Changes to socioeconomics and an evolving climate system are likely to play a vital role in how regions around the world use water into the future. Water projections for the future, while prolific, remain highly variable and dependent upon underlying scenario and model assumptions. In this study, the Global Change Assessment Model (GCAM) is used, where interactions between population, economic growth, energy, land, water, and climate systems interact dynamically within a market equilibrium economic modeling framework, to address how changing socioeconomic and climate conditions alter global water futures, and in turn, how water constrains the future of other systems. First, the impacts of efficiency changes are investigated with the addition of socioeconomically consistent water technologies across several sectors. Quantitative assumptions for the Shared Socioeconomic Pathways are extended to the water sector for the first time in a water constrained – Integrated Assessment Modeling framework. It is found that significant water use reductions are possible under certain socioeconomic conditions, provided the ability to adopt appropriate technological advances in lower income regions. Secondly, the relative contributions of climate and human systems on water scarcity are analyzed at global and basin scales under the Shared Socioeconomic Pathway-Representative Concentration Pathway (SSP-RCP) framework. Ninety scenarios are explored to determine how the coevolution of energy-water-land systems affects not only the driver behind water scarcity changes in different water basins, but how human and climate systems interact in tandem to alter water scarcity. Human systems are found to dominate water scarcity changes into the future, regardless of socioeconomic or climate future. However, the sign of these changes has a significant scenario dependence, with an increased number of basins experiencing improving water scarcity conditions due to human interventions in the sustainability focused scenario. Finally, the reliance on international agricultural trade is analyzed to understand how future socioeconomic growth and climatic change will impact the dependency on international water sources. The differentiation between renewable and nonrenewable water sources allow for the quantification of the various water sources needed to produce enough agricultural goods to meet global demands. The first Integrated Assessment Model projection of the evolution of external water sources to meet domestic agricultural demands show that there will be an increasing international dependencies. China, the United States, and portions of South America are pivotal in providing the necessary exports to meet demands in water scarce or high demand areas of the Middle East and Africa.