Freshwater

“ By JAMES G. NEEDHAM, Ph.D., Professor of Limnology and General Biology in Cornell University, and JOHN T. LLOYD, A.B., Assistant in Limnology in Cornell University.
This book is a broad presentation of the field of freshwater biology, primarily in its scientific aspects, also in its relation to commercial, civic, aesthetic and public health interests of man. There is no book in the English language covering the field. Copiously illustrated with photographs from Nature. ”

“ Of the whole earth's surface the freshwaters form a very small fraction, about a hundredth, but they make up for their smallness by their variety. We think of deep lake and shallow pond, of the great river and the purling brook, of lagoon and swamp, and more besides. There is a striking resemblance in the animal population of widely separated freshwater basins: and this is partly because birds carry many small creatures on their muddy feet from one water-shed to another ”

“ River-water is in general purer than spring-water; as the neutral salts washed down from the earth decompose each other, except perhaps the marine salt; and the earths, with which spring-water frequently abounds, is precipitated; yet it is not improbable, that the calcareous earth dissolved in the water of many springs may contribute to our nourishment, as the water from springs, which contain earth, is said to conduce to enrich those lands, which are flooded with it, more than river water. ”

“ The river is all the time bringing down fresh-water, and as the beach cuts off the sea, the water in the lagoon begins to grow fresh. From year to year the water tastes less like sea water, and more like river water. The poor plants were meant for the sea, and the brackish water does not suit them. The beautiful purple mosses, the long brown weeds, and the bright green sea-lettuce fade and die. They fall down, and make a black mould on the bottom of the lake. The poor fish feel it too. The clams and oysters miss the salt-water. ”

“ Rivers are to the globe what the veins are to the animal organization. They pick up the surplus moisture not needed in the growth of vegetation and for the sustenance of animal life, and carry it on, together with the débris that it gathers in its course, to the great reservoirs, the seas and oceans, where it is redistilled and purified by the action of the sun's rays. From here it is carried back in the form of invisible moisture and again precipitated in the purified state, to help carry on the great operations of growth—animal and vegetable. ”

“ Water is never found pure in nature; it is nearly pure when gathered in an open field, after a heavy rainfall, or from springs. For town and city supply, surface-water is furnished by some adjacent pond or lake. ”

“ RIVER, a current or stream of fresh water, which flows in a bed or channel, from its spring or source, and empties itself into the sea.
Rivers form one of the chief ornaments of the globe: while they serve not only to carry off superfluous rains and springs; but, from the great numbers and varieties of fish they contain, likewise afford a grateful food to mankind. They also greatly tend to fertilize the soils through which they flow; and the Mud, that subsides at the bottom, as well as the weeds which vegetate on their banks, form a valuable fertilizing Manure. ”

“ Water arising by land-floods brings along with it much of the most soluble parts of the manure from the higher lands to the lower ones. River-water in its clear state and those springs which are called soft are less beneficial for the purpose of watering lands, as they contain less earthy or saline matter; and water from dissolving snow from its slow solution brings but little earth along with it, as may be seen by the comparative clearness of the water of snow-floods. ”

“ The water imbibed by the soil in winter sinks until it meets a more or less impermeable or a saturated stratum, and then, by unseen conduits, slowly finds its way to the channels springs, or oozes out of the ground in drops which unite in rills, and so all is conveyed to the larger streams, and by them finally to the sea. The water, in percolating through the vegetable and mineral layers, acquires their temperature, and is chemically affected by their action, but it carries very little matter in mechanical suspension. ”

“ In later times, when an abundant and various soil covered the earth, when every river brought down to the ocean, not only its yearly tribute of mud or clay or lime, but the débris of animals and plants that lived and died in its waters or along its banks, when every lake and pond deposited at its bottom in successive layers the lighter or heavier materials floating in its waters and settling gradually beneath them, the process by which stratified materials are collected and gradually harden into rock is more easily understood. ”

“ The lake possesses no such intermediate vegetation. As the water freshens in its middle reaches, the algæ become dwarfish and ill-developed; one species after another ceases to appear, as the habitat becomes wholly unfavorable to it, until at length we find, instead of the brown, rootless, flowerless fucoids and confervæ of the ocean, the green, rooted, flower-bearing flags, rushes, and aquatic grasses of the fresh water. Many thousands of years have failed to originate a single intermediate plant. ”

“ The springs evidently have their source deep down in the earth and the flow of water never varies. When the water from the different springs is all united it forms a good sized brook. The water is conducted through pipes into the bath house, where it supplies a row of bath-tubs with water of any desired temperature. The surplus water flows into a large earthern tank or artificial lake and is used for irrigating a small farm that produces grain, fruits and vegetables. ”

“ 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. ”

“ Deep lakes are thus the best sources of water-supply for cities, for in summer they supply relatively cool water and in winter relatively warm water. Besides, the number of organisms in deep lakes is less than in small shallow lakes, in which there is a much higher temperature in summer, and consequently much greater organic growth. The deposits, which are formed along the shores and on the floors of lakes, depend on the geological structure and nature of the adjacent shores. ”

“ In view of certain investigations which have been made of water flora and fauna for special purposes, I add a few words on the place of the water flora in the economy of Nature. The lower vegetation is of very great importance, especially the microscopic plants, innumerable plantations of which inhabit extensive tracts of all, and especially of northern, lakes. They move around in the water in masses or singly, changing the deep blue color of the spots destitute of organisms into green or dirty yellow. ”

