WATER

WATER . In the mythical narratives in which it is frequently employed, the image of water takes on many different aspects. This article shall try to classify its appearances and seek to understand how the diverse functions that it fulfills are ordered.

At the Time of Origins

Many peoples tell how the world, already created in ancient times, was transformed and became what it is now. According to certain Australian traditions, the earth was originally surrounded by water, and in it were many spirits. Through the action of one of these spirits, the earth grew warm, and the first humans emerged from it. According to the Zuni Indians, a complex network of waterways circulates underground; the first Zuni were born there, at the lowest level. A pair of twins created by the Sun then made them climb to the surface. A pond marks the spot where they finally saw the light of day. A northern Australian myth tells the story of a dema (ancestral) deity. After one of his sons struck him with a lance, he threw himself into the sea; there, another of his children drew the lance out of his flesh where it had remained embedded. During the voyage the god then undertook, a spring appeared everywhere he rested. Finally, he plunged into the river Victoria, whose waters he proceeded to stir up until they formed deep branches in the forest; he then disappeared under a rock. From time to time he rises to the surface and causes storms; according to some accounts, he also occupies the region of the rainbow, where rain is formed.

Myths of this type show us water as present in the world from the most ancient times on, but they ascribe to it many different situations. Whether peripheral to the land or underground, water is first a significant element of the universal order. Sometimes it figures simply as a geographical feature—the sea or a river defining the shape of a country. However, there is something more to take note of. Water can be passive, with a spirit independent of it taking the sole initiative in the act of transformation. And yet water is tied mysteriously to the birth of the first humans or to the destiny of a god, who, after disappearing into its depths, remains bound up with storms and rain. The scope of these differences becomes clear when considering lengthier accounts.

In seeking the origin of all things, many peoples relate how water appeared in the course of cosmogonic events. Their explanations fall into three principal mythic systems. According to the first system, the world is created by a god who remains largely transcendent to it. In this case water, like the entire world, is a product of divine action. According to the Desána of South America, "Sun created the universe.… [He] created the earth, its forests and its rivers.… He also created the spirits and water demons" (Gerardo Reichel-Dolmatoff, Desana: Simbolismo de los Indios Tukano del Vaùpès, Bogotá, 1968, pp. 48–49). An African lament evokes "the one eternal God, the creator of the ocean and of dry land, of the fish in the sea and the beasts in the forest" (Louis Vincent Thomas, Les religions d'Afrique noire, Paris, 1969, p. 218).

In the second mythic context, the cosmogony takes on the aspect of a genealogy. The first ancestor is an entity whose simultaneously cosmic and divine attributes appear in the proliferation of his offspring. The waters that are then born throughout the generations are themselves generative. In a Greek system, the ancestral Earth gives birth to Heaven and to Pontos, the realm of the sea, composed of salt water. Earth then couples with each of these male principles. The first of the children she conceives from Heaven is Okeanos, a freshwater river, with deep eddies; he becomes the father of all the springs and rivers. Thus the deity who goes beyond the world remains immanent within it: In a way, he is present in the waters.

Finally, spirit may be presented as one of the primary agents of the formation of the world. Take for instance this Bambara myth: Out of the original void and motion a force, and then spirit, come forth. While the principles of things are being ordered, a mass falls and gives birth to the earth. However, a part of spirit arises; this is Faro, who builds the heaven. Faro then falls to earth in the form of water, thus bringing life to it. Dispenser of life, water is a manifestation of the divine spirit itself.

It is, however, in another type of cosmogony that the breadth and diversity of the functions of water become most intelligible. Here, water symbolizes what existed before the unleashing of the cosmogonic process, or the state of the world in the first phases of its history. There are numerous variations on this theme.

1

In its fluidity and elusiveness water may suggest the absence of form, the unsubstantiality and confusion from which the world will emerge. Inert, water has no power; a god or other beings independent of water will be the sole agents of creation. For instance, the following tale was told in the Admiralty Islands. In the beginning, there was nothing but an immense sea; in it swam a great serpent. Wanting a place where he could rest, he said, "Let a reef arise!" A reef then arose from the water and turned into dry land.

Biblical cosmogony illustrates the meaning of water in myths of this sort. The Bible brings together various symbols, including the desert, the void and darkness, the abyss, and the mass of water that the abyss contains and above which hovers the breath of God. This divine breath alone signifies reality. The other images have a negative value, evoking the idea of nonexistence; theologians will see in them a symbol of nothingness. Vedic language can go even further:

Neither Non-Being nor Being existed then.
Neither air nor the firmament above existed.
What was moving with such force? Where? Under whose care?
Was it the deep and fathomless water? (Ṛgveda 10.121.1)

In this question, the image of water alludes to the state of things prior to the distinction between being and nonbeing.

2

Water has no form of its own, but rivers have a bed and the sea has a bottom. This simple fact inspires several myths. Here is a Siberian example:

In the beginning, water was everywhere. Doh, the first shaman, flew over the primordial ocean in the company of some birds. Finding nowhere to rest, he asked the red-breasted loon to dive into the ocean and bring back some earth from the bottom. This the loon did, and on his third attempt, he managed to bring back a little mud in his beak. Doh made of this an island on the original ocean which became the earth.

The original ocean can thus cover some solid element. Moreover, despite its fluidity, water itself has substance; it is itself matter, and may contain suspended matter. In some myths the gods capture this matter or condense it. Thus the Atharvaveda (12.1) reads: "[The Earth] was originally a wave in the heart of the Ocean; the Sages went looking for it with their magic." A Guinean myth tells how Ha made an immense sea of mud and, then, by solidifying the mud, created the earth. According to the Kojiki, Izanagi and Izanami drove a lance into the sea that extended below them. When they withdrew it, the salty drops that fell from it solidified and formed the first land: the island of Onogoro. A Greek commentator on the myth of Proteus expresses himself in more abstract terms:

There was a time when all that existed was formless and muddy … there was nothing but matter that had been spilled out. A formless inertia reigned until the artisan of all things, having attracted order in order to protect life, imposed its imprint on the world. He disjoined the heavens from the earth, separated the continent from the sea, and each of the four elements … assumed its own form. (Heraclitus, Homeric Allegories 64ff.)

In this type of myth, water no longer signifies nothingness; it possesses a true existence. The gods use it, but it remains inert; they alone are active.

3

Very similar accounts, or even variants of the same myth, however, endow water with a certain spontaneity. This is the case in a story told by the Muskogee of North America. Before creation, they say, a vast expanse of water was the only thing visible, and two pigeons flew over the waves. At one end, they noticed a blade of grass growing on the surface of the waves. From this grass the earth gradually took shape, and at last the islands and continents took on their present form. One may also refer to an Orphic Greek cosmogony, according to which the primordial water appears to have been muddy. The matter it contained was condensed to become earth, and then from water and earth was finally born the mysterious god who would engender the cosmic egg. Despite their very different styles, both of these myths share one feature: Something happens in the original waters, without the intervention of any power external to the waters themselves. They therefore possess a certain intrinsic power. Other myths go on to explain the nature of this power.

4

In Hindu cosmogonies, waters are often represented as a receptacle of the divine egg or seed, which grows in the waters, carrying the god full of activity. But they do not give birth to what they carry. "In the beginning, he created only the waters, and then, in the waters, he laid his seed. And this became a golden egg.… In this egg Brahmā was born of himself, the ancestor of all living things" (Mānava Dharmaśāstra l.8–9). Auspicious for the development of the divine embryo, such waters fulfill an almost amniotic function. Egyptian mythology has a similar body of water, known as Nun. The primordial water is considered divine. It bears its own name and assumes human attributes. It can speak, and it can form a couple with its feminine double, the goddess Naunet. In Heliopolitan tradition, it is in Nun that the autogenous solar god is born and later rests. There he begins his creative or generative activity, and there, perhaps, the first gods begin their existence.

5

The image of a vivifying water that favors the birth of a god or the growth of an embryo is in fact very close to that of a fecund and procreative water. Some Egyptian texts give the impression that Nun himself engendered the solar god, whom he calls "my son." Nun has thus been called the "father of the gods." For a more clear-cut example of an image of procreative water, however, one may turn to the Babylonians. The Babylonians recognized two beings, Apsu and Tiamat, who existed prior to the formation of heaven and earth. They are at one and the same time waters, whose currents, in the beginning of time, mingled in a single mass, and two personified divinities, one masculine and one feminine. Their union produces another divine couple, who in turn will have their own offspring, so that Apsu and Tiamat become the ancestors of all creatures and, in this sense, the first authors of the cosmogonic process. Greece had a similar system, which Homer has preserved. Simultaneously currents of water and anthropomorphic deities, Okeanos and Tethys couple and give birth; their descendants will include all beings who will constitute, rule, or people the universe.

Essential to the life of plants, animals, and humans alike, water can be identified with the life-bearing forces and with fecundity itself. The regenerative nature can appear in a less biological fashion. One reads in the Śatapatha Brāhmaṇa (11.1.6.1): "In the beginning, the waters and the ocean alone existed. The waters had a wish: 'How shall we procreate?' They made an effort. They practiced ascetic heating [tapas ], and so it happened that a golden egg appeared." This egg contained Prajāpati. Thus not only is water filled with the desire for procreation (kāma ), it is also capable of truly creative effort and ascetic heat (tapas ).

When looking at the role water plays in the later phases of the creation of the world, one sees these observations confirmed. Within one and the same cosmogonic system, waters can successively assume attributes that enable one to distinguish different systems within the most ancient phases. For example, it was seen that the embryo of Prajāpati developed in the primordial waters. But then Prajāpati himself undertakes the creation of the waters. In the Śatapatha Brāhmaṇa (11.1.6.16–19), Paramestin, son and hypostasis of Prajāpati, wished to become all things on earth. So he became water. Similarly, Prajāpati will become breath, and Indra, the word. These notions are not contradictory; they represent different stages in creation. Whatever their amniotic qualities, the primordial waters are formless and not especially substantive, since Prajāpati still remains an embryo within them. After his birth, however, the god creates more defined and concrete waters outside of himself. In this way the text shows that the deity penetrates the waters just as he penetrates the entire universe.

