Turn on a tap in Riyadh, Jeddah or Dammam, and the water almost certainly started as seawater. Saudi Arabia is the world’s largest producer of desalinated water. For most of the Kingdom’s cities, desalination is not a supplement to the water supply; it is the supply itself.

This makes desalination plants more than industrial infrastructure. Each is a critical point of failure for the cities it serves.

Their most vulnerable point is not inside the plant, but in the stretch of open water in front of it. An intake continuously draws water from the sea, along with whatever it contains: an oil sheen drifting in from a shipping lane, an algal bloom developing over several days or a discharge from a neighboring facility. Each can reduce output or, in the worst-case scenario, force a shutdown.

Here is what I believe deserves more attention. Across the region, coastal water quality is monitored through a combination of periodic sampling, laboratory analysis and, increasingly, automated real-time monitoring. But these approaches answer different questions.

A laboratory sample can establish water quality at a particular moment. It tells you much less about what happens between samples. A monthly sample captures one moment; a system logging readings every 15 minutes captures roughly 2,900.

Everything in between can remain invisible. An algal bloom can develop, peak and clear between two visits without being recorded. By then, a plant may already be operating at reduced capacity. For a sector supplying drinking water to millions, waiting for laboratory results is a costly way to discover a problem.

A second issue compounds this challenge: long-term records of coastal water quality remain uneven across the region. That matters increasingly because the baseline itself is shifting. The Gulf is already one of the warmest and saltiest marine environments on Earth, and it is getting warmer. Warmer water holds less oxygen, potentially intensifying other pressures. Without consistent long-term records, it becomes harder to track these changes accurately or establish what constitutes normal conditions.

The answer is straightforward and relatively inexpensive compared with what it protects: continuous real-time monitoring at water intakes.

Instruments can take readings around the clock, with hydrocarbon detection at the intake boundary and alerts sent directly to operators in real time rather than weeks later in a report. The value lies not in the measurement itself, but in the time it buys to close an intake, switch sources or deploy appropriate containment measures before contaminants enter the treatment process.

That approach works only if the readings are reliable. Sensors need regular calibration and inspection to produce trustworthy data. Gulf conditions make this maintenance more demanding than many expect. Keeping it up is easier when engineers and spare parts are available regionally rather than several weeks away.

There is another benefit: a lasting record. Every site instrumented today begins building an archive that, in 10 years, could help operators anticipate problems rather than react to them. Saudi Arabia is developing extensive new coastlines along the Red Sea and around projects that did not exist a decade ago. Each presents an opportunity to install monitoring systems from the outset rather than retrofit them after an incident.

Water security is usually discussed in terms of capacity: how many plants and how many cubic meters of water they can produce each day. Capacity is only half the equation. The other half is knowing what is in the water those plants depend on, while there is still time to act.

We cannot protect what we cannot measure.