The management of water resources during the dry season is a major challenge associated with rainwater harvesting (RWH) technology, but is necessary given the human suffering that follows from resulting conditions of water scarcity. In this study, the parameters for dry season assessment are defined in terms of ‘no water days’ (NWD) and rainwater usage ratio. A simple socio-technical operational strategy making use of a water level monitoring system is proposed for NWD reduction. This involves water level monitoring, whereby daily water demand varies with user cooperation, as based on the available water in a tank. The results of our study show that an NWD as low as 10 can be achieved as compared with the current value of 115 days, before considering investment on additional roof catchments and tank volume. These parameters are useful for analyzing any type of rooftop RWH system. Furthermore, this operational strategy can be made practical and simplified by incorporating an easily visible and understood guideline onto the RWH system. This strategy is replicable anywhere in the world, with consideration of site-specific conditions such as rainfall amounts, roof sizes, and population.