This paper identifies over 50,000 patents filed worldwide in various water-related technologies between 1990 and 2010, distinguishing between those related to availability (supply) and conservation (demand) technologies. Patenting activity is analyzed — including inventive activity by country and technology, international diffusion of such water-related technologies, and international collaboration in technology development. Three results stand out from our analysis. First, although inventive activity in water-related technologies has been increasing over the last two decades, this growth has been disproportionately concentrated on supply-side technologies. Second, whilst 80% of water-related invention occurs worldwide in countries with low or moderate water scarcity, several countries with absolute or chronic water scarcity are relatively specialized in water efficiency technologies. Finally, although we observe a positive association between water scarcity and local filings of water patents, some countries with high water availability, in particular Switzerland or Norway, nevertheless appear as significant markets for water-efficiency technologies. This suggests that drivers other than local demand, like regulation and social and cultural factors, play a role in explaining the global flows of technologies.