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San Marcos Springs One of the greatest outflows from the Edwards is the San Marcos Springs. The Tonkawan Indians called them Canocanayesatetlo, meaning warm water. More than 200 springs burst forth from three large fissures and many smaller openings. A graphic picture of their original condition was written in 1846 by William A. McClintock:
The first Europeans to visit the San Marcos Springs were probably members of the Espinosa-Olivares-Aguirre expedition in 1709. For over a century the San Marcos Springs were an important stop on the Spanish Camino Real from Nacogdoches to Mexico. In 1854 German settlers built a dam just below the springs, which created Spring Lake and inundated the Springs. When Spring Lake was created it also sealed 12,000 years worth of archaeological artifacts underneath. This was a real boon for archaeologists in this century, who uncovered more than 50,000 artifacts from only 5% of the lake bed between 1979 and 1982 (Garza,1982). Many are on display at the site. Archaeologists believe this may be the oldest continually inhabited site in North America. In the 19th century the Springs were used to power a variety of mills and an ice factory, and the site was a stop on the Chisholm cattle trail from 1867 to 1895. In the 1900's, the springs were developed into a popular tourist attraction and resort called Aquarena Springs. Ralph the Swimming Pig and frolicking underwater mermaid dancers became trademarks. People held widely disparate views of what all this meant for the Springs. Many regarded the site as a wonderful family vacation spot, tourist attraction, and revenue generator for the city. Others came to regard San Marcos Springs as one of the saddest places in Texas. They felt it sad that for thousands of years awesome fountain springs were regarded as sacred and living by indigenous people, but now they could only be viewed in an underwater theater and through glass bottomed boats. Adding swimming pigs and mermaids ballets to the mix caused Del Weniger (1984) to write:
The Springs and resort were purchased by Southwest Texas State University in 1991 and continued to be operated as a theme park and resort. In February of 1996 the Board of Regents took what environmentalists hailed as a giant initial step toward restoring the dignity and natural beauty of this site. The Board voted to convert the facility from a theme park to "educational and general uses", ending the swimming swine's 30 year run. The dancing mermaid shows and theme-park like rides were eliminated. The University made plans to remove the infrastructure of rides to improve views of the lake and present a less cluttered appearance. Exhibits were completed on endangered species and on the many archaeological artifacts that have been recovered from the site. The underwater theater offered educational workshops instead of the mermaid show. However, the decision to end the amusements created ill will between the University and the community. The city lost a major tourist attraction, summer jobs, and $120,000 per year in tax revenues. To build a bridge back to the community, the University conceived a $5 million wetlands project that will eventually include several miles of nature trails that connect to the city's trail system, forming a 10-mile route along the San Marcos and Blanco rivers. There will also be a boardwalk over the Spring Lake slough. The first step in the project involved removing water hyacinth, a non-native fast-growing plant that covered the slough. Many additional plant and animal species present are not native, and the school plans to replace the introduced ones with native ones. Geese and swans have been removed, and there are plans to try to get rid of nutria, imported snails, hydrilla, elephant ears, and tilapia. Still, controversy surrounds the University's ownership and stewardship of the San Marcos Springs and Spring Lake. Some naturalists would like to see the Lake drained and the Springs restored to something more closely resembling their natural state. The dam suffered major damage during the October 1998 floods and some have argued it should be removed instead of repaired. They argue the dam is actually a threat to the endangered species present, and they point out that perhaps the most educational thing that could be done would be to let the area revert to it's natural state. The univerisity and federal officials have a different opinion. USFWS argues the endangered species have adapted to Spring Lake and would be worse off without it. There is also controversy over public access to Spring Lake. In Texas, the banks of a waterway can be privately owned, but the waterways themselves are publicly owned and no one can restrict access to them by swimmers or boaters. This applies everywhere in the State except at San Marcos Springs, which has always been used as private property. Whether or not it is legal to treat the Springs as private property and restrict access to them has not yet been tested in court. Usually courts do not retroactively enforce new laws, so if the area had been appropriated from the public domain before Texas' laws were set up, a case might be made that it should remain private property. One way to ensure the Springs become public property would be for the city of San Marcos to purchase them. In January 2000 the City Council began considering a nonbinding referendum to let voters voice their opinion on whether or not the City should try to purchase the site. The University said it isn't for sale.
Data from hydrochemistry studies and dye-tracer studies suggests that two nearly independent flow regimes contribute water to the various spring orifices. In one study, dye was injected in nearby Ezell's Cave, which is located along the San Marcos Springs fault (see the page on Faults & Caves). Eleven days later, dye was detected at Deep Hole, and 30 days after that dye was seen at Catfish Hotel. No dye appeared in any of the spring orifices farther north such as Weismuller and Cabomba. In 1979 a fault was mapped that separates the southern springs from the northern ones, which could have sufficient displacement to act as a groundwater barrier. Also, the fact that it took 30 days for water to move only 230 feet between Deep Hole and Catfish Hotel suggests minimal hydraulic connection and/or a zone of extremely slow ground-water movement possibly caused by a meeting of two separate pressure systems (Ogden, Quick, and Rothermel, 1986). In a second study by the same scientists, dye was injected in Rattlesnake Cave, located about 4,000 feet northeast of Spring Lake. After 40 days the dye emerged at all the monitored orifices in Spring Lake. The researchers concluded that groundwater from the San Antonio region moves northward, confined within a narrow fault block, and emerges primarily from just the southern orifices. This groundwater appears to be separated from the Blanco River and Sink Creek areas by a fault-controlled pressure boundary. This pressure boundary moves slightly in response to changes in hydrostatic head between the two ground-water flow systems and may allow flow to go in either direction under different conditions. This would explain why the dye emerged 40 days later at all the spring orifices. History does not record a time when the San Marcos Springs have ceased to flow. The lowest recorded flow rate was 46 cubic feet per second in August of 1956. At that time, the Comal Springs were dry. There is a relationship between the level of the J-17 index well and the flow at San Marcos Springs, but because of local recharge around the Springs the correlation is not as precise as with Comal Springs (see Flowpath Map). San Marcos Springs would cease to flow with a water elevation of about 574 feet at the springs. The "bad water" line is remarkably close to the springs. It runs through the facility's parking lot only about a thousand feet from the Spring outlets. There is a fault at this location which causes the Edwards limestone carrying fresh water to the Springs to be juxtaposed with denser, less permaeble limestone containing saline water. For the latest data on San Marcos springflows see the USGS Real-Time data page.
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