Other narratives make simpler distinctions among the successive states of water. If primordial waters are an inert mass, it would be logical for them, during the course of creation, to be influenced by the actions of the gods who rule them. In the Bible, God creates a space in the midst of the original waters, dividing it into two masses, the upper and the lower waters. After creating a solid mass, he then separates that from the lower waters, thereby forming the sea and dry land.

Waters also submit to the demiurgical action in more ambiguous accounts. Here is a Fali (African) myth: One of the first animals, the tortoise, gave the world its first structure by laying out a ditch on the waters. After the first crisis, when rain threatened to submerge all things, the toad—another of the first animals—completed the structure. He separated standing water from running water and opened up a second path for the waters, cutting through the earlier ditch. Thus he divided the world into four parts.

Passive waters can also be mere instruments in the hands of those who confront each other in the course of great cosmogonic battles. In Hindu mythology, the demon Vṛtra holds back the waters and prevents them from irrigating the earth. Indra, who is waging a difficult war against him, is finally victorious and gives life to the world by releasing the waters. Mesopotamian myths are more complex. When the god Enlil decides to destroy humanity, he first holds back the rains and prevents underground waters from reaching the surface. Then, in a second attempt, he unleashes the waters, causing a flood.

Although waters thus appear to be temporarily mastered by the gods who use them, they are not completely inert. Not only do they seem to help Indra in his combat, but they are used by the gods primarily because they have a power of their own. The gods retain them because they are fertilizing; they unleash them because they are destructive.

The life-bearing and generative qualities that have been recognized in some of the primordial waters become manifest in the later phases of the cosmogony. Thus in a later stage of the Sumerian cosmogony, Enki, the Sumerian water god, impregnates Nintur, a goddess close to the earth, by scattering his seed on a riverbank; he then becomes the father of the goddess Nimu. With Nimu he begets Ninkurra, and with Ninkurra, Ottu. Similarly in Greece, whether they be the primordial pair (as in Homer) or be born of Heaven and Earth (as in Hesiod), the river Okeanos and his spouse Tethys have many offspring in the form of springs and rivers; the latter also procreate. In this manner waters contribute to the growth and enrichment of the universe. They also do so in another way: Enki fills ditches, canals, and fallow land with water, thus participating in the organization of the world.

Amma, the Dogon creator god, also has close affinities with heaven and water. His children, the snake-shaped Nommo, who are associated both with water and with the primal word, are the most active and successful agents of the cosmogonic impulse. They contribute to the birth of sexuality and permit the birth of the first ancestors. The latter, who in turn acquire the dignity of Nommo, keep close ties with water. After eating the first dead person, one of them furnishes society with the principles of its structure by vomiting up water—a prefiguration of torrents and ponds, the source of the five rivers, and of the waters of parturition.

Finally, water is sometimes tied more specifically to the birth of humanity. A trout out of water couples with a man from the underground lakes to beget the first clans of the Desána. According to some New Guinea traditions, the dema deities once lived under the earth, except for one of them who dug a hole in the ground. The others came out through the hole; then it filled up with water, and fish began to swim in it. After a complex sequence of events the fish became men. Finally, in Greek mythology, men often appear by coming out of a river.

One may now consider instances in which waters are portrayed as destructive. Several examples can be found in the ancient Near East. The Ugaritic Baal, god of the storm and of rain, symbolizes the forces of life. He periodically struggles against Mot, the incarnation of drought and death. He must also combat and conquer Prince Yamm, that is, the sea prince. Because of the gaps in knowledge it is difficult to locate this conflict within the mythical history of the world. So much, however, is certain: Yamm is threatening, and Baal's victory is necessary to the survival of the universe.

Things are clearer in the Enuma elish. Troubled by the proliferation and activity of their offspring, Apsu and Tiamat, whose mingled waters had given birth to the most ancient beings of the Babylonian myth, one day tried to destroy their descendants. Apsu, who was the first to try, was quickly conquered by Ea's magic. Ea then built his temple on the waters of Apsu, which were henceforth underground. Tiamat, who tried next, was more formidable, but was killed in the end by Marduk. By blowing into and swelling up the monstrous body of Tiamat, the young god separated the celestial waters from the earth; he opened the way to mountain rivers as he imposed his order on the entire universe. The primordial beings thus appear to want to abolish the agitation that accompanies the rise of the world in order to recover the peace they knew in the undifferentiated state of the first ages. Their inertia proves destructive. Tiamat appears as a monster in the army of monsters she has raised. The original divine waters must be conquered before the organizing gods can accomplish their work by pushing them back to the ends of the world.

Water in the Present World

One again encounters the different qualities, functions, and powers of water when looking at the position it holds in the completed world. Waters are one of the great domains of the ordered universe. Evoking the totality of the world, an Egyptian tale lists the sky, the earth, the domain of night, the mountains, and the waters. The Ṛgveda refers more simply to the sky, the waters, the earth. But despite such seemingly straightforward classifications, water is not thereby reduced to its palpable appearance; it continues to occupy places that are inaccessible to us; it possesses unsuspected qualities and powers.

The cosmic waters

For many peoples waters constitute the limits of the universe. They make up a vast expanse, in the middle of which lies the earth, like an island. They may be divided into two oceans on either side of the world, or they may flow in a river that surrounds the world, like the Greek Okeanos. They also frequently occupy the lower regions of the world in a more or less complex network of waterways underground. Or again, sometimes the entire earth is believed to rest on water. Finally, water is also found in the upper regions, above the heavens. Thus water can surround the world in any of the three dimensions of space. For the Desána Indians, a region bathed in water extends under the earth; water also circulates in the filaments of the Milky Way. In Mesopotamian texts the earth is built on the waters of Apsu, while the waters of Tiamat occupy the space above the heavens.

Waters can also help to define the center of the world. According to the Fali myth already cited, this center is located at the intersection of two open trenches in the waters. A character from an Iroquois myth runs around a lake to make the earth grow; the earth then develops on all sides under his steps. The great Ugaritic god El dwells at the source of the rivers in the midst of the course of the two oceans. The Guaraní Indians call the original abode of their ancestress the "Gushing Spring." It is the true center of the earth, the true center of the land of their first last father.

Because they occupy highly significant parts of the universe, waters help to define cosmic order. The Śatapatha Brāhmaṇa says categorically: "The waters are the order of the world" (11.1.6.24). In particular, bodies of water often establish important boundaries. In one widespread image, a lake or river separates the land of the living from the world of the dead. Examples of such a body of water include the river one crosses to reach the Babylonian Land of No Return and the Acheron of the Greeks. Furthermore, just as one must cross the waters to enter the realm of death, one must also cross the waters to enter the land of the living; according to the Ewe people, a child crosses a river when it is born.

Not all peoples make an explicit relationship between cosmic waters and the waters nearer at hand. Several do, however. Thus rains are sometimes believed to come from the celestial waters, and rivers from waters underground, if not from the waters surrounding the earth. Some texts provide more complex images. In a Babylonian poem, springs and rivers arise from the head of Tiamat's corpse; they therefore seem to come from the waters that occupy the upper regions of the world, even if these are near the earth, at the ends of the horizon. In ancient India, the Ganges was thought to descend from the heavens.

Waters and the divine

Wherever they are found, waters are often bound up with divine powers. The Hindu world generally holds them to be goddesses. More explicitly, in other cases, it is the sea, certain rivers, and certain springs that are considered to be gods. People in Vedic India, for instance, sacrificed to rivers. The Tigris and the Euphrates appear in a list of Hittite deities. Rivers are invoked in one Homeric oath.

There is something remarkable about these water deities. They are something more than representations of a purely natural element. Thus while the Egyptian Nun is a waterway on which the boat of the Sun sails at night, he is also a personage who can speak. Similarly, the name of the Ugaritic god Yamm means the sea itself; another of his names evokes the image of a river, but he also appears with the features of a prince or judge who sends ambassadors to the divine assembly. The Greek Pontos is the salty expanse of the sea; he is also a masculine being who couples with Earth and sires offspring. In Egypt, the Nile (and its floodwaters) is honored as Hapi, an anthropomorphic god. Water is thus the manifestation of a divine power that does not exactly coincide with the tangible appearance of the liquid element. Nevertheless, its immanence within this element is such that water can be perceived as the divinity itself.

In other cases, however, waters simply serve as the abode of spirits or sacred powers. Such spirits may inhabit a lake, a river, or the waves of the sea, or like others may live in a grove, a rock, or a mountain. Several gods that exercise a more extended authority should be mentioned separately. First of all, there are lords of rain, who are in some sense believed to cause it. However, rain also depends on beings whose powers are not restricted to the control of rain. In order to obtain rain, therefore, one must invoke several gods together, or certain ancestors who have become powerful spirits. Rain is sometimes conceived of as a gift from the supreme being, or the god of rain may be made into the supreme being itself.

Several ancient Mediterranean and Near Eastern peoples had a storm god. He rides or gathers the clouds, causes thunder and lightning to strike, and makes the rain fall. This storm god occupies a preeminent position among the gods; he can reign over them, protect the cities or their kings, and extend his power over the entire universe. Less prominent in the Hindu pantheon, the storm god Parjanya is a destroyer of demons; in some texts, he seems to be in command of the whole world.

The power of the gods that reign over the waters in a more general fashion is similarly extensive. The Sumerian god Enki, who comes by sea from a faraway land, established his residence or temple on the underground waters of Apsu, whom he has subdued. Enki is the lord of the waters. After being the major organizer of the world and one of the creators of humanity, he remains the master of fate. Along with An and Enlil, he belongs to the supreme triad. The same can be said of Ea, his Akkadian counterpart. King of the abyss, god of the vast sea, lord of the terrestrial waters, Ea has his place in the celestial world, and his counsel is heeded by the gods. Thus the power of the god of water usually transcends the domain of water.