“ When conditions are right—when sun, summer temperatures, low inflows from the river above, and a heavy concentration of nitrate and phosphate nutrients all combine to make of the upper estuary one vast inspired pool of fertility—the whole surface of the river may be covered with a thick bright emerald mat, and boats that pass at speed leave wakes of green instead of white. ”

“ Lakes having outlets are drained away as their basin rims are cut down by the outflowing streams,—a slow process where the rim is of hard rock, but a rapid one where it is of soft material such as glacial drift.
Lakes are effaced also by the filling of their basins. Inflowing streams and the wash of rains bring in waste. Waves abrade the shore and strew the debris worn from it over the lake bed. Shallow lakes are often filled with organic matter from decaying vegetation. ”

“ In the sheets of water which we find distributed over that and every other inhabitable inland basin, we see reservoirs or evaporating surfaces just sufficient for the supply of that degree of moisture which is best adapted to the well-being of the plants and animals that people such basins. ”

“ Or a brook, which is a tiny trout stream, babbles on through the meadows and pastures, and has its attractions too. A stream is always the chief artery of the land, as in it are found the life-giving elements. All the birds, all the plants, flock to its banks, and its wooded sides are hushed by the subdued hum of insects. There are tall green brackens—brackens unfurling their fronds to the light, and full of the atoms of beautiful summer. ”

“ River shells such as the mussel, land shells such as those of snails, the bones of fishes and of such land animals as suffer drowning at times of flood or are mired in swampy places, logs of wood, and the stems and leaves of plants are examples of the variety of the remains of land and fresh-water organisms which are entombed in river deposits and sealed away as a record of the life of the time, and as proof that the deposits were laid by streams and not beneath the sea. ”

“ Stately and slow that river moves down to the bay, into which it empties its load. The rain that falls on hundreds of square miles of territory flows into the streams that feed this trunk. The little spring that is the headwater of the system is but one of many pockets in the hillsides that hold the water that soaks into the ground and give it out by slow degrees. Surface water after a rain flows quickly into the streams. It is the springs that hold back their supply and keep the rivers from running dry in hot weather. ”

“ It seems as if the polar water is specially favourable for the development of pelagic plant life, which makes the flora, and consequently also the fauna, flourish as soon as the ice covering disappears and the water surface is exposed to the full sunlight of the long Arctic day. At the same time the temperature of the water uses, and thus the conditions for the chemical changes of matter and nutritive assimilation are much improved. ”

“ Generally speaking again, under the natural flow theory, a riparian owner can take water for domestic purposes only, such as water for the family, livestock, and gardening, and he is entitled to have the water in the stream or lake upon which he borders kept at the normal level. ”

“ Quantity of fresh water in American lakes.—About two-thirds of all the fresh water on the surface of the earth is contained in the great American lakes; and though there be in the northern, as compared with the southern hemisphere, so much less sea surface to yield vapour, so much more land to swallow up rain, and so many more plants to drink it in, yet the fresh-water courses are far more numerous and copious on the north than they are on the south side of the equator. ”

“ If it shall be found that nearly all the rainfall should go into the soil and thence into the under-drainage, coming out slowly and steadily by seepage and by springs into the streams, clear and pure, these streams should present nearly ideal conditions for water-food, for water-power and for stream-navigation. An ideal solution of the soil problem may therefore solve the greater part of the whole complex of problems of which navigation is the last term. ”

“ A river flowing to the sea or emptying itself into an inland lake, carries its burden of gravel, sand, and mud, and sooner or later, as the rate of flow slackens, it deposits the materials in the river-bed or on the floor of the sea or lake. ”

“ The rain, which is pure water, except for the little particles of various things floating in the air which it brings down with it, soaks into the ground, forming springs, and helps to swell the ponds and lakes and rivers, and so it gets mineral and other substances in it again, especially salt, which is found in small quantities in all spring-water, and this impure water is carried to the ocean again to be purified ”

“ In winter, of course, they are not needed. But throughout the long and rainless summer, when vegetation withers up and blows away, the steady sea-breeze keeps the wind-mills going, and these pump up water for a thousand irrigating purposes. ”

“ If the stream receives no water of another kind, or scarcely any, not only the rivers, but likewise the lakes which receive these waters, are of the same nature as the springs, and serve the same uses ”

“ During the hot summer-time, when the level fields through which they meander are quivering with heat-haze, and the pastures and hedgerows are ablaze with the wild [Pg 351] flowers which love fat pastures and flourish upon them, the upper waters are choked with luxuriant tangles of aquatic vegetation, and the current is barely sufficient, without the frequent application of scythe and water-rake to the thickets below water, to turn the rustic mills planted upon their banks. ”

“ A more plausible opinion is that the substitution of ground that is cultivated, and consequently spongy and absorbent, for the natural soil of the prairies, has furnished a reservoir for the rains which are absorbed by the earth and carried gradually to the river by subterranean flow, instead of running off rapidly from the surface, or, as is more probable, instead of evaporating or being taken up by the vigorous herbaceous vegetation which covers the natural prairie. ”

“ And while all this grand and complete arrangement supplies vegetation with its bathing and drinking, as said before, it has nothing to do with the living and lasting supply of our springs, lakes and rivers. They are fed from a never failing and almost unchanging source—that is, by the immense supply taken in at the polar holes in a river over 4,000 miles wide at each end of the Earth’s axis. ”

“ Even richer, if that be possible, than the fauna of the river, and at any rate more diverse, is that to be found at the proper season on the shores and surface of all the lakes and larger water-pools which lie within the forest and are filled either by the spring rains or by the full floods of the river. ”