TRIAL OF PROTOCOLS AND TECHNIQUES FOR INTEGRATED GROUNDWATER MANAGEMENT IN ARID AND SEMI-ARID REGIONS TO COMBAT DROUGHT AND DESERTIFICATION

In order to combat drought and desertification, it is essential a holistic approach such as that one represented by the paradigm of the Integrated Water Resources Management (IWRM). IWRM can be considered as a flexible conceptual framework based on the principles of equity, efficiency and sustainability that indicates general guidelines for a more efficient water management. Within this framework, an effective solution consists, in particular in arid and semi-arid regions, in sustainable water management practices which include, in many cases, a combination of both water harvesting and managed aquifer recharge (MAR) techniques. This research was developed within the WADIS-MAR “Water harvesting and Agricultural techniques in Dry lands: an Integrated and Sustainable model in MAghreb Regions” demonstration Project (2011-2016) (www.wadismar.eu), funded by the EC under the Regional Programme “Sustainable Water Integrated Management” (SWIM) (www.swim-sm.eu). Among its objectives, the Project aimed at increasing groundwater availability through an integrated water harvesting and managed aquifer recharge system in two watersheds in Maghreb Region: Wadi Biskra in Algeria and Oum Zessar in Tunisia. Both areas are characterized by water scarcity, overexploitation of groundwater resources and high vulnerability to climate change risk. The overall objective of this research was to develop an interdisciplinary methodology to define guidelines for the design and implementation of integrated and innovative MAR systems that can be applied in arid and semi-arid environments. This methodology was tested in the two study areas in Algeria and Tunisia. As required by its application, with the support of the interdisciplinary research group of WADIS-MAR, the different components of the Water Resources System (WRS) at local level were defined: the water budget, the 3D hydrogeological model and the hydrogeochemical and isotopic characterization. Because of the lack of a sufficient number of quality data for hydrological modeling, a physiography-based indirect method for determining the runoff coefficient was applied at sub-basin scale for three watersheds (Koutine, Megarine-Arniane and Hajar) in the Tunisian study area. The water budget was estimated on a daily time scale basis, over a 10-year period (2003-2012), by using a simplified water balance model, through an agronomic approach, that considers effective infiltration as part of the surplus from water storage in the soil. An average Available Water Content (AWC) of soils and an average runoff coefficient were considered for each sub-basin. 3D hydrogeological models were implemented for both study areas through the realization of several balanced geological cross-sections and data processing in a 3D environment by 3D MOVE software. A detailed hydrogeochemical characterization was carried out, including bulk chemistry and multi-isotopic analyses of water and solid samples. The estimated average annual groundwater recharge of the aquifers resulted consistent with the reference values in literature. 3D hydrogeological model reconstruction showed that the groundwater circulation and the geometry of aquifers is strongly influenced by several tectonic structures and this evidence is confirmed by hydrogeochemical and isotopic results. All these results allowed to design MAR systems which are innovative because they present some technical innovations to improve the efficiency of managed aquifer recharge: the recharge chambers and the Passive Treatment System. Finally, the estimated potential recharge rate (m3 year-1) for the targeted aquifers related to the designed MAR systems were about 1.7 hm3 year-1 and 1.2 hm3 year-1 in Algerian and Tunisian study area, respectively.