Evaluation of River Water Quality: A Case Study of the Lea Navigation (NE London)
The Lea Navigation in the north-east of London, a canalized reach of the River Lea, is affected by episodes of very low levels of dissolved oxygen. The problem was detected by the Environment Agency from the confluence with Pymmes Brook (which receives the final effluent of Deephams sewage treatment works) to the Olympic site (Marshgate Lane, Stratford). In this study, possible causes and sources of the poor water quality in the Lea Navigation were investigated using algal bioassays and detailed spatial seasonal mapping of the physico-chemical parameters collected in situ. Results showed chronic pollution and identified polar compounds in the river water and high bacterial concentrations as possible causes of low dissolved oxygen levels. This study confirmed the negative impact of Deephams sewage treatment works (via Pymmes Brook) on the water quality of the Lea. However, whilst the Environment Agency had previously focused on the pollution created by the sewage treatment works, results showed evidence of other sources of pollution; in particular, Stonebridge Brook was identified as an uncontrolled source of pollution and untreated wastewater. This study demonstrates the value of conducting combined methodologies and detailed monitoring. Other possible sources include Old Moselle Brook, diffuse pollution from surface run-off, boat discharges and other undetected drainage misconnections.
KeywordsLea Navigation River water quality Bioassay Spatial digital maps Chronic pollution Wastewater
The authors would like to thank Mr. Peter Rudd from the Environment Agency in Hatfield for his help and assistance with provision of data and equipment.
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