Water quantity and quality at the urban-rural interface
Population growth and urban development dramatically alter natural watershed ecosystem structure and functions and stress water resources. We review studies on the impacts of urbanization on hydrologic and biogeochemical processes underlying stream water quantity and water quality issues, as well as water supply challenges in an urban environment. We conclude that converting forest lands to urban uses increases stormflow rates and volumes, alters baseflow dynamics, and degrades water quality by increasing impervious surface areas. Alterations of watershed water cycles are the root causes of many chain reactions of stream ecosystem degradation present in today’s urban areas. Knowledge gaps exist regarding interactions among processes of urbanization (land conversion, increasing impervious areas, new pollutants), hydrological functions (water budget change, infiltration and evapotranspiration processes), and ecological (biota change) functions at different temporal and spatial scales. Innovative implementation of watershed services is the key to mitigating impacts of urbanization on water and sustaining urban–rural ecosystems.