**7. Conclusions**

Smart water sensors can be integrated with water distribution infrastructure, distributed ledger technology, smart contracts, and automated control to support novel decentralized water markets to improve water savings in urban environments. This research demonstrates how a semi-decentralized water supply system can create water and energy savings by deploying existing smart city technologies and decentralized infrastructure within a centralized reclaimed water distribution system. In this research, we report the feasibility of a reclaimed water system that is augmented by prosumers, who pump harvested rainwater into the network at decentralized nodes. We construct an all-pipe hydraulic model for a hypothetical community to simulate demands exerted for non-potable uses at households and to evaluate hydraulics in the dual reticulation network. An agent-based modeling approach is developed to simulate household behaviors, including storing, pumping, trading, and withdrawing non-potable water. The agent-based model is loosely coupled with hydraulic modeling, and negative and positive demands of prosumers and consumers are used to modify input to the pipe network model. The simulation framework is applied using climate parameters for a location in the northwest U.S., which was selected based on the potential yield expected from rainwater harvesting, and a theoretical outdoor water demand model is used to simulate irrigation demands at households. Multiple scenarios are explored to demonstrate the feasibility of peer-to-peer non-potable water trading, and tradeoffs among the volume of traded water, energy savings, satisfaction of pressure constraints, and water quality are explored. The smart water grid is a complex system, and energy outcomes emerge based on reductions in the volume of water required by households, the volume of water provided by prosumers, and the dynamics of centralized water distribution infrastructure. The water and energy efficiency of scenarios depends on the reduction in the volume of water that is provided by the centralized system through traded rainwater. Higher volumes of water produced by prosumers increases both water and energy savings. Analysis demonstrates that there is a lower bound on the number of households that should participate as prosumers to meet pressure requirements, and an upper bound on prosumers to protect water quality. This research develops a novel water management system designed to further the use of decentralized infrastructure and smart city technologies in improving the sustainability of the built environment.

**Author Contributions:** Conceptualization: E.Z.B.; methodology: E.R., J.P., M.A.K.F., J.M.; formal analysis: E.R., E.Z.B., J.P.; data curation: M.D., E.R., J.P., M.A.K.F.; writing—original draft preparation: E.R., E.Z.B., M.D., M.A.K.F., J.P.; writing—review and editing: E.Z.B., E.R.; resources: E.Z.B., J.M.; supervision: E.Z.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported in part by North Carolina State University through a 2019 University of Adelaid—NC State Starter Grant.

**Conflicts of Interest:** The authors declare no conflicts of interest.
