Environmental and Social Impact Assessment - Gibe III

Gibe III – Environmental and Social Impact Assessment 300 ENV R CS 002 C - A9003099
Table 5.28: Results of chemical analysis
Gilgel Gibe 2
Power House (1)
Bele Bridge (2)
Altitude (m a.s.l.) 1.000 900 730
Ionic Chemicals
Ca2+ 10.6 12.3 14.08
Mg2+ 5.94 6.48 4.32
Na+ 4.6 5.4 6.7
K+ 2.9 3.2 3.6
NO3- 1.19 1.6 1.0
Cl- 2.82 1.88 1.88
SO42- 5.3 15.4 4.75
PO43- 0.948 1.58 0.759
Fe2+ 2.04 2.9 0.76
Salinity Nil Nil Nil
The water quality parameter measured are collected in the table below.
Parameter Measurement
Turbidity (NTU) (1) 198 – (2) 218 – (3) 116
Dissolved Organic Content (mg/l) (1) 70 – (2) 78 – (3) 82
Salinity Nil
PH (1) 7.34 – (2) 7.33 – (3) 7.5
Electrical conductivity (μS/cm) (1) 109.9 – (2) 104.7 – (3) 126.1
Gilgel Gibe 3
Dam site (3)
Considering very low salinity levels on the usual mineral water scale (Gualtierotti, 1978), the Omo River
water can be classified as earthy-brackish, alkaline, and with bicarbonate.
The values comparison carried out in three zones of Omo River, measured at Gilgel Gibe 2 Power House,
Bele Bridge and Gilgel Gibe III dam site, shows that the water quality is substantially similar if considered
between the three sampling sites.
The chemical differences may be linked to the different flow rates along the river due to effluent rivers,
living people and agricultural activities. Particularly this fact is evident if we consider the chemical
components in the area between Gilgel Gibe 2 Power House site and Gilgel Gibe 3 dam site. The zone,
corresponding to Bele Bridge is fully living, with roads and settlements and with people living on the
plateau.
Due to this fact, an amount in SO4 2- and PO4 3- is real.
After about two years of works for providing Gilgel Gibe 2 outlet area, building roads and settlements,
setting up disposal areas, it seems to be reasonable to compare chemical data in same places. In fact, during
drawing up of Gilgel Gibe 2 Environmental Impact Assessment, a water sampling campaign was done to
collect chemical data in specific sample points, particularly a sample was done at Gilgel Gibe 2 out coming
turbined water, that is near Gilgel Gibe 2 Power House for present sampling campaign.
The data collected in the two periods are in the table below. The sample water has been analysed within the
same parameters.
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