Introducing of Ce-Qual-W2 Model and Its Application - Water Quality Management: Assessment and Interpretation - page 111

Fig. 6.15 BOD in the study area during normal conditions (mg/l)

Table 6.2 Dissolved oxygen level (mg/l) for aquatic life (mg/l); Quality Criteria for Water ( 1986 )
(EPA 440/5-86-001)

Warm water conditions Cold water conditions

Other stages
of life

Early stages
of life

Other stages
of life

Early stages
of life

30 day average 5.5 6.5

- -

7 day average 6 (6.5) 9.5

- -

Minimum 7 day average 4.0 - 5.0 -

1 day minimum 3.0 5.0 4.0 (5.5) 8.5

Studying the water quality of the river under critical conditions is then consid-
ered as the quality is not affected much during normal conditions. Figure 6.15
presents the changes in DO in low low greatly

affects the Dissolved Oxygen variations due to incoming pollutants, and a lower
DO with greater variations is noticeable. Based on Table 6.2 aquatic life at early
and other stages of life is endangered in the cold season as DO falls to about 6 mg/l.
However, it passes Iran

low periods. The reduction in

s criteria for water quality compared to Table 6.3 .
Figure 6.16 illustrates BOD variations in the K

'

ā r ū in River during low ow

periods. BOD variations are also more considerable in low low periods and the

changes due to receiving pollutants are much greater than in the normal ow as

shown in Fig. 6.16 . Comparing the values to General Criteria for Water Quality in
Iran (Table 6.3 ) and EPA Dissolved Oxygen Levels for Aquatic Life (Table 6.2 )
again proves the BOD is in agreement with the current standards and is not con-
sidered critical.
The daily freshwater discharge in the K

ā ū

in River during 2005 was higher than in
many other years and may not be representative of the danger to

r

fish survival during