Final answer:
The 'WU of products added to water' likely refers to the water footprint of products, highlighting the total volume of freshwater used in their production and accounting for virtual water trade.
Step-by-step explanation:
The subject in question seems to regard the water footprint and how it is measured not just by the water withdrawal but also by considering the virtual water content of products. The water footprint includes all of the freshwater used throughout the production process of a product.
These measures are becoming increasingly relevant as they account for international trade and the consumption of products outside their country of origin. Therefore, understanding the water footprint can provide insight into the actual water usage of a country, which includes both domestic water use and the water embodied in goods produced for export.
For example, the water footprint of different diets, particularly those that include different levels of meat consumption, can vary greatly due to the significant amounts of water required for livestock production compared to crops. Such considerations are crucial for sustainable water management and policymaking.
In contrast, ion-product of water, another topic mentioned, relates to the chemical aspect of water in terms of its dissociation into ions, which is a separate concept.