This document discusses concepts and applications related to virtual water and water footprints. It provides definitions of virtual water and water footprint over time. It discusses using virtual water and water footprint concepts for policymaking, business planning, and international trade analysis. The document proposes applications like analyzing virtual water trade between the UK and Spain, surveying Spanish farmers, and developing food certification standards. Formulas are provided for calculating components of water footprints based on factors like crop water requirements, yields, and trade.