Blue Infrastructure: The Confluence between Green and Grey Infrastructure in Integrated Urban Water Management

There is recognition that to achieve the desired good ecological status of waters in most countries including the US and member states of the European Union, there is going to be the need to improve the quality of wet-weather induced discharges from urban catchments.The real challenge, however, particularly in the highly urbanized catchments, is that space is usually at a premium. So though the current trend towards “Green Infrastructure” (GI) is the direction to go in terms of more sustainable water management approaches and practices; in the “Urban Retrofit” context, the space requirements for GI are often such that they are not feasible solutions on their own. These space constraints particularly in ultra-urban catchments is resulting in a re-evaluation of the traditional Low Impact Development (LID) and Sustainable Urban Drainage Systems (SUDS) practices with an increasing recognition of the role that proprietary systems termed here “Blue Infrastructure” can (and have to) play in integrated urban water management.The paper describes case examples of the use of “Proprietary Systems” in the confluence of “Grey” and “Green” Infrastructure to provide cost effective solutions to problems of urban water management in a number of urban catchment contexts; with major cost savings being realized. Proprietary Systems are shown to facilitate the maximum use of existing infrastructure proving to be a “middle way” and the “bridge” between the traditional “Grey Infrastructure” and the emerging “Green Infrastructure”. They are seen to be an essential part of the required comprehensive “Tool Box” of appropriate solution sets that can be tailored to suit site specific needs in integrated urban water management.