The purpose of this research is to develop an analytical and modelling approach that allows for the quantification of trade-offs between the water, energy and food nexus at different scales; allowing to go from national analysis of nexus stress by identifying and quantifying key intersectoral claims and trade-offs, up to a more detailed and even local specific analysis of the trade-offs. These trade-offs and the system understanding created by following the proposed steps for the analysis of nexus stress, inform them the design of Climate Smart Solutions and Strategies that make use of the most powerful leverage points and introduce or exploit existing synergies between the water-energy-food sectors. The national and local scales analyses following the proposed methodology have been applied to Ethiopia. At the national scale the integration has been done by making use of system analysis techniques in combination with the use of diverse modelling techniques for the quantification of the key trade-offs identified. The soft-linking Deltares Water Allocation Model (Ribasim) and TIAM-ECN model for optimization of Energy Systems allowed for the quantification of trade-offs between the water and the energy sectors given the national plans to make significant increase in hydropower dams. This modelling exercise was complemented with excel calculations to quantify the trade-off between biomass production for energy and land available for food production, as well as to quantify the complex linkages between water and food security.