The water-supply in the Tucuman district consists, primarily, of numerous evenly flowing streams which come down the eastern flank of Aconcagua (Lules, Famailla, Angostura, Gastona, Medinas, etc.). They join the Sali to the south of Tucuman. The Sali is an irregular torrent which rises in the sub-Andean depression to the north and Tucuman, and, after squeezing Aguadita between the north-eastern extremity of Aconcagua and the sub-Andean chain of Burruyacu, enters the plain at Tucuman. It then flows southward, meandering over a large bed of shingle in which it has not had force enough to excavate a valley, and the inclination of the land on its left bank (to the east) is toward the east and south-east. The lands on the right bank of the Sali are consequently better provided with water than those on the left bank. The difference is so marked that, as the estates on the right bank get most of their supply elsewhere, the water of the Sali nearly all goes to the left bank. In 1912 a siphon was actually constructed underneath the bed of the Sali to convey the unused water of the Rio Lules to the right bank. Lastly, to the north of Tucuman the Sierra de Burruyacu provides a few intermittent streams of water, which the _estancias_ (ranches) formerly conducted, with great labour, to their _represas_. These do not suffice for irrigation on a large scale. The sugar-cane was first grown at the gates of the town and, to the east, at Cruz Alta, on the left bank of the Sali. These were some distance from the mountain because, as there was less rain and the soil was fairly dry, the natural vegetation was less luxuriant, and it cost less to prepare the ground.[33] The Central Cordoba Railway, which passes along the right bank of the Sali south of Tucuman, is the axis of another zone of cultivation and of old factories. Colonization afterwards went further west. A new provincial railway, describing a section of a circle, was grafted at Tucuman (1888-90) and Madria upon the Central Cordoba line. It keeps close to the foot of the range, the _falda_, and enables farmers to settle on it. The new estates have not confined themselves to the alluvial plain; they have crept up the foot hills, and are constantly going higher. In the latitude of Tucuman the mountain approaches within eight or twelve miles of the Sali, and the possibilities of extension westward are strictly limited; indeed, they are already exhausted. Further south, on the contrary, the plain extends more than fifteen miles to the east of the provincial railway. West of Monteros, Concepcion, and the existing line of works, there is a reserve of available land; there is room for a fresh advance westward. There is also room for expansion to the north-east, at the foot of the sub-Andean chain of Burruyacu, where the frosts are slight. It is in this direction that most of the clearing is now going on.