Ukraine, facing water resource scarcity, finds it increasingly challenging to provide high-quality drinking water for both its population and industries, particularly in times of war. Harvested rainwater, among these sources, aligns well with water resource protection and management measures to counteract drinking water shortages. A literature review indicates that domestic needs in cities (flushing toilets, cleaning, and laundry) account for over 50% of drinking water demand, which could be supplemented by harvested rainwater. The estimated volume of harvested rainwater for a residential building in Odesa and Uzhgorod showed a drinking water saving to 15% and 36.5%, respectively. Similar calculations were carried out for residential microdistricts with high-rise buildings in these cities, showing a saving of drinking water due to the use of rainwater to 9% and 19%, respectively.