The inverse phenomenon is also found. The authority of a more universal god is exercised in privileged fashion on the aquatic world. In the Veda, for example, Varuna is a major god who rules over nature, gods, and humans; he is the guardian of ṛta, the religious order of things. He is often closely linked to water. With Mitra, he can cause rain; with Indra, he can declare: "It is I who have swelled the rushing waters" (Ṛgveda 4.42). He rests on the waters, and his golden house is built on them. The two oceans are his entrails; he is hidden in each drop of water.

The situation is more highly defined in Greece. Poseidon, the god of the sea, is not essentially an aquatic deity. His name and several myths prove that he has close affinities with the earth. Son of the ancient king Kronos, he was given sovereignty over the seas when the paternal heritage was divided up; one of his brothers got the netherworld and the other, the heavens. Thus he commands the waters and raises tempests, but he is not immanent in them. Other gods—Pontos, Nereus, and Proteus—are more intimately tied to water. But in the case of Poseidon, sovereignty originates in a region beyond the domain where it is exercised. Whatever their wealth and power, waters are not the source of a political type of power. Political power is closer to the heavens; this is why it cannot be held by a god of the storm.

The qualities and powers of water

In their varied manifestations, the water gods and the waters themselves possess in the present world qualities or traits comparable to those that have been seen in the primordial cosmogonies. The waters that extend beyond the world and delimit it may in some cases be a symbol of the void, as they once were of nothingness; but this is not certain. These faraway waters sometimes feed terrestrial waters: They must have the same density. Water's fluidity and elusiveness are, however, manifested in the faculty of metamorphosis found in certain aquatic spirits or divinities. In a Vietnamese tale, a water spirit takes the shape of a seductive boy. Hindu nymphs turn into birds, and Greek sea gods, Proteus, Nereus, and his daughter Thetis, assume several forms in succession to escape those who attempt to detain them. This ability can be transferred. In Burmese narratives, the water of a certain pond transforms the person or animal who drinks it, the former into an ape, and the latter into a human.

Water is essential for human life; it ensures human nourishment by fertilizing the land. It is more than nourishment, because it is the source of nourishment. It may, therefore, be compared not only to milk, but more particularly to the cow. Because of its utility, it is perceived as a privileged support of vital forces. The Vendas, for instance, equate water with the blood, while the Desána view the rivers as umbilical cords joining people to the amniotic waters underground. In both Hindu and African texts, it is common to speak of the waters giving life and engendering humankind.

This is why water is found associated with sexuality. The Diola sing: "Women's sexual organs are full of water …, if Ata Sembe sleeps with a woman, he will always get her pregnant" (Louis Vincent Thomas, Les religions d'Afrique noire, Paris, 1969, p. 202). In this respect, waters often assume a feminine character. The Apsarasas of India and the Greek Naiads and Nereids are young women, caught up in erotic adventures. But the waters can also be masculine. "They rest on sperm, as Varuṇa rests on the waters," says the Bṛhadāraṇyaka Upaniṣad 3.9.22. To the Greek poets, the heavens send rain, like seed, to the earth, in an amorous outburst. The Egyptian god of the floodwaters of the Nile—Hati, the dispenser of life—is androgynous, and the Nile is imagined as half man and half woman. Its waters are male, and its arable land is female. Together, they are father and mother. In Greece the rivers are strongly masculine, and like the gods of the storm and of rain, have the attributes of a bull.

As vital principle, water allows people to ward off illness and to keep death away. Because water makes the plants of the pharmacopoeia grow, or because of the effects of its intrinsic qualities, the Veda associates it with the origin of medicine. In particular, water is believed to be highly effective against the venom of snakes. In a more positive sense, water is said to give vigor, make old men young, and prolong life.

Water is even capable of conferring immortality. Gilgamesh finds the herb of life, which enables people to escape death, at the bottom of the waters. Several peoples speak of a "water of life" that bestows immortality. Similarly, to give her son Achilles eternal life, Thetis wants to plunge him into the waters of the Styx. The Greeks in general establish a relationship between Okeanos and ambrosia, as the Indians do between water and soma.

There is a more enigmatic aspect of water: It possesses wisdom and knowledge. Water seeks the truth, one reads in the Vedas. The Mesopotamian water god Ea, full of wisdom, dispenses counsel to the gods. As a sage, he protects the mythical old wise men who were born in the abyss in the form of fish. The most ancient Greek water gods engender daughters whose names denote qualities of intelligence. Among the Oceanids, these are Metis ("prudence") and Idyia ("the knowing one"); among the Nereids, Panopeia ("the all-seeing one") and Nemertes ("the veracious one"). The latter, says Hesiod, has the same quality of spirit as her father. Nereus is in fact frank, loyal, and gentle, always concerned with justice. He resembles Proteus, who knows the present, the past, and the future.

Where does this wisdom of water come from? A Guaraní narrative establishes a relationship between the freshness of water and the freshness of the soul accompanied by moderation. In a Vedic text the waves, which stave off all evils, also keep away lies. A Greek text associates the extent of knowledge with the immensity of the depths of the sea. But perhaps the wisdom of the water gods is a function of their age. In the Hellenic world, the wisest among them are called "the old men of the sea."

Waters, which at one and the same time are sages and generative forces—to the point of symbolizing at times the creative power itself—are close to the word. To the Dogon, water and the word are joined in the person of the Nommo, whose civilizing activity simultaneously links the arts of civilization with the word and with wetness; one finds similar associations among the Bambara. In Ṛgveda 10.125, the ritual word itself, whose efficacy is cosmic, says of itself: "My origin is in the waters, in the ocean." Water is not always beneficent, however. In the present world, water can be hostile to humans, just as it could be destructive in the remote time of myth. There are catastrophic rains and floods; people drown in rivers and seas. These are not simply accidents but the manifestation of evil powers allied with the liquid element. One example alone illustrates this: Indigenous peoples of the north of Australia have a serpent-shaped spirit that lives in the clouds during the dry season and in marshes during the rainy season. It is he who drowns humans in floods, he who swallows them up when they venture out into swamps.

The negativity of water can take other forms. For the Desána, water is a symbol of illness. In one Mesopotamian text, bad coughs are caused by Apsu. An account from Gabon goes even further: The water spirit embodies rain, cold, and death. Mesopotamia also has waters of death, just as it has waters of life.

This hostile power is sometimes incarnated in monstrous creatures. The Desána believe that a formidable centipede lives in the sea; they also talk of maleficent serpentine creatures, some of whom eat children. The descendants of Pontos, the Greek god of the sea, include several hybrid beings with destructive powers, such as the Gorgons, who dwell near the waters of Okeanos, and the Hydra, in the marsh of Lerna. One recalls that Tiamat took on the form of a monster. Such monsters survive in the beliefs of ancient Israel; they are the leviathan, Rahab, and the dragon Tannin.

In the Hebrew scriptures, the ocean itself is often represented as an adversary of Yahveh. Of course, in imposing his order on the world, Yahveh conquered the waters and subdued the monsters they harbor; he is henceforth their master. However, their menace continues; the sea monster might reawaken, and if he does, God, who watches him, will kill him.

At times beneficent and at others maleficent, close to the principles of life and to creative power but nonetheless capable of destruction, a relative of gods and monsters, water bears within it all the ambiguities of the sacred. It is an agent of purification not only because it bathes, dissolves, and carries off material filth; its cathartic power is even more mysterious. According to a Babylonian text, water banishes all evils, even those that have not yet had an impact but that have been foretold by bad omens. In a Vedic hymn, water frees humanity from the consequences of false oaths and from all the sins people have committed.

The purity conferred by water is a positive trait. Water conveys to humankind certain of its virtues. It causes vision, according to a Vedic text. In a Greek legend, Pherecydes predicts an earthquake after drinking some water from a well. When Okeanos and Tethys purify Glaucus, they render him capable of undergoing the deification process to which he is subject. Thus, waters are fully purifying to the extent that they are also, to a certain extent, sacralizing.

Several of the qualities of water just discussed are manifest in the world of the dead. For certain Zuni societies, the ancestors inhabit a village at the bottom of a lake. The members of the society believe that when they die they will go to sleep and wake up as young children in this village, at the bottom of the "whispering waters." These waters seem to be the symbol of a blissful condition where ancestral life and childhood commingle. The beliefs of the Desána go even further. A region bathed in water, Axpicon-dia, extends beneath the earth; from there came the first organizer of the world. It is a uterine domain, the source of all life, to which the people yet to be born are tied by a sort of umbilical cord. The best of the Desána will go there after death. Happy death is thus conceived as a return to the amniotic waters. Among the Polynesians, the dead inhabit a sad region, located beyond the seas; the chiefs, however, go to a different land, where the god Tane gives them a water of life that brings them back to life.

Nun, the primordial water, crosses through the Egyptian land of the dead. At night, the boat of the sun sails over its waves to the east. In some texts, the dead board this boat and make its journey with it. In other texts, they bathe in Nun, into which the sun god also dives. Assimilated to him, they come out again, regenerated. But the infernal waters are not always beneficent and life-giving. They contain reefs that the ferryman's boat must steer clear of; they contain dangers and are disquieting. The Nun was supposed to be the site of mysterious drownings.

Among the Greeks, Hades contains rivers and lakes. The names of two of these rivers reveal their nature: Pyriphlegethon (Puriphlegethōn ) means "burning and flaming like fire"; Cocytus (Kōkutos ) means "groan, lamentation." The rivers terminate in the abyss of Tartaros where, according to Plato, evil souls suffer a temporary punishment. Other souls, however, purify themselves on the banks of the lake Acherousias, where they pass before reincarnation. Proclus states more clearly that the souls purified in Acheron attain a better fate.

