The Phenomenon That Makes Costa Rica’s Rio Celeste Turquoise

Hidden deep within Costa Rica’s Tenorio Volcano National Park is one of the wildest and most beautiful sights I’ve ever experienced as a traveler.  We’ve all seen crystal clear mountain streams, or the occasional emerald or bright blue lake, but never before my visit to Rio Celeste had I witnessed that particular bizarre and enchanting color of pure turquoise.  What began as an accidental point of interest, turned into my favorite part of the entire trip to Costa Rica.

With every adventure I embark on, I begin the research and planning phase by typing “beautiful nature” and the name of my destination (in this case “beautiful nature Costa Rica”) in Google Image search.  It’s a nice way to get an overview of the various points of interest and locations you might not immediately find on tourism websites.  Last year, when planning a short trip to Costa Rica, at least five images of unbelievable turquoise water — a color so bizarre that it borders on artifice — appeared on the first page of search results alone.  After some preliminary research, I discovered that the iconic color of was not photoshop trickery but the real deal, belonging to Rio Celeste, in a more remote and less touristed area of the Guanacaste/Alajuela border.

We arrived at the trailhead after a bumpy and laughter-filled hour spent white-knuckling in the back of a pick-up truck, refilled our water bottles and started the hike through a dim and dense jungle.  For me, hikes like this are always filled with anticipation and excitement.  The research I did at home suddenly feels less distant as memories of beautiful thumbnail-filled pages of search results pop back into my head.  Finally, after hearing the roar of an impending waterfall grow gradually over the past ten minutes, we reached the top of a very tall staircase leading down into the jungle.  I thought I knew the beauty that awaited me, but I was totally unprepared.

With photography as a primary interest in my travels, I spent quite some time composing and recomposing shots of the waterfall and magical pool before me.  I paid careful attention, memorizing the color of the water so I could match it in post-processing should the white balance in my images fall short of doing that epic turquoise justice.  I’ve visited hundreds of waterfalls in my life, most taller or wider, but nothing like this.  Not ever.   It’s a remarkable feeling to stand and look at something that utterly defies what you’ve previously seen in your life.  That was my experience at Rio Celeste.

We climbed back up the tall staircase, muddy from morning rains and ambient humidity, to rejoin the trail and follow the river to its source.  The trail parallels the river for some distance through lush jungle, along sandy riverbeds, over narrow “bridges”, and past pools of brilliant turquoise, all calling you to slip off your shoes and wade in.  Then, you reach a truly bizarre and inexplicable sight.  The source of Rio Celeste provides an even greater sense of magic as two absolutely transparent streams merge to immediately burst into beautiful, saturate color right before your eyes.

The remarkable turquoise water of Rio Celeste was a scientific mystery for some time. Scientists were unsure how Celeste could be fed by two clear rivers (Quebrada Agria and Río Buena Vista), and yet when the rivers meet, create this vivid other-worldly color. For a while, it was believed that the color change was due to a chemical reaction from the volcanic soil.  The smell of sulfur is very present along the river and at the waterfall so it’s no wonder that it was considered as a cause.  More recently, scientists determined that the color has less to do with chemical reactions and more to do with the optical appearance of sunlight reflecting off suspended particles:

Investigators were surprised that the water only remained blue in the river bed, as upon putting the water in test tubes, it looked completely transparent through the glass.  They then continued to investigate and found that the blue color seen by the human eye in the waters of the river is not a chemical phenomenon, but rather optical. This means that the blue is not produced by a chemical that colors the water, but that it is related to human eye perception and the scattering of sunlight caused by the water.

Sunlight contains the entire color spectrum, similar to the way we see them all in a rainbow. In any other river sunlight penetrates to a certain depth and no particular color is deflected or reflected back to the surface, so it looks transparent, while in the Río Celeste the water passes some of the Sun’s rays, but reflects the bluish tone group. So the water appears blue to the human eye. This also applies to devices made like the human eye, such as cameras. (The Costa Rica Star)

So each river contains a certain size of suspended particles.  Alone, the particles reflect light in the traditional, non-remarkable way and the source rivers appear clear. Yet when the rivers combine, the particles merge and fill in each other’s gaps to form the perfect reflective surface for the eye to perceive this specific turquoise hue.  Rio Celeste is only uniquely beautiful because of the confluence and cooperation of two entirely separate, non-remarkable rivers — and the beauty is truly in the eye of the beholder.

A purely scientific explanation did little to diminish the magic of Rio Celeste for me.  As a photographer, I was inspired by the beauty and visual impact of the phenomenon.  As a writer, my mind filled with romantic metaphors about cooperation, strength, and beauty — the whole truly greater than the sum of its parts in such a literal, obvious way.  As a traveler, I began to wonder what other unique and extraordinary sights like this exist in the fringes of international awareness.  A trip to Costa Rica’s Rio Celeste sparked a reinvigoration for me both artistically and as an explorer, reminding me that the world is a wild and beautiful place and that a life spent exploring is a life well spent.