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Retrofitting urban watersheds with wireless sensing and control technologies will enable the next generation of autonomous water systems. While many studies have highlighted the benefits of real-time controlled gray infrastructure, few have evaluated real-time controlled green infrastructure. Motivated by a controlled bioretention site where phosphorus is a major runoff pollutant, phosphorus removal was simulated over a range of influent concentrations and storm conditions for three scenarios: a passive, uncontrolled bioretention cell (baseline), a real-time controlled cell (autonomous upgrade), and a cell with soil amendments (passive upgrade). Results suggest the autonomous upgrade matched the pollutant treatment performance of the baseline scenario in half the spatial footprint. The autonomous upgrade also matched the performance of the passive upgrade; suggesting real-time control may provide a ‘digital’ alternative to existing, passive upgrades. These findings may help site- and cost-constrained stormwater managers meet their water quality goals. 

“Smart” water systems are transforming the field of stormwater management by enabling real-time monitoring and control of previously static infrastructure. While the localized benefits of active control are well-established, the potential for system-scale control of watersheds is poorly understood. This study shows how a real-world smart stormwater system can be leveraged to shape streamflow within an urban watershed. Specifically, we coordinate releases from two internet-controlled stormwater basins to achieve desired control objectives downstream—such as maintaining the flow at a set-point, and generating interleaved waves. In the first part of the study, we describe the construction of the control network using a low-cost, open-source hardware stack and a cloud-based controller scheduling application. Next, we characterize the system’s control capabilities by determining the travel times, decay times, and magnitudes of various waves released from the upstream retention basins. With this characterization in hand, we use the system to generate two desired responses at a critical downstream junction. First, we generate a set-point hydrograph, in which flow is maintained at an approximately constant rate. Next, we generate a series of overlapping and interleaved waves using timed releases from both retention basins. We discuss how these control strategies can be used to stabilize flows, thereby mitigating streambed erosion and reducing contaminant loads into downstream waterbodies.