Many kind of information about hydrology, such as water level, current speed, flow rate and rainfall is important for the river management. Particularly the current speed measurement is essential for the accurate water management. We developed the new current sensor using RF technology and the river flow information system. The river flow information system is composed of RF current sensor, water level gage and the flow calculator. The current sensor installed usually under the bridge measures the surface current flow of the river. Multi-sensors (up to 20 units) are used for the wide river. The flow calculator calculates the total river flow using the data of multi-current sensors, water level and the dimension data of the river cross-sectional area which has been inspected previously. The river flow information system provides user with real time river information including video image of web-camera via internet. Each unit which constitutes the system has remote maintenance functions. Those systems are installed in upper, lower streams and branches along the river. We can collect all data via internet together with the many other sensors information like rain gages and can analyze the various phenomena happening in the river basin area in real time. This information system will be used for the better river management such as the precise water resource management and the practical flood forecasting. This paper describes their functions, actual data at the large rivers and typical applications.