EFFECT OF DRAINAGE ON STREAMS AND RIVERS.
Drainage Hastens the Supply to the Streams, and thus Creates
Freshets.--Effect of Drainage on Meadows below; on Water
Privileges.--Conflict of Manufacturing and Agricultural
Interests.--English Opinions and Facts.--Uses of Drainage
Water.--Irrigation.--Drainage Water for Stock.--How used by Mr.
Mechi.
The effect of drainage upon streams and rivers, has, perhaps, little to
interest merely practical men, in this country, at present; but the time
will soon arrive, when mill-owners and land-owners will be compelled to
investigate the subject. Men unaccustomed to minute investigation, are
slow to appreciate the great effects produced by apparently small
causes; and it may seem to many, that the operations of drainage for
agriculture, are too insignificant in their details, perceptibly to
affect the flow of mill-streams and rivers. A moment's thought will
convince the most skeptical, that the thorough-drainage of the wet
lands, even of a New England township, must produce sensible effects
upon the streams which convey its surplus water toward the sea.
In making investigations to ascertain what quantity of water may be
relied upon to supply a reservoir, whether natural or artificial, for
the use of a town or city, a survey is first taken of the district of
territory which naturally is drained into the reservoir, and thus the
number of square miles of surface is ascertained. Then the rain-tables
are consulted, and the fall of rain upon the surveyed district is
computed. The ascertained proportion of rain-fall, which usually goes
off by evaporation, is then deducted, which leaves with sufficient
accuracy, the amount of water which flows both upon the surface, and
through the soil, to the reservoir. With proper deductions for waste by
freshets, when the water will overflow the reservoir, and for other
known losses, a reliable estimate is readily made, in advance, of the
quantity of water supplied to the reservoir.
Now, these reservoirs Nature has placed in all our valleys, in the form
of lakes and ponds, and the drainage into them is by natural springs and
streams; and the annual amount of the water thus naturally flowing into
them may be readily computed, if the area within their head-waters be
known. If the earth's surface were, like iron, impervious to water, the
rain-water would come in torrents down the hill-sides, and along the
gentle declivities, into the streams, creating freshets and inundations
in a few hours. But instead of that, the soft showers fall, often on the
open, thirsty soil, and so are gradually absorbed. A part of the
rain-water is there held, until it returns by evaporation, to the
clouds, while a part slowly percolates downward, finding its way into
swamps and springy plains, and finally, after days or weeks of
wandering, slowly, but surely, finds its outlet in the stream or pond.
If now, this surplus of water, this part which cannot be evaporated, and
must therefore, sooner or later, enter the stream or pond, be, by
artificial channels, carried directly to its destination, without the
delay of filtration through swamps and clay-banks; the effect of rain to
raise the streams and ponds, must be more sudden and immediate.
Agricultural drains furnish those artificial channels. The flat and
mossy swamp, which before retained the water until the Midsummer
drought, and then slowly parted with it, by evaporation or gradual
filtration, now, by thorough-drainage, in two or three days at most,
sends all its surplus water onward to the natural stream. The stagnant
clay-beds, which formerly, by slow degrees, allowed the water to filter
through them to the wayside ditch, and then to the river, now, by
drainage, contribute their proportion, in a few hours, to swell the
stream. Thus, evaporation is lessened, and the amount of water which
enters the natural channels largely increased; and, what is of more
importance, the water which flows from the land is sent at once, after
its fall from the heavens, into the streams. This produces upon the
mill-streams a two-fold effect; first, to raise sudden freshets to
overflow the dams, and sweep away the mills; and, secondly, to dry up
their supply in dry seasons, and to diminish their water-power.
Upon the low meadows which border the streams, the effects of the
drainage of lands above them are various, according to their position.
In many cases, it must subject them to inundation by Summer freshets,
and must require for their protection, catch-waters and embankments, and
large facilities for drainage.
The effect of drainage upon "water privileges," must inevitably be, to
lessen their value, by giving them a sudden surplus, followed by
drought, instead of a regular supply of water. Water-power companies and
mill-owners are never careless of their interests. Through the patriotic
desire to foster home-manufactures, our State legislatures have granted
many peculiar privileges to manufacturing corporations. Indeed, all the
streams and rivers of New England are chained to labor at their wheels.
Agriculture has thus far taken care of herself, but is destined soon to
come in collision with the chartered privileges of manufactures. Many
questions, touching the right of land-owners to change the natural flow
of the water, to the injury of mill-owners; many questions touching the
right of mill-owners to obstruct the natural course of streams, to the
injury of the farmer, will inevitably arise in our Courts. Slowly, and
step by step, must the lesser interest of manufactures, recede before
the advance of the great fundamental interest of agriculture, until, in
process of time, steam, or some yet undiscovered giant power, shall put
its hand to the great wheel of the factory and the mill, and the pent-up
waters shall subside to their natural banks.
That these are not mere speculations of our own, may be seen from
extracts which will be given from answers returned by distinguished
observers of these matters in England and Scotland, to a question
proposed to them as to the actual effects produced by extensive
drainage. Some diversity of opinion is observable in the different
replies, which were made, independently in writing, and so are more
valuable.
_Mr. Smith._--"During dry periods, more particularly in Summer, the
water in the streams is greatly lessened by thorough-draining; for
there is so great a mass of comparatively dry and absorbent soil to
receive the rain, that Summer showers, unless very heavy and
continuous, will be entirely absorbed."
_Mr. Parkes._--"The intention and effect of a complete and
systematic under-drainage is the liberation of the water of rain
more quickly from the land than if it were not drained; and
therefore the natural vents, or rivers, very generally require
enlargement or deepening, in order to pass off the drainage water
in sufficiently quick time, and so as to avoid flooding lower
lands.
