ABSTRACT
There are quite a number of practical issues that one will encounter when carrying out a water footprint assessment. In many cases this manual will give sufficient guidance, but in some cases there is an obvious need for further development of practical guidelines. A major question will often be how to handle the lack of required data. What default data should be used under such circumstances and what simplifications can be reasonably made? A major challenge is therefore to develop more detailed guidelines regarding what default data can be used when accurate local estimates are not available. In this context it is relevant to develop a database with default water footprint estimates for a large variety of processes and products, differentiating between production regions (such as countries). This would be very helpful for assessing the water footprints of consumers or producers, who know what they buy but often do not know all relevant details on the production and supply chain of the things they buy.
