Krasnodar GRES Project Volume I11 Environmental Assessment

4.2.1.8 Water Quality
Table 4.29 summarizes the chemical composition of the Laba river upstream of
Labinsk (data by North-Caucasian UGKS).
4.2.1.8.1 Bacterial and Viral Indices
E. Coli index - is not higher than 1000.
4.2.1.9 Sediments
4.2.1.9.1 Transport of Sediments
Water erosion in the Laba basin is widespread, particularly in the upper and middle
reaches, where the main tributaries combine and there are favorable conditions for
the formation of sediment runoff (large slopes, rapid flow, presence of weak
fragmentary material).
The Laba river near Kaladzhinskaya is characterized by considerable fluctuations
in the maximum discharge of suspended sediments. The highest daily average
discharge of river suspended sediments varies from 44 kg/ s to 2400 kg/s. In the
Laba river basin, the sediment runoff of the summer season accounts for 52-55%,
that of spring up to 40%. The sediment drift in fall and winter is reduced and
accounts for only 7% of the annual runoff of suspended sediments.
The highest turbidity in the Laba river is observed in the spring-summer flood
period. The highest annual turbidity of the Laba river water near Kaladzhinskaya
over the period from 1931 to 1980 changed from 300 g/m3 (1 934) to 17000 g/m3
(1 954). Table 2.1 6 shows monthly average water turbidity, averaged over a long-
term period of observations.
I
Table 4.30
Monthly Average Water Turbidity in the Laba River Near Kaladzhinskaya (glm3)
12
11
33
111
99
IV
280
V
360
VI
380
VII
210
Table 4.31. displays the particle size distribution of suspended sediments, and
Table 4.32 shows their discharge rate.
Vlll
150
IX
84
X
78
XI
63
XI1
38
Year
230
PAGE 4-31