Tuesday, August 14, 2012

Things Ultrarunners Know: Hydrology

[photo by Gary, Greenbriar River near Durbin, WV]

For some time I've wanted to do a series of posts about some of the ancillary disciplines that Ultrarunners get at least a bit proficient in, as a result of our backcountry running passion.

I, for one, am extremely cognizant of surface streams.  Here where I live in south-central PA, the underlying rock strata is limestone, which is soluble and can contain very complex subterranean drainage systems.  In the area surrounding my home, there are only a couple surface streams, and those issue from limestone springs.

As I run I like to look out across the farm fields to scope out the slope of where rainfall will drain to.  Around here, rainwater usually flows across the surface for a bit until it reaches a gravitational dead end...then it slowly seeps into the ground to join the water table.

At some later time it will re-emerge as a spring. All these hydrological  characteristics are called karst:

Due to subterranean drainage, there may be very limited surface water, even in the absence of any rivers and lakes. Many karst regions display distinctive surface features, with cenotes, sinkholes or dolines being the most common. However, distinctive karst surface features may be completely absent where the soluble rock is mantled, such as by glacial debris, or confined by one or more superimposed non-soluble rock strata. Some karst regions include thousands of caves, although evidence of caves large enough for human exploration is not a required characteristic of karst.

Anyway, I wonder where the water goes.  Of course, in the backcountry, we need to be alert to potential water sources if our run will keep us out longer than the water we carry will hold out.  In that case, we need to know where the safe-to-drink springs are, or stream water than can be treated with a purifying agent.

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