The Argentine Republic: Its Development and Progress

by Pierre Denis

The need of irrigation is due to the scarcity of rain, but it is accentuated by a number of causes which tend to increase the aridity. The valles are the scene of scorching day-winds, the zonda, like the Föhn of the Swiss Alps, which, there being no snow, dry up the water of the springs and of the irrigation trenches, or use the deposits left by the waters to form dunes, which they push southward, sometimes like veritable glaciers of sand. Moreover, the soil of the valles is generally composed of coarse and permeable alluvial deposits, which absorb the rain-storms immediately. There is at the foot of both sides of the hills which enclose each valle an immense and far-lying bed of imperfectly rounded shingle. This double zone of detritus is strangely desolate, for the vegetation on it is restricted to isolated bushes of jarilla and tola. From the sheepfolds on the mountains to the oases in the valleys one hardly meets a single house. The bed of the valley is not so desolate. A broad ribbon of sand marks the dry bed of a torrent, and on the clays of its banks, if the sheet of water underground is not too deep, one finds, in spite of the goats and asses and charcoal-burners, little forests of algarrobas, which the foundries use for fuel.

The modern alluvial beds, gravel and sand, represent the upper stratum of a considerable series of continental deposits which lie on the Paleozoic crystalline rock of the Andes.[16] They chiefly consist of red sandstone and coloured marls, which crop up here and there through the alluvial covering and give the landscape a rugged character, worn by water and wind. There is no trace of humus: nothing to soften the vivid colours of the rock. Bodenbender, to whom we owe the first general attempt to classify the series, points out the importance of distinguishing the different strata in connection with the question of water supply and the conditions of human life.[17] A complete geographical study would have to follow the geological description in detail. In places—on the eastern edge of the Sierra de los Llanos—the fine modern clays are in contact with the granites of the hills and form above them a thick bed that is rich in fresh water. In other places—south-westward of the Sierra de la Famatina, as far as the Bermejo—the outcrop is of red sandstone only. The tablelands of Talampaya and Ischigualasta, which are cut across by the gorges of the tributaries of the Bermejo, form one of the most conspicuously desert regions in the whole Republic. Wherever the gypsiferous marls of the Calchaqui are near the surface, the springs are saline. The undulations of the impermeable rocky substratum bring to light the water that gathers in the alluvial beds. Thus the streams which come down the Famatina range in the west disappear in the alluvial beds on the fringe of the Sierra, but re-appear presently in the oasis of Pagancillo.

Hence the valles are by no means wholly productive. The oases represent only a limited portion of them. It would be impossible to imagine a more striking contrast than that of the freshness and life of the oases compared with the surrounding desert. Screens of poplars shelter them from the zonda. The water runs along trenches paved with round pebbles under the spreading vines, at the foot of which, to economize water and space, lucerne is sown. Each garden feeds a family. Near the raw-brick houses there are large earthenware vessels, as tall as a man, in which the corn is kept. The hammering of the cooper fills the air.

In places the oasis is watered by a stream. In those cases there is on each side of the bed of the stream a narrow fringe, a continuous ribbon, of smiling gardens, which hide the path. Above and below Santa Maria a trench is opened every mile in the wet sands of the Rio. The water rises in it and fills it, and is directed by it toward one of the banks, where it is jealously collected and distributed. The water which flows from the irrigated fields and returns to the river, as well as that which the porous side of the trench has permitted to escape, goes to fill another trench and supply other fields farther on. The region of Los Sauces, in the northern part of the province of La Rioja, to the south of Tinogasta, shows a different type of irrigated cultivation, on account of the sandy course of the stream. The fields follow the feeding artery for about fifty miles. It is bled at the beginning of each bend, the waters remaining underground like hidden wealth.

In most cases however, the valle has no running water. What reaches it from the lateral quebradas is lost in the alluvial beds accumulated at the point where the quebrada enters the valle. In order to make use of it the cultivated areas are grouped on the cone of deposition; at least, that is the position in the great majority of the oases. A costa is a line of separate oases with their backs to the same slope. When the valle is narrow, the costas on either side of the sterile depression face each other, like two parallel roads. The water of the quebrada is never sufficiently abundant to irrigate the whole of the cone of the torrent. In order to create an oasis there, they have selected the most easily cultivable zone, which is usually the foot of the cone, where the deposits are finer and more fertile, retain the moisture better, and require less watering. The summit of the cone is composed of coarse stones, the first to be dropped by the torrent as it loses its strength. These are bad lands, where the water is wasted.

To meet the occasional drought and the danger of sudden floods in this fluvial zone, which is entirely the domain of the torrent, there is need of constant care and ingenuity. At Colalao del Valle the cultivated fields are five or six miles from the summit of the cone. After a number of successive years of drought the stream of water which reached them on the flanks of the cone lost half its volume and threatened to disappear altogether. They then built a stone dam at the outlet of the quebrada, and the water accumulates behind this during the night. At three o'clock in the morning the sluices are opened, and the stream, having thus nursed its strength, reaches the fields down below about seven o'clock. Then the sun and the wind rise, just at the time when the reservoir is empty, and by the middle of the day the stream ceases, and irrigation is suspended. At Andalgala, above which rises the glittering crest of Aconcagua, the waters of the melting snows which feed the torrent have not time to be "decanted" before they reach the valley. They come down laden with mud and sand. Above the points where the irrigation-channels begin the people make, in the bed of the torrent, a dam of branches of trees which filters the water. It is swept away by every flood that occurs, and is at once restored.

What is even more admirable than the ingenuity of the vallista in utilizing the natural resources is the minute detail of the water-rights. It seems as if the vallista is even more cunning in protecting himself from his neighbour than in dealing with nature. The water-customs of these Andean valleys are worth an extensive study. The water does not belong to the State, and is not used by concession from the State. It is private property. The owner uses or abuses it as he pleases on the lands which he has selected. A man may be poor in land and rich in water, which he accordingly sells. There are frequent business deals in regard to water-rights, just as in regard to the soil and its produce. Appropriation of water often precedes appropriation of the soil. Many oases are communities where the non-irrigated lands are common to the whole population, and the irrigated fields alone are divided.

A primary group of customs regulates the relations to each other of communities higher up and lower down the same stream. At Catamarca the water of a certain stream is shared by Piedra Blanca and Valle Viejo. Piedra Blanca, in the upper part, absorbs the whole of the water for a week, but it must then suspend its irrigation during the following week and permit the stream to flow down the valley. The same evening, or the next morning, according to the season, the water reaches Valle Viejo. It is a custom known as the quiebras in the southern valleys of the desert side of Peru, where it allows different stages of cultivation to proceed simultaneously. In the same way, above Santa Maria, where several communities (S. José, Loro Huasi, etc.) receive the water brought by a channel from the Rio Santa Maria, each of them has a right to the full output of the channel for three days. At the end of that time the sluices are closed, and the water passes to the next community. There is grave trouble for any oasis that has its rights infringed or does not compel the communities higher up to respect them.