18 June 2010

River flows at Attabad

Posted by Dave Petley

Thanks to Dr David Archer of the University of Newcastle for an analysis of the dates of peak flows on the Hunza.  The analysis is for Danyor (sometimes spelt “Dainyore”), which is near to Gilgit downstream of Attabad (there is no hydrograph data for Attabad itself), but it provides a clear insight into the current vs maximum flow in the river.

  Danyor (Dainyore) Bridge (from here)

This table shows the mean date of occurrence in the season of specific percentages of the peak flow based on the 33 year period from 1966 to 1998:

Flow                         Mean date                                 Standard Deviation (days)
Peak                         29th July                                   14
50% of peak             26th June                                  11
20% of peak             3rd June                                    9
10% of peak             18th May                                  11
5% of peak               2nd May                                    9

This suggests that on average the current flow would be somewhere between 20% and 50% of the peak summer flow – i.e. that the spillway is going to have to cope with a great deal more water yet this summer.  Assuming that the data are described by a normal distribution, we would expect that in 68% of years (representing 1 standard deviation) the peak flow would occur within 14 days of 29th July (i.e. between 15th July and 12th August.