Green-Gray Analysis: Assessing the Costs and Benefits of Green Infrastructure for Water Supply Systems

This downloadable guide gives stakeholders a way to value the costs and benefits of integrating green or natural infrastructure into water supply systems to improve performance. It builds on existing case studies of green and grey infrastructure analysis rooted in classic decision and public investment theory. It couches valuation of green infrastructure within a broader analysis of portfolios of green and grey options to meet a specific water management investment objective.

The method consists of six key components for an effective general methodology that optimizes performance and financial benefits:

1. Clearly define the investment objectives and constraints;
2. Specify investment portfolios that include both green and gray investments;
3. Model the outcomes of the portfolios;
4. Conduct the economic valuation of the portfolios;
5. Compare the cost-benefit analyses between portfolios; and
6. Conduct a risk and uncertainty analysis.