Apologies for the lack of posts over the last few days - I have been in a meeting in Bermuda that has left little time to tend to this blog. Meanwhile, although small scale blasting of the spillway has reportedly continued, as of yesterday the lake level at Attabad is continued to rise by 10 to 20 cm per day, with the effect of both further drowning houses, hotels and roads upstream, and increasing the volume of water in the lake. Unfortunately I do not have any information about the blasting, or any pictures, but my analysis of the flow of the data is that the short term lake level graph now looks like this (correct to yesterday morning)
I am intrigued to know whether this increased discharge has started to drive a new wave of erosion downstream. Finally, this graph compares inflow and spillway flow over the last ten days or so:
It is clear that at the moment inflow and outflow are directly linked - i.e. that the increase in spillway flow is due at least in part to increasing inflow. The grey line represents the point at which spillway flow equals inflow - i.e. the point at which the lake volume should stop increasing. This does not account for seepage, but as this is now a tiny fraction of spillway flow this is not a major problem. It is clear that recent increases in inflow were not being balanced by increasing outflow.
It should be expected that the inflow will continue to rise over the next few weeks, so this graph will be interesting to observe. Hopefully the spillway operations will start to increase the outflow in a controlled manner in the next few days, such that the lake level starts to fall.
In regards to the last graph: If the lake is rising, then the outflow is less than the inflow.
ReplyDeleteHas anyone seen new pics of the dam?
ReplyDeleteWhere are the glaciers in relation to the lake and spillway? Whatever the increased inflows are, they will take time -- hours to days -- to appear at the spillway. So, it seems likely that whatever is done at the spillway end, the upper part of the lake will continue to rise as the glacier melting increases.
ReplyDeleteI very much miss the excellent photos provided by FOCUS and Pamir Times photographer Zulfiqar Ali Khan. Without them, the world is blind to the state of the
ReplyDeletespillway.
Hopefully the Chinese engineers reported to have visited the site can get something efective happening -- which counts more than feeding our curiosity.
"Whatever the increased inflows are, they will take time -- hours to days -- to appear at the spillway."
ReplyDeleteOnce the water arrives at the lake, the lake level at all points is raised. The lake level is the same at all points in the lake, even if there are a few waves...
The rate of inflow being greater than rate of outflow is what causes the lake to rise. The outflow is restricted by the bottleneck of the dam. If the spillway were wide enough, then the lake level would not rise.
This, however, is not true:
"So, it seems likely that whatever is done at the spillway end, the upper part of the lake will continue to rise as the glacier melting increases."
If the spillway were lowered, then the lake level would go down.
(There is a bit of fluid flow dynamics in play here--a river flows down a gradient; it's not instant. But at the same time, the water in the lake seeks a single elevation.)
Tropical, this is not correct by any means. Even a moderate wind will cause the water to move, such that for example the water level at the spillway end might reduce whilst the upstream end might increase. This effect can be substantial. Thus, a reported rise in the water level at the spillway may well not mean that the overall lake level is rising.
ReplyDelete