The accurate extraction of rivers is important for survey of water resources

time series change detection on water usage

assessment of large-scale water conservancy facilities

and so on. The general methods of river extraction are difficult to be applied widely because of the disruption by clouds

snow

shadow of mountains

and lakes in remotely sensed images. In this paper

we propose a new index calculation model for river extraction

which is based on an improved water index

named Gaussian normalized difference water index (GNDWI). The model can remove the interference factors effectively by the aid of a DEM. The experiment for the extraction of Ili River from Landsat images show that the new model can automatically and rapidly extract the river in very complex environments. Furthermore

shadows and other useless information can also be effectively removed with a high accuracy.