Potter County Water

As the son of the high school Ag teacher, growing up here in Potter County I was exposed to a lot of “farmer talk.” Early in my pre-pubescent development I heard and learned a lot of stuff that turned out to be totally useless to me personally, but important to remember as it ultimately became the ticket to broad social acceptability in this rural community. One of these was learned discussions of the “water table.”

Water table is, of course, just a click away from rain, which is shorthand for weather and what farmer isn’t conversant about the weather. My earliest impressions of the mythical water table was that it was somehow this huge underground lake (without legs, I might add) from which all things watery derived. Poor rainfall and lamentations about the “low water table” prompted visions of a de-watered underground labyrinth with empty, troll-like caves! Heavy rains would invariably prompt the “good for the water table” refrain.

It wasn’t until I began to fish that I began to seriously look into the subject. Some of this education proceeded from reading about and talking with fishermen from other parts of this state. Some of them from down state seemed to have an entirely different, almost casual, take on the subject. Some, in fact, couldn’t figure out what I was talking about. But mostly it was because without decent stream flows, the fishing sucked.

So what, exactly, is a “water table?” Dictionary first: the depth below which the ground is saturated with water. Simple enough, right? It should follow then, since most settlement in these parts is on the bottomland where the streams flow, that the water table would be somewhere below the town. And underneath the streams.

But as I spent more and more time on the stream it became apparent that something was wrong with the model. Why, for example, could one find water seeping from the ground high on a hillside? And why didn’t we all suddenly and universally run out of water when the streams dried up. Sometimes we did, but very rarely. Reports of homesteaders on ridge tops running out and having to re-drill their water wells only led credence to the mistaken notion of the vast underground water table that now required even deeper wells to reach. And why, during extended periods of heavy torrential rain didn’t the underground water rise and rise until it pushed out of the ground just about anywhere, which it didn’t.

Clearly there had to be something more to it than a simple reservoir underneath our feet. The answer turns out to be a little lesson in geology and a big lesson in locating trout.

Let’s try a definition from the glossary of a geology text: The position in the earth’s crust below which cracks and other opening are filled with water…The position of the water table below the ground surface is a function of the topography of an area and of local climatic conditions. Now we are beginning to get somewhere: note “cracks and other openings” and “topography” (the lay of the land, in laymen’s language). Just a bit more hardcore geology and we may have it.

It turns out that about 400 million years ago this area of Pennsylvania was at the bottom of a huge inland sea. This sea stretched from the Adirondacks, down through central and southwest New York State, and from there it covered most of what is today called Middle America. Into this sea came an unending flow of silt and sand from surrounding higher land. Eventually, about 200 million years ago, the bottom of this inland sea rose due to immense tectonic forces. As the bottom of the sea rose higher and higher, more and more water sluiced and cut its way toward lower ground. The rivers and streams we see today were being formed. Normally, we think of rivers as beginning where the highest rainfall lands and following a well-defined path to the sea. Instead, our rivers and streams cut away the silt, sand and other material as they worked their way upward. The network of streams advanced upward following the path of least resistance.

The end result of all of this activity is our flat-topped mountains and the many valleys and hollows; the tops of these mountains are really what remains of that long ago sea bottom. Fossils of animal and plant life that lived in and around the sea can be found here – ferns, clams, ancient lizards, etc. Looking up the slope of a Potter County mountain from the valley bottom, one might think that the mountain rose up; but, in fact, the valley was carved out rather than the mountain built up.

Because our mountains were originally layers of sediment laid down at the bottom of the inland sea they were susceptible to crumbling and weathering when exposed. Freezing and other geological forces further fractured the many layers of sediment. Over the millions of years the interiors of these mountains became like vast sponges, capable of absorbing large amounts of water from rainfall and snow melt. And as lichens, forests and other forms of vegetation became established, the mountains were able to retain this moisture for longer lengths of time.

