A river colored by mountains
The Katun River's striking turquoise color is not caused by tropical warmth, but of immense cold and pressure. The river begins at the Gebler Glacier, which sits on the southern slopes of Mount Belukha, the highest peak in the Altai Mountains at 4,506 meters. As this and other glaciers grind their way down the mountain, they pulverize the bedrock into a fine silt known as glacial flour or rock flour. These silt-sized particles become suspended in the glacial meltwater.
The resulting cloudy water gets its color from the physics of light scattering. The fine particles of rock flour suspended in the water absorb the longer wavelengths of light (reds and yellows) and scatter the shorter wavelengths (blues and greens). This gives the water its milky, blue-green appearance. The intensity of the color changes with the seasons. It is most bright in the late spring and summer when melting glaciers release large volumes of this sediment-laden water. In the autumn and winter, when the river is fed more by groundwater, the flow decreases, the sediment settles, and the water becomes clearer.
An artery of the Golden Mountains
The Katun River flows for 688 kilometers, draining a basin of 60,900 square kilometers before it joins the Biya River to form the Ob River, one of Siberia's largest rivers. The river and its surrounding area are part of the Golden Mountains of Altai, a UNESCO World Heritage Site. The designation recognizes the region for having the most complete sequence of altitudinal vegetation zones in central Siberia, from steppe to alpine biomes.
The river carves a dramatic path, dropping over 2,000 meters in elevation from its source to its mouth. This steep gradient creates numerous rapids, making it a popular destination for whitewater rafting. The cold, oxygen-rich waters, which rarely exceed 15°C even in summer, support a distinct aquatic ecosystem. Fish species adapted to these conditions include the Siberian grayling, lenok, and the taimen. The river receives water from 254 tributaries, many of which are also fed by glaciers, contributing to the Katun's unique chemistry and color.