Obiettivo - To define the limits of sustainable groundwater development in the continental intercalaire (CI) and Complexe Terminal (CT) aquifer in Algeria/Tunisia;- To determine the extent of modern recharge and the recharge history over the past decades (relating to climate change) using geochemical techniques;- To examine and evaluate the interface between recent recharge and palaeowaters for this aquifer system and the extent/risks of salinisation;- To define the sustainable limits to development of the aquifer.Expected Outcome- The study will provide a synoptic overview and a concise synthesis of the limits to development of the aquifer system, which is a type-basin-basin for other parts of North Africa;- ln combination with the existing knowledge of the area an up-to-date, bilingual report with Arabic summary on the overall conditions in the aquifer will be produced, providing to planning authorities the basis for appropriate management and conservation of the CI and CT aquifer systems.Results- The deep groundwaters of the Continental Intercalaire have been sampled (90 sites along four representative cross sections) in sites in Tunisia and Algeria between 2.20.00 E and 9.00.00 E and extending to 28.00.00 N. The principal east-west cross section spans some 350 km along a flow line (maximum depth 1800 m) which extends from M'Zab to the Gulf of Gabes. The isotopic evidence shows that these waters are palaeowaters many of which are beyond the range of radiocarbon dating. The average recharge temperatures of these waters however is around 17°C, indicating that they were derived from rainfall some 5°C cooler than the present day. Other information has been obtained on a wide range of chemical and isotopic indicators that are helping to solve the questions of residence times, source areas, heterogeneity and potability of these waters. For the overlying Complexe Terminal aquifer system, a similar number of samples have been obtained and clearly many of these have been recharged during the past 10000 years under climatic conditions similar to the present day.- The extent of modern recharge across the region of the Grand Erg Orientale has been carried out by studies of the moisture profiles of the unsaturated zone. Three boreholes have been drilled at Tozeur into Miocene sands of the Complexe Terminal and further profiles are being obtained at Redjem Maatoug in southern Tunisia and also at El Baguel in the West of the studied area. The approach adopted for recharge calculation is to use chloride (concentrated by evapotranspiration) contained in the unsaturated zone as a conservative record of inputs of atmospherically derived solutes. Chemical analysis of rainfall has been carried out in both countries as part of the recharge studies. Using the geochemical investigation of the unsaturated zone it is also possible to investigate recharge history over the recent decades and to investigate the extent of falling water tables. Recharge studies have also been carried out in the vicinity of wadis and in the Atlas foothills in both countries.Follow-up- An end of project seminar will be held in Damascus, Syria in collaboration with ACSAD (Arab Centre for the Studies of Semi-arid Zones and Drylands) in November 1997 at which the implications for the exploitation of groundwater from other large basins in the Arab region will be explored in the light of the Avicenne geochemical studies. Several papers are currently being prepared on the results and these will be presented at international symposia and the scientific literature.- Characterisation of the palaeowater system is being carried out through geochemical sampling for major and trace elements, stable isotopes, radioisotope, inert gas and in situ measurements of chemical parameters. Work is being carried out along several key traverses of each aquifer; - Recharge studies are based on field sampling and analysis of historic hydrogeological data, i.e. water table variations in oasis. Estimation of recharge is being carried out using geochemical methods and to support this rainfall sampling and analysis is being carried out over two seasons;- Recharge via wadi systems is being studied in two localities using the existing network of shallow wells; - Recharge via the Atlas foothills is being studied using existing data and through new geochemical sampling;- Salinisation is being studied at about 20 sites in two environments : near the Chotts and in the coastal zones to study the state of present day saline intrusion to confirm the source of salinity and establish the residence times of the saline pollution. Programma(i) IC-AVICENNE - Avicenne Initiative (Science and technology cooperation with the Maghreb and the countries of the Mediterranean Basin), 1991- Argomento(i) Data not available Invito a presentare proposte Data not available Meccanismo di finanziamento CSC - Cost-sharing contracts Coordinatore NERC British Geological Survey Contributo UE Nessun dato Indirizzo Nicker Hill NG12 5GG Keyworth Regno Unito Mostra sulla mappa Costo totale Nessun dato Partecipanti (2) Classifica in ordine alfabetico Classifica per Contributo UE Espandi tutto Riduci tutto Centre de Développement des Techniques Nucléaires Algeria Contributo UE Nessun dato Indirizzo 2,Bd Frantz Fanon 16000 Alger Mostra sulla mappa Costo totale Nessun dato Ecole Nationale d'Ingénieurs de Sfax Tunisia Contributo UE Nessun dato Indirizzo 3038 Sfax Mostra sulla mappa Costo totale Nessun dato
