Why water service interruptions happen even if dams overflow?

When a series of typhoons, capped off by Typhoon Ulysses, ravaged the country and unleashed heavy rainfall enough to overflow dams in Luzon, plenty of Filipinos were perplexed that water supply was suddenly interrupted. Doesn’t an immense amount of water in a dam indicate a surplus of water supply? The answer is no.

While there is literally an overflowing amount of raw water, this water is far from potable and therefore cannot be supplied to consumers instantaneously. Here’s why:

Turbidity

To easily visualize what a dam might look like if its walls were see-through – just like an aquarium – imagine a tall glass of hazy water with dirt at the bottom. The water is hazy because of minerals, soil, clay, etc., that flow into the dam with the water coming from mountain tops. The dirt at the bottom of the glass we are visualizing are called sediments—all the aforementioned minerals, dirt, and contaminants which eventually settled down.

When heavy rain strikes the dam water continuously, it’s as if you were mixing the glass of water and dirt with a spoon, eventually turning the water into one that may look like a chocolate drink with almost no clarity. This is called highly turbid water.

Simply put, turbidity refers to how clear or “muddy” water is. And while technology to treat turbid water exists, when turbidity is high and unlikely to settle anytime soon because of continuously pouring rain, it becomes very difficult to clean and supply to consumers at a normal rate.

From Dam to Home

Okay so the water is dirty and difficult to treat at a regular pace, thus the constriction and regulation of supply to ensure consistent quality. But how come some water service providers do not halt water supply even when turbidity is high?

Well this is because some water service providers have a huge impounding reservoir for raw water. When the raw water coming from dams is stored inside a reservoir first before it is allowed to enter a treatment facility, excess sediments naturally settle to the bottom by gravity. The result: Raw water becomes less turbid, allowing for easier and less costly treatment.

Water service providers that are not afforded the luxury of a similar impounding reservoir for raw water end up directly receiving muddy water from the dams during the rainy season. This highly turbid raw water is more difficult to treat. The result: Lower water production leading to service interruptions.

So why don’t they just build a reservoir for storing raw water? The short answer is that there is simply no space for one. Hundreds of hectares of unoccupied land near the treatment facilities would be needed. With our country as densely populated and highly urbanized as it is, one would be lucky to have land for a tiny house.

Hence, the only option for water service providers that don’t have a storage facility for raw water is to invest in more expensive treatment technologies.

Addressing water shortages

The good news is that investments for better water treatment are being made, as water service providers are aware of the impact of climate change and environmental degradation on our country’s raw water sources. Such investments are needed for long-term water security.

Meantime, water consumers can do something to ease the effect of water supply interruptions resulting from highly turbid raw water. A precaution we can take is to always have a supply of water stored for emergency use. And make sure to store just enough water for when the service will be disrupted. This is because the scheduled service interruption might lengthen if all consumers draw too much water simultaneously in a panic.

A good tip would also be to follow your water service provider on social media as they usually announce specific schedules through these channels.

All that being said, with all these investments and ongoing upgrades, the time will definitely come when we won’t have to worry about opening an empty faucet anymore.

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