Water stress, explained

We often speak of a “water shortage”, but the technical term is more precise: water stress. Understanding what it covers helps to grasp the Tunisian situation.

Defining water stress

Water stress refers to the situation where demand for water exceeds the amount available over a given period, or where the quality of the water restricts its use.

A common indicator is the amount of renewable fresh water per inhabitant per year. Reference thresholds are widely used:

• below 1,700 m³ per inhabitant per year: a situation of stress;
• below 1,000 m³: scarcity;
• below 500 m³: absolute scarcity.

Tunisia lies lastingly below the scarcity threshold, at around a few hundred cubic metres per inhabitant — one of the lowest levels in the region.

Why Tunisia is in the red

Several causes combine:

• a naturally limited resource, with scarce and irregular rains;
• rising demand — population, irrigated agriculture, tourism;
• significant losses in the distribution networks;
• overexploited groundwater, which recharges more slowly than it is drawn down.

The effect of climate change

Climate disruption acts as a multiplier of this pre-existing stress:

1. less average precipitation, and more irregular;
2. more evaporation, driven by the heat;
3. a rising sea, salinising some coastal aquifers.

The result is not simply “less water”, but less reliable water, harder to mobilise in the right place at the right time.

What this implies

Faced with this, the levers lie above all in adaptation: reducing network losses, reusing treated water, adjusting crops to the real resources, and better distributing a water that will remain scarce.

Going further

To place this factor among the others: Why Tunisia is particularly exposed