toads, whether the Rhine river or the North Atlantic, continue to be vital links in transportation.
Modern men are becoming increasingly aware of the resources contained in the many waters of the world. From the seas and oceans come foods in the form of fish, plants,
and other marine life. Many persons believe that the world will become more and more dependent on food from the oceans as population increases and as much of the land is worn
out by continued crop production. Seaweed, in addition to furnishing food, provides potash and iodine as well as stuffing for cushions and mattresses. Salt water furnishes salt and,
recently, has furnished large quantities of magnesium. It is even a possible large-scale source of an additional fresh water supply, since saltwater conversion processes have been perfected.
The sea contributes other materials also, from furs and hides to pearls and sponges. Similarly, many fresh waters also provide fish, shells, and furs.
Whether seashore, tree-lined brook or river, small pond, or large lake, water is useful to swim in, to go boating and fishing on, or just to look at. Many a small lake has proved to
be a “gold mine” when developed for resort purposes, and many a piece of land has sold for a sum far above ordinary market price merely because it contained a bubbling spring or a small
stream. Even the little lily ponds or artificial lagoons in a city park reflect the artistic and the recreational value of water.
3.2 Oceans and Seas
As previously noted, most of the earth is covered by interconnected bodies of water. Not only do these bodies vary great1 in size and depth, but also in the many patterns which
they produce as they trace their edges against the land. To draw the outlines of the major water bodies is to delineate automatically the outlines of the land masses.
Names and Terms. In order of decreasing size, the oceans are the Pacific, Atlantic, Indonesian, Oceans is sometimes referred to as a sea.The term sea is indefinite. It is applied,
in general, to bodies of water which are conspicuously smaller than the oceans and which are “tucked into” the land in such fashion as to leave only narrow oceanic connections or no
connections at all. Ocean bottoms and depths. Formerly, it was thought that the bottoms of the great water bodies were mainly comprised of smooth plains and monotonous plateaus. It
was reasoned that sediments washed in from the land, materials dropped physically and precipitated chemically in waters far offshore, and the accumulation of skeletons of myriads
of marine organisms would collect in low places until inequalities of sea bottom would cease to exist. It is now known that the floors of the seas and oceans possess landforms nearly as
varied as those of the continents themselves. There are towering mountain ranges, broad plateaus, hilly regions, and plains of varying relief.
In addition to the major landforms. There are countless smaller ones. Even the ancient notion of ocean basins has broken down partly. For example, we still speak of the
Pacific Basin as though it were a washbowl whose sides slope uniformly downward to a central low spot. The facts were brought to light largely through the invention and use of the
sonic depth finder. This instrument sends an impulse downward through the water and receives the echo of that impulse back at the instrument a bit later. The speed of the impulse
through the water is known and by recording the time necessary for it to travel to the bottom and back, and dividing by two, the depth of the water can be calculated. The depth finder has
been so perfected that a vessel traveling at full speed can make a continuous record of depths along its course. With thousands of soundings thus quickly and cheaply obtained, it is a
relatively simple matter to prepare contour maps of the ocean bottom. As might be expected, most of the shallow waters are adjacent to the edges of the
continents and large islands, although there are some which occur even in mid-ocean. The
shallow waters next to the continents lie on the continental shelf a gently sloping extension of the continent itself and a reminder of the times when large shallow seas covered most of what
are now the land masses, either in whole or in part at a given time. The oceanic regions of greatest depth have their bottoms so far below the surface that they are known as deeps.
Those huge synclinal down-folded depressions which lie out in front of great mountain arcs are known as fore-deeps. They owe their existence to the same crustal deformations which
produced neighboring hills or mountains. Water Movements. While one may think of the seas and oceans in only two
dimensions, as “so long and so wide,” they are actually three-dimensional. Their restless waters move not only horizontally, but also vertically and obliquely. Some of these
movements result in the transportation of significant amounts of water from one part of the ocean to another, like the flow of polar waters equator ward and of tropical waters toward the
poles, or like the up-welling of water from a depth of several hundred feet and the slow descent of surface waters.
Other movements, such as storm, tidal, and seismic waves, do not result in any significant transportation. In tidal movements, the waters merely bulge in obedience to the
mass attraction df the moon and sun. Because the earth notates, the bulges travel, but the water in them merely goes up and down and there is little, if any, transportation. The
movements which do result in transportation of large quantities of ocean water are called currents. These are of many sorts, some are cold and others warm, some are highly saline arid
others only weakly saline, some operate at great or intermediate depths and others move at and near the surface. Of them all, it is those at or relatively near the surface which are most
significant geographically. It is these surface currents which affect ship navigation, the presence and numbers of commercial fish, and water and air conditions in shore and near-
shore areas. Their effects on air climatic conditions will be mentioned later in the discussion of climatic controls in
The warm surface waters which move toward and tend to pile up against the Eastern parts of islands and continental shores of much of the tropics are forced to turn poleward.
This is a result primarily of their bumping into the land and secondarily of deflection incident to their movement on the surface of a rotating earth.
