Urban evolution: The role of water

Background/Question/Methods

The structure, function, and services of urban ecosystems evolve over time scales from seconds to centuries as Earth’s population grows, infrastructure ages, and sociopolitical values alter them.  In order to systematically study changes over time, the concept of “urban evolution” was proposed.  Here, we define a glossary of core concepts for studying urban evolution and explore mechanisms driving urban evolution of water over the previous two centuries.  The role of water is vital to urban evolution as demonstrated by historical changes in drainage, sewage flows, hydrologic pulses, and long-term chemistry. 

Results/Conclusions

We explore multiple empirical examples using historical data including:  (1) evolving urban drainage from stream burial to stormwater management, (2) evolving sewage in response to treatment processes, (3) evolving amplification of hydrologic pulses due to impervious cover and climate, and (4) evolving salinization and alkalinization of fresh water.  Finally, we propose a new conceptual model for the urban evolution of water from the Industrial Revolution to present day based on empirical trends and available historical information.  Ultimately, we propose that water itself is a critical driver of urban evolution constantly altering and transforming the structure, function, and services of urban landscapes, waterways, and civilizations over time.