Pakistan
[Lake Update] Water discharge through spillway has increased to 360 Cusecs
PT Report
Gilgit, May 31: Water discharge through the spillway at Hunza lake barrier has increased to around 360 Cusecs as measured at 6 O’clock today.
The cumulative water outflow from the lake has increased to around 700 Cusecs, including seepage discharges.
The total discharge might reach 1000 Cusecs by tomorrow morning. Down cutting and erosion at toe of the barrier also continued during the reporting time.
Thank you very much for update. Keep up dating from time to time and if possible kindly post current picture of Shishket, Gulmit and Hussaini.
Rahim
Aktau Kazakhstan
is the water level of the lake decreasing or the river and glacial melting still bringing in more water than the outflow ?
Thanks for the updates, including numerical information and specificity as to surface spillage versus seepage. Any more photos updates as well as your usual good text reporting? Seeing that your reporting serves a scientific and engineering purpose (humanitarian purpose) as well as a more usual reporting purpose, I would say that more information, more facts and figures, more photos, is better than less.
Also, since some readers and and blog writers are annoyed with the fact that outburst flooding is not an exact science and has its own complexities, even beyond that of weather science, it might be good if you would at least stress where experts have indeed been fairly on track. Such as Dave Petley’s predictions that slow increases in drainage would occur during the first few days. There is no harm in reporting that many experts are learning from this experience, because of the unique and complex aspects of this particular dam (the ingestion of lake sediments has made it really complicated). It’s worth noting that the longer this process of filling while slowly draining goes on, the more dangerous the lake. It is also true that hope lies in the same observations; if you imagine an eventual peaceful drainage, then it has to go through this type of gradual evolution. So the danger and potential losses of property increase even while the hope increases: a very peculiar mix. The potential loss of life at this point is entirely in the hands of the residents. They know that they should not be staying in the danger zone, and they know where that danger zone is.
Thanks for updating and providing a technical and realistic gist of the latest situation.
Hopefully the cutting of the channel in the barrier develops gradually and lake discharge remains in control till a complete drain of lake is achieved.
Although there has lot of upstream damage which has occurred by water swelling in the lake and peoples have suffered a great deal loss in terms of submerging of houses, orchard and other properties.
But there is a bigger danger which is lurking there that lake barrier is going through a process of slow erosion; hopefully this does not have a rapid breach which may bring a havoc. It may cause a massive flood on diminishing of barrier holding the massive water in the lake.
There is need to keep the peoples living downstream to be repeatedly warned and I hope you paper will serve the best to ask people (time and again) to avoid the area marked as danger zones so that loss of life is kept to minimum in an unfortunate event.
There are three scenarios of how the situation may develop over the next week or so:
1. The river cuts down through the spillway in a gradual manner leading to a controlled discharge of the lake.
2. The river cuts down rapidly through the spillway leading to an uncontrolled discharge of the lake.
3. The spillway remains stable and the lake continues to rise until the outflow through the spillway balances the inflow into the lake.
Scenario 1 is the ideal situation leading to a safe discharge of the lake. Taking Anon’s volume of 460M cu m for the lake, for a discharge through the spillway of 2000 cu m/sec (cumecs), it would take 2.6 days for the lake to be discharged. A discharge of 2000 cumecs though high is probably not exceptional for this area (GLOFs?)
Scenario 2 involves a rapid discharge of the lake in an hour or so, leading to an exceptional river flow and probably significant damage downstream. If people have been evacuated, there should hopefully be no loss of life, however there may be significant damage to property, land and livelihoods as well as damage to infrastructure such as bridges and roads.
Scenario 3 results in permanent flooding to the valley upstream of the landslide to approximately the current extent. There should be no loss of life, but there will be significant humanitarian impacts such as loss of property, land and livelihoods for the whole of the flooded area, as well as the need to replace over 17km of the KKH, including the potentially challenging stretch through the unstable landslide area. In the interim there will continue to be disruption to life in the upper valley until proper communication can be set up.
One other unfortunate circumstance of Scenario 3 is the fear that future flooding events could initiate a Scenario 2. The mean monthly river discharge at Dainyor 100km downstream of the landslide is over 5 times greater in July and August that in May. Peak flood discharges will exceed this mean monthly figure. Any flood in excess of that experienced previously could trigger an uncontrolled discharge of the lake. Therefore, in the interests of safety, evacuation of people downstream of the landslide may be required on a periodic basis for years to come.
Let us all hope that Scenario 1 comes to pass, but as Dave has stated now is not the time to lower the guard. The risk will remain for many days yet.
ref: http://www.adab-arz.co.uk/
Many thanks for updating us,
By my opinion the slow erosion is a positive effect and it will contribute for lake dimension reduction while the biggest risk is and remains further landslide in the water creating a “Vajont Effect” (big waive).
AKF Helicopter Project – Switzerland