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The coordinates will take you to the entrance of the Aquarena Nature Center.
THE EARTHCACHE SITE ==================================== Congratulations to BulldogBlitz for his FTL (first to log)! Once a well known Attraction and Amusement Park (known for Ralph the Diving Pig and mermaids), the Center is now owned and administered by Texas State University. Visiting the center is free, although a ride on a glass bottomed boat requires a paid ticket. Hours vary but the Center should always be open for the core hours of 10 am to 4 pm (visit their Aquarena Center website for hours, prices, and other contact information: https://tshaonline.org/handbook/online/articles/dua02 ). The Center is closed on New Years Day, Thanksgiving, and Christmas. Handbook of Texas Online AQUARENA CENTER http://www.tshaonline.org/handbook/online/articles/AA/dua2.html The best history of the area can be found at http://www.edwardsaquifer.net/sanmarcos.html . Packed with information, a map of the springs, and pages of photos (including many historical shots from the theme park days), it's a must-read for the Aquarena fan and would-be fan. INTRODUCTION ==================================== The Edwards Aquifer stretches roughly along the route of IH-35. Taking in water along its western flank, springs often are found wherever faulting or erosion have exposed the rock. One of the most famous of these springs is the San Marcos Springs, better known to many as Aquarena Springs. Over 200 individual springs have been identified at this site. Most are associated with three large fractures but many more appear from smaller geologic features. Early accounts of the springs indicate that the large ones were under such high pressures that they fountained from the fissures, with water spraying several feet above the surrounding stream. Dammed in 1849, the Springs now lie at the bottom of Spring Lake. Once an attraction that included an amusement park, now Texas State University owns and manages the property. The springs may still be viewed from the vintage glass-bottomed boats. Evidence of the force of spring flow can still be seen by observing the sand boils. The Springs are the main source of the 83-mile long San Marcos River. Together, the river and the Springs have been designated as critical habitat for five endangered species. These are the Fountain Darter, the Texas Blind Salamander, the San Marcos Salamander, the San Marcos Gambusia, and Texas Wild Rice. Interesting as all that is, it’s not why you’re here Earthcaching. The earth science mechanics of this cache are nearly identical to GC26DNK CTU – WATER FROM A STONE (Edwards Aquifer), but where THAT cache requires a technical hike to see the Edwards Aquifer in action, this spot is essentially wheelchair accessible. Plus, if you like, you can take a boat ride. What a deal! EDWARDS AQUIFER ======================================== From the edge of Spring Lake, you can observe the limestone cliff opposite. It is formed of layered limestone rock. The limestone here is essentially Edwards Formation. Particularly susceptible to “chemical weathering processes” (e.g. the rock dissolves in water), the Edwards Formation is, in a word, porous. These holes vary from microscopic to full-on cavern systems, and karst features are typical. As you examine the cliff, you can see this writ in stone, as it were. All those holes – vugs, voids, caverns – form a system of arteries and capillaries, which water loves to travel THROUGH rather than over. More, the Edwards Formation has been bracketed by denser rock – making it rather like a sponge cake between layers of hard candy frosting. And where this ‘sponge cake’ is exposed – by faulting action and/or erosion – the water comes tumbling out in seeps and springs. Throughout Central Texas springs, grottos, seeps, and creeks from ‘nowhere’ abound. Up in Austin, Barton Springs is the best known example (see GC17XNX The Limestone Manifold), as well as Seider Springs (see GC26PT8 CTU – SEIDER SPRING FLING). Here in San Marcos, we have the equally famous Aquarena Springs. This water movement is not simply local runoff. According to the Edwards Aquifer Website “Because the movement of water in the Aquifer is highly complex, the waters we pump from the ground and drink are a mixture of waters of many different ages. In some places water moves only a few feet a day, but in other places water has been shown to move up to 2 miles a day or more…. The average residence time for water in the aquifer is around 200 years; so much of the water that [for example] San Antonians drink today probably