Abstract: River forecasting and tracking is one of key technologies for developing waternet to prompt water utilization efficiency. Taking the region of Guandi reservoir-Ertan reservoir-estuary in the Yalong River basin as a case study site, the authors try to establish a river forecasting model based on the hydrological-hydraulic methods to forecast the water regime on the scales of time and space. In the model constructions, taking outflow of Guandi reservoir as inflow of the region, the Guandi-Ertan reservoir model uses the Muskingum method to route in the river channel and adopts the Xinanjiang model (XAJ model) based on the use of a digital elevation model (DEM) to make the model have a certain foreseeable period; for Ertan reservoir, the authors use its operation rules to get the outflow; and for the channel, from Ertan reservoir to estuary, one-dimension unsteady flow implicit difference scheme solution is adopted to simulate the absolute Saint Venant equations and obtain the hydrological processes of any cross-section along the river channel. So that, the hydrological forecasting results with a certain leading time have been extended on any cross-section of the river channel, and accurate forecasting and process controlling have been realized for the channel from the Ertan reservoir to estuary. The model is calibrated and validated strictly based on the daily hydrological data series from 2007 to 2009. The analysis results of this study show that the model performed very well with the absolute water level error of the Xiaodeshi station less than 0.30 m, the relative error of daily flow obtained from the Tongzilin station less than 10%, and a coefficient of determination higher than 0.989. The findings from this research could provide an essential technical support for the construction of a digital Yalong River, and be used as a valuable technical and methodological reference for real-time regulating and process controlling of multi-water resources of the internet of water.