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What is a Blue River?

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The science behind a blue river like Rio Pejamo - A great spot for taking dips

PART I – Posted June 2017

Let’s dive straight into the blue-waters of Costa Rica’s rivers. They are so blue it looks like you could bottle it and take it home; but unfortunately, that’s not possible!

There is a scientific explanation for blue-rivers. First off, the blue-color is an optical illusion created when clear water flows over a riverbed coated with special chemicals. Those chemicals are transported by the river from beneath the volcano and settle, coating the riverbed. At the source of the river the chemicals can be seen bubbling-up in the water and then settle as they flow down-stream. Water flowing over these coated sections reflects the colors of the spectrum in manner permitting the blue-rays to appear as the dominant color.

Much speculation over the cause of the brilliant blue-water continues today. The confusion arose when no one could explain what they saw on the renowned blue river, the Rio Celeste. Between the provinces of Alajuela and Guanacaste, two crystal-clear rivers flow through the Tenorio National Park and then join. These rivers, the Quebrada Agria (Broken Ravine) and Rio Buena Vista (River with a Good View) flow independently as crystal clear rivers before meeting at Teñidero (dye point). At Teñidero, these clear waters turn turquoise-blue and continues on thereafter.

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The cause remained a mystery for many years, until the University of Costa Rica’s research confirmed no chemical or mineral concentrations made the water blue. Instead, the blue color is an optical phenomenon; the result of light rays being deflected by certain minerals coating the riverbed as sunlight passes through the water. The water acts as a prism and separates the sunlight into the seven primary-colors. Each color is a ray of light with its own specific wavelength. The seven colors combining to make white light are- violet; indigo; blue; green; yellow; orange; and red. Each color’s ray has a different wavelength; as explained in <Phillip Gibbs May 1997>.

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When light passes through certain mediums, some ray’s wavelengths are amplified and others reduced. In the case of the Blue River’s water, the blue rays are amplified while others are reduced where the water flows over those sections of the riverbed coated with the compound ‘aluminum-silicate’.

Blue Rivers of Costa Rica - Blog Contents

Intro - Costa Rica's Blue Rivers
A special allure

Part II - Rio Celeste vs. Rio Azul vs. Rio Penjamo
Fantastic Eco-tourism and adventure in and along these blue rivers

... Back to our Costa Rica Blog
... Picture Gallery of Blue Rivers
... Visit Blue River Resort & Hot Springs

Part III – Volcanoes Create Blue Rivers
Rivers, rain, hot springs, irrigation - an almost continuous source of water for the lush tropical rainforests and growing world beating exports.
Part IV - Costa Rica’s Blue Rivers
Names and descriptions of the major colored Costa Rica Rivers - blue, while, yellow, green, black and more.

Eco-Adventures
1-Day Tour: Blue River Adventure & Hot Springs
Drop-ins & Hotel Guests: Blue River & Grand Waterfalls

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