Study of the landscape evolution of the Huanglong tufa based on the grey system

Abstract：Tufa in Huanglong is the product of several ten thousand years of karst geological processes. In recent years, the tufa has gradually dried up, blackened and been sandified, which has seriously affected the aesthetic characteristics. Water resources have played an important role in the development and change of the Huanglong tufa. The authors have collected and analyzed the monitoring data in the area and found that the monitoring system is not sound and that the data of the time sequence are lacking. According to these features, the authors choose a grey system model which does not require too much of the data of the time sequence and may yield a good result of prediction. They predicted the tufa development using pH as a proxy and used the kriging method to make interpolation of the results of prediction and thus obtained the prediction results of the tufa in the whole Huanglong area. Based on the pH values, the tufa development is divided into three types: strong erosion, weak erosion and accumulation. The Huanglong tufa is now in the stage of dynamic balance and decline and recombination.