Abstract
Urban river catchments face multiple water quality challenges that threaten the biodiversity of riverine habitats and the flow of ecosystem services. We examined two water quality challenges, runoff from increasingly impervious land covers and effluent from combined sewer overflows within a temperate zone river catchment in Greater Manchester, North-West UK. Sub-catchment areas of the River Medlock were delineated from digital elevation models using a Geographical Information System. By combining flow accumulation and high-resolution land cover data within each sub-catchment and water quality measurements at five sampling points along the river, we identified which land cover(s) are key drivers of water quality. Impervious land covers increased downstream and were associated with higher runoff and poorer water quality. Of the impervious covers, transportation networks have the highest runoff ratios and therefore the greatest potential to convey contaminants to the river. We suggest more integrated management of imperviousness to address water quality, flood risk and, urban wellbeing could be achieved with greater catchment partnership working.
Highlights
Urban land covers such as infrastructure, urban greenspace and woodland, residential, and industry and commercial covers can modify water quality either by enhancing or reducing runoff [1]and in turn contaminant levels entering freshwaters from surrounding terrestrial ecosystems [2,3].Changes in land cover from human activities or natural drivers, can both affect the quality of the river catchment and thereby compromise the ecosystem services they provide [2,3]
The size of the catchment area at the gauging station (GS) was calculated at 65.9 km2, which is larger than the catchment area reported by the Centre for Ecology & Hydrology (CEH, 57.5 km2 )
The distribution of land covers extracted from CORINE for the sampling locations and the GS are shown on Figure 3a–f
Summary
Changes in land cover from human activities or natural drivers, can both affect the quality of the river catchment and thereby compromise the ecosystem services they provide [2,3]. Urbanized areas are often characterized by rapid development, modified or canalized rivers, and a high proportion of impervious land [4,7,8,9,10,11,12]. Impervious surface covers which prevent infiltration of water to the soil, include transport systems (roads, parking lots), roof tops and residential development are a key indicator of the environmental impacts of urbanisation [3]. Point source pollution collected from impervious urban areas contributes to river flows, changes river hydrology, alters physicochemical processes [13] and degrades assemblages of benthic macroinvertebrates [4,12].
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