Will Yangtze River drought threaten Three Gorges power output?

The water level of the lower reaches of the Yangtze River is at its lowest since records began in 1877. The water level in Chongqing, further upstream, is only 0.35 metres higher than the record low in 1987 and one million people in Chongqing are suffering water shortages, according to a Xinhua report on Monday.

On January 11, Xinhua reported that the Three Gorges Corporation planned to open the dam’s floodgates to reduce the water level in the reservoir from 155 metres to a possible 144 metres - just three months after the level was raised from 135 metres, to much fanfare of course. On January 18, Xinhua reported that the measure had met with little success:

The Three Gorges dam has opened its floodgates to feed the river, but statistics from monitoring stations in central China’s Hubei province and east China’s Jiangsu province have shown no perceptible rise in water levels.

So what effects will all this have on the power generating targets of the Three Gorges Project? The dam generated 49.2 billion kilowatt-hours of electricity in 2006, according to Guess Who (well I do have unavoidable access to the Xinhua database seven hours a day so forgive my bias). This figure was down 16.1 billion kwh from the previous year and well below the target of 62 billion kwh set at the beginning of 2006. The drop was not explicity acknowledged in the Xinhua report but an unnamed official appeared to blame it on the lowest volume of water to flow through the dam area for 137 years.

Even more suprising then are the comments reported in Monday’s Xinhua story:

Sources with the China Three Gorges Project Corporation said the water shortage in the upper reaches had not affected the world’s largest water storage facility.

I’m not a hydrology expert but I do subscribe to the hydropower station formula of less water = less power. If the drought continues, the Three Gorges Corp has a serious problem. It generated less than 50 billion kwh last year and if they continue at that rate, it will generate 250 billion kwh over the next five years. This does not meet the 300 billion kwh of electricity it has already presold to the State Power Grids for the 2006-2010 period. Their long-term plan of producing 84.7 billion kwh of electricity (a stat tacked onto the end of every Xinhua story about the Three Gorges Dam) does look ambitious at this point.

But despite all this doom and gloom over fast-appearing sections of riverbed and reports that severe drought will last until May (and return for 30 days in the summer), Chinese Water Resources Vice Minister E Jingping is warning everyone about the possibility of flooding along the Yangtze. His assertion is of course based on the soundest of evidence: the Yangtze has “not seen serious floods in recent years” so this increases the chances of flooding according to “the law of nature”.

Beijing has suffered sandstorms in recent years so surely it can’t happen this March - according to the law of nature, averages, whatever you want to call it.