Environmental and Social Impact Assessment - Gibe III

Gibe III – Environmental and Social Impact Assessment 300 ENV R CS 002 C - A9003099
Z (m a.s.l.)
910
900
890
880
870
860
850
840
830
820
810
800
790
780
770
760
750
740
730
720
710
700
690
680
Table 3.2: Spillway chute hydraulic analysis
CHUTE
Q E u/s H W h max h Mix,max V max V take_off smin
[m 3 /s] [m a.s.l.] [m] [m] [m] [m/s] [m/s] [-]
MIN 900 875.5 2.5 0.4 0.6 27.9 23.5 0.26
mean AUG 1,500 877.0 4.0 0.5 0.9 31.6 29.0 0.21
5 yr 3,400 880.0 7.0 1.0 1.6 36.0 34.7 0.17
100 yr 6,500 883.5 10.5 1.8 2.6 38.3 37.5 0.16
10000 yr 10,600 887.5 14.5 2.7 3.7 39.7 39.1 0.16
PMF 18,500 893.0 20.0 4.7 5.9 40.9 40.4 0.16
670
660
0
-40 -20 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
3.9 Outlet works
3.9.1 Middle outlets
X (from spillway sill) (m)
Energy grade line
Water profile
Chute (Z)
Water and air mixture profile
Lateral walls
Flow velocity
Figure 3.6: Water profile and velocity on the chute with the PMF
The scope of the two middle outlets is to:
• Control the reservoir impounding
• Safely drawdown the reservoir up to the power tunnel intake elevation 780 m a.s.l.
The middle outlets are included in the lateral blocks of the dam body (non overflow sections), nearby the
spillway.
Each outlet is composed of:
• Shaped inlet, protected by steel grid with very wide mesh
• A steel conduit within the dam body composed of
CESI SpA - Mid-Day International Consulting Engineers Page 57
60
50
40
30
20
10
V (m/s)