Adaptability of the GM(1,1) model for simulation of Jinci Springs discharge

To tackle of the examination problem of the adaptability of GM (1, 1) model to simulate spring discharge, we set up GM (1, 1) models by using different lengths of observed spring discharge data series of Jinci Springs China. Then we evaluate their adaptability by error analysis. Results showed the average errors of GM (1, 1) models declined from three to five dimensions, kept stable from six to fourteen dimensions, and increased sharply from fifteen to twenty dimensions. So GM (1, 1) models from five to fourteen dimensions are adaptable to simulate spring discharge of Jinci Springs. It means that the evolving processes of groundwater system always have relative stable period and GM (1, 1) model can reflect the processes. We also found that the errors after 1992 become larger than before. Meanwhile an important fact is Jinci Springs became dry in 1994. Those facts reveal that the Jinci groundwater system experienced an unstable period before being dry.