Surface water resources are also constrained by the irregularity in rainfall between months and years. Moreover, surface water resources have a very high inter-annual variability, with a minimum of 780 MCM/yr, as observed in 1993-1994

With below 500 m3/cap/yr, Tunisia is facing a serious water deficiency. Groundwater extraction often exceeds natural recharge, resulting in a progressive decline of the groundwater table and a deterioration of the water quality. The situation is expected to worsen due to population growth and urbanization as well as the effect of climate change on the availability and variability of water resources.