Underwater 'Giant Curtain': A Warm Barrier for Fish

This year marks the 20th anniversary of the "Lucid waters and lush mountains are invaluable assets" concept? philosophy that profoundly embodies the dialectical relationship between ecological conservation and economic development, and has become a core guiding principle for building an ecological civilization in China. Let us journey to the banks of the Qingshui River and listen to a warm symphony of harmony between humans and nature.

The "Cold Water" Challenge for Fish Reproduction

Upstream of the dam of Sanbanxi Hydropower Station, a 200-meter line of orange-and-blue floating pontoons spans the river. Suspended beneath them—reaching 160 meters deep and 400 meters wide—is a massive thermal insulation curtain. This underwater structure was developed to solve the critical "cold water" problem threatening local fish reproduction.

After the Sanbanxi reservoir was filled, a stable thermal stratification formed: surface temperatures hover around 25 ℃, while bottom-layer water remains a chilly 8-10 ℃. The release of this cold deep water lowered downstream temperatures in April and May below 18 ℃—the critical threshold for fish spawning. This led to a decline in plankton diversity, delayed spawning for key species like carp and bronze gudgeon, and a 30% drop in their populations. The biodiversity of the Yangtze River basin was at risk, calling for an urgent solution to regulate water temperatures.

Cross-Disciplinary Ingenuity: The Flexible Curtain

How could this cold water problem be solved? Traditional solutions like blocking dams or stop-log gates were prohibitively expensive and ineffective. After over a decade of research, Sanbanxi Hydropower Station achieved a breakthrough in 2013 by integrating concepts from "deep-sea fishing nets" and "suspension bridges," pioneering the flexible thermal insulation curtain technology. This innovation offers a novel solution for managing cold water releases from existing large reservoirs worldwide.

This eco-engineering project combines expertise from hydraulic, marine, and bridge engineering. It uses high-strength, waterproof flexible fabric as the main curtain, supported by cable towers on both banks and a pontoon system that allows the curtain to rise and fall with the water level. This composite "deep-water ground anchor + cable tower/pontoon + flexible curtain" system can precisely control the flow depth, dynamically improving water temperatures without disrupting power generation—a true breakthrough in "dynamic water management."

A Harmonious Resonance of Ecology and Economy

Completed and commissioned in 2023, this underwater "giant curtain" has created a warm ecological barrier for downstream aquatic life. During trial operation, the curtain increased the temperature of released water by up to 4.5 ℃. During the critical May-June spawning period, temperatures rose by 1.0-1.8 ℃, reaching the 18 ℃ threshold for fish spawning.

The Sanbanxi Cold Water Management Project challenges the notion that environmental protection must come at an economic cost, delivering both ecological and economic benefits. The Deep-Water Flexible Curtain Technology System has secured 36 patents, providing a replicable model for over 300 similar large dams worldwide and offering a Chinese solution for ecological restoration of existing reservoirs.