TAIYUAN, Feb. 6 (Xinhua) -- The once roaring Hukou waterfalls on the middle reaches of the Yellow River, China's second longest waterway, have fallen silent this winter, as the flow has been covered by thick ice.

The Hukou Waterfalls are where the streams of the river narrow suddenly and drop 30 meters into a deep river bed. It is known for its yellow water and thunderous sound.

Temperatures at the waterfalls recently dropped as low as minus 17 degrees Celsius. Since Feb. 3, the waterfalls have been covered by ice.

"The waterfalls were only partly frozen in the past few years, but are totally covered this year due to the extreme cold," said Lyu Guiming, a local photographer who had been observing the waterfalls for about 20 years.

The waterfalls lie on the boundary of Yichuan County of Shaanxi Province and Jixian County in Shanxi Province.