Groundwater resources of a multi-layered aquiferous system in arid area: Data analysis and water budgeting

The Maknassy basin in central Tunisia receives insignificant precipitation (207 mm/y), but the hydrological system retain very small quantities of water due to the steep topography and surface water resource partially mobilised witch is evacuated toward the basin outlet. However, the Maknassy plain support agriculture based on ground water irrigation with increasing water demand last decades. These developments have boosted agricultural productivity in the region. While these problems are mainly due to poor surface water management strategies in the region, the groundwater resources in this basin should be properly assessed and suitable measures taken for uniform surface water mobilization. As a first step in this direction, groundwater resources have been assessed. Regional specific yield (0.017) and groundwater recharge have been estimated on the basis of water table fluctuation method. Groundwater recharge amounting to 61.5 10(6) m(3) in a year takes place in the region through infiltration of rainwater (48.1 * 10(6) m(3) for phreatic aquifer and 13.4* 10(6) m(3) for the deep one), and recharge due to the infiltration in the Leben quady bed (1.57* 10(6) m(3)). Recharge to deeper aquifers has been estimated at 0.1* 10(6) m(3) during dry seasons. Assuming that at least 40% (102.61* 10(6) m(3)) of the total precipitation water (256.64* 10(6) m(3)) makes the runoff water, this important resource can be mobilized in order to increase groundwater recharge. Subject to an and climate, such region requires an integrated water resource management. It permits to keep aquiferous system equilibrium and participate to the sustainable development which integrates natural resource management.