Aquifer

“ The shale above the sandstone and limestone aquifers in the figure is “tight” and does not permit water to escape upward to the level at which it enters the aquifers in the intake areas. The water is under natural pressure. When a well is drilled through the shale and into the aquifers, water rises, seeking its own level. Most of the deep wells in northern Illinois are artesian wells, though few of them flow at the surface anymore. ”

“ Effluents from maximum standard treatment processes, for instance, can be injected into underground strata as recharge water for aquifers—a process mentioned earlier as one alternative in the emerging package of water supply techniques—or may be spread over the surface of large areas of rural land [Pg 54a] where they serve as irrigation water and fertilizer combined, as well as soaking down into underlying aquifers. ”

“ Shallow and deep wells are those which are sunk through a permeable stratum, and form, as it were, reservoirs, into which the land springs may filter and accumulate; whilst artesian wells are those which [37] are sunk through an impervious upper stratum, to reach a subterranean water-bearing stratum lying, in its turn, upon an impervious upholding bed. In the former cases, the quantity of water obtainable is simply that which can filter through the sides of the well to replace the water removed, or which may accumulate in any reservoir formed below ”

“ Wells and springs are fed by ground water, which is merely natural drainage. Drainage water usually moves with the slope of the land. It always dissolves part of the mineral, vegetable, and animal matter of the ground over or through which it moves. In this way impurities are carried into the ground water and may reach distant wells or springs.
The great safeguards are clean ground and wide separation of the well from probable channels of impure drainage water. It is not [ 8 ] enough that a well or spring is 50 or 150 feet from a source of filth or that it is on higher ground. ”

“ The shore is bold, and, with the bed of the [121] river, is of gravel and rock formation, washed clean by an active current at all seasons of the year. Pumping works may be located at this point without any objectionable and expensive inlet-pipe; while the adjacent hills afford an excellent site for a storage reservoir, 307 feet above extreme low water, and 75 feet above the Garden of Eden Reservoir. On the lower level there is a fine plateau for locating, not only the pumping house, but subsiding reservoirs and filtering basins. ”

“ The wheel, being turned by oxen, delivers the water into a trough which passes into a reservoir, roughly fashioned with clay, from which, small channels of about ten inches in width radiate through the plantation. The fields, divided into squares like a chess-board, are thus irrigated by a succession of minute aqueducts. The root of this principle is the reservoir. A certain steady volume of water is required, from which the arteries shall flow throughout a large area of dry ground; thus, the reservoir insures a regular supply to each separate channel. ”

“ CHAPTER XIII. THE DISCHARGE OF SEA OUTFALL SEWERS. The head which governs the discharge of a sea outfall pipe is measured from the surface of the sewage in the tank, sewer, or reservoir at the head of the outfall to the level of the sea. As the sewage is run off the level of its surface is lowered, and at the same time the level of the sea is constantly varying as the tide rises and falls, so that the head is a variable factor, and consequently the rate of discharge varies. A curve of discharge may be plotted from calculations according to these varying conditions, but it is not necessary ”

“ There are several springs or sources for this aqueduct, and also several ponds to collect the rain-water, made in the clay, the water from all of which was collected into a central reservoir cut in the rock, with a large well over it. There are also seventeen wells visible in two lines, eight in one and nine in the other, converging and meeting in the central reservoir. The soil is clay upon stone. The specus is here a large tunnel cut in the rock, and the wells descend into it. ”

“ The formation may be looked upon as almost equally permeable in all directions, and the whole mass may be regarded as a reservoir up to a certain level, from which, whenever wells are sunk, water will always be obtained more or less abundantly, This view is very fairly borne out by experience, and the occurrence of the water is certainly not solely due to the presence of the fissures or joints traversing the rock, but to its permeability, which, however, varies in different districts. ”

“ If it meet a flat layer of gravel lying upon clay, and having a free outlet, it will follow the course of the gravel,—laterally,—and find the outlet; if it meet water which is dammed up in the soil, and which has an outlet at a certain elevation, as at the floor of a drain, it will raise the general level of the water, and force it out through the drain; if it meet water which has no outlet, it will raise its level until the soil is filled, or until it accumulates sufficient pressure, (head,) to force its way through the adjoining lands, or until it finds an outlet at the surface. ”

“ Sometimes the strata are disposed in the form of a basin. In this case, the water percolating through the more elevated ground—near [83] what may be called the rim—collects in the lower parts of the strata towards the centre, there forcing its way to the surface, if the upper impervious beds be thin; or, if otherwise, remaining a concealed reservoir, ready to yield its supplies to the shaft or boring-rod of the well-sinker, and sometimes forming a living fountain capable of rising many feet above the surface. It is in this way that what are called Artesian wells are formed. ”

“ The former part of the volume is occupied with discussion of the laws that govern stream-flow, rainfall, evaporation, ground storage, surface storage, and surface or flood flows. Gauging flows and the method of computing them are next considered. The local water systems are then described. The latter part of the book is devoted to generalizations as to water supply, chemical analyses, public water supplies, water power, evaporation, ground storage, effects of vegetation, and stream-flow; and a list of the developed water powers and the drainage systems is given in the appendix. ”

“ This sort of travel of underground water is common in many parts of the world. It should be clearly understood that such water does not flow freely as in a pipe along subterranean passageways, but rather it slowly works its way between the grains of porous rock. Where such water moves distinctly downward, and the porous layer has both above and below it an impervious rock layer like shale or clay, it gradually gets under greater and greater pressure. In some cases such pressure has actually been found by deep drilling to be equivalent to that of a column of water several thousand feet high. ”

