24 July 2010
Large drop in the lake level at Attabad
Posted by Dave Petley
The latest NDMA update (released yesterday) reports a further very substantial drop in the level of the lake. The report is that the level of the lake fell by 28 inches (71 cm) in the 24 hour period to 9 am (local time) on 23rd July. This means that the lake level graph looks like this:
The cause of this reduction appears to be a dramatic decrease in inflow, caused by the substantial drop in temperature in recent days. Regular reader and commenter BeforeGorekneel pointed out that hydrographs for some of the major Indus flows are available online in real neartime here. The data supports the view that the river flows have decreased markedly in the last few days:
Flow through the spillway is declining slowly in consequence, but as of yesterday remained quite high. This is my calculation of spillway flow, which is the NDMA data for Ganish Bridge less the seepage and downstream component:
Finally, reader and commenter Torsten has provided a comparison of images from 14th June and the somewhat grainy Pamir Times image of 18th July. This rather helpfully helps to show the magnitude of the volume loss on the downstream side of the dam:
The lines are intended to assist in comparing the two images. The amount of volume loss is remarkable.
Finally the Pamir Times reports that the government is “all set” to begin blasting in order to lower the lake level. I wish them well.
There was always a seepage point along the eroded embankment, maybe it's gotten more effective. It pushes material into the stream which sweeps it away.Dave, what's the pressure in this system?
Back to Dr. David Archer's report:The peak flow mean is July 29th with a standard deviation of 14 days. Without getting analytical, we have probably passed 2010 peak flow.
There are news that Blasting will soon begin to break the dam.