Mathematical modelling of effects of Irawan irrigation project water abstractions on the Murzuq aquifer systems in Libya

The Murzuq basin in southwest Libya contains some of the main aquifers providing water for meeting the various water demands in the country. In particular, the Murzuq basin serves a number of irrigation agricultural development projects, including the large-scale Irawan Agricultural project. However, despite its strategic significance for the overall water balance in the country, very limited studies have been undertaken on the Murzuq to determine the long term impacts of the extensive water abstractions taking place in the basin. The aim of this study was to develop and apply a modular finite-difference groundwater flow (MODFLOW) model of the Murzuq. Extensive validation of the model showed it to be capable of adequately reproducing historic water levels within the aquifer. The validated transient model was then used to assess the impacts of medium and long-term water abstractions at Irawan on the piezometric levels in the aquifer. The results show that, with current farming practices at Irawan, the piezometric surface in the centre of the field closest to the cluster of the pumping wells will stabilize in year 2033 at 470 m.a.s.l., representing a maximum drawdown of 30 m. Further significant depression may not occur unless agricultural practices change, such as through an increase in the area cultivated or change in crops grown.