Quantifying Cumulative Effectiveness of Green Stormwater Infrastructure in Improving Water Quality
31 Pages Posted: 16 Apr 2020 Last revised: 12 Jun 2020
Date Written: March 23, 2020
Stormwater runoff is one of the main sources of pollution in streams and receiving water bodies of major cities. Green Stormwater Infrastructure (GSI) is a set of distributed stormwater best management practices that mimic natural systems, absorbing excess water, filtering out sediment and pollutants, and helping to recharge groundwater. Despite the increasing popularity of GSI as means of stormwater management, our knowledge of their performance is limited. Even though studies have shown effectiveness of individual installations in many cases, it is not clear whether the combination of these plants will deliver the same benefits. This research studies the effectiveness of GSI in improving the water quality of four major receiving water bodies of Seattle, Washington at the watershed scale. Using the monthly time series data of water quality indices from 2004 to 2017, as well as a set of nine control variables, we predict the counterfactual water quality levels in absence of GSI in each watershed and estimate the cumulative effect of GSI using a Bayesian structural time series model. Our findings show that GSI improves some physical water quality indices such as chlorophyll a, Secchi depth and light transmission, but increases the temperature in some waters.
Keywords: green stormwater infrastructure, stormwater management, climate change adaptation, water quality
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