One frequently recurring idea is that the dead are thirsty. Drink refreshes them; thanks to it, they regain some form of life, as suggested by Egyptian texts. Not all waters, however, are equally beneficent to the dead. In certain Greek traditions, there are two springs in the netherworld; the initiate knows he must drink from the one that comes from the Lake of Memory. Plato mentions a Plain of Forgetfulness where the Lake of Negligence is found. One of the infernal waters thus suppresses memory while the other maintains and reaffirms it, acting like the water of wisdom and knowledge already discussed. The importance of this opposition is apparent in the privilege granted to Pythagoras and Empedocles, who were said to have been allowed to retain the memories of their previous existences. It would appear from a reading of Empedocles that this privilege belongs to the souls who will shortly escape reincarnation.

Conclusion

In conclusion, the wide range of meaning given to the image of water is not without limits, and even opposing meanings given in different myths are not incoherent. These diverse meanings are in large part suggested by the diversity of human experience of water as a natural phenomenon.

Water can be ambiguous. As a fluid, it can symbolize a pure absence or an as yet still amorphous material that will be used by the gods. It may fulfill a positive function. It bathes, dissolves, and purifies. Essential to human life and necessary for the growth of plants, it symbolizes a generative or life-giving quality, very similar to creative power. It is thus divine and sacralizing. Yet it is also capable of playing a negative role. The gods can utilize the destructive power of its waves. Active in itself, whether divine or monstrous, water erodes everything that takes form and tends to annihilate all distinctions in its own inconsistency. Finally, just as rivers and seas contribute to defining the contours of a country, so the dividing of the waters helps to define cosmic order.

The image of water therefore is not univocal. It can never be interpreted without considering the totality of the myth in which it figures. But it is not indifferent, defined only by the position it holds in the mythic system of a given society. Capable of calling forth the memory of various concrete experiences and numerous emotions, it carries specific meanings within it in a potential state. Each narrative actualizes some of these meanings.

No rule of logic requires that the meaning that water assumes in the evocation of the time of origins must remain unchanged during the course of the cosmogonic process or in the present world. On the other hand, in the small number of mythic systems that this author has studied in some depth, it has been striking that the uses of the image of water, often quite diverse, nevertheless remain coherent, owing to the theological intention that inspires the whole of a given system.

See Also

Ablutions; Baptism; Flood, The; Lakes; Rain; Rivers; Spittle and Spitting; Tears.

Bibliography

Bachelard, Gaston. L'eau et les rêves. 4th ed. Paris, 1978.

Eliade, Mircea. "Baptism, the Deluge, and Aquatic Symbolism." In his Images and Symbols: Studies in Religious Symbolism, pp. 151–169. New York, 1961.

Kaiser, Otto. Die mythische Bedeutung des Meeres in Ägypten, Ugarit und Israel. 2d ed. Berlin, 1962.

Lüders, Heinrich. Varuṇa, vol. 1, Varuna und die Wasser. Göttingen, 1951.

Ninck, Martin. Die Bedeutung des Wassers im Kult und Leben der Alten. Leipzig, 1921.

Nola, Alfonso di. "Acqua." In Enciclopedia delle religioni, vol. 1. Florence, 1970.

Raymond, Philippe. L'eau, sa vie, et sa signification dans l'Ancien Testament. Leiden, 1958.

Rudhardt, Jean. Le thème de l'eau primordiale dans la mythologie grecque. Bern, 1971.

New Sources

Capdeville, Gérard, ed. L'eau et le feu dans les religions antiques. Actes du premier colloque international d'histoire des religions organisé par l'Ecole Doctorale Les Mondes de l' Antiquité, Paris 1995. Paris, 2004. 22 contributions in French and one in Spanish concerning the role played by water and fire mostly in the Greek and Roman worlds but also in China, India, Iran, Israel, and ancient Gaul.

Ginouvès, René, ed. L'eau, la santé et la maladie dans le monde grec. Actes du colloque de Paris 1992. Athens, 1994.

Loicq, Jean. "Eaux (Culte chez les Celtes et les Gallo-Romains)." In Dictionnaire des religions, edited by Paul Poupard, pp. 561–566. 3^rd edition, Paris, 1993.

Lurker, Manfred. "Wasser." In Wörterbuch der Symbolik. Stuttgart, Germany, 1983, pp. 753–754.

Masson, Denise. L'eau, le feu, la lumière d'après la Bible, le Coran et les traditions monotheistes. Paris, 1985.

Ries, Julien. "Eau." In Dictionnaire des religions, edited by Paul Poupard, pp. 559–561. 3^rd edition, Paris, 1993.

Varenne, Jean. "Eaux (Dans l'hindouisme)." In Dictionnaire des religions, edited by Paul Poupard, pp. 566–567. 3^rd edition, Paris, 1993.

Wild, R. A. Water in the Cultic Worship of Isis and Sarapis. Leiden, 1981.

Jean Rudhardt (1987)

Translated from French by Erica Meltzer
Revised Bibliography

WATER

Because of its scarcity, water plays a central role in Middle Eastern politics and society.

Nowhere in the world is water more important than in the Middle East and North Africa. In no other region do so many people strive so hard for economic growth on the basis of so little water: here is found 5 percent of the world's population but only 1 percent of its fresh water. Of the ten nations with the least water per capita, six are in this region. No wonder that both Jewish and Muslim scriptures are full of references to water.

Role of Climate

The more heavily populated parts of the Middle East are semiarid, with rainfall of 10 to 29 inches (250 to 750 mm) per year. However, low rainfall is less of a problem than variability in rainfall. The great bulk of the rain falls in four winter months, with none falling during the rest of the year. Rainfall also changes rapidly with distance, from more than 20 inches (500 mm) on the coast of Lebanon to 8 inches (200 mm) in the Biqa, only an hour away by road but across the Lebanon mountains.

Seasonal and spatial variations in rainfall are sharp but predictable. What makes planning difficult is the sharp variation from one year to the next. Reliable flow in the rivers (the flow that can be expected nine years out of ten) is only 10 percent of the average. In northern latitudes, water planning can be built around statistical averages; here, it must be built around extremes.

This already difficult water situation will likely get worse. Population growth rates are high, and most climate change models suggest higher temperatures, lower rainfall, and more frequent droughts for the region.

Role of History

Development in the Middle East and North Africa has always been more dependent on water than on any other resource, including oil. By the fourth millennium b.c.e., the Sumerians had built a paradise in what is now Iraq through intricate canals for irrigating crops; two millennia later it had largely collapsed because of salinization of the soil. Ancient cities, such as Palmyra in Syria, were possible only because of carefully engineered tunnels, called qanats (foggaras in Iran), to bring water from springs tens of kilometers away.

Over the years, the peoples of the Middle East have made water a preoccupation, and each nation has a central agency, typically a full ministry, to deal with water. Many of the principles for good water management were worked out in the Middle East—although just as often they were ignored for political, financial, or social reasons.

Water Sources

The Middle East includes two of the mightiest river systems in the world. The Nile has two main branches: The White Nile originates in Uganda, and the larger Blue Nile (together with the Atbara) originates in Ethiopia; they join near Khartoum and flow northward through Egypt to the Mediterranean. The Tigris and Euphrates both originate in Turkey and flow south-southeastward through Syria and Iraq before joining and flowing into the Persian Gulf via the Shatt al-Arab, at the Iranian border.

The region also includes numerous mediumsized rivers, such as the Jordan, which flows from three springs through the Sea of Galilee (one of the few natural lakes in the region) and into the Dead Sea, 415 meters below sea level. Only Turkey has an
abundance of river water, but its big rivers are only found in the eastern part of the nation. Finally, there are small coastal rivers (many of them ephemeral), and a few major wetlands, such as the marshlands in southern Iraq and the Sudd swamp in southern Sudan.

The construction of new dams and pipelines to deliver water from major rivers in the Middle East will cost two or three times as much per unit of water as current supplies, and if construction occurs in upstream countries, such as Ethiopia and Turkey, it will reduce flows downstream. Therefore, the region will increasingly shift toward the use of underground water, which has the great advantage of not evaporating. (Lakes and reservoirs in the region lose meters of water per year to evaporation.)

Historically, underground water was tapped by shallow wells dug in unconsolidated materials to get small flows of water. Today, much larger volumes of water are extracted from wells drilled tens to hundreds of meters into aquifers, which are rock layers with pores that contain water. Renewable aquifers are replenished (generally slowly) by rainfall; non-renewable, or fossil, aquifers contain water trapped in sediments laid down millions of years ago.

Just more than 10 percent of the water supply for the region comes from aquifers, but in Israel and Jordan the share approaches 50 percent, and in Kuwait and parts of the Arabian Peninsula it approaches 100 percent (apart from desalination). Libya's Great Man-Made River pumps water from fossil aquifers in the south of the country and moves it 930 miles (1,500 km) to farms and cities in the north.

The third most important source of water in the Middle East is recycled sewage, which is treated and reused, mainly for irrigation. Despite common
belief (shared by both Muslims and non-Muslims), there is no objection in Islamic law to the reuse of sewer water provided it is properly treated.

More than half of the world's desalination capacity is found in the region, mainly in the oil-producing nations of the Arabian peninsula with lots of by-product natural gas that was formerly flared. (Desalination is an energy-intensive process.) Costs for desalination have fallen to a level that makes it feasible as a source of potable water but still too expensive for irrigation.

Other sources of water are individually small but collectively provide sizable amounts of water. Water harvesting gathers rain that falls over a wide area and directs it to one field through small channels and micro-barrages. The technique can allow crops in areas where rainfall is only 4 inches (100 mm) per year. Rainwater is also collected from rooftops and stored in cisterns. If handled carefully, rooftop water can be used for drinking.

Uses of Water

By far the largest share of water in the region goes to agriculture—as much as 90 percent of total water use in some countries, and 60 percent in the more industrialized countries.

Drinking requires only a relatively small volume of water, but it must meet higher standards than that used for irrigation. Thirty liters of potable water per person-day is generally regarded as the minimum for drinking, cooking, and washing.

Industrial water use is low. Food and beverage processing are the largest industrial consumers. More is withdrawn for cooling but most of this water is recycled or returned to the watercourse.

