Mineral particles from heavy rain likely turned Perak River blue

Unusually heavy rainfall and changes in water flow are the primary suspected causes behind a recent phenomenon where sections of the Perak River in Hulu Perak turned a striking shade of blue. Environmental science expert Dr. Abdul Rani Abdullah explained that the Hulu Perak region is naturally abundant in minerals, which are then transported into the river system via runoff during periods of intense rain.

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When it rains, we associate it with runoff. The effect of runoff is greater when its source is an open area.

Dr. Abdul Rani, an Adjunct Professor at Universiti Kebangsaan Malaysia, elaborated that the blue coloration is not a constant occurrence. It depends on a confluence of factors: the presence of specific minerals, a sufficient concentration of these minerals, and suitable water flow conditions. He noted that the river's flow slows considerably as it widens, allowing these mineral particles to accumulate and remain suspended in the water for longer durations.

When light interacts with these suspended fine mineral particles, it causes scattering and reflection, resulting in the bluish appearance. Minerals such as copper, iron, aluminum, and silica are known to influence water color, with particle size also playing a role in light dispersion. This phenomenon is not unique to the Perak River, having been previously observed in other Malaysian locations like Bau in Sarawak, Semenyih in Selangor, and Bukit Ibam in Pahang.

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The water does not turn blue all the time. It happens from time to time and depends on several factors that must exist simultaneously.

While some have speculated about rare earth element (REE) mining activities contributing to the discoloration, Dr. Abdul Rani pointed out that similar blue water events were recorded in the area around 2019, predating current mining operations. Nevertheless, he did not entirely dismiss the possibility that mining activities could contribute mineral substances to the river system.

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When the flow slows down, it gives certain minerals an opportunity to accumulate or remain in a particular area for a longer period.