The living architecture of Tat Sae
The cascading tiers of Tat Sae don't just exist in the landscape; they are actively built by it. These waterfalls are a travertine dam system. Travertine is a form of limestone deposited by mineral springs. The water of the Nam Khan river, which feeds the falls, is rich in dissolved calcium bicarbonate. This mineral-rich water flows over a series of limestone formations, and as it does, a remarkable transformation occurs. The structure of the waterfall is made by microscopic life, primarily cyanobacteria, which create the conditions for rock to form.
This process is a combination of biology and chemistry. Photosynthetic microbes, such as cyanobacteria and other algae living in biofilms on the rock surfaces, pull dissolved carbon dioxide out of the water. This removal of CO2 shifts the water's pH, making it more alkaline and causing the dissolved calcium bicarbonate to precipitate out of the solution as solid calcium carbonate (CaCO3) — the primary component of limestone. This newly formed mineral encrusts everything it touches, from the riverbed to mosses and leaves, building up the waterfall's structure layer by layer. The process can deposit several millimeters of new rock each year.
Turbulence and tufa
The physical environment of the waterfall dramatically accelerates this rock-building process. The rate of limestone deposition increases in areas of turbulence. As water tumbles over the cascades and splashes into the pools below, a physical process called degassing occurs. The agitation releases large amounts of carbon dioxide directly into the atmosphere, further encouraging the precipitation of calcium carbonate. This purely physical mechanism works with the biological action of the cyanobacteria.
The resulting porous rock, often called tufa when formed in ambient-temperature water, creates a unique and complex habitat. The constant deposition means the waterfall is a dynamic, ever-changing environment. These travertine systems build natural dams that create a series of interconnected ponds and cascades, altering the flow of the entire river system. The porous limestone structures also provide a specialized habitat for a variety of other organisms, from other algae to insects and small fish, which adapt to the distinct water chemistry and physical structure of the falls. The turquoise color of the pools results from the high concentration of calcium carbonate, which reflects light to create the bright hue.