A hidden but critical amount of water must be left in place to support fisheries and hydropower, as well as to protect habitat. This use is typically neglected by governments when they drain swamps, canalize rivers, or extend land. As a result, not only has the environment been degraded, but fish catches have declined and the salinity of groundwater has increased.

Problems

The nations of the Middle East all face three overlapping sources of stress in their water management: 1) quantity, which has been a source of stress since history began; 2) quality, which is a newer stress but increasingly important; and 3) equity, which occurs when the same water is subject to competing demands.

Quantity. Iran, Iraq, Lebanon, Sudan, Syria, and Turkey are fairly well endowed with water, with more than 1 million cubic meters (Mcm) per capita; Algeria, Egypt, Israel, Morocco, and Palestine form a middle group; and Jordan, Libya, Tunisia, and the countries of the Arabian Peninsula are least well endowed, with less than 500 Mcm per capita. However, water availability is declining in every nation, which means that current patterns of water use are not sustainable. Some projections for the Jordan River basin suggest that by 2025 household and industrial uses will require all the fresh water, leaving none for farmers. Most nations are also drawing down their renewable aquifers and mining fossil ones. Some have annual water deficits of several thousand Mcm.

Water quantity problems in the region can be resolved in small part by exploiting additional

sources of supply but in much larger part by better use of the water that is already available. People in the region use less water than those elsewhere in the world, but as a result of poor management and misguided economic policies conservation here (as in most other parts of the world) remains far short of its potential. Many nations lose half the water put into municipal systems to leaks, and they typically deliver piped water at low (or no) price. Cost-effective savings of 25 to 50 percent are possible in most uses.

Moreover, every country in the region provides water to farmers at highly subsidized prices. Under the influence of higher prices, Israeli scientists developed drip irrigation systems that have cut water use per hectare by 40 percent. However, drip irrigation is expensive and not appropriate for all crops. Lower-cost sprinkler systems, used at night to minimize evaporation, can also increase irrigation efficiency, as can irrigating only at times critical to plant growth.

Most analysts find that water is tens of times more valuable in industrial or household uses than in agriculture. Therefore, crops grown in the region will gradually be replaced by imports. It takes roughly a thousand tons of water to produce one ton of wheat. Using that ratio, Middle Eastern nations already import grains with a virtual water content equal to the flow of the Nile.

Quality. Much of the limited fresh water in the Middle East is polluted from growing volumes of human, industrial, and agricultural waste. Three problems stand out: 1) Overpumping of wells causes a decline in the water table—by as much as a meter a year in some areas. This decline adds to pumping costs and permits lower-quality water (or, if near the coast, seawater) to flow inward and contaminate the aquifer. The only way to avoid the problem is to match pumping rates to inflow. 2) Agricultural runoff is the major non-point source of water pollution—mainly sediment, phosphorus, nitrogen, and pesticides. Better farming methods, such as conservation tillage, contour planting, and terracing can control soil erosion and cut pollution by half or more. 3) Urban sewage systems have either begun to deteriorate or cannot handle the growing loads placed on them. Large investments are needed to improve their physical infrastructure.

Equity. Most of the larger rivers in the region cross an international border—some cross several borders—or form a border. No tabulation exists for aquifers that underlie national borders, but there are many.

Despite many statements suggesting that the next war in the Middle East will be over fresh water, there is little evidence for this. Not a single war has been fought over water for hundreds of years, but many treaties dealing with water have been signed. Water will be a source of conflict, but the conflicts will mainly be intranational rather than international. Likely sources of conflict include rural and urban users contending for the same water and rising demands from poor farmers, who are often disadvantaged in their access to water, and from women, who typically want more water for their households while men prefer to use it to grow cash crops. Israeli control of water in the West Bank is contentious, but even here experts have shown that compromise is feasible.

None of the three stresses on water in the Middle East will be easily resolved. Most of the nations in the region have already reached or are fast approaching the limits of their indigenous water supplies. Although higher prices for water and technological advances may defer the crisis, the only long-term solutions involve much greater efficiency in use, full reuse of wastewater, and gradual shifts of water from agriculture to other sectors. All of the nations of the Middle East and North Africa must revise their water policies to provide for a sustainable future, and they must find equitable ways to share water within and between nations.

Bibliography

Amery, Hussein A., and Wolf, Aaron T., eds. Water in the Middle East: A Geography of Peace. Austin: University of Texas Press, 2000.

Beaumont, Peter. "Water Policies for the Middle East in the Twenty-first Century: The New Economic Realities." International Journal of Water Resources Development 18, no. 2 (2002): 315–334.

Brooks, David B., and Mehmet, Ozay, eds. Water Balances in the Eastern Mediterranean. Ottawa: International Development Research Centre, 2000.

Kolars, John. "The Spatial Attributes of Water Negotiation: The Need for a River Ethic and River Advocacy in the Middle East." In Water in the Middle East: A Geography of Peace, edited by Hussein A. Amery and Aaron T. Wolf. Austin: University of Texas Press, 2000.

Lonergan, Stephen C., and Brooks, David B. Watershed: The Role of Fresh Water in the Israeli-Palestinian Conflict. Ottawa: International Development Research Centre, 1994.

Postel, Sandra. Pillar of Sand: Can the Irrigation Miracle Last? New York: Norton, 1999.

Rogers, Peter, and Lydon, Peter, eds. Water in the Arab World: Perspectives and Prognoses. Cambridge, MA: Division of Applied Sciences, Harvard University, 1994.

Shapland, Greg. Rivers of Discord: International Water Disputes in the Middle East. New York: St. Martin's Press; London: Hurst, 1997.

Waterbury, John. The Nile Basin: National Determinants of Collective Action. New Haven, CT: Yale University Press, 2002.

Wolf, Aaron T. "Transboundary Fresh Water Database." Department of Geosciences, Oregon State University. Available from <http://www.transboundarywaters.orst.edu>.

david b. brooks

WATER

Water is the liquid of life and is crucial to every type of organism, from simple bacteria to megafauna, as well as to many of the physical processes that shape the planet, as in the weathering of mountains and valleys. For life in all forms, water is more important than even oxygen, because there exist anaerobic bacteria that can live without air but no anhydroxic bacteria that can exist without water. When astrobiologists seek to determine the possibility of life on other planets, their first question concerns the presence of water. Throughout human history, however, water has had as much a symbolic as biological significance, and human beings have adapted to environments both abundant and scarce in water, through different technological, ethical, and political engagements. Water is so rich in metaphor that it cannot be reduced to merely H₂O, nor to a fluid circulated in pipes, metered, and then distributed by authorities. The duality of meaning that water embodies includes the fact that it can be both deep and shallow, life-giving and destructive, a blessing and a curse, and something that cleans the surface and also purifies the inner soul.

Water in Science

As a chemical compound water is composed of one atom of oxygen and two of hydrogen. Because acids are characterized by hydrogen ions (H⁺) and bases by hydroxide ions (OH⁻); water (H₂O) may be described as neither acidic nor basic, rather equally both: The structure of water is: Oxygen is attached to two hydrogen atoms with two covalent bonds leaving two nonbonding pairs of electrons. Hydrogen bonding is particularly important in biochemical systems, because biochemical molecules contain many oxygen and nitrogen atoms that participate in hydrogen bonding. Hydrogen bonds between water molecules are responsible for the interesting physical properties of water that made it the solvent of life. Together with the extended temperature range between its solid (ice) and gaseous (steam) states, that makes liquid water able to serve as the foundation for those extremely complex carbon formations that constitute living organisms.

When present at a depth of at least two meters (six feet), pure water is a pale blue, odorless, tasteless, and transparent liquid. Other observed colors are due to various impurities, nonliving and living. It is mostly "blue water" that flows in rivers and into lakes and aquifers. "Green water" refers to the precipitation that is directly used by nonirrigated agriculture, pasture, and forests, and to evapotranspiration.

In its liquid and solid forms, water covers 71 percent of the surface area of the globe. Humanity's anthropocentric worldview explains why this mostly "blue" planet was (mis)labeled Earth. Of all the water on the planet, only 3 percent is freshwater, a figure that includes glacial ice and other hard-to-reach water sources. Of this, only 0.003 percent of the surface and subsurface water is usable by humans.

Hydrology is the science of the properties, distribution, and circulation of surface and subsurface water. In hydrologic terms, water that collects in rivers, lakes, or reservoirs is called surface water. That which seeps into the shallow or deeper layers of Earth is called aquifer. The gaseous, solid, or liquid phases of water affect both the element's chemistry such as its bonding and its physics such as its density. Water is an excellent solvent, and hence it has many constituents that are dissolved or suspended in it. These facilitate chemical interactions, which aid complex metabolisms. This explains why water is critical for all life-forms.

Pure water can be obtained through painstakingly and costly mechanical processes. Water is then the most benign of all chemical compounds known to humans. Water that contains dissolved carbonates such as calcium and magnesium is known as hard water. People notice this because it suppresses the formation of lather with soap, and when boiled, it leaves a "lime scale" that is seen in cookware. Soft water is free of such carbonates.

Water circulates from the ocean and surface of Earth to the atmosphere and then gravitates back in various forms including snow, rain, and fog. Human activities affect this hydrological cycle, most prominently through the building of physical barriers such as dams and through modifications of watersheds. Most water resources are renewable except for fossil (or connate) water that is laid down in sedimentary rocks and sealed off by overlying beds. Nevertheless, human contamination of groundwater stock, and alterations of watersheds (or, in British parlance, "drainage basins") through, for example, deforestation or paving over hydrologically critical areas can reduce aquifer recharge, alter flow characteristics, and, in severe cases, deplete a formerly renewable resource.

Many large watersheds lack time series data, and scientists in riparian states (those who study watersheds) often use different methodologies for collecting their data, which makes data sharing among water basin states ineffective and integrated management of the river system difficult.

