Defining Infrastructure

Introduction to Green Infrastructure, Blu Infrastructure, and Grey Infrastructure

Anyone who considers where their clean water comes from recognizes the critical role of infrastructure to deliver and maintain a safe and sustainable water supply.

Today, we have signifcally advanced our knowledge and understanding of stormwater management, flood mitigation, and effective water treatment. In addition, this also includes the way in which water in managed on infrastructures. Part of this increase in alternatives includes conversations and actions around Green Infrastructure, including consideration of performance measures and cost effectiveness.

Both Green Infrastructure and Grey Infrastructure can play an important role in water management. However, it is important to understand the differences and challenges these alternatives bring from economic, environmental, and social perspectives.

One of the challenges surrounding Green Infrastructure and Grey Infrastructure is a lack of clear and consistent definitions of the terms. Green Infrastructure and Grey Infrastructure both refer to work outside of just water. This includes buildings or transportation, while having an impact on water management.


Grey Infrastructure

The human-engineered infrastructure for water resources such as water and wastewater treatment for plants, pipelines, and reservoirs. It typically refers to components of a centralized approach to water management.


Green Infrastructure

“Strategic use of networks of natural lands, working landscapes, on roof or structures, and other open spaces to conserve ecosystem values and functions and provide associated benefits to human populations.” (Allen, 2012)


Blu-Green Infrastructure

A term used interchangeably with green infrastructure to describe things like Rain Gardens, BluGreen Roofs, or Reed Beds that treat wastewater. Green infrastructure is generally decentralized. Water is captured and treated where it falls, rather than being transported to a treatment facility.


Blu Infrastructure

Used to describe the use of proprietary, small footprint, high-efficiency devices installed and retrofitted within existing water collection systems. It can be used to connect the benefits of green and grey infrastructure, and is especially useful in challenging environments such as urban areas. Blu infrastructure aims to mimic green infrastructure’s principles.


Compared to Green Infrastructure, Grey Infrastructure currently has a clear asset life, depreciation, and return on investment (ROI). 

Challenges surrounding Grey Infrastructure include funding and public investment, maintenance, and increased urbanization. Urbanization presents a water management challenge due to hard surfaces. Hard surfaces such as concrete or asphalt contribute to high volumes of stormwater runoff because of the reduction of infiltration. In result, it's relative size, construction requirements, and limited life are seen to be inflexible.

Challenges surrounding Green Infrastructure include the measure of ROI, risk management, and effectiveness in urban areas. Current or absent regulations at the federal, provincial, and local levels have also created obstacles. Many Green Infrastructure projects don't fit traditional wastewater treatment construction models, so they often don't meet the standands or codes to govern how the projects should be implemented. 

Green Infrastructure is a largely untested concept. Because of this, it faces socio-political acceptance and scientific and decision making uncertainty. 

Knowledge and experience for people making decisions and designing and operating green infrastructure presents challenges for traditional approaches. For instance, green infrastructure is thought of more as an urban design because of the scale and dispersed nature of the works compared to a large, engineering-focused infrastructure project.

Green Value Calculator

This calculator by The Centre for Neighbourhood Technology (CNT) in the U.S. compares performance, costs, and benefits of green infrastructure and low impact development solutions for stormwater management. To view and use the calculator click here.


Green Infrastructure is not a replacement for Grey Infrastructure

Green Infrastructure complements grey infrastructure to help reduce energy costs and create more livable cities for the future.

Hybrid Approach

Most countries are recognizing the value of a hybrid approach to water issues such as stormwater management. For example, Green Infrastructure can reduce the pressure on Grey Infrastructure through naturally filtering out non-point source pollutants.


Awareness of the various options available to tackle individual scenarios and localized environments is growing throughout the water industry, watershed and environmental organizations, and all levels of government.


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