Strategic design and finance of rainwater harvesting to cost-effectively meet large-scale urban water infrastructure needs

Sjon Van Dijk,Amanda W Lounsbury,Arjen Y Hoekstra,Ranran Wang

doi:10.1016/j.watres.2020.116063

Sjon Van Dijk, Amanda W Lounsbury + Show 2 more

Open Access

https://doi.org/10.1016/j.watres.2020.116063

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Abstract

Many cities are confronted with both water scarcity and urban flooding as centralized water infrastructures becoming increasingly inadequate in a changing climate. Decentralized infrastructures like rainwater harvesting (RWH) can ease both issues. Yet, most studies find RWH offers limited infrastructure capacity at high cost. Previous assessments, however, fail to consider two critical advantages: multi-functionality and high adaptability. By improving the incorporation of these advantages in our analysis of 1.06 million buildings with distinct design and water demand characteristics and 20-year hourly precipitation records in New York City (NYC), we demonstrate, contrary to existing studies, that strategically designed, financed and implemented rooftop RWH systems in all or a subset of the buildings can meet large-scale infrastructure development needs for water supply and stormwater management. RWH implementation featuring public-private partnerships (PPP) in 43–96% of the buildings can serve 17–29% of the city’s non-drinking water demands while reducing the public expenditure per unit of water supply by 13–85%. The distributed citywide RWH implementations prevent 35–56% of rooftop runoff from entering the sewage system, rivers, and/or waterways per month, with observed rooftop runoff reductions as high as 90% for a single rain event.

Highlights

Global urbanization and climate change present an urgent need to develop more efficient and sustainable urban water systems worldwide (Nations, 2019)
We found that the runoff reduction rates of rainwater harvesting (RWH) are especially high in the city’s poor neighborhoods which are densely occupied by small residential houses
The results indicate RWH as a profitable climate change adaptation strategy in urban areas that are densely populated with low-rise buildings, which are known to be more vulnerable to climate change impacts (USGCRP, 2018)

Summary

Introduction

Global urbanization and climate change present an urgent need to develop more efficient and sustainable urban water systems worldwide (Nations, 2019). In most high-income countries, drinking water treatment and delivery systems are aging and decaying while critical maintenance and repairs are backlogged or neglected, posing great health risks, comparable to the 2004 surprise lead contamination in Washington D.C.’s water supply (Renner, 2004), and more recently, problems of dilapidated water infrastructure exacerbated by climate change and population growth in London (Cooper, 2019). Drinking water systems are under pressure to comply with more stringent water quality standards and newly identified contaminants of concern to safeguard human health (Can~edoArgüelles et al, 2016; Rosario-Ortiz et al, 2016). The European Parliament regularly reviews and updates the EU Water Directives like the enforced EU water quality standards applicable to surface water that recently added pharmaceuticals to a new watch list (European Union, 2018)

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