Technologies of Water

Natural water is managed through a system of wells, dams, artificial reservoirs, conveyance systems, and human-made ponds. Humans withdraw untreated water from surface sources and pump it from aquifers. The water is treated and then pumped into carefully laid-out distribution systems such as water mains, which are connected to underground networks and sometimes to (elevated) storage facilities.

The geographical setting of the source of water, water treatment, its distribution, return flow collection, and return flow treatment—each requires a unique technological approach in order that people can access and use the resource. Economic considerations and regulations regarding human health and environmental protection also affect the choice of technology.

Easy-to-tap water sources were the first to be developed. Growing water needs require new and innovative technologies because water is increasingly extracted from deeper wells and piped in from further and further locations; furthermore, in a growing number of countries that have exhausted their supplies, freshwater is obtained by removing the salts and other contaminants from sea water (desalination). Growing water scarcity is inducing the development of water-efficient technologies. Given that agriculture is by far the largest consumer of water, drip irrigation techniques offer huge water savings, especially when compared to sprinkler irrigation or the traditional, but low-cost, flood irrigation.

Historically, the water wheel, a wheel with paddles or buckets attached to the outside, was first used to lift water from a river onto irrigation channels. Eventually, a water-powered wheel was developed and used in the Middle Ages for extracting power from a flow of water. Its applications included milling flour and machining and pounding linen for use in paper. Similarly, the steam engine contributed to Europe's economic development especially during the Industrial Revolution. This engine coverts the potential energy of the pressure in steam to mechanical work.

Water systems have been targets in warfare, and the threat of terrorism is requiring new technologies and strategies to protect water supply systems, especially in large metropolitan centers, and in countries where in which the majority of the population depends on a few desalination plants. Efforts are afoot to develop remote but real-time water-quality monitoring systems that not only encompass the traditional water-quality parameters but also can detect currently unmonitored biological agents that could threaten freshwater supplies, such as bacteria, viruses, and protozoa.

Ethics of Water

Water is central to the health of the ecosystem, central to the beliefs and customs of many religious communities, and vital to the maintenance of the economic well-being of modern and traditional lifestyles. Allocating water across competing users must thus be tempered by extensive stakeholder participation and weighed against any adverse social or ecological impacts that a solely economic approach may cause.

The increasing demand for freshwater is related to population growth, trends toward more protein-based diets, and overall improvements in the quality of life. Countries typically tap their lowest cost and most reliable sources of water first. As these sources become fully utilized, the development of new sources carries with it heavier financial costs and environmental consequences.

The equitable allocation and sustainable use of water require good governance that is rooted in policies that are scientifically, culturally, and economically sound; in institutional structures that are community friendly and invite public participation; and in decision makers who are competent and fair, and have the support of the political forces. It also requires employing modern technologies that have been adopted in many Western countries but are beyond the reach of poorer ones.

In 2002 the United Nations Committee on Economic, Social and Cultural Rights declared water a human right. It stated that the human right to water entitles everyone to sufficient, safe, acceptable, physically accessible, and affordable water for personal and domestic uses. An adequate amount of safe water is necessary to prevent death from dehydration, reduce the risk of water-related disease, and provide for consumption, cooking, and personal and domestic hygienic requirements. The signatories to the International Covenant on Economic, Social and Cultural Rights are required to progressively ensure access to clean water, equitably and without favoritism.

Politics of Water

Negotiating water-sharing agreements on for international rivers tends to be complex. Allocation agreements among competing users often involve a combination of geoclimatic factors as well as legal, historical, technological, demographic, political, and ethical considerations. In the case of international rivers, upstream states are generally seen as having leverage in influencing the allocation process simply because they control the "water tap."

Water allocation arguments include the largely discredited view that a country has an absolute sovereignty over resources that originate inside its political boundaries. Prior appropriation agreements state that the earliest users of water have rights to it. This convention is widely used in the American Southwest and by a few other countries, such as Iraq in connection with its share of the waters of the Tigris and Euphrates rivers. Before a balanced allocation formula can be reached, several factors need to be carefully considered and fairly weighted for every riparian country. These factors include a country's contribution to the total flow of the river, current and projected population size, area of arable land, and the extent to which the health of the national economy is dependent on water. A sustainable and ethical management strategy must also consider and protect the needs of aquatic life, upstream habitats (especially forests), wetlands, and floodplains, as well as the water needs of future generations. International agreements make the integrated (and sustainable) management of river systems easier.

Acute and protracted water scarcity is likely to be a source of violent conflict especially in countries where the agricultural sector is a vital contributor to national economic health. This danger has helped place water scarcity high on the world's political agenda. Globally, the overwhelming majority of water is consumed by the agricultural sector. There has been a gradual and continuing shift away from supply management to demand management of water, whereby people are asked to make the most out of their existing resources. Communities try to maximize their crop yields per unit of water (more "crop per drop") and their financial returns by planting suitable, lucrative crops. Similarly, a few arid and semiarid countries are gradually shifting away from water thirsty crops such as citrus to ones that are more suited to their own climatic and physical environments such as wheat, lentils, and chickpeas.

Immense amounts of water are wasted through leakage from antiquated urban supply networks and unsustainable irrigation strategies. Existing technologies such as the efficient, water-saving drip irrigation technique and microsprinklers have been around for decades but used on only around 1 percent of all irrigated lands. Even relatively small improvements in efficiency through the transfer of appropriate irrigation technologies and the implementation of various policy incentives and/or disincentives will result in substantial water savings.

One proposed strategy would involve governments gradually charging farmers the real and full cost of water. Progressively higher charges per unit of water consumed would induce most users to think before they turn on the water. Water quality can be protected by raising people's awareness about the adverse effects of pollution, making it prohibitively expensive to pollute, and by building sanitation infrastructures and wastewater treatment plants. This will minimize pollution levels and provide the public with recycled water to be used in nonhuman ways that do not directly affect food production, such as car washes and irrigation of lawns.

When national sources are exhausted, countries seek alternatives such as importing water, usually from nearby countries. Globalization and the opening of international markets are likely to encourage large-scale trading of freshwater across international borders. This is a controversial because of the likely environmental impacts and the political implications that a dependency on imported water may create.

Desalination, however, is an increasingly promising water-augmentation method. This process entails removing soluble salts from water to make it suitable for various human uses. Technological advances have been steadily decreasing its unit price, which is inducing more countries and facilities to use it. A growing number of countries have been increasingly adopting desalination technologies to augment their national or area-specific freshwater supplies.

HUSSEIN A. AMERY

SEE ALSO Acid Mine Drainage;Air;Dams;Deforestation and Desertification;Earth;Environmental Ethics;Fire.

BIBLIOGRAPHY

Al-Jamal, M. S.; S. Ball; and T. W. Sammis. (2001). "Comparison of Sprinkler, Trickle, and Furrow Irrigation Efficiencies for Onion Production." Agricultural Water Management 46(3): 253–266.

Amery, Hussein A., and Karen B. Wiley. (2003). "Resolution of International Water Conflicts: From the U.S. Southwest to the Euphrates River Basin States." International Journal of Global Environmental Issues 3(2): 226–239.

Amery, Hussein A., and Aaron T. Wolf, eds. (2000). Water in the Middle East: A Geography of Peace. Austin: University of Texas Press.

Birkett, James D. (1984). "A Brief Illustrated History of Desalination: From the Bible to 1940." Desalination 50: 17–52.

Faruqui, Naser I.; Asit K. Biswas; and Murad J. Bino, eds. (2001). Water Management in Islam. Ottawa: International Development and Research Centre; Tokyo: United Nations University Press. A unique anthology that outlines the potential role culture and religion could play in the protection and efficient management of water resources.

Gleick, Peter H. (2004). The World's Water, 2004–2005. Washington, DC: Island Press. A biannual report that contains impressive current data on various aspects of water resources from around the globe, and a few state of the art articles.

Illich, Ivan. (1985). H2O and the Waters of Forgetfulness. Dallas: Dallas Institute of Humanities and Culture.

Olivera, Marcela, and Jorge Vian˜a. (2003). "Winning the Water War." Human Rights Dialogue 2(9). Also available from http://www.cceia.org/viewMedia.php/prmID/951

Postel, Sandra. (1999). Pillar of Sand: Can the Irrigation Miracle Last? New York: Norton. The book examines the role irrigation played in the rise and fall of ancient civilizations. It draws on this to examine how the current growing reliance on irrigation, the mounting water scarcity, salinization of soils, and the rising tensions between riparian states affects countries and could impact them in the twenty-first century.

Stumm, Werner, and James J. Morgan. (1996). Aquatic Chemistry, 3rd edition. New York: Wiley.

Swan, C. H. (1978). "Middle East: Canals and Irrigation Problems." Quarterly Journal of Engineering Geology 11(1): 75–78.

United Nations. World Water Assessment Programme. (2003). Water for People, Water for Life. New York: UNESCO Publishing.

U.S. National Research Council, Committee on Sustainable Water Supplies for the Middle East; Israel Academy of Sciences and Humanities; Palestine Academy for Science and Technology; and Royal Scientific Society, Jordan. (1999). Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: National Academy Press. Examines the need to enhance and protect sustainable water supplies in the West Bank and Gaza Strip, Israel and Jordan. It proposes criteria needed for developing sustainable water resources while maintaining environmental support systems. The collaborative study brought scientists and engineers from the U.S. National Academy of Research and from other countries in the region, and it marked unprecedented cooperation among Israel, Jordan and the Palestinian organizations.

World Commission on Dams. (2000). Dams and Development: A New Framework for Decision-Making. London: Earthscan.

Water

If a person knows nothing else about chemistry, he or she will likely know that water is H₂O. The chemical formula for water is common knowledge, used in advertisements, elementary school science classes, and casual conversation. But more than just a conversation piece, the formula H₂O can tell a chemist a great deal of information.

