Many factors are currently driving the need for water and wastewater utilities to take a more holistic view of the systems they operate and the water resources system in which they are embedded. Some of these factors include growth and redensification, regulatory uncertainty, climate uncertainty and vulnerability to hazards, growing social equity demands and environmental demands. A “One Water” method to planning, implementing, operating and managing water has surfaced as a promising approach. One Water, however, is sometimes perceived either as a loosely defined approach -making it unattractive- or as a synonym or water reuse -limiting the potential additional benefits of its implementation.

This paper will emphasize the early stages of a One Water plan seeking surface water quality and supply benefits and resulting investments, with case studies. It will offer definitions and principles consistent with One Water, including integration of water sector elements, public engagement, formal risk assessments, the pursuit of multiple objectives and organizational and governance factors. It will explore ways to avoid common pitfalls in the implementation of One Water projects that can result in stalling or stopping One Water projects at different stages, including the operations phase.

The paper will explain methods, processes and tools that can be used to build a robust business case for a One Water project with surface water quality benefits, and to sustain support from internal stakeholders, institutional stakeholders outside the water utility, elected officials, regulators and the general public. Finally, the paper will present the value of integrated modeling tools such as systems models and digital twins for planning, design and operations phases of One Water projects.