"The sluggish rivers of the midland and southern counties of
England especially, oppose great obstacles to land-drainage, being
usually full to the banks, or nearly so, and converted into a
series of ponds, by mill-dams erected at a few miles distance below
each other; so that, frequently, no effectual drainage of the
richest alluvial soil composing the meadows, can be made, without
forming embankments, or by pumping, or by resort to other
artificial and expensive means.
"The greater number of the corn and other water-mills throughout
England ought to be demolished, for the advantage of agriculture,
and steam-power should to be provided for the millers. I believe
that such an arrangement would, in most cases, prove to be
economical both to the landholder and the miller.
"Every old authority, and all modern writers on land drainage in
England, have condemned water-mills and mill-dams: and if all the
rivers of England were surveyed from the sea to their source, the
mills upon them valued, the extent of land injured or benefitted by
such mill-dams ascertained, and the whole question of advantage or
injury done to the land-owner appreciated and appraised, I have
little doubt but that the injury done, would be found so greatly to
exceed the rental of the mills, deduction being made of the cost of
maintaining them, that it would be a measure of national economy,
to buy up the mills, and give the millers steam-power."
_Mr. Spooner._--"The effect which extensive drainage produces on
the main water-courses of districts, is that of increasing the
height of their rise at flood times, and rendering the flow and
subsidence more rapid than before. I have repeatedly heard the
River Tweed adduced as a striking instance of this fact, and that
the change has taken place within the observation of the present
generation."
_Mr. Maccaw._--"It has been observed that, after extensive
surface-drainage on the sheepwalks in the higher parts of the
country, and when the lower lands were enclosed by ditches, and
partially drained for the purposes of cultivation, all rivers
flowing therefrom, rise more rapidly after heavy rains or falls of
snow, and discharge their surplus waters more quickly, than under
former circumstances."
_Mr. Beattie._--"It renders them more speedily flooded, and to a
greater height, and they fall sooner. Rivers are lower in Summer
and higher in Winter."
_Mr. Nielson._--"The immediate effect of the drainage of higher
lands has often been to inundate the lower levels."
In a prize essay of John Algernon Clarke, speaking of the effect of
drainage along the course of the River Nene, in England, he says:
"The upland farms are delivering their drain-water in much larger
quantities, and more immediately after the downfall, than formerly,
and swelling to the depth of three to six feet over the 20,000
acres of open ground, which form one vast reservoir for it above
and below Peterborough. The Nene used to overflow its banks, to the
extreme height, about the third day after rain: the floods now
reach the same height in about half that time. Twelve hours' rain
will generally cause an overflow of the land, which all lies
unembanked from the stream; and where it is already saturated,
this takes place in six or even in two hours. Such a quick rise
will cause one body of flood-water to extend for forty or fifty
miles in succession, with a width varying from a quarter of a mile
to a mile; but it stays sometimes for six weeks, or even two
months, upon the ground. And those floods come down with an
alarming power and velocity--bridges which have stood for a century
are washed away, and districts where floods were previously unknown
have became liable to their sudden periodical inundations. The land
being wholly in meadow, suffers very heavily from the destruction
of its hay. So sudden are the inundations, that it frequently
happens that hay made in the day has, in the night been found
swimming and gone. A public-house sign at Wansford commemorates the
locally-famed circumstance of a man who, having fallen asleep on a
hay-cock, was carried down the stream by a sudden flood: awakening
just under the bridge of that town, and being informed where he
was, he demanded, in astonishment, if this were 'Wansford in
England.'"
The fact that the floods in that neighborhood now reach their height in
half their former time, in consequence of the drainage of the "upland
farms," is very significant.
Mr. Denton thus speaks upon the same point, though his immediate subject
was that of compulsory outfalls.
"Although the quantity of land drained was small, in comparison to
that which remained to be drained, the water which was discharged
by the drainage already effected found its way so rapidly to the
outfalls, that the consequences were becoming more and more
injurious every day. The millers were now suffering from two
causes. At times of excess, after a considerable fall of rain, and
when the miller was injuriously overloaded, the excess was
increased by the rapidity with which the under-drains discharged
themselves; and as the quantity of water thus discharged, must
necessarily lessen the subsequent supply, the period of drought was
advanced in a corresponding degree. As the millers already saw
this, and were anticipating increasing losses, they would join in
finding a substitute for water-power upon fair terms."
It is not supposed, that any considerable practical effects of drainage,
upon the streams of this country, have been observed. A treatise,
however, upon the general subject of Drainage, which should omit a point
like this, which must, before many years, attract serious attention,
would be quite incomplete. Whether the effect of a system of
thorough-drainage make for or against the interest of mill and meadow
owners on the lower parts of streams, should have no influence over
those who design only to present the truth, in all its varied aspects.
As some compensation for the evils which may fall upon lands at a lower
level, by drainage of uplands, it may be interesting to notice briefly
in this place, some of the uses to which drainage-water has been
applied, for the advantage of lower lands. In many cases, in Great
Britain, the water of drainage has been preserved in reservoirs, or
artificial ponds, and applied for the irrigation of water meadows; and
as is suggested by Lieut. Maury, in a letter quoted in our introductory
chapter, the same may, in many localities, be done in this country, and
thus our crops of grass be often tripled, on our low meadows. In many
cases, water from deep drains, will furnish the most convenient supply
for barn yards and pastures. It is usually sufficiently pure and cool in
Summer, and is preferred by cattle to the water of running streams.
On Mr. Mechi's farm at Tiptree Hall, in England, we observed a large
cistern, in which all the manure necessary for the highest culture of
170 acres of land, is liquified, and from which it is pumped out by a
steam engine, over the farm. All the water, which supplies the cistern,
is collected from tile drains on the farm, where there had before been
no running water.