Popular Science Monthly/Volume 13/July 1878/Water-Supply of Rivers
|WATER-SUPPLY OF RIVERS.|
By GEORGE CHAHOON.
IN the year 1871, three kilns were built on lot 54, Jay Tract, town of Wilmington, Essex County, New York, for the purpose of burning wood into charcoal, to be used in making iron in the Catalan forges, on the Ausable River. At the time these kilns were built, the side of the mountain upon which they are located was covered with a heavy growth of spruce-timber. Near the top of the mountain there is a pond, covering about one acre of ground. This pond was undoubtedly scooped out on the southeast side of the mountain during the Glacial period, and at the outlet the water is confined by a wide, low moraine dam, such as, upon a larger scale, distinguish all our moraine lakes. This pond, some 2,000 feet above the level of the sea, forms the head or source of a small trout-brook that flows down the side of the mountain past where the kilns have been erected.
I first visited this pond in August, 1874, and was very curious to know where the water came from, for I could not understand how the small extent of country drained could supply so much water during such a warm, dry time.
In the summer of 1876, after a thousand acres of timber had been cut, a fire broke out in the woods, not only killing the standing timber, but destroying the corded wood in the kiln-yard, and doing considerable other damage.
It was part of my business to prevent this destruction, as far as possible. Men were sent to the fire, and worked there for several days. In going to the kilns, the road leads up the mountain, by the side of the brook. The season was very dry, and the water in the rivers unusually low; but, in going up the mountain, I was surprised to notice that there was as much water in this brook as I had ever seen, except after some long, heavy rains, and my judgment in this matter was confirmed by all the men working at the kilns, with whom I spoke on the subject.
The fire was very fierce, and, after leaving the standing timber, spread across the cleared ground, burning the soil as far down as it was dry; and it actually ran through a field of potatoes freshly hoed, leaving the half-grown, scorched, and burned potatoes, lying upon the top of the ground. This fire lasted several days, and I was at the kilns every day during its continuance, and was every day surprised that the brook, fed largely from the drainage of the burning land, seemed to increase with the fierceness and extent of the fire. In some places, when cleared land had been burned over and dried under the scorching sun, in one or two days afterward the fire ran over it again, taking off another shaving of soil. This continued until the fire was finally quenched by rain.
Afterward, in making an examination of the soil, I found that it consisted of from two to four feet of what is known among the woodsmen of Northern New York as "spruce-duff," which is composed of rotten spruce-trees, cones, needles, etc. This "duff" has the power of holding water almost equal to the sponge, and, when it is thoroughly dry, burns, like punk, without a blaze.
I was told by Mr. Cooper, who has the direct charge of the kilns, that, in sledding wood down the mountain, the sleds frequently wore off the "duff," and came to ice.
On June 30, 1876, while the fire was still burning, I tested the water and soil, as far down as I could conveniently dig with my hands, with a thermometer, and found a temperature of from 37° to 40° Fahr. I afterward dug down, in several places, through the "duff," and in each place found ice or frozen ground.
After this, it was perfectly clear to my mind that this "duff" became thoroughly saturated with water during the fall rains, and that it was frozen to the bottom during the long, severe winters of this climate. It is not an uncommon thing for the ground in the valleys, hundreds of feet below the level of these kilns, to freeze to the depth of four feet during the winter.
The "duff" being frozen at the bottom accounts for the brook increasing in size with the increase of the fire, for the heat from the burning of the top "duff" would cause the ice to melt, and the water would find its way into the brook. This "duff," like all woody substances, is a poor conductor of heat, and when once frozen and protected, as it is in its natural state by the shade of the timber, would thaw out very slowly, and would continue to furnish a supply of water all summer; and very hot weather, causing low water in other places, would tend to increase the supply from this source.
During the latter part of the summer of 1877 I examined "duff" in several places, but did not find any ice; but found the "duff," in every instance, thoroughly saturated with water. It should be remembered that the summer of 1877 was unusually wet, and that water is an excellent conductor of heat, and that water from the rains, running over the ice, would melt it much sooner than it could be melted by what heat could be communicated from the sun, through its woody covering, in a dry season. At most, this would tend to show that the ice lasts only part of the summer, but, if that is a fact, the frozen "duff" would furnish a reservoir as long as the ice lasted, and, during the rest of the summer, would act as an absorbent, taking up and holding the showers, and gradually letting the water down into the streams, tending to prevent floods after heavy rains by holding back the water, and preventing scarcity of water during droughts by gradually releasing the water gathered from the storms.
In addition to the "duff," the sides of many of our mountains are covered with a heavy moss, which also acts as a sponge in the manner described above, in preventing floods and supplying water during dry seasons; and this moss, like the "duff," entirely disappears when the land is cleared, and, like the "duff," does not form again under the pines and deciduous trees that follow the spruce. The spruce-timber affords a dense shade, and, as long as the timber is left standing, this "duff" seldom gets dry enough to burn, but, when the timber is cut, the top of the "duff" dries, and is burned, as far down as it is dry enough to burn, by the forest-fires that are so common in this part of the country. This is repeated, year after year, until the "duff" is all burned off, and the sand and bowlders appear upon the surface; after this, white poplar and white birch spring up, which, however, are liable to be burned at any time, as the fire runs freely through all deciduous timber in the spring, before the leaves are out, or during a very dry time in summer.
It is generally understood that the clearing away of the forests has the effect of causing low water during the summer season, and the reasons given for it are, the more rapid evaporation of water from the soil, on account of the greater exposure to the sun in cleared than in timbered land, and to this may be added the more rapid drainage, particularly in sandy soils, after the rotten logs, leaves, and other absorbents, have been removed; and it is also claimed that more rain falls upon a section of country when it is timbered than after the land has been cleared. The first of these reasons is undoubtedly correct, and there is a great deal to show that the second is correct also, though I do not think we know enough about the subject to justify us in stating, as a scientific fact, that the amount of rainfall is affected by the growth of timber.
I have never known the existence of the spruce "duff" to be recognized, as a fact of any importance, in governing our water-supply during dry seasons; but, unless I am greatly in error, it is a matter of the greatest importance, and the destruction of the "duff," with the destruction of the forests, will prove as damaging to our streams as the increased evaporation caused by the greater exposure of the land to the sun.
The waters from this immediate section of country flow into Lake Champlain, and thence into the St. Lawrence River. The country around the principal feeders of the Hudson River is almost identical with the country described above, and the same causes that affect the water-supply of the Saranac and Ausable govern the water-supply of the Hudson.
The water-supply of the Hudson is a matter of very great importance to the people of New York, and any facts tending to throw light upon the natural laws governing it should be received with interest by the intelligent people whose health, comfort, and prosperity, are partially dependent upon the quantity and purity of the water in this noble river. Hundreds of square miles of the country upon whose drainage the Hudson is dependent for its supply of water is covered with this "spruce-duff," which, in the early spring, is a solid body of ice, holding untold millions of gallons of the purest water, to be slowly thawed out and given up to this river during the summer. In many places, and in most seasons, part of this ice lasts through the whole summer; in most places it lasts well into the summer, and even after the ice is gone the "duff" absorbs and stores away the rain, and, like a prudent housewife with her confections, gives up her treasures in such a way as not to injure the health of her children with her lavishness, nor exhaust her larder before a fresh supply can reasonably be expected. I am convinced that careful investigation will demonstrate that the preservation of the "duff" is another and a very important reason why the destruction of the forests around the head-waters of the Hudson should be discontinued.