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Land and Water

The Land

St. Brigid's oakThe Headwaters Sanctuary is primarily a riparian forest, meaning it is near a river or creek and supports plants adapted to periodic flooding. This forest is fairly young, as forests go: most trees are only 25 to 30 years old.  Much of this land has been cleared repeatedly in the last 70 years (see aerial photos) although there are very old live oak trees at the west and south edges of the sanctuary, on slopes less suitable for pasture or cropland.  As this forest matures, the mix of plant species will change slightly; but now, the dominance of hackberry and cedar elm is about what we would expect. Over time, slower-maturing trees will gain a foothold: species like pecan, Texas oak, Texas persimmon, and walnut. See a list of plants (pdf) documented in the sanctuary.

raccoonBecause we are surrounded by dense development and busy roads, the sanctuary does not support wide-ranging mammals like deer.  We do have smaller critters such as raccoons, skunks, possums, mice, and foxes. We are a haven for birds too: wrens, warblers, kingfishers, and cardinals are common, as are hawks and owls. Waterbirds pop in frequently: wood ducks, egrets, and herons among them. See bird list.

mushroomsThere is still much we do not know about who and what lives here. We are continuing to inventory plants and animals in the sanctuary. As we restore the balance of the land, we will track changes in the variety and abundance of species as an indicator of overall ecosystem health.


The Water

Blue HolePart of what makes this area special is the abundance of water, from Olmos Creek and the San Antonio River, and from the myriad springs, including our most famous, the Blue Hole. The Headwaters Sanctuary is a visible interface with the Edwards Aquifer, source of drinking water for San Antonio. When the aquifer is high, springs and seeps pop up all over the sanctuary. These springs create small temporary pools and permanent wetland areas. Other springs, like the Blue Hole, feed the creek and river.

seepWhile the Blue Hole is commonly called the “source” of the San Antonio River, it is actually part of a much larger headwaters system. The headwaters of the San Antonio River is the Olmos Creek catchment basin, of which our sanctuary is a part. This basin starts at about Interstate 10 and Loop 1604 and spans 34 square miles!  All the land within this 34-square mile area slopes generally down toward Olmos Creek; thus rainfall and other surface water in this zone is “caught” by Olmos Creek. 

Olmos CreekAlthough it flows through heavily urbanized areas, Olmos Creek appears pretty clean.  The creek met federal drinking water standards in its first 4 years of testing (2002-2005) by University of the Incarnate Word (see water quality data pdf). We will continue to monitor water quality and increase the number of testing sites to provide more complete data.




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Of all the wonders of nature, a tree in summer is perhaps the most remarkable; with the possible exception of a moose singing "Embraceable You" in spats. ~Woody Allen

Restoring the Balance

What do you mean, “restore the balance”?

In addition to the native plants mentioned, there are many non-native species living in the sanctuary, such as ligustrum, chinaberry, catclaw vine, Chinese tallow, honeysuckle, loquat and nandina.

Non-native species

Chinese tallow
Chinese tallow



We have nothing against these plants per se; however, they tend to outcompete native species and become dominant. This creates a chain reaction, reducing the diversity of plant and animal life in the whole forest.

Our goal is to reduce the number of invasive, non-native plants and allow the ecosystem to support the greatest diversity of native wildlife possible.  The Headwaters at Incarnate Word feels that undoing past damage brought by man is one way to respect the earth.

Learn more in our October 2007 Newsletter.

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