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Abstract

Water quality is subject to frequent changes in the Drean-Annaba alluvium aquifer. Water-rock interaction can not be the only process that produces the observed modification, but dryness that the country knew during the last two decades has highly contributed to the water quality changes. During this period, irregularities in the distribution of rainfalls, in time and space, have been observed. As a result, a periodicity in hydrochemical changes in water of wells and rivers is noticed. Statistical, the principals components analysis (PCA) tools and Tickel diagram have been used to show, through chemical presentation, these effects. The results show, indeed, seasonal changes of water quality for the period 1999-2000. From a cationic point of view, a competition between alkaline and alkaline earths is shown. On the other hand, from an anionic point of view, there is a transition from chlorides to sulphates and may be to bicarbonates. The present work was carried out in a relatively small area and this was useful to show the relationship that existed between dryness and water quality of both the aquifer system and surface water.

Abstract

Morphostructural, hydrogeological and hydrochemical approaches were applied to Hammamet plain and its surrounding mountains in the eastern part of Algeria to characterize the groundwater system and its potential for exploitation. The Essen and Troubia Mountains form the natural boundaries of Hammamet plain. The objective of this study is to utilize remote sensing techniques combined with structural analysis, hydrogeology and hydrogeochemistry to identify the potential fracture zones for groundwater in the strongly fractured and karstified deep aquifers. The delineated zones of potential groundwater resources are verified by detailed hydrogeological field surveys.

From a hydrogeological point of view, these two mountains, constitute a unit limited by faults oriented ENE-WSW, NNW-SSE and NNE-SSW. Specifically, fractures of the latter two directions influence the compartmentalization and the hydrogeological functioning of this unit. According to the degree of fracturing and/or karstification, two basic types of aquiferous behaviour have been distinguished: fissured aquifer (Essen Mountain and Troubia Mountain), and porous aquifer (Hammamet plain).

The study of the hydrochemical characteristics of groundwater samples shows that the majority of samples are mainly of HCO3 and Ca2+ water type. The ionic speciation and mineral dissolution/precipitation was calculated with the PHREEQC software. The chemical composition of the water is influenced by the dissolution and/or precipitation processes during the water–rock interaction and by the cationic exchange reactions between groundwater and alluvial sediments. The high content of CO2 in the water samples suggests that they circulate in a geochemical open system. The isotopic analysis of some groundwater samples shows a similarity with the meteoric waters, which reflect their short residence time and a low evaporation of the infiltrated water.