According to official data from the National Disaster Management Agency (BNPB), in 2021, flooding was Indonesia’s most frequent and destructive disaster. Thus, better disaster management, including early warning systems (EWS) and disaster mitigation based on accurate rainfall data, is essential. This paper was written based on preliminary research on the development of citizen science in Wonosobo and Banjarnegara regencies, Central Java, which aims to develop a very early warning system (VEWS) and community-based rainfall data management. Modified rain gauges are installed in elementary schools in the upstream Serayu watershed. Students, in turn, do data recording. This effort ensures continuity of observation, the introduction of science and technology, and increased literacy about floods and landslides and their mitigation. From the initial research, it can be stated that the integration of the citizen science model into compulsory subjects for elementary school children is very prospective for accelerating students’ understanding of subjects related to natural sciences. A citizen science approach that is carried out correctly is able to produce accurate rainfall data continuously. These two things are enabling factors for the effective and efficient implementation of the VEWS flood disaster in the upstream watershed.

Rainfall data is vital in analysing hydro-meteorological disasters, e.g., floods, landslides, or droughts. Currently, the location of climatological stations or rain gauges is preferred in areas that require climatological data, such as airports and near settlements. On the other hand, rainfall analysis for disaster mitigation purposes is more for remote areas, which are often far from the nearest rainfall station. This study aims to obtain accurate rainfall data through the placement of suited rain gauge locations and utilising community participation. The method used in this study is a literature review. This preliminary study was held upstream of the Serayu river basin, an area where it is usually challenging to access rainfall data. The references used are information about tropical rain, how to utilise a rain gauge network, and how to take advantage of community participation. The result shows that an Early Warning System should be developed in line with determining the location of the rain gauge because each location has a different rainfall threshold in each disaster. The placement of the rain gauge is strongly influenced by the landscape, the altitude of the place as well as the slope and aspect. For this study, the location of schools in remote areas is another parameter to determine the placement of a rain gauge since school children will be involved in the community participation.