| The elemental issue to the karst resources and environment evolution is identification geomorphic symbols of water level change. The horizontal corrosion groove(HCG) is a typical symbol that recorded the water level variation. To reveal the relationship between development mechanism of HCG and water level changes, we measured the characteristics of HCG on the clints in Shilin and simulated the shapes of HCG with gypsum mine column. The HCG in Shilin was divided in four types: side grooves was developed on the shore side of lakes; mushroom-like grooves in soaking water; necked grooves; HCG in moisture soil. All HCG types and growth levels were affected by the rock types, hydrodynamic conditions and duration, and climate. In the water physical and chemical characteristics of similar cases, the dissolution rate of gypsum mine column in flowing water is bigger than in hydrostatic one. The depth of HCG is controlled by not only the hydrodynamic conditions, but also the duration. The average depth of the bottom HCG is 26.03~94.58 cm, and the dissolution rate of carbonate by natural water is 32 ~ 94.5mm/ka. The water level changed severely and vegetation disappeared sharply in nearly 2420 yrs. Now, because of climatic change and human activity, the water level is declining. By the soil erosion experiment, the clints were exposed with a soil loss rate of 1.02~3.5cm/a. The average height of bottom HCG is 1.94 m above the soil. So, we can conclude that the exposed time of HCG is approximately 55~190yrs before now. To protect the lakes, the reasons of lakes dried up were analyzed and some countermeasures were put forward. |
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