Vulnerability of water quality in intensively developing urban watersheds

As cities grow they first impose substantial stress on their surrounding water environment, but then, as comprehensive wastewater infrastructure is installed, much of that stress is removed. It becomes possible to talk of rehabilitated watersheds, in which the river network, with its re-invigorated ecological health, passes through the urban landscape of (now) potentially intense polluting activities. Surface water quality becomes vulnerable to the transient pollution events arising from all manner of accidents, faults, failures, and contaminated-runoff events associated with the city's metabolism, including unreliability in the performance of its wastewater infrastructure. The paper examines the role of High-Performance Integrated Control (H-PIC)-a combination of real-time control (RTC) and Integrated Urban Water Management (IUWM)-as an approach essential to managing water quality in such intensively developing watersheds. Rather than promoting H-PIC as the logical stage of operations that will follow planning, design, and construction in the life cycle of an infrastructure, discussion is set in the context of the sustainability of cities, in particular, in association with a measure of sustainability expressed in terms of the frequency spectrum of disturbances to which the aquatic environment is subject. In this more strategic setting, it is argued that control engineering (for achieving H-PIC) should be seen as having relevance beyond merely its conventional interpretation of closed-loop unit-process automation, e.g., in opening up analyses of the stability and ecological resilience of an entire urban water infrastructure. It is acknowledged that “integration”, as in IUWM and H-PIC, is likely to be realized in practice, because of the need for it expressed in the highest political circles of the sustainability debate. Given this, the paper examines the implications of the ongoing shift-from the technocracy of the past century to the democracy of stakeholder participation in the present century-for the more widespread use of information and communication technologies in managing water quality in urban water environments.