Risk Assessment of Urban Water Systems for the City of the Future

It is now widely accepted that water scarcity and lack of safe drinking water are the most serious challenges of the twenty - first century. Presently, one third of the world’s population lives in water-stressed countries, and over 1- billion of people lack access to clean water. These challenges are widening in coming future due to global change pressure. Expected results of the global changes could be more frequent droughts and increased occurrence of high-rainfall storms pose increased threat to cities; including water supply shortages, increased risk of flooding, ground water table depletion, pollution by overflowing sewer and contamination by treated or untreated wastewater. As a result, future cities will experience difficulties in effectively managing scarcer and less reliable water resources, as well as satisfying water uses/services and waste water disposal, without creating environmental, social and/or economic damage.

In order to deal these future challenges and approach the ideal goal of sustainable development, we must have a clear understanding of the global change pressure in a natural system in which we live, the dynamics of societal system in which we interact with one another, and the synergistic effects of these two interdependent systems. However, these dynamical systems and their interdependencies are extremely complex and difficult to comprehend and model. Good decisions and research must address these uncertainty and variability associated with global changes. This is true, for example, when planning for a reliable water supply, when analyzing environmental impacts, or when assessing health consequences. Quantitative evaluation of the degree and impact of uncertainty and variability is often referred to as risk analysis.

It has only been in the last decade that risk analysis methods have been explicitly integrated into decision- making. The integration has provided the risk- cost and risk-net benefit tradeoffs, and distributions of net benefits. These provide additional information for decision making and a better understanding of how an investment in urban water system works. By explicitly examining risk-cost tradeoff, it is possible to reconsider the value of requiring some standards assumption and criteria in all instances. Allowing some flexibility can reduce project costs will only small sacrifice in project performance.

This research attempts to analyze and quantify the major dimensions of uncertainties and risks in urban water systems due to global change pressure. It will explore not only of current know about a given problem, but also the gap between that level of knowledge need to know to fully comprehend the dimensions of the problem. Finally, it will provide a framework for establishing risk indicators that can be used for an integrated assessment of the risk associated with urban water systems. The indicators will be used in a quantitative way (using physical models, fact generators) and a qualitative way (using management models and decision support systems, judgment generators). Hence, the framework will enable the developed risk indicators to be translated into tangible design, control, and management strategies for the city of the future. This work has been supported by UNESCO-IHE and SWITCH project (EU funded) and expected to be completed at the end of 2010.