Drainage basin

“ If we have only to take care of the water that falls on our own field, from the clouds, that is quite a different matter from draining the whole adjoining region, and requires a different mode of operation. If your field is in the middle, or at the foot, of an undrained slope, from which the water runs on the surface over your land, or soaks through it toward some stream or swamp below, provision must be made not only for drainage of your own field, but also for partial drainage of your neighbor's above, or at least for defence against his surplus of water. ”

“ A consideration, too, of the varying inclinations of surface, of which instances will frequently occur in the same field, necessitates a departure from uniformity, not in direction only, but in intervals between drains. Take, for instance, the ordinary case of a field, in which a comparatively flat space will intervene between quickly rising ground and the outfall ditch. It is clear that the soak of the hill will pervade the soil of the lower ground, let the system of drainage adopted be what it may ”

“ Whether, in a particular case, a header alone will be sufficient to cut off the flow of water from the higher land, or whether, in addition to the header, an open catch-water may be required, must depend upon the quantity of water likely to flow through or upon the land. An under-drain might be expected to absorb any moderate quantity of what may be termed drainage-water, but it cannot stop a river or mill-stream; and if the earth above the tiles be compact, even water flowing through the soil with rapidity, might pass across it. ”

“ The heavy storms and showers fill the surface soil beyond saturation, and the water gushes out, literally, into the cellars and other low places. A dry well, sunk through the clay, conducts this water into the gravel bed, and this carries it away. This idea is often applied to land drainage. It is believed that there are immense tracts of fertile land at the West, upon limestone, where the surface might readily be relieved of surplus water, by conducting the mains into wells dug for the purpose. ”

“ We cannot, however, against the overwhelming weight of authority, and against the reasons for deeper drainage, which, to us, seem so satisfactory, conclude, that even three feet is, in general, deep enough for under-drains. Three-foot drains will produce striking results on almost any wet lands, but four-foot drains will be more secure and durable, will give wider feeding-grounds to the roots, better filter the percolating water, warm and dry the land earlier in Spring, furnish a larger reservoir for heavy rains, and, indeed, more effectually perform every office of drains. ”

“ The whole area of land which naturally discharges toward the drain is not always taken into account. It is generally thought that land lying at some distance from the drain, though sloping toward it, does not affect the capacity required for the drain, whereas in times of heavy rains, when drains are taxed to their utmost, water flows from those more distant parts over the surface to the ground acted upon by the tile drain. We must then provide for the drainage not only of land contiguous to the drains but for an additional amount of water coming from adjoining slopes. ”

“ He states, that there are large tracts of land having clay soil, with sand or gravel beneath the clay, which yet need drainage, and suggests that this may be effected by merely boring frequent holes, and filling them with pebbles, without ditches. In all such soils, if the mode suggested prove insufficient, large wells of proper depth, stoned up, or otherwise protected, might obviously serve as cheap and convenient outlets for a regular system of pipe or stone drains. ”

“ Immense damage has been done by “water-logging” of the soil when irrigation water has been supplied to a tract of flat country and the clearance and improvement of the natural drainages has not been attended to. Any drainages crossed by the banks of the irrigation channels should be provided with syphons or aqueducts or else the drainage diverted into another channel. Very frequently the main line of a canal—whether great or small—in the upper reaches near the hills, has to cross heavy drainage channels or torrents and large and expensive works are required for this. ”

“ Remembering that on the map, the line of steepest descent is exactly perpendicular to the contour lines of the land, it will be profitable to study carefully the system of drains first laid out, erasing and making alterations wherever it is found possible to simplify the arrangement.
Strictly speaking, all angles are, to a certain extent, wasteful, because, if two parallel drains will suffice to drain the land between them, no better drainage will be effected by a third drain running across that land. ”

“ The outlet is the place, of all others, where obstruction is most likely to occur. Everywhere else the work is protected by the earth above it, but here it is exposed to the action of frost, to cattle, to mischievous boys, to reptiles, as well as to the obstructing deposits which are discharged from the drains themselves. In regular work, under the direction [177] of engineers, iron pipes, with swing gratings set in masonry, are used, to protect permanently this important part of the system of drainage. ”

“ The fact is, that Nature drains thoroughly the greater portion of all our lands; so that artificial drainage, though it may remove surplus water from them more speedily in Spring, cannot make them more dry in Summer. And what thus happens naturally, on most of the land, without injury, cannot be a dangerous result to effect by drainage on lands of similar character. By thorough-drainage, we endeavor to make lands which have an impervious or very retentive subsoil near the surface, sufficiently open to allow the surplus water to pass off, as it does naturally on our most productive upland. ”

“ Although the rain-fall in England is much less in quantity and much more regular than in this country, yet it is believed that the use of two-inch pipes will be found abundantly sufficient for the admission and conveyance of any quantity of water that it may be necessary to carry off by drainage in common soils. In extraordinary cases, as where the land drained is a swamp, or reservoir for water which falls on the hills around, larger pipes must be used. ”

“ 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. ”

