Based on a review of the development of hydrologic science during the 20~(th) century and the challenge and opportunities in hydrology, a suggestion is made that in the digital information era the traditional hydrology must be reformed by making full use of the digital information techniques. The new hydrologic information system should be a digitized one with both data observed in situs and remote sensing, covering the whole space (watershed or region), crossing a range of scales (temporal and spatial), including various kinds of hydrologic data products,and serving the entire society and relative scientific researches.