Polluted water of Indus delta threatens coastal life, ecology
KARACHI: All 18 creeks of the Indus delta have been polluted to the extent of giving rise to serious health and ecological implications, reveals a recent study conducted by Karachi University’s Institute of Environmental Studies.
Out of 18 creeks surveyed, 11 are located in Shah Bundar while seven exist in the Keti Bundar area. The largest creek is Torshan, approximately 34km long.
Titled ‘Water quality appraisal of Keti Bander and Shah Bander creeks of the Indus delta’, the study is published in a UK-based journal Desalination and water treatment (2017). Authored by Dr Aamir Alamgir under the supervision of Prof Moazzam Ali Khan, it’s the third study conducted to examine water quality within these designated areas and the first to evaluate pollution levels in the creek system.
Thirty-six samples collected during six field surveys were analysed for heavy metal contents such as arsenic, cadmium, lead and zinc as well as for cyanide, oil and grease, biochemical oxygen demand, dissolved oxygen, total phosphate, phenol and total organic carbon values. The objective was to assess levels of pollution in the Indus delta creek system.
According to the study, the complex distributary system (creeks) of the Indus towards the sea created the world’s second largest submarine fan in the Arabian Sea. The creek system of the Indus covers an area of about 5,000 square kilometres, which finally merges into the Indus delta. The major changes of the river Indus had occurred near its mouth and the main channels shifted significantly westward four times until it occupied the present course.
“The wide channels of eastern delta (Khar, Wari, Kajhar, Sir and Kari creeks) penetrate deep inland leading to floods during summer monsoon particularly in lower delta plain and the Rann of Kutch. Because of gradual shifting and reduced flow in the river, the tributaries of the river have converted into tidal creeks having high salinity values. The pollution of these creeks is also a major problem affecting the delta region,” the study says.
Progression of seawater
The three-year study found high salinity along with low dissolved oxygen values, indicting progression of seawater into the creek system. It also found bacterial load exceptionally higher in all samples in terms of organisms of public health importance that mainly attributed to domestic waste water originating from nearby squatter settlements.
Oil and grease content of water was also substantial, suggesting operation of faulty boats in the area. It also suggests that the natural system of removal of oil through the process of photo-oxidation and biodegradation is not working efficiently because of lesser availability of oxygen.
“Excessive concentration of oil and grease could be deleterious to marine life. The concentration of phosphate ranged between 2.1 to 4.6 mg/L mainly attributed to the agriculture runoff,” it says.
The mean dissolved oxygen concentration of creek water samples ranged between 4.2mg/L to 5.7mg/L. The lowest dissolved oxygen concentration was observed at Khaddo and Bhorro creek while highest was observed at Sattah Wah.
Low dissolved oxygen concentration, according to the study, could be due to high biochemical oxygen demand which indicates the stress of the creek ecosystem.
The sites showing relatively higher biochemical oxygen levels are close to human settlements. This suggests that the organic load is mainly of anthropogenic origin. Similar results were also reported by other researchers, indicating that the oxidation of organic matter results in the reduction of dissolved oxygen concentration.
The highest concentration of phosphates was observed at Torshan creek (4.6mg/L), the main tributary of the Indus. This area represents extensive agriculture on both sides.
The concentration of heavy metals was in the order of zinc, nickel, lead, arsenic, chromium and cadmium. High level of these metals can harm creek ecosystems, plants, and animals and cause health problems in humans. The mean cyanide concentration was also high, though the source of cyanide could not be traced and needs further study.
“In essence, the study reveals that creeks of the Indus delta are heavily polluted mainly because of anthropogenic sources. The continuous accumulation of pollutants in the creek area may have severe ecological and health implications,” the study says.
Ground, surface water contamination
Earlier, studies conducted in 2015 had showed that ground and surface waters in the areas of Keti Bandar and Shah Bandar were not fit for human consumption.
For the ground water analysis, 56 samples were taken at depths ranging from 30 to 50 meters for bacteriological and physico-chemical analyses. Interviews with community representatives indicated that the water was also used for drinking purposes.
The findings showed concentrations of sulphate and phosphate well within the tolerance limits but high levels of organic and faecal pollution followed by turbidity and salinity.
Concentrations of metals including arsenic, cadmium, chromium, iron, zinc, lead and nickel were also determined. Of them, lead and nickel exceeded health standards.
“Ground water pollution can only be addressed through improvements in irrigation strategies, sanitation and sewerage infrastructure. Research into how farmers can be incentivised to refrain from overexploitation of groundwater is promising to reduce levels of salinity.
“These efforts are particularly important in the coastal areas where global climate change is likely to increase frequency of floods and storms,” the study says.
The results of another investigation into surface water contamination revealed that water was not suitable for drinking as per WHO guidelines and National Standards for Drinking Water Quality Pakistan.
Under the study titled ‘Vulnerability to climate change of surface water resources of coastal areas of Sindh, Pakistan’, 17 water samples were collected from canals, some owned by the government and others by private individuals, as well as from downstream river Indus.
“Most of the residents were found using polluted water for drinking purposes. Agriculture run-off, sewage leaks and metals quite often contaminate the surface water resources. None of the inspected canals, however, were protected in any way from contamination of the water after it had been discharged from the source,” the study says.
Increasing variability in rainfall pattern and reduced flow in the Indus downstream had aggravated water shortage problem, it added.