Energy Metrics for Water Distribution System Assessment

Water and energy, more than key inputs to most human activities and important ecosystem services, share an important nexus. By analyzing the connections between these resources, more holistic, and sustainable solutions can be achieved. In water distribution, electricity consumption is responsible for a significant part of greenhouse gas emissions and costs. Furthermore, since energy is proportional to the product of pressure and flow, it integrates these two key parameters of the system. Therefore, how energy is transformed and displaced throughout the network is an indicator of other system characteristics. The present study proposes energy related sustainability metrics for water distribution systems: energy supplied, lost, dissipated, potential, and delivered. These respectively correspond to energy provided to the system, lost through leaks, used to overcome friction, used to overcome differences in elevation, and delivered to the user in the form of pressure

and demand. The metrics are based on EPANET hydraulic modeling outputs. Aggregate results of the system are indicators of capacity, efficiency, and costs. When mapped, the metrics provide a geographical snapshot of the system, and allow for better identification of pressure districts, or even specific mains, pumps, and tanks, where dissipations are high or energy delivered is in excess, and changes are most beneficial. Through this deeper understanding of the cost generating and revenue producing parts of the system, more effective stewardship can be achieved; rate structures, and even standards can begin to be rethought.