Water is our most precious resource — and managing it wisely is essential for our future. Across the Mediterranean, water scarcity is becoming one of the defining challenges of our time. The TWISTT project is pioneering a new way to understand, measure, and manage water use — from the soil beneath our feet to the policies that shape our future. TWISTT uses Earth Observation (EO) and geophysical data to create a comprehensive, transparent picture of how water is used and replenished across agricultural and natural systems. By distinguishing between blue water (from rivers, reservoirs and aquifers) and green water (stored in the soil and used by plants), the project aims to define realistic and sustainable levels of water withdrawal and consumption for all users — including ecosystems. What makes TWISTT unique is its multi-scale and multi-actor approach. At the farm level, geophysical measurements provide a non-invasive view into soil and groundwater conditions, revealing what’s happening beneath the surface — even when satellite imagery is unavailable. At regional and basin scales, EO-based soil and energy balance models allow water use to be tracked with unprecedented accuracy. Together, they close the gap between surface observations and subsurface processes, helping to bridge farm-level practices with catchment-level policies. This innovation goes hand in hand with collaboration. TWISTT brings together scientists, engineers, farmers, and policymakers to co-develop practical tools that are transparent, FAIR (Findable, Accessible, Interoperable, and Reproducible), and open-source. TWISTT is a PRIMA-funded initiative coordinated by ICA-CSIC and implemented by leading institutions across the Mediterranean — Politecnico di Milano (POLIMI), FPN, CDU, INRAT, and Xcalibur Smart Mapping. Together, the consortium combines expertise in hydrology, geophysics, Earth Observation, and socio-economic sciences to advance sustainable and equitable water management.