In response to this desire for improved corporate water accounting, several methods and supporting tools have emerged. The different origins, functionality, and evolving applications of the various approaches are currently poorly understood by stakeholders. There is a perceived need among businesses, civil society, and academia alike to elucidate the relation of these methods and tools to one another in order to help companies determine which approaches are best suited for particular applications. Improved clarity should also minimize duplication of efforts and promote coordination among the initiatives developing such methodologies. This stocktaking exercise, a joint effort of UNEP and the CEO Water Mandate, will fulfillthe need to clarify commonalities and differences among existing and emerging water accounting methodologies and tools being used in the private sector. Specifically, this report is intended to: Elucidate commonalities and differences among emerging methods and practice; Identify gaps and challenges; Suggest where accounting methods might benefit from harmonization and increased field testing. Though this analysis will cover a number of water accounting methods and tools of relevance to businesses, it will emphasize perhaps the two most significant methods: 1) water footprinting (as managed by the Water Footprint Network) and 2) emerging Assessment. The authors note that the term “water footprinting” in and of itself is the source of confusion in this fast-evolving field and that it is currently being used to mean different things in various settings and arenas. The term “water footprint” was coined almost a decade ago by Professor A.Y Hoekstra of the University of Twente and refers to a specific methodology for water-use measurement. Since that time a community of practice has emerged that has built on Hoekstra’s methodology. In the last couple of years the term has increasingly been used metaphorically by laypeople broadly referring to the concept of water accounting. There is seldom a formal definition associated with this lay usage of the term, and indeed, it is likely the concept is understood differently depending on the circumstance and individual user. Because of the lack of a formal definition, the authors have given little weight to this vague use of the term in common vernacular. In that same time span, the term has also entered the lexicon of Life Cycle Assessment (LCA) practitioners who have had a newfound interest in water. In this LCA context, the term is often used similarly to the term “carbon footprinting,” insofar as it includes the characterization of water-use volumes according to local or regional context. Nonetheless, for sake of clarity, unless otherwise specified, the term “water footprint” will be used in this report only in reference to the formal methodology developed by Hoekstra and currently managed by the Water Footprint Network, as this is the longest-standing use of the term. That said, the way in which this term is used and understood by water accounting practitioners, water resource managers, and the general public in the future is still to be determined. The authors have no judgment on the most appropriate use of this term, but note the urgent need for experts and practitioners in both the LCA and WFN communities to come together to derive a shared understanding of this concept. In addition to water footprinting and LCA, this analysis examines in lesser detail the WBCSD Global Water Tool and GEMI’s on-line water sustainability tools. It also provides a cursory comparison of the ecological and carbon footprinting methods, particularly as they relate to corporate water accounting. Metrics such as those in the Global Reporting Initiative’s G3 Guidelines and Carbon Disclosure Project’s Water Disclosure Information Request may be an important starting point for communicating corporate water accounting results to external audiences. However, asthey do not provide methodologies or tools through which to measure or assess water use (but rather a framework and indicators through which to report those types of measurements), they are not included among the accounting methodologies assessed in this report. This study does not offer specific recommendations for the advancement of each method, but rather provides general comparisons that will help stakeholders to identify the best prospective applications for each method and support the developers of these methods to work in a more coordinated and integrated fashion.