**Elizabeth Ramsey\*, Jorge Pesantez, Mohammad Ali Khaksar Fasaee, Morgan DiCarlo, Jacob Monroe and Emily Zechman Berglund**

Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, NC 27695, USA; jpesant@ncsu.edu (J.P.); mkhaksa@ncsu.edu (M.A.K.F.); mdicarl@ncsu.edu (M.D.); jgmonroe@ncsu.edu (J.M.); emily\_berglund@ncsu.edu (E.Z.B.)

**\*** Correspondence: evramsey@ncsu.edu

Received: 30 September 2020; Accepted: 29 October 2020; Published: 2 November 2020

**Abstract:** Water availability is increasingly stressed in cities across the world due to population growth, which increases demands, and climate change, which can decrease supply. Novel water markets and water supply paradigms are emerging to address water shortages in the urban environment. This research develops a new peer-to-peer non-potable water market that allows households to capture, use, sell, and buy rainwater within a network of water users. A peer-to-peer non-potable water market, as envisioned in this research, would be enabled by existing and emerging technologies. A dual reticulation system, which circulates non-potable water, serves as the backbone for the water trading network by receiving water from residential rainwater tanks and distributing water to households for irrigation purposes. Prosumer households produce rainwater by using cisterns to collect and store rainwater and household pumps to inject rainwater into the network at sufficiently high pressures. The smart water grid would be enabled through an array of information and communication technologies that provide capabilities for automated and real-time metering of water flow, control of infrastructure, and trading between households. The goal of this manuscript is to explore and test the hydraulic feasibility of a micro-trading system through an agent-based modeling approach. Prosumer households are represented as agents that store rainwater and pump rainwater into the network; consumer households are represented as agents that withdraw water from the network for irrigation demands. An all-pipe hydraulic model is constructed and loosely coupled with the agent-based model to simulate network hydraulics. A set of scenarios are analyzed to explore how micro-trading performs based on the level of irrigation demands that could realistically be met through decentralized trading; pressure and energy requirements at prosumer households; pressure and water quality in the pipe network.

**Keywords:** rainwater harvesting; water trading; dual reticulation; decentralized water supply; water distribution system; agent-based modeling; urban water management; smart city
