Combination grey model of sewage quantity forecasting

Based on the grey forecasting theory, this paper discussed a modeling process used in forecasting sewage quantity. The combination grey model is constructed based on the residual grey forecasting model and new information and equal dimensional grey forecasting model. The sewage quantity of Rongchang County was forecasted with the basic grey model, the residual modification GM ( 1, 1) model, the improved new information and equal dimensional grey model and combination grey model. As for wastewater quantity of 2012, the improved models attain the lower residual of only 0.4% and -0.7%. As compare to the combination grey model, the lowest residual is only -0.05%. The results showed that forecasting sewage quantity with grey theory is simple and practical. The combination grey model greatly enhanced the forecasting precision and can be the tool of forecasting the long-medium sewage quantity. © 2013 by CESER Publications.