| A regional overview of the water quality and ecology of the River Lee catchment is presented. Specifically, data
describing the chemical, microbiological and macrobiological water quality and fisheries communities have been analysed, based on a division
into river, sewage treatment works, fish-farm, lake and industrial samples. Nutrient enrichment and the highest concentrations of metals and
micro-organics were found in the urbanised, lower reaches of the Lee and in the Lee Navigation. Average annual concentrations of metals were
generally within environmental quality standards although, on many occasions, concentrations of cadmium, copper, lead, mercury and zinc were
in excess of the standards. Various organic substances (used as herbicides, fungicides, insecticides, chlorination by-products and industrial
solvents) were widely detected in the Lee system. Concentrations of ten micro-organic substances were observed in excess of their environmental
quality standards, though not in terms of annual averages. Sewage treatment works were the principal point source input of nutrients, metals and
micro-organic determinands to the catchment. Diffuse nitrogen sources contributed approximately 60% and 27% of the in-stream load in the upper
and lower Lee respectively, whereas approximately 60% and 20% of the in-stream phosphorus load was derived from diffuse sources in the upper and
lower Lee. For metals, the most significant source was the urban runoff from North London. In reaches less affected by effluent discharges,
diffuse runoff from urban and agricultural areas dominated trends. High microbiological content, observed in the River Lee particularly in
urbanised reaches, was far in excess of the EC Bathing Water Directive standards. Water quality issues and degraded habitat in the lower
reaches of the Lee has led to impoverished aquatic fauna but, within the mid-catchment reaches and upper agricultural tributaries, less nutrient
enrichment and channel alteration has permitted more diverse aquatic fauna.
Keywords: River Lee, River Thames, water quality, nutrients, metals, ecology, hydrology, diffuse and point source pollution |