INTRODUCTION
The Bloukrans River is an important river to Grahamstown, it transports the waste
produced by the community, and downstream of Grahamstown the farmers use the
river for irrigation purposes. As part of an ongoing research, the SASS5 method was
used in November 2005 and June 2006 to assess the water quality and the health of
the river.
METHOD
The health of the rivers is determined by assessing the biota in rivers. Biomonitoring
was done at the Bloukrans River using SASS5 following the method explained in
Dickens CWS and Graham PM (2002). Basic water quality parameters (electrical
conductivity, dissolved oxygen, pH and temperature) were measured at each site.
SITES SAMPLED
All sites surveyed are from the Bloukrans River.
Site1 is a section of non-canalized river below small road-bridge near Fort England
Hospital. 33˚18’47”S 26˚32’29”E. Stones, vegetation and gravel sand and mud
(GSM) were sampled both in November 2005 and June 2006.
Site 3 is a section of river below farm road-bridge close to N2 highway bridge.
33˚19’04”S 26˚34’06”E. In November all the biotopes were sampled but in June only
the vegetation and GSM were sampled.
Site 4 is a section of river below railroad bridge and immediately below road bridge.
33˚19’26”S 26˚35’59”E. Stones, vegetation and GSM were sampled in both seasons.
Site 5 is a section of river below a weir on Mr. Duncan’s farm. 33˚19’25”S
26˚38’39”E. Stones, vegetation and GSM were sampled in both seasons.
RESULTS
Table 1 summarises the SASS5 scores, total number of taxa and ASPT values
calculated. The SASS score is simply the sum of the assigned scores of the families
encountered in the sample of all the biotopes. The ASPT is calculated by dividing the
SASS score by the number of taxa found in the sample.
Table1. Summary of SASS5 scores, number of taxa collected and ASPT values at
each site along the Bloukrans River. 17 November 2005 and 14 June 2006.
Site1
Site3
Site4
Site5
Biotope
S
VG GSM S
VG
GSM S
VG
GSM S
VG
GSM
Sass score Nov 05
9
3
7
39
32
32
26
26
13
20
47
31
No. of taxa Nov 05
4
2
3
10
7
8
7
7
5
6
12
8
No. of taxa Jun 06
4
5
4
9
4
10
8
5
8
7
9
ASPT Nov 05
2.25 1.5
2.33
4
3.7 3.7
2.6
3.3
3.9
3.9
ASPT Jun 06
5.5
3.4
3.5
3.22 3.75
4
3.63 4.2
3.88 5.86 3.56
Sass score Jun 06
22
17
14
29
15
40
29
21
31
41
32
No. of taxa Jun 06
4
5
4
9
4
10
8
5
8
7
9
3.9 4.6
Sass scores
stones
60
40
Nov 05
20
Jun 06
0
1
3
4
5
sites
Fig.1. Graph representing the SASS5 scores calculated for the stones biotope
collected in the Bloukrans River in November 2005 and June 2006.
Sass scores
vegetation
60
40
Nov 05
20
Jun 06
0
1
3
4
5
sites
Fig.2. Graph representing the SASS5 scores calculated for the vegetation biotope
collected in the Bloukrans River in November 2005 and June 2006.
Sass scores
GSM
40
30
20
10
0
Nov 05
Jun 06
1
3
4
5
sites
Fig.3. Graph representing the SASS5 scores calculated for the gravel, sand and mud
biotope collected in the Bloukrans River in November 2005 and June 2006.
No. of taxa
stones
15
10
Nov 05
5
Jun 06
0
1
3
4
5
sites
Fig.4. Graph representing the number of different invertebrate taxa for the stones
biotope collected in the Bloukrans River in November 2005 and June 2006.
No. of taxa
vegetation
15
10
Nov 05
5
Jun 06
0
1
3
4
5
sites
Fig.5. Graph representing the number of different invertebrate taxa for the vegetation
biotope collected in the Bloukrans River in November 2005 and June 2006.
No. of taxa
GSM
10
Nov 05
5
June 06
0
1
3
4
5
sites
Fig.6. Graph representing the number of different invertebrate taxa for the gravel,
mud and sand biotope collected in the Bloukrans River in November 2005 and June
2006.
ASPT scores
stones
6
4
Nov 05
2
Jun 06
0
1
3
4
5
sites
Fig.7. Graph representing the Average score per taxa (ASPT) calculated for the stones
biotope collected in the Bloukrans River in November 2005 and June 2006.
ASPT scores
vegetation
8
6
4
2
0
Nov 05
Jun 06
1
3
4
5
sites
Fig.8. Graph representing the Average score per taxa (ASPT) calculated for the
vegetation biotope collected in the Bloukrans River in November 2005 and June
2006.
ASPT scores
GSM
6
4
Nov 05
2
Jun 06
0
1
3
4
5
sites
Fig.9. Graph representing the Average score per taxa (ASPT) calculated for the
gravel, sand and mud biotope collected in the Bloukrans River in November 2005 and
June 2006.
Table 2. Summary of the water chemistry parameters measured in the Bloukrans
River in November 2005
Water chemistry Nov 05
Site 1
Site 3
Site 4
Site 5
Temperature (˚C)
20
20
20
19.9
Electrical conductivity (mS/m)
10.36
7.3
9.13
5.8
pH
7.55
7.51
7.45
7.41
Dissolved Oxygen (mg/L)
1.48
7.16
5.23
7.99
Table 3. Summary of the water chemistry parameters measured in the Bloukrans
River in June 2006.
Water chemistry Jun 06
Site 1 Site 3 Site 4 Site 5
Temperature (˚C)
13
13.4
11
10.4
Electrical conductivity (mS/m)
10.12
10.02
9.85
9.6
pH
8.19
7.29
7.27
7.71
Dissolved Oxygen (mg/L)
9.31
5.2
8.56
8.8
8.5
pH
8
Nov-05
7.5
Jun-06
7
6.5
1
3
4
5
Sites
Fig 10. pH in the Bloukrans River in November 2005 and June 2006 at each site.
Temperature
25
20
15
Nov-05
10
Jun-06
5
0
1
3
4
5
Sites
Fig.11. Temperature in the Bloukrans River in November 2005 and June 2006 at each
site.
Electrical conductivity
(mS/m)
12
10
8
6
4
2
0
Nov-05
Jun-06
1
2
3
4
sites
Fig.12 Electrical conductivity in the Bloukrans River in November 2005 and June
Dissolved oxygen
(mg/L)
2006 at each site.
10
8
6
Nov-05
4
Jun-06
2
0
1
2
3
4
sites
Fig.13 Dissolved oxygen in the Bloukraans River in November 2005 and June 2006 at
each site.
DISCUSSION
Based on SASS5 scores obtained the survey conducted in November 2005 reveals that
the river was heavily polluted upstream but below the sewage treatment works there is
gradual recovery of the river health. In June 2006 site 1 showed an improvement of
water quality and deteriorates as you go downstream, but there is an improvement of
water quality at site 5. At site 1 the electrical conductivity is high at both the surveys;
the introduction of the treated sewage water reduces the conductivity