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Key terms and definitions

Many definitions, terminology and units have come into use in the field of water management over time. ExxonMobil uses the following definitions:

For freshwater withdrawal and consumption, we follow the IPIECA-API-OGP “Oil and Gas Industry Guidance on Voluntary Sustainability Reporting,” 2010 edition. Withdrawal refers to the volume of fresh water removed from all sources for use by a facility or project. Consumption is the difference between fresh water withdrawn and fresh water returned by a facility or project. Water evaporated; transpired; incorporated into products, crops or waste; consumed by humans or livestock; or otherwise removed is considered consumed. Water that is lost during transport or that becomes so polluted it can’t be further used by others is also considered consumed.

Water use is a general, colloquial meaning referring to the removal of water from its natural location or the changing of its qualities as a result of human activity. We prefer the terms freshwater withdrawal and consumption when technical clarity is required. (Reuse and recycle are also defined in IPIECA 2010.)

Total dissolved solids
Chart — Total dissolved solids

The definition of fresh water varies in accordance with local statutes and regulations. For reporting purposes, IPIECA 2010 defines it as water with a total dissolved solids (TDS) concentration of less than 2000 milligrams per liter.

A variety of indices define water shortage, scarcity and stress1. One of the most widely used is the Falkenmark indicator, which describes the “stress state” in terms of the total annual runoff available for human use per capita. An area is said to experience water stress when this level drops below 1,700 cubic meters per person per year, or scarcity when the level drops below 1,000 cubic meters per person per year.

Another index from the International Water Management Institute (IWMI) distinguishes between physical water scarcity (insufficient water to meet human and environmental needs) and economic water scarcity (adequate water is present, but substandard infrastructure or poor management prevents its delivery). Both the Falkenmark and IWMI indices are used in the IPIECA Global Water Tool for Oil and Gas. Note that these and other water stress indices are based on conventions, definitions and data sets that are still evolving, and provide only a global approximation to actual situations in a given locality.

We follow the conventions of the ExxonMobil “Outlook for Energy” in classifying the oil and gas industry as an industry separate from electrical power generation. While they are sometimes classified together as “the energy industry,” power generation and oil and gas have very different uses for water in their operations.