"Synthèse hydrogéologique sur la region d’El-Oued Sahara nord oriental – Est Algérien"

Abstract

"On the North-east of the big Erg Oriental (low Sahara) and under the Saharan Climate (hyper dry type), which reigns over all the Southern Algerian, is located « El Oued valley ». low rainfall and high temperature have an impact on the other climate aspects. It covers an area of 11738 km sudivised into 18 Townes. The latter, is based on the most important water resources in the world: the reservoir of continental infill contained in the lower cretaceous formation hence its name « Albion web » covers 600000 km2. Overcome by the final complex reservoirs ( first and second web miopliocene limestone aquifer senonian-eocene ) which covers the are350000 Km2 a offend finally the web is the most requested for irrigation purposes contained in the sandy and clay alluvial formation Quaternary. It is unfit for the AEP and even for irrigation (by location) after the results of chemical analyzes. Geology within the study area consists of sedimentary series stratigraphically going from lower cretaceous to Quaternary. After the piezometric measurements the direction of flow is from the Southwest to the Northeast. The interpretation of pumping tests allowed defining the different hydrodynamics settings. The rising groundwater level from 1980’s is causing phenomena that become thorny and subsequently alarming is the upwelling of the shallow aquifer. We have two different phenomena and inverse relative to each other. A layer that suffers from the arrival of water from the deep and a layer which suffers from intense protruding samples the ground water recharge. These two phenomena have disturbed the natural balance of their operation which caused an increase in the salinity of water and soil, and let to a corrosion of water pipes by extremely high levels of sulfates and chlorides. The recommended solutions to the hydrodynamic context are the creation of new agricultural irrigation from groundwater. Reduce or eliminate irrigation from deep aquifers. Follow continuously the evolution of fluctuation in the shallow aquifer. For hydro geochemical context and environment, the solutions consist of softening water, irrigation and water supply networks and consider conventional chemical and bacteriological treatments"