went underground around the time of the American Revolution.” It should also be noted, in “all karst aquifers, most of the water storage occurs in the matrix, and most of the water movement occurs in conduits. In the Edwards, there are many large caverns, but one should not picture the underground reservoir as a vast pool. Rather, think of it as a saturated sponge with pipes. The rock matrix has many pore spaces similar to the holes in a sponge, and some of them are connected by well defined conduits through which water can readily flow. Pores that are not connected to other pores or to a conduit cannot provide much water. The measure of pores that are connected and can provide water is called effective porosity. Water enters the Aquifer easily in the recharge zone, but the subsurface drainage is generally inadequate to hold all the water that falls in large rain events. Recharge conduits and sinkholes quickly become filled up with water. This is one reason why the region floods so easily. The honeycombed rock matrix stores 95% of the water in the Aquifer. To move long distances, water leaves the matrix and enters a well-defined conduit [such as a river or creek], where it may be transmitted very far rather quickly.” KEEP THE WATER FLOWING =================================== Evidence exists that the springs here have flowed for generations upon generations. There is evidence that the area around the Springs is one of the oldest continually inhabited areas in North America. Traces of human habitation can be found continuously for as far back at 11,000 years. A graphic picture of their original condition was written in 1846 by William A. McClintock: “Two miles north of St. Marks we crossed the Blanco, a mountain torent of purest water, narrow and deep, there is the finest spring of springs (for they are not less than 50 in a distance of 200 yds.) I ever beheld. These springs gush from the foot of a high cliff and boil up as from a well in the middle of the channel. One of these, the first you see in going up the stream, is near the center, the channel is here 40 yds. wide, the water 15 or 20 feet deep, yet so strong is the ebulition of the spring, that the water is thrown two or three feet above the surface of the stream. I am told that by approaching it in canoe, you may see down in the chasm from whence the water issues. Large stones are thrown up, as you've seen grains of sand in small springs, it is unaffected by the dryest season. I am persuaded that the quantity of water which is carried off by this stream in the course of a year is greater than that by the South Licking, it is about 60 feet wide and 3 feet deep on an average, with a curant of not less than ten or fifteen miles per hour. Great numbers of the finest fish; and occasionally an alligator may be seen sporting in its crystal waters... In the eddies of the stream, water cresses and palmettoes grow to a gigantic size.” THE TEST ================================================ As you enjoy the peaceful setting of this marvel of nature, think about the following questions and email me the answers to these *relatively* straightforward questions (please don’t put them in your log): 1> Is San Marcos Springs one spring or a series? 2> Do you think the flow is: .....a> Intermittent (rain runoff) .....b> Seasonal .....c> Year round 3> Get on the Internet and go to: http://waterdata.usgs.gov/tx/nwis/uv/?site_no=08170500&PARAmeter_cd=00065,00060 This gives the streamflow data for the San Marcos River at San Marcos. What was the flow (cubic feet per second) on the day that you visited the Springs? 4> Now visit: http://waterdata.usgs.gov/tx/nwis/uv/?site_no=08172000& This gives the streamflow data for the San Marcos River at Luling. What was the flow (cubic feet per second) on the day that you visited the Springs? 5> Given that the flow in the River at San Marcos is essentially the discharge of the Springs, what percentage of the flow at Luling comes from the Springs? LOGS WITHOUT VERIFYING EMAIL WILL BE REGRETFULLY DELETED (though not without due notice). I don’t demand it, but pictures with your logs are encouraged (of you and/or the scenery … whatever strikes you as NEAT!) -- as are logs with actual content, describing your adventures in the park and what you thought about this nifty perfectly earthcachable spot. Thanks for visiting! PS> Bonus points! For those who mix waymarking with your geocaching, there are a number of waymarks set in the Aquarena Center. Some are frivolous as the penny smasher in the Gift Shop, others supply further information about the Springs.
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