So, the water table is wherever your drill strikes water, be it on a hillside (and you’ve tapped into a layer of water bearing sands left over from millions of years ago) or on the valley bottom (and your bit strikes an underground spring or stream). On the flat tops of some of our mountains your will often find the water table at the surface in the form of a pond or bog. Unlike Florida or the Cumberland Valley of Pennsylvania, there is no underground aquifer, with its more or less stable pool of water. Such aquifers are created in an entirely different way, geologically speaking. In central Pennsylvania, streams fed by the aquifer are called limestone streams, while here, in the Appalachian Plateau region, streams are referred to as freestone streams.

All well and good, you say, but what in the heck does this have to do with fishing?

Trout need water, preferably cool water. Our streams are completely dependant on rainfall, rainfall that replenishes the sponge-like formations deep inside our mountains. Generally speaking, in the early weeks of the season fishing is good as a result of snow melt and spring showers. But as the season advances, stream levels normally drop. The trees and other vegetation take up most of the available moisture and rain shows up more and more in the form of torrential thunderstorms. This water runs off rapidly, doesn’t get absorbed into the system, and is of little long term use.

The ideal arrangement for a good trout season is to have a certain amount of rainfall in the form of showers every week, preferably in the evening when evaporation is slowed down. Under these conditions stream levels stabilize and trout will be found in your familiar haunts. This past season came very close to this ideal, but it doesn’t happen very often.

As the stream levels drop, the water warms. Sections of certain streams that just a few weeks before were chock full of trout now seem to be empty. Often, erroneously, we hear that it is “all fished out.” Prolonged periods of no rain, a drought, can actually result in a completely dry stream bed, especially on small streams. Severe droughts can result in large fish kills.

Trout are not dumb. As the water warms and drops, they will seek out places that are habitable. The obvious holding spots are where tributaries and shaded brooks enter the main stream. Not so obvious are the many small seeps and underground springs that are present on almost all of our streams. Mill Creek, for example, is fed by scores of very small seeps, most of them not obvious to the casual observer. In low water they can be found by looking for a damp water stain on the river bank and more than normal vegetation. Such seeps can lower the water temperature just enough to attract a small pod of trout.

Underground springs that feed the stream from the stream bottom, while more difficult to locate, are a favorite holding place. Often the angler will stumble upon these serendipitously – suddenly he has caught several trout in a place that he normally wouldn’t rate very promising. Once located, it pays to remember the spot.

A lot of fishermen give up with the approach of the “dog” days of July and August. My approach has always been a little different. In some ways, low water makes fishing easier as the trout will have moved to places where they can survive. One can concentrate on the productive spots of cooler water and not waste time on stretches of marginal value. Over time an observant fisherman will have accumulated enough “hot spots” to warrant a trip a stream in all but the most severe droughts.

A few weeks ago I asked our resident geologist, Carl Roberts, some questions about “our water table.” Carl graciously pointed out some errors in my thinking on the subject, and went on to say, “You’d think that a geologist would know where and how to drill for water, wouldn’t you? Well, guess my chagrin when I drilled for water here in downtown Coudersport and came up with a dry hole! And I’m supposed to know what I’m doing.”

I’d guess that present day well drillers may talk about the “water table” but that they know perfectly well they are trying to strike a water seam or water bearing sands in these old hills.

Cross-section of a typical Potter County valley showing how water entrains into
the former sediment layers that have been fractured and eroded over millions of years.

When stream levels drop seeps and springs become exposed.
These are likely holding spots for trout.

Sources:

Rivers of Pennsylvania, Tim Palmer, Keystone Books, PSU Press: 1980

Joe Humphrey’s Trout Tactics, Joe Humphrey, Stackpole: 1982

Rocks of the Inland Basin, The Paleontological Research Institution -
http://www.priweb.org/ed/TFGuide/NE/rocks/rock_files2/rock_pdfs/ne_rocks1.pdf.