“ This has thus far, been our own poor and unsatisfactory mode of protecting our drains. It is only better than none, but it is not permanent, and we hope to see some successful invention that may supply this want. So far as we have observed, no such precaution is used in this country; and in England, farmers and others who take charge of their own drainage works, often run their pipes into the mud in an open ditch, and trust the water to force its own passage. ”

“ Both here and in England, much of the land requires no under-draining, as it has already a subsoil porous enough to allow free passage for all the surplus water; and it is no small part of the utility of understanding the principles of drainage, that it will enable farmers to discriminate—at a time when draining is somewhat of a fashionable operation with amateurs—between land that does and land that does not require so expensive an operation. ”

“ It should be unnecessary to state that no effort should be spared to see that there is sufficient fall, and for the purpose of ensuring this it is often necessary to take the levels. Sufficient thought is rarely given to drainage. The site of the main drains and the whole scheme of drainage should be very carefully studied, and it is of special importance to take into consideration the nature of the subsoil and position of the water level. In peat, on the other hand, it is frequently advisable to drain below the peat, even if this extends to a depth of 6 feet or more. ”

“ It is easily demonstrable, too, that drains at right angles with the mains, and so parallel with each other, are the shortest possible drains in land that needs uniform drainage. They take each a more uniform share of the water, and serve a greater breadth of soil than when laid at acute angles. ”

“ In proportion to the completeness and efficiency of the means for the removal of surplus water from the soil:—in proportion, that is, to the degree in which the improved tile drainage described in these pages is adopted,—will be the completeness of the removal of the causes of disease. So far as the drying of malarious lands is concerned, it is only necessary to construct drains in precisely the same manner as for agricultural improvement. ”

“ 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. ”

“ While we would not lay down an arbitrary arrangement for any farm, except upon a particular examination, and while we would by no means advocate what has been called the gridiron system—of drains everywhere at equal depths and distances—yet some system is absolutely essential, in any operation that approaches to thorough drainage. ”

“ Wherever one stream flows into another, there must be more or less interruption of the course of each. If the water from the minors enters the main with a quick fall, the danger of obstruction in the minor, at least, is much lessened. A frequent cause of partial failure of drains, is their not having been laid with a regular inclination. If, instead of a gradual and uniform fall, there should be a slight rising in the bed of a drain, the descending water will be interrupted there till it accumulate so high as to be above the level of the rising. ”

“ The lateral drains themselves constitute the real drainage of the field, for, although main lines take water from the land on each side, their action in this regard is not usually considered, in determining either their depth or their location, and they play an exceedingly small part in the more simple form of drainage,—that in which a large tract of land, of perfectly uniform slope, is drained by parallel lines of equal length, all discharging into a single main, running across the foot of the field. ”

“ By some it was urged that drainage is necessary to lessen the chance of the earthwork slipping. Others contended that any drain which penetrates the dam must facilitate the percolation of water from the reservoir. It is clear that some of the speakers regarded the dam downstream of the core-wall as being partly staunch, and some as being wholly support. If for any reason there seems a chance of water leaking through the core-wall, it is desirable to regard the earth-filling next to it as staunch. ”

“ Very often, drains are filled up and ruined by these deposits; and, unless the fall be considerable, and the drain be laid with even descent, if earth of any kind find entrance, it must endanger the permanency of the work. To guard against the admission of everything but water, lay drains deep enough to be beyond the danger of water bursting in, in streamlets. Water should enter the drain at the bottom, by rising to the level of the tiles, and not by sinking from the surface directly to them. If the land is sandy, great care must be used. ”

“ The modern drainage system may be assumed to have been at first consequent, that is, dependent for its direction on the slope of the uplifted plain, but it was not long before the effect of geologic structure began to make itself felt. ”

“ It is well always to interrupt the direct descent of water by percolation from the surface to the top of the tiles, because, in passing so short a distance in the soil, the water is not sufficiently filtered, especially in soil so recently disturbed, but is likely to carry with it not only valuable elements of fertility, but also particles of sand, which may obstruct the drain. ”

“ Water goes down, then, by its own weight, unless there is something through which it cannot readily pass, to bring it out at the surface. It will go into the drains, only because they are lower than the land drained. It will never go upward to find a drain, and it will go toward a drain the more readily, in proportion as the descent is more steep toward it. ”

“ When the water cannot be discharged from the outfall at all times by gravitation, [440] we must enlarge the main and tributary drains, so that they may serve as reservoirs to contain the drainage water during the time that the outfall sluice is closed in consequence of the water in the river or the sea, where the outfall sluice may be placed, being higher than the level of the water in the main and interior drains. ”

“ Sand scarcely diminishes at all in bulk by drying; but peat shrinks one-fifth in bulk, and strong agricultural clay nearly as much." By laying drains in land, we take from it that portion of the water that will run out at the bottom. The sun, by evaporation, then takes out a portion at the top. The soil is thus contracted, and, as the ends of the field cannot approach each other, [325] both soil and subsoil are torn apart, and divided by a network of cracks and fissures. ”