Investigation of the possibilities of using rainwater harvested from the greenhouse roof in irrigation

The amount of available water and the adverse impacts on water resources worldwide and in our country are increasing day by day due to global climate change, population growth, excessive consumption, and pollution. Therefore, the efficient use, conservation, and management of water have become increasingly important, making the rational and productive utilization of existing resources through new strategies inevitable. One of these strategies is rainwater harvesting. In this study, the potential use of rainwater collected from the roofs of high tunnels located at Bilecik Şeyh Edebali University, Agricultural Practice and Research Center, for irrigation in greenhouses was investigated. Various scenarios were developed considering the year-round cultivation of tomato, lettuce, and green onion under high tunnels, and the extent to which the harvested water would meet irrigation needs was determined. The annual crop water requirements of the selected plants were estimated using the CROPWAT software. According to the calculations, under the climatic conditions of 2024, the total annual amount of water harvested from the greenhouse roofs was estimated at 115.45 m³. It was determined that the harvested water could enough 35% of the annual irrigation water requirement for tomato, 33% for lettuce, and 36% for green onion. These findings indicate that while the total irrigation demand cannot be fully met through rainwater harvesting, it can significantly reduce the pressure on existing water resources.