Ice conditions. Some small icebergs are derived from local valley glaciers along mountainous coasts, like those of southeastern Alaska, but they are short-lived and few in
number. The bergs which are large and numerous come from the Greenland ice and from the vast ice layers of Antarctica. The tabular Antarctic bergs, unlike the jagged Greenland type
do not menace any major shipping lanes, nor do they regularly move as far from points of origin. Only the occasional whaling and scientific exploration vessel must be on guard
against them, particularly during fogs or storms. The extreme equatorial limits of icebergs sizable enough to be hazardous are shown.
Considering the great size of the seas and oceans, the smaller water bodies seem insignificant. However, significance cannot be measured by size alone. A lake, or group of
lakes, may have a local or even an extralocal importance far out of proportion to the area or depth of water involved. Lakes may furnish domestic and industrial water, transportation,
fish, and recreational opportunities. in such mariner, they may be more truly and directly entwined with the lives of many people than are seas and oceans.
In contrast to the vast regions with few or no lakes, there are others in which lakes are numerous. Most of the large regions with numerous lakes are areas of glaciation, chiefly
of continental glaciation and to a lesser extent of valley glaciation. In such regions, the characteristic unevenness resulting from both glacial scour and glacial deposition normally
results in numerous depressions which have no low-level outlet. It so happens that most such
depressions are in humid climates so that there is abundant water to fill them. Streams are busily engaged in cutting through the rims, but there has been insufficient time since the
glaciers disappeared for the streams to have drained the lakes of their waters or for the lakes to have become filled with plants and sediment. Some lake regions were not glaciated and
lakes in them owe their origin to other causes. The lines of moving water which thread their way across the surface of the land vary
in size from mere rills and brooks to broad, full-flowing rivers. Where land masses and drainage basins are large and precipitation plentiful, streams are numerous and permanent;
where drainage basins are small and especially where precipitation is meager, streams are small and intermittent.
The presence or lack of streams affects man’s movements and settlements in a wide variety of ways. Primitive man camped at places along or neat streams where water and fish
were available and where he had a highway for his raft or crude boat. Man, primitive or not, has often settled on islands in rivers where the encompassing water provided a barrier against
enemies. River junctions have been strategic points for the control of, and participation in, the trade which moved on the streams. Rivet mouths, making union with the sea, gave access to
ocean routes. When industrial centers arose, the riverbank position provided large quantities of water for rapidly growing urban populations and supplied water for power and the
processing of materials. In many areas, the fine dark alluviums of river flood plains attracted agricultural populations. In the eastern United States and to a lesser extent in the drier West,
the bulk of the westward movement was locally carried and directed by the streams which floated men and their belongings. These are only a few of the ways in which rivers and men
have been and, in many ways, still are related. In regions of humid climate, all except the smallest tributaries are normally
permanently flowing waters. Their volumes may vary with seasonal differences in the
amount of water available from precipitation, surface drainage, and underground drainage. High and low stages represent ordinary behavior, but the streams are always there. In some
streams, there may be little difference between highest and lowest water. This is true particularly where rainfall is of comparatively even distribution throughout the year and
where waters are not partly locked up in the form of ice during the winter season. Variations in flow are significant as part of the physical picture of an area, but they are more significant
in their relations to man and his activities. It is readily apparent that a permanent stream which is in, high flood during part of the year and barely flows at another time is of much less
utility than one which maintains a relatively uniform level. The most common stream pattern is the dendritic pattern. The term “dendritic”
means treelike, and a stream system with this plan possesses a main trunk and branches which join it at acute angles. This pattern develops where the running water is cutting rocks,
whether loose or consolidated, which are relatively uniform in their reaction to erosion. Thus, this pattern will occur in a region where streams are running on granite alone, or on a
homogeneous sandstone, or wholly on loose clays, and so on. Presents the actual plans of some streams large and small, which have the dendritic pattern.
Other major stream patterns are the trellis, radial, annular, braided, and glacially deranged. Over the land surface as a whole, they are much less common than the dendritic
pattern, but in areas where they do occur, they are just as observable and significant. The trellis pattern is comprised of relatively straight lines which join each other at right angles.
This pattern occurs where there is a definite banding of the rocks or a pattern of structural weakness in the earth’s crust. The radial pattern is found where there is a centrally located
area of higher land from which the streams flow out in all directions like spokes from the hub of a wheel. Also occurs in areas where there is a ceritral low section and streams flow in from
all, or many, directions. The annular, or ring, pattern occurs most frequently as a result of the
erosion of structural domes. Its plan reflects rock controls which are made operative as soon as the donies have passed the initial stage in their dissection. In a sense, the annular pattern is
a curved or bent trellis pattern. The braided pattern, characteristic of streams which are overloaded and have hence dropped materials to clog their former channels, is one of many
joining and rejoining lines. indicates, better than words, the nature of this pattern. The glacially deranged pattern will be discussed which includes mention of continental and valley
glaciation. Stream patterns are important in many ways. They provide part of the physical plan
of a countryside and they affect the distribution of other physical features. One example is seen in the streams of Kansas; their patterns are largely dendntic and so are the patterns of the
accompanying flood plains. Water is more abundant in the flood-plain soils and trees are able to maintain themselves there. Thus, fingers and lines of trees stand out in dendritic pattern
and in sharp contrast to the drier, grassy interstream areas. In the ridge-and-valley region of eastern Tennessee, the stream pattern is trellised and this is the key to distribution of the
richer bottomland soils, as well as- to the location of those types of natural vegetation which require more moisture than do the types on the ridges. These are only two examples, chosen
more or less at random, but they serve to illustrate some of the relationships between stream patterns and other natural features.
