Urbanisation: Hydrology, water quality, and influences on ecosystem health

Abstract

Urbanization significantly alters the hydrology of catchments, the transport of sediment, nutrients, and pollutants and consequently has a degrading impact on urban stream biota. In response to these impacts, water sensitive urban design (WSUD) is often seen as an approach to reduce the hydrological and pollutant risks for receiving waterbodies. We explored the impacts of urbanization across three stream types: an urban system, one subject to upstream WSUD development, and a forested stream. Our results suggested that there were strong differences in the hydrology, water quality, and macroinvertebrate assemblage composition between the FOREST site and the two sites impacted by urbanization; the WSUD and the URBAN sites. Despite the upstream WSUD development, both the WSUD and URBAN sites had hydrology characterized by higher rates of rise and fall of flood peaks. However, very little variation in macroinvertebrate assemblage composition across the three streams could be directly attributed to the changed hydrology. Rather it was differences in water quality that showed the strongest influence on the biota, suggesting that even when measures are implemented to help restore more natural flow patterns, degraded water quality can have an overriding influence on stream ecosystem health