Climatic and anthropic forcing on groundwater resources in a semiarid area: the case of the Ghriss plain, north western Algeria.

摘要

The drought which has been affecting north western Algeria for the three last decades has had important effects on all water resources and more particularly on the groundwater resource. The overexploitation of this resource, in order to supply the various water uses of the local populations and especially those of agriculture, threatens its perennity. The water-level drawdown of the Ghriss Plio-Quaternary aquifer towards alarming levels is causing major concern for the population of the area as well as for local and national authorities. This study examined whether this phenomenon has a natural or anthropic origin. Comprehending the structure and hydrodynamics of the Ghriss plain aquifer system is the initial and a necessary stage in analysing the total situation of the groundwater resource. The analysis of the rainfall recharge evolution in the study area showed a clear reduction since 1973 estimated at 25%. The pluviometric deficit was recurrent for several years, resulting in the reduction of the flow of the principal river of the Ghriss plain, the Fekan Wadi, before its total drying the last few years. The water table of the Ghriss Plio-Quaternary aquifer decreased drastically by more than 60 meters from 1970 to 2001 in some sectors. The restrictions of groundwater pumping imposed by the authorities since the beginning of 1990 have contributed to a decrease in withdrawal. The estimated recharge of the Ghriss plain aquifer system is 65.3 million m3/year and the total withdrawn volume is 64.7 million m3/year. A fragile equilibrium between recharge and withdrawal in the Ghriss plain aquifer system has been noted since the year 2000 resulting in a stabilization of the piezometric heads of the Plio-Quaternary aquifer.