22 July 2010
The NDMA daily report for today (22nd July) reports a dramatic decrease in lake level – 19 inches (48 cm) in the last 24 hours. This is by far the largest fall recorded to date, producing a lake level the looks like this:
This is quite surprising. Assuming that the surface area of the lake is 1202 hectares (in fact it is probably a little larger in reality), this implies that about 5.8 million cubic metres of water has left the lake in the last 24 hours, representing a rate of about 67 cubic metres per second. However, the reported spillway discharge has not increased substantially – discharge at Ganish Bridge was 20,800 cubic feet per second yesterday and 20,837 cubic feet per second today.
So what is going on? Well it could be a measurement error, perhaps of the discharge. Alternatively it could be that the inflow has dramatically reduced, maybe because the weather has cooled.
Either way it is a surprising observation.
Finally, I somehow missed until today this low resolution image published in the Pamir Times a few days ago of the dam:
I am astonished at how much downstream erosion there has been since I last saw an image of the site.
Comments and thoughts welcome please.