A landscape dissolved by water
The Surxondaryo karst springs emerge from the foothills of the Kugitangtau mountains, a range defined by its unique geology. This region is a classic karst landscape, formed by the dissolution of soluble bedrock, primarily Jurassic limestone and gypsum. Rainwater and snowmelt, made slightly acidic by atmospheric carbon dioxide, seep into fractures in the rock. Over millennia, this weak carbonic acid has dissolved the rock, carving out an extensive network of subterranean channels and caves. This hidden underground drainage system captures surface water and funnels it through the mountains.
The speed of this underground water flow is remarkably fast. Dye tracing experiments, a standard method in hydrogeology, have demonstrated this directly. Scientists introduce a harmless, fluorescent dye into a sinkhole or sinking stream and then monitor nearby springs. In this region, dye has been observed to travel 40 kilometers through the underground network to a spring in just three days. This velocity, averaging over 550 meters per hour, indicates that the water is not slowly seeping through porous rock but flowing freely through open, cave-like conduits.
The springs' surface expressions
The endpoints of this subterranean flow are numerous springs that discharge large volumes of water. One of the most significant is the Oq-suv spring, which forms a major tributary to the Surxondaryo River. These springs are the primary discharge points for a vast underground water basin. The water emerges with a consistent year-round temperature, typically between 18-20°C, reflecting the stable temperatures deep within the earth.
The water is rich in dissolved minerals, especially calcium bicarbonate, picked up during its passage through the limestone. When this mineral-laden water emerges at the surface, the change in pressure and temperature causes the carbon dioxide to release, and the calcium carbonate precipitates out of the solution. Over time, this process builds up deposits of a type of limestone called travertine, creating terraces and other formations around the spring outlets. The mineral-rich water is an important resource for the region, supplying drinking water and irrigation for agriculture. Local legends often attribute healing properties to the springs, and places like Khuzhamaikhona have become local shrines.