Meeting the Sustainable Development Goals is a complex challenge for the coming decades and obtaining water security for all is central to that challenge. Unsustainable approach to development that has emerged over the last 150 years has led to degraded ecosystems that themselves impair water security. New research shows that in the pursuit of water security, humanity pays an enormous tax to recover lost ecosystem services otherwise provided by healthy catchments. Looking to the middle of the 21st century, global annual expenditure on water security engineering is projected to be $2.3 trillion. Preserving the remaining natural capital of healthy catchments around the world offers up to $3 trillion per year globally, in avoided costs. In other words, a business-as-usual approach to development that continues to degrade catchments would see the costs of water security more than double. Blending nature-based solutions with traditional water security investments to avoid these costs and achieve a sustainable, water secure planet is an opportunity to meet the SDGs.