For starters, H₂O indicates that water is composed of two hydrogen atoms and one oxygen atom. That this is so can be demonstrated using very simple apparatus—a couple of pieces of wire, a battery, and some tap water. Electrolysis—the decomposition of water molecules with electricity—will result when the wires are connected to the ends of the battery and the other ends are immersed in the water with a small gap between them. One electrode releases bubbles of pure oxygen and the other pure hydrogen. Measuring the volume of gases released reveals that twice as much hydrogen is produced as oxygen. Twice as much gas means two hydrogen atoms for every one oxygen atom. Of course, this is our modern understanding of water. When these experiments were first tried, around 1800, an explanation for the results was not available. But the experiments did force scientists to think about the nature of water.

From our modern understanding of both the formula of water and the Periodic Table, we also know that the hydrogen atoms in water are bound to the oxygen. That is, water is "HOH" and not "HHO." We know that atoms can form either covalent or ionic bonds to give molecules. In water, the interaction of hydrogen and oxygen is a polar covalent bond, meaning that the two elements share a pair of electrons and that each atom contributes one of the electrons in the pair. Since hydrogen is the first element of the Periodic Table, it has only one electron and can form just one covalent bonding interaction. In the case of water, hydrogen bonds by sharing its electron with the oxygen. If hydrogen shared its electron with the other hydrogen atom in this instance, there would be no electron available to interact with the oxygen. Indeed, hydrogen gas, H₂, results when two hydrogen atoms form a covalent bond, and hydrogen gas is very different from water.

In a pure (nonpolar) covalent bond, both atoms have possession of the electron pair exactly the same amount of time. In a polar covalent bond, there is unequal sharing that results from an inequity in the distribution of the electrons due to the effective nuclear charge on the atoms. This polarization of the O-H interaction is critical to explaining all of the properties of water. It results in water having a dipole with the hydrogens having a slight positive charge and the oxygen having a slight negative charge. (More precisely, the advanced explanation is that the molecular orbital that describes the oxygen-hydrogen interaction has more oxygen character, resulting in a skewed electron distribution.)

If we consider oxygen's position in the Periodic Table, we know that it starts with six valence electrons, and since it has two bonds with hydrogen, two of its electrons are involved in bonding pairs. This means that the oxygen has four electrons remaining. These electrons are organized into two "non-bonding" pairs. That is, the oxygen of water has four pairs of electrons around it—two that are interacting in polar covalent bonds with hydrogen and two that are not interacting when water is in the gaseous state. Four electron pairs means that the atoms adopt a tetrahedral arrangement with the two hydrogens occupying two corners and the electron pairs occupying the other two.

In a perfect tetrahedron, the angle between the hydrogens would be 109.5°, but because the lone pairs occupy a little more space, the experimentally measured angle in water is actually 104.5°.

The presence of two lone pairs plays a very important role in "hydrogen bonding," which is one of the most critical properties of water. The positively charged hydrogen of one water molecule can be attracted to the lone pair of an adjacent molecule, resulting in a weak hydrogen bonding interaction. This bonding is much weaker than the polar covalent bond that holds a water molecule together, but it is a substantial inter-molecular interaction resulting in two water molecules being attracted to one another. Water forms an extended network of hydrogen bonding interactions, with each water molecule capable of both creating and accepting two hydrogen bonds. As a result each and every water molecule in the liquid or solid state is surrounded by four hydrogen bonded neighbors. The presence of hydrogen bonding interactions means:

• that water has an anomalously high melting and boiling point;
• that solid water or ice is less dense than liquid; and
• that water has a high surface tension.

Melting and Boiling Point of Water

Phase changes in matter result because of a change in the translational motion of molecules. A solid is a solid because its molecules are stuck in place. In a liquid, molecules can move past one another but are still closely associated. In a gas, molecules move independent of one another and only occasionally collide. It would make sense then that lighter molecules would shift from a solid to a liquid to a gas at lower temperatures than heavy molecules because they require less energy to get moving. Consider the molecular substances in Table 1.

Hydrogen gas, being the lightest and smallest molecule in the list, has the lowest melting point ( −259°C or 14.15 K or −434°F) and boiling point ( −253°C or 20.15 K or −423°F). Similarly, of the second row compounds with hydrogen, methane (CH₄) has the lowest melting and boiling points. However, water does not follow this trend. Its melting point is 0°C or 32°F. Its boiling point is 100°C or 212°F. Compared to the other molecules around it or its heavier cousin, hydrogen sulphide (H₂S), water has melting and boiling points that are anomalously high. This is due to the fact that the hydrogen bonds between water molecules must be broken for a phase transition to occur. The extra energy required results in more heat being necessary and a higher temperature.

Density of Ice

Hydrogen bonding interactions between water molecules hold the molecules in place in the solid state. The O-H^....O interaction spaces all of thewater molecules in an orderly array, much like students sitting in rows of desks. This spacing provides an open structure. When water is in the liquid state, the water molecules hold on to each other through hydrogen bonding interactions, but individual molecules can occupy the space between rows. The result is that at a molecular level, more liquid water molecules can occupy a given volume than when water is in the solid state. More students will fit in a classroom if they are allowed to stand than if they are arranged in nice neat rows. More molecules or more mass in a given volume means a higher density.

The decrease in density between water and ice has a number of important implications for the world around us. Ice floats because it is less dense than liquid water. This is not true of any other liquid/solid equilibrium. Solid methane sinks in liquid methane and solid ammonia sinks in liquid ammonia. Floating ice means that ponds and lakes freeze from the top down, allowing fish and other biota to live protected from the cold weather of winter. If water froze from the bottom up, life as we know it would not have evolved on Earth.

Surface Tension

Surface tension is a bulk property of matter and results in liquid water trying to contract to the smallest possible surface area for a given volume. Surface tension explains why water beads up on the surface of a freshly waxed car and droplets of water in a fog are spherical. The sphere is the shape with the minimum area for a given volume. Surface tension results because of the asymmetry of forces at the surface of liquid water. Water molecules at the surface are missing their hydrogen bonding interactions on one side. They are being "tugged" back into the bulk of solution.

Of course, occasionally water molecules have sufficient energy to leave the surface, resulting in evaporation. Conversely, sometimes water molecules in the gaseous state strike the surface of a drop of water and have insufficient energy to leave again. The result is condensation. The competing rates of evaporation and condensation lead to the formation of clouds and fog, to cloudy mirrors after a shower and iced-up windows on a winter's day.

Surface tension is also critical to capillary action. A surface that is covered in suitable molecules or functional groups, such as a glass surface or the cellulose of paper, will interact with water molecules and can actually draw the molecules out of the bulk. In this case, the interaction with the surface is stronger than the hydrogen bonding interaction between adjacent water molecules. As a result, water will creep up a glass tube or adsorb into paper. The latter is critically important in mopping up a spill or mess.

Universal Solvent

Water is often called the "universal solvent," as it is capable of dissolving a wide range of compounds—from sugars to salt, from DNA to hydrogen. Again, hydrogen bonding interactions play a role. For example, sugar dissolves because of the hydrogen bonding interactions between the hydroxyl groups on the sugar molecules (-OH groups) and the water molecules. But of equal importance to the dissolution of substances in water is water's capacity to act as a dipole. Water's negatively charged oxygen binds to sodium ions in salt while the positively charged hydrogens interact with the chloride ions. The result is that sodium chloride or table salt dissolves into ionic species that are more energetically stable with the sodium and chloride ions surrounded by water.

The ability of water to dissolve a wide variety of substances makes it the ideal medium for living organisms. Water's great solvency is also the reason that water pollution is so pervasive. Almost any substance will dissolve in water, including pesticides, herbicides, industrial waste, household byproducts, and a wide variety of other potentially harmful compounds. Indeed, we rely on the dissolving properties of water to get our clothes clean.

But the dirt and grime from our clothes must end up somewhere, and that somewhere is in the water that we discharge from our homes. The Law of Conservation of Matter says that matter can be neither created nor destroyed. The atoms and molecules that we dissolve into the water in our washing machines are only being removed to another location.

Dealing with the pollution of water is a huge task, and for too long the philosophy was "the solution to pollution is dilution." Dilution is no longer an acceptable approach, as it just shifts the problem instead of addressing it. Significant effort is being spent in both addressing the real problems of water pollution and in ensuring that we have access to clean water sources. There are many techniques for purifying water, with distillation providing the cleanest and purest water. Unfortunately, distillation requires a lot of energy as it is difficult to overcome the hydrogen bonds between water molecules. Distillation also leaves behind the polluting material, which must be disposed of in a manner that does not allow it to come in contact with water and thus simply dissolve again. The difficulties of maintaining clean water is one of the major challenges facing us in the twenty-first century. For without water, life as we know it would not exist. It is because of the shape and the interactions of that very simple molecule, H₂O, that water is the most essential of all chemical compounds.

see also Green Chemistry; Molecular Geometry; Valence Bond Theory; Water Pollution; Water Quality.

Todd W. Whitcombe

Bibliography

Atkins, Peter W. (1987). Molecules. New York: Scientific American Library.

Leopold, Luna B.; Davis, Kenneth S.; and the Editors of Life (1966). Water. New York: Time Incorporated New York.

Stanitski, Conrad L.; Eubanks, Lucy Pryde; Middlecamp, Catherine H.; and Pienta, Norbert J. (2003). Chemistry in Context : Applying Chemistry to Society. New York: McGraw-Hill.

Internet Resources

United States Geological Survey Water-Resources Investigations Report 98–4086. "Water Science for Schools." Available from <http://ga.water.usgs.gov/edu/index.html>.

Water

Hydrogen bonding

Three physical states

Essential to living things

What is water?

An unusual liquid

Today and tomorrow

Resources

Water is a chemical compound (H₂O) composed of a single oxygen (O) atom bonded to two hydrogen (H) atoms, which are separated by an angle of 105°. Because of this asymmetrical arrangement, water molecules have a tendency to orient themselves in an electric field, with the positively charged hydrogen toward the negative pole and the negatively charged oxygen toward the positive pole. This tendency results in water having a large dielectric constant, which is responsible for making water an excellent solvent. Water is, therefore, commonly referred to as the universal solvent. Water is the most abundant liquid on Earth. It covers more than 70% of Earth’s surface. Including the clouds (which are, of course, also water), it makes the entire planet look blue and white from space. About 97.5% of Earth’s water is contained in seawater. Approximately 1.875% is found in polar ice caps. The remaining 0.625% is drinkable water.

