关键词: 喀斯特洼地, 水文地质意义, 发育机理, 饱水带, 石灰岩, 管道流, 土壤层, 裂隙流, 地表流, 溶蚀作用

Abstract: AbstractThe development of karat depressions in limestone terrains is not duly controlled by the lithology and geological structures, but also highly affected by the biogenic and hydrodynamic conditions. The depression evolution is strongly influenced by the overland floiw, soil flow, surface flow, subcutaneous flow, vadose flow, shaft flow, fissure flow and conduit flow. This paper has preliminary studied the mechanism of karst depression development and established a theorilical model for it.Though the hydroloigic structure in the karst depressions is very complicated, but there is a binary hydrologic structure. The subcutaneous aquifer is formed by the larger or smaller openning fractures. The lower parts of the fractures, which are closed, constitute the fracture vadose zone with very low flow velocity──a relative impermeable blocks. With the development of the depression, the subcutaneous aquifer will be developed downward to the saturated zone and the permeability of the vadose zone is greatly improved, as a result, the binary hydrological structure is gradually destroyed. When the depressions are developed into the stage of depression or batein, the grounid-water table is closed to the basin or depression bottom, and the fissure layer (including the fracture vadose zone and the subcutaneous aquifer) becomes the relative homogeneous fissure aquifer. The conduit flow exists in the limestone block between the depressions or basins.The subcutaneous aquifer is very important to solve the problems of water supply and agricultural irrigation which does not need too much water in some places. For building surface reservoirs in depressions and basins, great attention should be paid to the existance of the relative homogeneous fissure layer under the big depressions and basins and the character of Quaternary deposits, and also to some corresponding engineering measures. The conduit flow between the depressions or basins is one of the main points to comprehensively develop and utilize the karst waiter resources in limestone areas.