Methods and systems are provided for learning a transport delay for individual cylinders that is associated with maldistribution of water among cylinders during a water injection event. Differences in knock intensity between individual cylinders, following a water injection, are used to identify water maldistribution. Differences in the amount and timing of an engine dilution effect following a manifold water injection are learned via an intake oxygen sensor and used to reduce cylinder-to-cylinder imbalance in water delivery.