Agent-based modeling to assess decentralized water systems: Micro-trading rainwater for aquifer recharge

Decentralized aquifer recharge programs are an alternative to centralized stormwater aquifer recharge systems and can improve groundwater tables in urban areas. In a decentralized aquifer recharge program, households and property-owners collect and store rainwater from rooftops and replenish aquifers through small gravity -fed recharge wells. This research presents a micro-trading rainwater for aquifer recharge (MRAR) system as a decentralized peer-to-peer water market that can recharge groundwater resources. Through a decentralized water market, households act as prosumers who collect and sell rainwater to consumer households and convey traded water via a shared aquifer. This research develops an agent-based modeling framework as an approach to evaluate the performance of a MRAR system to replenish groundwater resources and reduce energy required to pump water. Agents represent (1) prosumers that collect rainwater, sell rainwater to consumers, and replenish the groundwater system through dry wells, and (2) consumers that exert irrigation demands, buy rainwater from prosumers, and pump water from the groundwater system. The agent-based model is coupled with a groundwater flow model to evaluate the effects of micro-trading on groundwater resources. The agent-based modeling framework is applied for a virtual city to assess the performance of a MRAR system for scenarios that vary in the ratio of consumers to prosumers, location of prosumers and consumers, and aquifer properties. Model outcomes demonstrate the optimal ratio of consumers to prosumers based on the volume of traded water, improvements in groundwater head, and improvements in unit energy of water. Findings demonstrate that the optimal ratio of consumers to prosumers is consistent across different values for hydraulic conductivity. The location of prosumer and consumer households affects the unit energy of water and has a negligible effect on the groundwater table and total energy consumed to pump water. This manuscript proposes and demonstrates MRAR as a new decentralized water system and provides a modeling approach to assess the performance of a MRAR system to improve urban groundwater resources.