The real wild card for political and social unrest in the Middle East over the next 20 years is not war, terrorism, or revolution—it is water. Conventional security threats dominate public debate and government thinking, but water is the true game-changer in Middle Eastern politics.

Scholarly work on water has often focused on shared rivers as a potential cause of war between countries. But countries in the Middle East have not gone to war over their rivers, and diplomats have been successful in keeping tensions to a minimum. Instead, finite supplies of underground water within national borders pose a more immediate and strategically consequential challenge. Groundwater has fed the agriculture that many regional leaders have used to cement political loyalties. Its potential exhaustion threatens existing political balances.

Water is a fundamental part of the social contract in Middle Eastern countries. Along with subsidized food and fuel, governments provide cheap or even free water in order to ensure the consent of the governed. But when subsidized commodities have been cut in the Middle East, instability has often followed. Water’s own role in prompting unrest has so far been relatively limited, but that record is unlikely to hold. Water has no substitutes, and while cheap in its natural state, water is expensive to process and transport. Future water scarcity will be much more permanent than past shortages, and the techniques governments have used in responding to past disturbances may not be enough.

The Middle East’s water problem grew out of its successes. The “green revolution” that swept the Middle East in the 1980s and 1990s made it possible for countries to sustain agriculture and feed growing populations, and high levels of agricultural investment continue today. In general, however, countries have focused too much on ensuring water supply and not enough on tamping demand.

Groundwater depletion will have a range of consequences for how Middle Eastern governments function and manage relationships with the governed. Migration will be one major problem, as populations dependent on agriculture find they can no longer make a living in rural environments. Political alienation will pose another challenge. As part of a system of agricultural patronage, water use is often a point of pride among certain populations or elites, who see it as a sign of their government’s favor. When groundwater runs out, it could challenge these perceptions—and the stability to which they contribute.

Preventing crisis is in part a matter of continuing to ensure adequate water supply. Investment in advanced technologies for water production, treatment, and reuse is a feasible route for some countries, particularly wealthy ones. On the demand side, countries must impose comprehensive water pricing systems and offer incentives for responsible use. In all countries, it will be crucial to change the perceptions of ordinary people about water and appropriate uses for it. If water appears to be a free resource, it will continue to be treated as an inexhaustible one.

Effective reform is within reach if governments work as much as possible within existing political and economic structures—framing water conservation in terms that citizens can understand and rewarding it with the kinds of incentives to which they are accustomed. But reform will need to happen quickly. A combination of government action and inaction has shaped the Middle East’s water problems, and only government action can prevent them from causing sudden upheaval.