Since mineral salts and organic materials can dissolve in water, it is the ideal medium for transporting life-sustaining minerals and nutrients into and through animal and plant bodies. Brackish and ocean waters may contain large quantities of sodium chloride (NaCl) as well as many other soluble compounds leached from the crust of Earth. For example, the concentration of mineral salts in ocean water is about 35,000 parts per million. Water is considered to be drinkable if it contains less than 500 parts per million of salts. Water can be reused indefinitely as a solvent because it undergoes almost no modification in the process.

Hydrogen bonding

Hydrogen bonding, which joins water molecule to water molecule, is responsible for other properties that make water a unique substance. These properties include its large heat capacity, which causes water to act as a moderator of temperature fluctuations; its high surface tension (due to cohesion among water molecules); and its adherence to other substances, such as the walls of a vessel (due to adhesion between water molecules and the molecules of a second substance). The high surface tension makes it possible for surface-gliding insects and broad, flat objects to be supported on the surface of water. Adhesion of water molecules to soil particles is the primary mechanism by which water moves through unsaturated soils.

Three physical states

Water is the only common substance that occurs naturally on Earth in three different physical states. The solid state, ice, is characterized by a rigid crystalline structure occurring at or below 32° F(0° C) and occupying a definite volume (found as glaciers and ice caps, as snow, hail, and frost, and as clouds formed of ice crystals). The liquid state exists over a definite temperature range 32 to 212° F (0° C to 100° C), but is not rigid nor does it have a particular shape. In other words, it has a definite volume but assumes the shape of its container. Liquid water covers three-fourths of Earth’s surface in the form of swamps, lakes, rivers, and oceans as well as found as rain clouds, dew, and ground water. The gaseous state forms at temperatures above 212° F(100° C), and neither occupies a definite volume nor is rigid. In other words, it takes on the exact shape and volume of its container. It occurs naturally as fog, steam, and clouds. One phase does not suddenly replace its predecessor as the temperature changes, but for a time at the melting point or boiling point, two phases will coexist. As water changes from the gaseous form to the liquid form, it gives off heat at about 540 calories per gram, and as it changes from the liquid form to the solid form, it gives off about 80 calories per gram. The turbulence of thunderstorms is in large part due to the release of large amounts of energy into the atmosphere as water condenses into water droplets or into crystals of ice (i.e., hail). Pressure affects the transition temperature between phases. For example, at pressures below atmospheric pressure, water boils at temperatures under 212° F(100° C), so food will take longer to cook at higher elevations.

Water can pass directly from the solid phase to the gaseous phase without going through the liquid phase. This process occurs at low temperatures and greatly reduced pressures through a process called sublimation. Dehydrated foods are produced by sublimation, in which foods are quick-frozen and then placed in evacuation chambers. Dehydration by sublimation requires less energy than other methods, reduces physical deterioration that accompanies prolonged or excessive heating, and decreases the loss of volatile aromatic compounds responsible for flavor.

Essential to living things

Earth’s supply of water is constantly being recycled. It is evaporated from the oceans by the sun and is given off by the forests. The vapor condenses into clouds, which rain out onto the land. The land water runs off into the lakes and rivers, which then run back to the seas, and the cycle is complete. The total amount of water on Earth, in the form of oceans, lakes, rivers, clouds, polar ice, etc., is 1.5× 10¹⁸(one-and-a-half billion) tons, occupying a total volume of 8.7 million cubic miles.

It is impossible to overstate the importance of water to almost every process on Earth, from the life processes of the lowest bacteria to the shaping of continents. Water is the most familiar of all chemical compounds known to humans. It is essential to all living things, plant and animal. Humans drink it, wash with it, play in it, and cook in it. In fact, human bodies are more than one-half water.

Scientists never see absolutely pure water because it dissolves so many substances. If people want pure water, then scientists have to prepare it laboriously by such means as distillation, ion exchange, and reverse osmosis. Moving water even dissolves rock slightly, to form caves and to wear away mountains. All of the water on Earth, therefore, is in the form of solutions. The dissolved substances change the properties of water from what they would be in pure water. They affect its freezing point and its boiling point, among many other physical and chemical properties. The dissolved or suspended substances in water can be in the form of ions, molecules, or larger particles. For drinking water, bacteria must also be killed.

What is water?

Water is an odorless, tasteless, transparent liquid that appears colorless but is actually very pale blue. The color is obvious in large quantities of water such as lakes and oceans, but it can even be seen in a full bathtub. It is a single chemical compound whose molecules consist of two hydrogen atoms attached to one oxygen atom. The chemical formula of this compound is therefore H₂O. The two hydrogen atoms are attached to the oxygen atom in such a way as to make an angle-shaped molecule. The angle is not 90°, however, but 104.5°—close to a right angle, but a little wider.

The formula H₂O means that no matter how much water is talked about, it always contains exactly twice as many hydrogen atoms as oxygen atoms. Considering that a hydrogen atom weighs only about one-sixteenth as much as an oxygen atom, most of the weight in water is due to oxygen: 88.8% of the weight is oxygen and 11.2% is hydrogen. That goes for everything from a single molecule to a lake.

Water can be made (synthesized) from hydrogen and oxygen, both of which are gases. When these two gases are mixed, however, they do not react unless the reaction is started with a flame or spark. Then, they react with explosive violence. The tremendous energy that is released is a signal that hydrogen and oxygen are very eager to become water. Another way of saying that is that water is an extremely stable compound, compared with loose molecules of hydrogen and oxygen. It is hard to break water molecules apart into its components.

Not only that, but water molecules are stuck quite tightly to each other—at least when compared with similar compounds. The molecule-to-molecule stickiness is caused mainly by the fact that the water molecule is a dipole, because the oxygen atom pulls electrons away from the hydrogen atoms, giving the oxygen corner of the molecule a slight negative charge and the two hydrogen ends a slight positive charge. The negative part of one water molecule then attracts the positive parts of others like a magnet, although they can still slide around over each other as molecules do in any liquid. Water molecules stick to each other also by hydrogen bonds.

An unusual liquid

The strong attractions that water molecules have for each other are responsible for many of water’s highly unusual properties, as compared with other liquids of about the same molecular weight. Among these are:

1. Its unusually high boiling point (if it were similar to the other liquids, it would be a gas at room temperature).
2. Its high heat of vaporization (the amount of heat it takes to change the liquid to a gas).
3. Its high heat of fusion (the amount of heat it takes to melt solid ice).
4. Its high heat capacity (the amount of heat it takes to raise its temperature by a certain amount).
5. Its world-champion rank among liquids as a solvent (it has been called the universal solvent because it dissolves so many different substances).
6. The low density (the lightness) of ice, which makes it float on the surface of liquid water. As water is cooled to make ice, it gets slightly denser, like all liquids. But at 39.2° F(4° C) it reaches its maximum density; when cooled below that temperature, it gets less dense until it reaches 32° F (0° C), at which time it freezes and suddenly decreases to 91.7% of the density of the water. Being less dense than the water, the ice floats.

The normal boiling point of water is 212° F (100° C), and its freezing point is 32° F (0° C). In fact, zero and 100 degrees on the Celsius scale are defined as the freezing and boiling points of water. Water is also the standard by which many other quantities are measured. For example, the density of a material is often expressed as its specific gravity or specific weight: how many times denser it is than water.

In pure water, one out of every 555 million molecules is broken down—dissociated—into a hydrogen ion and a hydroxide ion:

H₂OH⁺ +OH^-

These ions are enough to make water a slight conductor of electricity. That is why water is dangerous when there is electricity around. The slight dissociation of water is responsible for the acid and base balances of all of the chemical reactions that take place in water, and that includes almost all the chemical reactions that take place anywhere, including those in the human body. Acid-base balance is probably the most important single factor that affects chemical reactions.

Today and tomorrow

Water is a major geologic agent of change for modifying Earth’s surface through erosion by water and ice. Water is also an important recreational medium, supporting fishing, swimming, and boating, and is a major factor in the tourism industry.

Water is scarce in many parts of the world, while it is plentiful in others. Many water resource experts state that water will become the next major commodity traded internationally. It has been called such phrases as liquid gold and the oil of the twenty-first century because of the increasing demands made by humans on water.

See also Groundwater; Hydrologic cycle; Hydrology; Irrigation; Precipitation; States of matter; Water conservation; Water pollution.

Resources

BOOKS

Black, Maggie. Water, Life Force. Toronto, Canada: Between the Lines, 2004.

Editors of I.B. Tauris. A History of Water. London, UK, and New York: I.B. Tauris, 2004.

Hancock P.L., and Skinner B.J., eds. The Oxford Companion to the Earth. Oxford: Oxford University Press, 2000.

Herschy, Reginald, and Rhodes Fairbridge, eds. Encyclopedia of Hydrology and Water Resources. Boston: Kluwer Academic Publishing, 1998.

Kandel, Robert S. Water from Heaven: The Story of Water from the Big Bang to the Rise of Civilization and Beyond. New York: Columbia University Press, 2003.

Lide, D.R., ed. CRC Handbook of Chemistry and Physics Boca Raton: CRC Press, 2001.

McConnell, Robert, and Daniel Abel. Environmental Issues: Measuring, Analyzing, Evaluating. 2nd ed. Englewood Cliffs, NJ: Prentice Hall, 2002.

Oxtoby, David W., et al. The Principles of Modern Chemistry. 5th ed. Pacific Grove, CA: Brooks/Cole, 2002.

OTHER

United States Environmental Protection Agency. “Water.” <http://www.epa.gov/water/> (accessed November 7, 2006).

United States Geological Survey, U.S. Department of the Interior. “Water Science for Schools.” <http://ga.water.usgs.gov/edu/> (accessed November 7, 2006).

Robert L. Wolke