The provision of water security for humans generally requires a stable supply of high quality water, which is in contrast to the importance of variability in water quality and quantity for ecosystems. In this chapter we address this apparent conflict and seek congruence between humans and the environment. We discuss the concept of ecosystem health, its use for monitoring, reporting and evaluating of the aquatic ecosystem condition and how this can be used to guide the environmental component of water security. We then discuss the apparent conflict and congruence between humans and the environment in the quest for water security and seek opportunities where water security can be provided to humans with minimal reductions of ecosystem health. We argue that knowledge from ecological science can provide guidance toward this goal.