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.
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.
"Assuming that the data are described by a normal distribution…"But we know that it's not normally distributed. It's negatively skewed; the negative skew is a result of glacier melt and runoff rates.
"the peak flow would occur within 11 days of 29th July (i.e. between 18th July and 9th August."A little mistake – according to the table it should be:"the peak flow would occur within 14 days of 29th July (i.e. between 15th July and 12th August. In general – your blog is a great site.
So what does the future hold?
Apparently the gov has decided to take active steps to widen the spillway.http://www.apakistannews.com/plan-underway-to-widen-attabad-spillway-190383Not much detail about when and how.
According to PamirTimes a deal has been struck between the villagers who worked to enlarge the spillway and the agency in charge called NDMA:The agency has promised to blast some boulders that obstruct the flow within ten days of the agreement. If it fails to do so the villagers will resume their attempt to widen the spillway by their own means.Khamomil
A Local Newspaper says boulder has started sliding a little and hence decision about blasting has been delayed for two days.