“ The quantity of water mechanically disseminated through rocks, which serve merely as a natural reservoir for the time, must be, in the aggregate, very considerable, though it is impossible to form any very accurate estimate of it. Even in those rocks which merely supply springs, the amount of disseminated water must be enormous; for they so far resemble filters, that are necessarily charged with the fluid before they permit it to pass out. ”

“ A stream may be dammed and its water allowed to spread over the area to be studied, or the water may be carried to the proper place by deflecting the stream or by digging a canal. The construction of earth reservoirs makes it possible to obtain almost any per cent of soil water by varying the size of the reservoir or the height of the wall or bank. Near a base station, such as Minnehaha, where there is a simple system of water-works, the experimental area may be watered whenever desirable by means of a hose. ”

“ When the basset-edge of the strata is covered with gravel or sand, any body or stream of water will readily percolate downwards through it, and fill up the porous interstices between the coal-measures, till arrested by the face of a slip, which acts as a valve or flood-gate, and confines the water to one compartment of the basin, which may, however, be of considerable area, and require a great power of drainage. ”

“ In fact, its operators are successful only in regions in which ground water occurs in definite sheets in porous material, or in more or less clayey deposits, such as pebbly clay or till. In such regions (which are extremely common) few failures can occur, for wells can get water almost anywhere. Ground water occurs under certain definite conditions, and just as surface streams may be expected wherever there is a valley, so ground water may be found where certain rocks and conditions exist. ”

“ Besides this surface fitting of fields there is a wide application of additional methods aiming to conserve both rainfall and soil fertility, one of which is illustrated in Fig. 58, showing one end of a collecting reservoir. There were three of these reservoirs in tandem, connected with each other by surface ditches and with an adjoining canal. About the reservoir the level field is seen to be thrown into beds with shallow furrows between the long narrow ridges. The furrows are connected by a head drain around the margin of the reservoir and separated from it by a narrow raised rim. ”

“ In this way the outflow and inflow of the large reservoir are scarcely perceptible, and yet there is no difficulty in regulating the small one. With us, the reverse is done. If there is a shortage of water in the large reservoir we draw on the small one and, in order to increase the water in the large reservoir by perhaps an inch, we empty the small one altogether, or else in order to decrease the amount of water in the large reservoir by an inch, we fill the small one to overflowing. ”

“ The drainage of the whole tract irrigated by a canal must be carefully seen to. The subsoil water level of a tract of country is nearly always raised by an irrigation canal. The rise near to a canal or distributary is due to percolation from the channel and is inevitable. [3] The rise at places further away, if it occurs, is due to over-watering or to neglect of drainage. ”

“ In considering the principles of well supplies it is important to bear the following facts in mind. The crust of the earth, so far as it is permeable and above the sea-level, receives from rainfall its supply of fresh water. That supply, so far as it is not evaporated or absorbed by vegetation, passes away by the streams or rivers, or sinks into the ground. If the strata were uniformly porous the water would lie in the rock at different depths below the surface according to the previous quantity and distribution of the rainfall. ”

“ When burned, they are from twelve inches to fourteen inches long, with an interior diameter of from one to eight inches, and with a thickness of wall, (depending on the strength of the clay, and the size of the bore,) of from one-quarter of an inch to more than an inch. They are porous, to the extent of absorbing a certain amount of water, but their porosity has nothing to do with their use for drainage,—for this purpose they might as well be of glass. ”

“ A stream having a depth of flow sufficient to immerse solid matter held in suspension, to a certain extent lifts it and carries it forward. The entire surface is also exposed to the action of the current. A stream having an equal velocity but a less depth in proportion to the diameter of the solid matters to be transported, evidently has less transporting power. * * * An amount of sewage which can be properly transported by a circular sewer of a given size, cannot be as efficiently transported by one of larger diameter. ”

“ If the outcrop of the reservoir be notably above the site of the well, and if it be kept full by frequent rains, the “head” will be strong, though the water at the well will not rise to the level of the outcrop of the reservoir. Experience has shown that an allowance of about one foot per mile of subterranean flow should be made. ”

“ Deep wells usually yield more water than shallow driven wells, and the supply increases perceptibly when the water level in the well is lowered [Pg 36] by pumping. While surface wells draw upon the rainfall percolating in their immediate vicinity, deep wells are supplied by the rainfall from more remote districts. Deep wells are either non-flowing or flowing wells. When the hydrostatic pressure under which the water stands is sufficient to make it flow freely out on the surface or at the mouth of the well, we have a flowing, or true artesian well. ”

“ It is a common error, to imagine that some large stone water-course must be necessary to carry off so large a flow as will be collected by a system over a ten or twenty-acre field. Any one, however, who has watched the full flow of even a three-inch pipe, and observed the water after it has fallen into a nearly level ditch, will be aware, that what seems in the ditch a large stream, impeded as it is by a rough, uneven bottom, may pass through a three inch opening of smooth, well-jointed pipes. ”

“ When the stratum in which the water is found is very porous, as in the case of gravel and some sorts of chalk, the water flows freely; and a yield has been obtained in such situations as great and rapid as the pump has been able to lift, that is 600 gallons an hour. ”

“ When sinking in gravel or clay, the bottom of the well tube is liable to become filled up by the material penetrating through the holes; and before a supply of water can be obtained, this accumulation must be removed by means of the cleaning pipes. ”

“ Many orifices through which water at first only dribbled were thus caused to discharge water with great force, and entirely free from sand, against the opposite side of the well, while the general result was to increase the inflow of water many times, and to entirely prevent the intrusion of sand. Where, however, a firm rock of any kind is encountered, the yield of a well (under a given head of water) can only be increased by enlargement of the main well in depth or diameter, or by boreholes or adits. ”