Appling GM(1,1) model and its residual modified model to predict the density of pollutants in Weihe's water in Tianshui from 2004 to 2010,the prediction accuracy of latter is not higher than that of former and the accuracy of both is lower to some pollutants.In this situation,information renewal GM(1,1) is used to forecast Weihe's water quality and mutant moments of pollutants in the next five years.The results of analysis indicated that the informat ion renewal GM(1,1) predicting model could obviously impr...