Stormwater drainage and wastewater disposal are primary pathways through which urbanization degrades streams. These technologies and management practices change over time, reshaping the urban template and affecting the environmental challenges a city will face in the following decades to centuries. Spatial and temporal asynchrony in the implementation and replacement of these technologies and the adoption of new management approaches means that the mechanisms of the urban stream syndrome will be heterogeneous. Thus, promoting ‘one size fits all’ global panaceas for urban streams may be less effective than local solutions based on the unique urban templates and socioeconomic factors governing streams. Understanding the cumulative effects of spatiotemporal changes in urban templates on streams is critical to protecting and managing them because: 1) existing water infrastructure in many countries (especially high-income countries) is aging and requires replacement, 2) urbanization in rapidly developing countries requires ever more infrastructure, and 3) demand for higher levels of environmental quality is transforming technological and management approaches globally. The management and technological decisions made during the current infrastructure replacement or new construction cycle will define the future urban template and select the trajectory and character of the urban stream syndrome during the coming decades.

Urban streams display many similar symptoms around the world, but awareness is growing that the mechanisms and severity of the symptoms differ among regions. Climate is a key contributor to these differences via: 1) variation in the initial conditions of streams across climate (and their sensitivity to urbanization), 2) interactions between climate and urbanization, and 3) indirect effects of climate on the form of urbanization or management via effects on human behaviors. We discuss the direct and indirect pathways by which climate shapes the structure and function of urban streams and how differences in climate affect how the urban stream syndrome is manifested. For some symptoms, such as stream flashiness, climate can affect the direction and magnitude of response, whereas for others, such as losses of sensitive taxa, climate can affect the magnitude of the response. Mechanisms linking urbanization with ecological degradation, even when responses are similar, can differ among climates. Limited ...