July 24, ICT - A new dam being constructed on the Nyang river between Yamdrok lake and the town of Gyantse is for producing electricity to pump water back up into Yamdrok lake, according to local sources. The hydro-electric plant on Yamdrok lake which drains lake water to produce electricity for Lhasa during peak demand, needs water replenished from a river below during off-peak hours, which requires a separate power source. This new dam is said to be that source.

The dam, located along the road about 20 miles east of Gyantse, is being constructed by a large Chinese work force who have built a sizable town on the north banks of the river. In addition, the large construction project has spurred a wave of Chinese urban growth in the eastern end of Gyantse, a town which had been known for being the one large Tibetan settlement retaining a distinct Tibetan character.

The controversial Yamdrok Tso power station, which reportedly started generating power in June is a pump-storage plant. They are used in areas with high peak hour demands, and are shut down at the end of the evening power demand peak. The generators are then converted into their other mode - acting as electric motors to drive the turbines in the reverse direction and pumping the same water back up in to a reservoir. Water is pumped back up when power demands are low and surplus low-rate power is available from other generating stations.

The pump-back storage principal is advantageous because the generating units can rapidly respond to varying patterns of daily and seasonal power demand. In the case of Lhasa, seasonal demand varies widely because so many Chinese leave the Lhasa area during the winter months, and come back in the spring.

For Yamdrok Tso, the only other substantial pump-back power source in the area is the Yangpachen thermal plant, but demand there already far exceeds output. Whether Yangpachen can produce the electricity to pump Yamdrok Tso's water back up until this new power source is completed is unknown. This new dam is not likely to be completed for 2 - 3 years. However, it is not even clear whether a storage catchment area near the generators has been constructed to store the water to be pumped back up. In the meantime, if the generators are going on-line, when and will water begin to pumped back up to maintain the environmentally sensitive water table in Yamdrok Tso?

[Photo of construction available from ICT.]