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Wageningen University (1978)

Drainage and reclamation of salt-affected soils in the Bardenas area, Spain

Martinez Beltran J.

Titre : Drainage and reclamation of salt-affected soils in the Bardenas area, Spain

Auteur : Martinez Beltran, J.

Université de soutenance : Wageningen University

Grade : Doctor 1978

Résumé partiel
Chapter 1 The Ebro basin is situated in north-eastern Spain and forms a geographic unit bounded by high mountains. The Bardenas area lies in the Ebro basin and forms part of the Bardenas Alto - Aragón irrigation scheme, which was designed to make use of the surface water resources from the Pyrenees.
Chapter 2 The Ebro basin is a tertiary sedimentation basin in which the Ebro river and its main tributaries have incised alluvial valleys. The tertiary sediments consist mainly of mudstone, locally with interbedded gypsum layers, and very fine siltstone. Both sedimentary rocks are fine textured and, because they were deposited in a brackish lacustrine environment, contain harmful soluble salts. The main landscape-forming processes were erosion, transport, and deposition under semi-arid climatic conditions. The highest parts of the landscape consist of old tertiary formations which form the uplands of a dissected plain. At a lower level mesas occur, which consist of coarse alluvium covering the underlying tertiary sediments. Most of the eroded sediments were removed from the area but local sedimentation also occurred. Owing to the semi-arid conditions, both sediments and salts were deposited. The highest salt concentrations are found in the lowest parts of the alluvial formations, especially where the alluvium was derived from the eroded mudstone and siltstone. Between the residual uplands and the low-lying alluvial formations, piedmont and colluvial slopes occur. Within the Bardenas area ten major physiographic units were defined, each of them subdivided into minor components and indicated on the soil map. The Ebro basin is the driest part of northern Spain. The climate is semi-arid and becomes drier from the borders to the centre of the depression. The seasonal variation in temperature is great. Potential evapotranspiration exceeds total precipitation, which is extremely variable and is not concentrated in distinct rainy seasons. Wind velocity is high and both cold and warm dry winds are common. Evaporation thus occurs even in winter when temperatures are low. A great part of the area is cultivated, so that natural vegetation is restricted to residual and eroded soils not used for agriculture and to salt-affected soils where halophytes grow. Irrigated farming is influenced by soil conditions. Salt-free soils are under full irrigation, the main crops being maize, lucerne, sugar beet, and some horticultural crops. The cropping pattern on the saline soils depends on the degree of salinity. Barley and sugar beet are grown on moderately saline soils and lucerne on succesfully leached soils. On the higher lands, not under the command of the irrigation scheme, barley is grown.
Chapter 3 The study area comprises two drainage basins. The northern part drains to the Aragón river, the southern part to the Riguel river, which is a tributary of the Arba river. Drainage and salinity of the groundwater depend on the situation of each geomorphological unit and its relation to adjacent units. The groundwater in the fluvio-colluvial formations of the northern basin is shallow and highly saline. An ephemeral perched water table is found in the mesas, where the groundwater is non-saline. No shallow water table was found in other physiographic units. The irrigation water is of good quality as its EC is at the lower end of the C 2 -range. The SAR is also in the lowest range S 1 and the RSC is zero, so there is no danger of alkalinization. ....

Mots clés : alkaline soils / drainage / improvement / irrigation / land / polders / reclamation / saline soils / salinization / sodium / soil / soil science / solonchaks / spain / iberian peninsula / unproductive land


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Page publiée le 21 janvier 2015, mise à jour le 14 janvier 2018