27 July 2010
The lake level at Attabad is rising again – the latest NDMA report suggests that the level has increased by 19 inches (41 cm) in the last 24 hours:
It is now clear that the lake level is controlled primarily by local environmental conditions (which in turn are changing the inflow), rather than the spillway properties. Compare the following two graphs. The first is the lake level through July to date:
The second is the Pakmet hydrograph for the same period for Besham, which is much further down the Hunza valley:
The similarity in patterns is not because Attabad is controlling the flow at Besham (the Attabad discharge is just a fraction of that at Besham) – the similar patterns are because the flow at Besham is being controlled by air temperature (i.e. the rate of melt on the snowfields and icecaps), as is the flow, and hence the lake level, at Attabad.
Regular commenter BeforeGoreKneel kindly pointed out that temperature graphs are available online here too. The temperature graph for Gilgit is as follows:
The role that temperature is playing in controlling this system is clear.
Meanwhile, it is still not clear as to whether the Frontier Works Organisation (army) has started their operations to lower the lake.