One potential flood-prone area is Ponorogo Regency, which has a medium to high river flow status due to water coming from other areas. The information dissemination regarding the potential for floods in the Ponorogo region is still done manually through the monitoring of relevant department personnel. The water level measuring device in the Ponorogo District uses water level estimation boards attached to the river's edge. This tool is not effective and efficient in providing anticipatory warnings to the public because its measurements can only be continuously monitored from the estimation boards. There is a need for a monitoring and early warning system accessible to the community that is easy, fast, flexible, and can serve as anticipation for the community to face incoming floods. Based on the above phenomenon, the author came up with the idea of creating an early warning system with the title "Rancang Bangun Deteksi Ketinggian dan Debit Air pada Pertemuan Tiga Aliran Sungai Berbasis Internet of Things" to determine the possibility of flooding using a web service to provide information about the statistics of water level and flow rate with high accuracy using three water level status levels, namely safe, alert, and danger, which have been programmed. The device is integrated with a Telegram Bot application that sends notifications of river water flow and water level status to the public. The results of this research show that early information regarding the possibility of flooding at the three downstream river confluences can be detected with an error rate of 0.05% - 2.01%, an accuracy rate of 97.98% - 99.94%, and can be conveyed in real-time on Telegram, as well as a device data recapitulation system using a web service that can be accessed by personnel and residents living near the riverbanks.