There are also significant relationships be Streams tween road patterns and drainage patterns. The problems of road alignment and bridge construction in an area of glacially
deranged drainage are very different from the same problems in a region of dendritic stream pattern. Again, the above are only a few examples of the relationships between stream
patterns and cultural patterns; they could be multiplied many times.
There has been a growing emphasis on the development of power from streams. Particularly is this true of rivers in humid middle latitude regions or those which obtain
enough water from humid areas to enable them to continue as streams through dry country. At this point, it should be noted that, although important, only a small part of the
world’s electricity is produced from water power. Most of it is produced by means of coal, petroleum, and natural gas. Even today, hydroelectric energy in the United States supplies
only a small part of the total energy used. Further, this part may well be challenged by expansion in the field of nuclear energy.
Beyond engineering know-how, location in reference to markets, size of markets, and the like, the generation of hydroelectricity has certain physical requirements. There must
be a large volume of water of relatively steady flow and a sufficient fall of that water. In addition, if artificial dams have to be built to improve natural conditions, there must be sites
available where construction is safe and economically feasible. The dams must be located in parts of valleys where sufficient amounts of water can be impounded. Thus, purely physical
conditions such as nature of bedrock and shape of valley become significant. The physical conditions requisite to water-power production are most fully met in regions of continental
and valley glaciation.
As we shall see later, stream behavior in regions of arid or semiarid climates s much different from that in humid lands. The streams, except for those which are exotic, are
intermittent rather than permanent and they are smaller and less numerous. Yet these intermittent streams present many vexing problems. They pour floodwaters onto settlements
and play havoc with transportation system. Extensive flood prevention works are necessary for the protection of towns and cities, as well as of roads and railroads. It is somewhat
paradoxical that floods arid flood damage may be as severe in deserts as in lands of plentiful moisture.
The reasons for these difficulties lie basically in the amount and distribution of precipitation; that is, the problems are fundamentally climatic in origin. Because the water
does not flow permanently, it drops flood-stage loads and channels are clogged. The next floodwater spreads out over wide areas, carving new channels soon glutted with debris as the
water disappears. Except where channels are deeply entrenched, such behavior means that flood areas are usually broad and not too well defined; nevertheless, they are the natural drain
ways, and man must pay the penalty if he settles in them and builds his transport lines across them. Very often, he seems to know so little about stream behavior under such conditions that
he fails to recognize that he is in the natural line of water flow.A portion of the moisture derived from the air sinks into the upper part of the earth’s crust to become ground water.
Though not visible, it is just as important as surface water. From it come springs and well water and some of the moisture which is so necessary for the growth of natural vegetation
and crops. As water moves downward from the surface, it fills the spaces among soil particles arid also the crevices and cracks of the bedrock as far down as such exist in the earth’s crust.
The zone in which all spaces ate filled is the zone of saturation. The top of the zone is the water table. The water table follows approximately the profile of the land above, al though. It
is closer to the surface in low places than in high places. Where it intersects the surface in low spots, the results are swamps, ponds, lakes, or springs. In general, the groundwater table
lies closer to the surface in regions of humid climates than it does in the areas of arid or semiarid climates. Even in the latter areas, it may reach the surface in a few low spots and in
these, salt marshes are the normal result. The amount of moisture present in the soil is a very critical factor in the growth of
natural vegetation and crops. Soil moisture is of three kinds: gravitational water, hygroscopic water, and capillary water. Gravitational water is the water which moves downward, by force
of gravity, toward the zone of saturation. If gravitational water is too abundant, soils become
waterlogged and useless for crops although such drowned soils are still capable of supporting several types of swamp vegetation. Hygroscopic water exists as an extremely thin film
around each soil particle, somewhat as though each particle were “wrapped in cellophane.” It is often referred to as “unavailable water” because plants cannot obtain it. Capillary water is
the water which moves by capillary action, or attraction, in the same fashion that spilled ink may be drawn into and among the fibers of a blotter. Its ability to move even against the pull
of gravity is significant for, as topsoils dry out, capillary water is drawn to the upper portion of the soil where it supplies the needs of plants. However, if such action is too long
continued, particularly if the water is drawn all the way to the surface, soils become either weakly or strongly saline. This occurs when the water, drawn to the surface, is evaporated
and leaves its minerals behind. If there is insufficient precipitation to wash the minerals, or mineral salts, back down into lower parts of the soil, permanently saline soils are created. If
they are mildly saline, a few mineral salt-tolerant crops may be grown; with high salinity, no crops can grow although a few specially adapted types of natural vegetation halophytes may
be able to exist.
3.3 Some Water Problems
