Development of an Assessment System to Evaluate the Ecological Status of Selected Rivers in the Hindu Kush-Himalayan Region” (ASSESS-HKH) Water Quality Mapping around Dhaka City
Lower Gangetic Plains: Moist Deciduous Forest (IMO 120) Professor M. Fazlul Bari and Professor A.B.M. Badruzzaman
Bangladesh University of Engineering and Technology (BUET), Dhaka 1 Introduction:
Rivers around Dhaka city are affected by industrial activities, municipal sewage disposal, faecal contamination, agro-chemicals and sediment loading and population pressure
Maintaining a sufficient supply of clean water for the growing population is one of the major challenges, especially in the densely populated Dhaka city.
2 Sampling design
• Sampling period: April 1- April 8, 2007 (Dry season)
Rivers selected: - Turag, - Balu, - Buriganga, - Shitalakkhya and - part of Dhaleshwari.
3 Sampling design
Sampling Locations: Based on reconnaissance visits and discussion with local people 20 sites on 5 rivers around Dhaka city were selected for sampling and analysis. On the western side of Dhaka city: Part of Bongshi river and Turag river from Tongi bridge upto its confluence with Buriganga. Southern side of Dhaka city: part of Dhaleshwari river and Buriganga Northern side of Dhaka city: Tongi khal and part of Balu river
Eastern side of Dhaka city: Balu river and part of Shitalakkhya river 4 Sampling for water quality mapping
Steps followed:
• Sampling at selected sites(10 samples/site)
• Analysis of physical and chemical parameters
• Field sorting and Identification of macroinvertebrates
• Further identification of macroinvertebrates in the Laboratory
5 Level of pollution based on common macroinvertebrates
No pollution to slight pollution
Moderate pollution
Severe pollution 6 Site Selection Criteria
Based on Sources:
1. Point sources; e.g. industrial effluent, municipal waste etc. and
2. Non-point sources; e.g. agricultural runoff
7 Site Selection Criteria
1) Selection of Reference Sites Water quality (WQ) Class I
2) Selection of impaired sites WQ Class II, III, IV, V Stressor types – Organic pollution (eg.Balu, Turag, Buriganga etc.)
Based on species abundance and richness numerical scores were assigned to potential water quality classes, viz.
• Class I (none to very slight organic pollution), • Class II (moderate pollution), • Class III (critical pollution), • Class IV (heavy pollution), and • Class V (very heavy to extreme pollution). 8 Pollution Sources
Pollution source
Point source Non-point source
Industrial effluent Municipal waste Agricultural runoff Others
Textile
Tannery
Dyeing
Others 9 Source of Pollution
Industrial wastewater discharge Sewage discharge in Balu river in Turag river 10 Source of Pollution
Waste materials dumping in Turag river Sewage discharge in Bongshi river
11 Sampling for water quality mapping
Sampling in Dhaleshwari river Sampling in Balu river 12 Sampling for water quality mapping
Sampling in Turag river Sample sorting at Shitalakkhya river
13 Sampling for water quality mapping
Sample sorting at Balu river Identification of macroinvertebrates at Turag river 14 Chemical parameters measured for water quality mapping
Electrical conductivity measured at Field measurement of dissolved field oxygen 15 Water Quality Class Per Site
River Site Water Quality Class Balu1 Demra IV Shitalakkhya 2 Demra III Balu 3 Lanchata V Balu 4 Ichhapura IV Turag 5 Bindan V Turag 6 Thermog IV Balu7 Dhopapara III Balu 8 Pipulia III Turag 9 Istema field IV Turag10 Tiebpur III
16 Water Quality Class Per Site
River Site Water Quality Class Turag11 Chapai II Turag12 Ashulia IV Buriganga13 Postogola V Dhaleshwari14 Ferighat III Dhaleshwari15 Charkundolia III Dhaleshwari16 Dharmaganj IV Shitalakkhya17 Katchpur IV Turag18 Baimile V Turag19 Boroibari III Bongshi Sutrapur III
17 Water Quality Mapping around Dhaka city Five colors have been used to denote the WQ Classes blue for water quality Class I green for water quality Class II yellow for water quality Class III orange for water quality Class IV and red indicates water quality Class V
18 River Water Quality Map around Dhaka City
19 Conclusion
Water quality may be a useful tool for water resources managers and decision makers involved in sustainable management and utilization of river resources.
Remarks: Screening protocol works better as visual examination corroborates the findings. NEPBIOS based scoring may not be similar to the screening protocol as species diversity is different in each country. US approach based on order of macroinvertebrates may be compared with the ASSESS-HKH approach
Physico-chemical parameters pH, BOD5 , etc. are not reflected in the water quality map. Seasonal variation of the WQ should be addressed.
20 21