This article argues for the systematic, coordinated, and ongoing collection of primary data on humans, spanning beliefs, perceptions, behaviors, and institutions, alongside data about the water environments in which people are embedded. Such an enterprise would not only advance water science and related policy and management decisions, but also generate basic insights into human cognition, decision making, and institutional development. Input from a convenience sample of water scientists and managers suggests that natural scientists and engineers have less experience with social data than social scientists with natural system data, both groups have strong interest in human dimensions of water science, and there are disciplinary differences in data priorities.