10 July 2010
Interesting developments at Attabad, as various press reports suggest that the lake level increased substantially once again yesterday. The Pamir Times for example reports that the lake level went up by 11 inches (28 cm) yesterday; this magnitude of increase is reported elsewhere too. I have used the data and the graph in the NDMA daily reports to build a dataset of the lake level with time:
If these reports of an 28 cm increase are true then the lake level is probably very close to the previous maximum level. Any further increases could of course lead to more losses upstream, and increase the potential energy stored behind the dam. This increase in lake level is interesting though because at the same time the reported outflows have declined from those of a week or so ago. The estimated spillway flow graph is as follows. I have assumed that the seepage rate has remained constant, and there is a considerable uncertainty in these media reported values:
The resulting relationship between the lake depth and the spillway flow is shown below. For clarity I have plotted the five most recent points as open diamonds:
It is not clear to me as to why the spillway discharge has declined even though the lake level has increased. There are a number of possible explanations, but it t is difficult to speculate with so little information and no images, and so at this stage I will not do so.
Meanwhile the Pamir Times also reports that there were 13 large rockfall events yesterday, some of which created waves on the lake. Secondly, a rather strange report in The News says that “…construction of road leading to Attabad lake is underway. Deputy Commissioner Hunza Nagar Zafar Waqar Taj told Geo News that the construction of road will be completed within a week followed by installation of a floating bridge through which five big trucks will be pass at a time. It will make possible transportation of goods in huge quantity between Pakistan and China and swift delivery of relief items to upper Hunza Gojal affectees.” That is an intriguing possibility, involving a major development over a very short period of time. I cannot quite work out what is meant by this!