Water use in a global context indicator: data sources and methods, chapter 5

5. Caveats and limitations

The definition of total renewable water used by the Organisation for Economic Co-operation and Development (OECD) ignores differences in water storage and represents the maximum quantity of water available on average.

Mine water and drainage water are included in the water abstraction estimates, whereas water used for hydroelectricity generation, considered an in situ use, is excluded.

In many countries, systematic collection of environmental data has a short history; sources are typically spread across a range of agencies and levels of government, and information is often collected for other purposes.

Definitions and estimation methods used by countries to compile data on water abstractions and supply may vary considerably and change over time. Inter-country comparisons require careful interpretation.

The OECD totals are the OECD Secretariat's estimates based on linear interpolation to fill missing values.

The indicators refer to the national level and may conceal major sub-national differences.

If the water is returned to a surface water source, abstraction of the same water by the downstream user is counted again when compiling total abstractions and may lead to double counting.