Río Celeste (Sky-Blue River) in Tenorio National Park (Costa Rica), a river that forms from the mixing of two colorless or normal streams—Río Buenavista (Buenavista River) and Quebrada Agria (Sour Creek). The combined river has striking blue color that seems almost unnatural while the tributary rivers have no color at all. There are several theories as to why this river turns blue after the confluence including the legend that god dipped his pain brush here after painting sky blue. Unlike glacier fed lakes like Lake Moraine in Banff that have bright blue color due to fine particles of rock flour suspended in water, resulting from glacial erosion, Rio Celeste is not a glacial fed river.
El Teñidero-Dye point -Nature’s chemistry lab
The nerd in me was very happy when I found out why the 2 colorless rivers merge to form such brightly colored river. It’s pure chemistry! The last stop on the hike in Tenorio national park is called “El Teñidero” (dye point). The sky-blue color appears immediately after the dye point and the river maintains its bright blue coloration over a distance more than 14 km including at the waterfall Río Celeste.
The scientific explanation for this color change is that both rivers contain aluminosilicate particles, but the size and concentration of these particles are too small to scatter light to get the blue color on their own. Here is where science does its magic. Quebrada Agria or Sour creek as it is aptly called is fairly acidic (pH of 3.1), and Río Buenavista was rather neutral with a pH of 6.8-7. When the acidic and neutral waters of the two rivers meet, their aluminosilicate particles clump together, resulting in enough particle concentration and size to scatter light and the vivid blue color appears!
Other noteworthy points to stop on this hike are the laguna Azul and the borbollones as well as the view point to see the volcano. Laguna Azul is very peaceful, and we saw a turtle hanging out on a log here.
Borbollones or the boiling point reminds you that you are in an active volcano area and you smell the sulphur gases before you see the bubbling river.
Rio Celeste waterfall
The main attraction in this park is the Rio celeste waterfall and most people tend to turn back after seeing the waterfall but the hike from the waterfall to the end point is only 1 km and it is worth the hike.
The waterfall has an amazing blue color and you need to get down few steps before you can reach the viewpoint. We spent lot of time here appreciating the beautiful color as well as the setting in the middle of lush green rainforest. The contrast of colors is absolutely gorgeous.
Practical Information on how to get to Rio Celeste:
Rio Celeste opens at 8:30 am, but you can arrive at 8 am to get tickets. The park allows 1200 visitors per day and pre-purchasing the tickets is not possible. The latest admission to the park is 2 pm, and everyone has to exit by 4 pm. Here is a good blog on information about visiting the Rio Celeste.
Word of Caution : Water won’t have the bright blue turquoise color it is famous for after heavy rain. Check the weather and rainfall in the area before going. Some rain is normal for this area, and it pretty much rained every day when we visited.
We did a guided tour through Canoa Aventura in La Fortuna which included lunch at restaurant Tenory. This was a great restaurant with lots of vegetarian options and it is about 5 min from the entrance of the Tenorio Volcano national park. We saw bunch of animals including some venomous snakes and monekyes.
Peaks to Palaces 