volume which results in fluctuations of the head within 80% range of the rated head and
this can not be justified.
Review of the studies made for the Se Kong 5 dam project permits the following
to be noted:
- in the above studies, the dam site remained practically unchanged
- in the above studies FRL is recommended at elevation of 500m;
- in the above studies the layout has a 200m high dam with tunnel penstocks;
- the project site is suitable both for rockfill and concrete dams, underground and
surface power houses;
- considering the canyon type of the dam site, flow can be diverted only through
a tunnel.
It should be noted that in the above studies there is a big scatter of hydrological
inputs in the Project design of Se Kong 5: long term average flows at the project site in
[1] - [2] differ as much as 1.5 times, the maximum flows are limited by probability of
0.01%, while in some studies by 0.1% probability which does not meet the requirements
of the current international practice. All this requires finalizing because credible
estimation of the river flow at the site in question will affect not only the design and cost
of the spillway structure but also safety of the whole works, while credibility of data on
inter-annual flow variation over the long term period will influence the water and power
characteristics of the hydroelectric plant.
Attention is also drawn to inconsistency of topographic inputs used in different
studies which govern, in a great measure, work quantities and hence the cost of the
Ptroject Works.
Parameters of the Se Kong 5 HEP recommended by studies [1] - [3] are given
in table 2.2.