifespan of 5-6 years. Males sing to attract mates and defend their territory, which is usually 2-4 acres in size. The Black-capped Vireo was placed on the endangered species list on October 6, 1987.