Drainage and Reclamation of Salt-Affected Soils 24. [antikvár]

1. Introduction The Ebro basin is situated in north-eastern Spain and forms a geographic unit that is bounded to the north by the Pyrenees, to the east by the Catalan Coastal Mountains, and to the south-west by the Spanish 2 Plateau. It covers about 85 500 km . The basin is drained by the Ebro river and its tributaries, which rise in the Pyrenees and the Iberian Mountains. The region is the driest part of northern Spain because it is surrounded by high mountain ridges which isolate it from any Atlantic and Mediterranean influences. If water is available, however, the climate permits irrigated agriculture, the main crops being maize, lucerne, and fruit trees. The oldest irrigation schemes consist of canals diverted from the Ebro river. Construction of the Canal de Tauste on the left bank commenced in 1252 and the system of the Canal Imperial de Aragón, which irrigates the right bank downstream of Tudela, was finished in 1 786. Early in the 20th century new irrigation plans were made to use the surface water resources from the Pyrenees for agriculture. The Canal de Aragón y Cataluna and the Canal de Urgel were first constructed and some years later the Bardenas-Alto Aragón irrigation scheme was designed. This irrigation scheme consists of a series of reservoirs which will regulate the flow of the three main tributaries of the Ebro river along its middle reach, i.e. Aragón, Gállego and Cinca, and three main irrigation canals. Although parts of these canals had previously been constructed, 1