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In-field rainwater harvesting (IRWH), a runoff farming system, is a beneficial water management technique for crop production in arid and semi-arid areas. In-field rainwater harvesting is influenced by rainfall characteristics, and hence this study aimed to identify and characterize rainfall events, and determine rainfall parameters that were of significance in in-field runoff. Two algorithms of event identification were developed. The algorithm that identified events spanning over a 24-h day limit as a single event, gave better identification results which were then characterized. This enabled systematic grouping of rainfall parameters. About 33% of the total rainfall amount received had zero potential to be harvested as runoff in the IRWH system. Therefore, a runoff harvesting practice needs to use the remaining 67%. Rainfall events that lasted 30 min or longer were of water-harvesting importance. This could be the minimum duration guideline when simulating rainfall for rainwater harvesting studies. Rainfall event amount and intensity were of significant importance for IRWH runoff determination. Copyright (C) 2012 John Wiley & Sons, Ltd.