Resumen
The failure in the past to acknowledge the limits of water supply and to decouple economic development from water demand has resulted in a water dependent growth model currently threatened by increasing scarcity and droughts. Consequently, there is now an urgent need to use sparse water resources in a more sustainable and efficient way. This demands a comprehensive understanding of water productivity and the linkages among economic sectors to illustrate the tradeoffs in water reallocations from productive sectors to priority uses (household and urban uses). This paper develops a methodology based on the Hypothetical Extraction Method to estimate inter-temporal direct and indirect water productivity. The method is applied to the Spanish region of Castile and León. Results confirm the existence of a relevant water productivity gap between the agriculture (the largest water consumer) and that of the other sectors, which are nonetheless largely dependent on the agricultural output (and thus, on agricultural water demand). Results also show that Gross Domestic Product (GDP) growth, say about 1%, results in an increase of indirect water productivity in the manufacturing blocks (0.49% and 0.38%), energy and water (0.39%) and service blocks (0.41%), providing evidence of the existence of a Verdoorn?s Law for water.