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Zhang Y.,Institute of Karst Geology
Cave and Karst Science | Year: 2010

Current data indicate that the recorded caves within China include 78 that are more than 5km long and 60 that are deeper than 250m. There are 15 cave chambers with individual floor areas greater than 25,000m2, and 23 separate underground river systems whose lengths total more than 50km. Most of these caves and cave river systems are in southwestern China, where massive, thick and continuous sequences of carbonate rock are at outcrop across terrain that experiences a warm and humid climate. © British Cave Research Association 2010. Source


Karst aquifers are commonly simulated based on conceptual models. However, most karst conceptual models hardly consider the function of turbulent conduits. The conduit network acts as the main draining passage of the karst aquifer and may also have a strong influence on the hydrological processes, especially during storm events. A conceptual model with a nonlinear reservoir and a turbulent pipe (representing the conduit system) in series is proposed according to the basic structure of a typical karst aquifer, to simulate the karst spring. The model indicates whether the spring discharge is influenced by the turbulent pipe; this not only depends on the parameters of the nonlinear reservoir and turbulent pipe, but also depends on the volume of spring discharge itself. Even though the spring discharge is strongly influenced by the turbulent pipe during the storm, this influence decreases with the rainfall intensity and volume of spring discharge. In addition, an ‘evapotranspiration store’ is used to consider the moisture loss through evapotranspiration and to calculate the effective rainfall on the proposed model. Then, this simple conceptual model is used to simulate a karst spring (named S31) near Guilin city, China, with satisfactory results, especially with respect to discharge peaks and recession curves of the spring under storm conditions. The proposed model is also compared with the Vensim model of similar complexity, which has been applied to the same spring catchment. The comparison shows the superiority and better performance of the nonlinear reservoir-pipe model. © 2015, Springer-Verlag Berlin Heidelberg. Source


Guo F.,Changan University | Guo F.,Institute of Karst Geology | Wang W.,Changan University | Jiang G.,Institute of Karst Geology | Ma Z.,East China Mineral Exploration and Development Bureau of Jiangsu Province
Shuikexue Jinzhan/Advances in Water Science | Year: 2014

Lihu subterranean river in South China was selected to study the contaminant transport behavior and self-purification capacity of a karst aquifer. The subterranean river was investigated through water sampling along the stream reach for one year. Analysis of inorganic ions and trace elements in different seasons and at different locations showed the major contaminants are NO2 --N, NH4 +-N, COD, As, Cd, and Hg, due to domestic waste, mining industrial waste, and fertilizer application in the recharge area. Along the course of the karst conduit, a self-purification process was observed because of significant decrease in some ions concentration. The mechanism of self-purification was caused by dilution and nitrification, which was determined by the suterranean river's structure and hydrogeological condition. By comparing the attenuation quantity and percentage of ions, it was found that ammonium had the highest, while chloridion had the lowest percentage. According to the attenuation rate, four types of attenuation character could be classified. Firstly, the ions decayed completely after they entered the karst aquifer, such as TFe, Zn, and Al; secondly, the ions had the highest attenuation rate when they traveled underground through the aquifer, such as K, Na, Mg, F, Cl, HPO4, and TP; thirdly, the concentration gradually decreased from upstream to downstream, which was represented by NH4 +-N, CODCr, and BOD5; and finally, they had the highest attenuation rate when transformed from surface stream to underground stream, but secondary suspension of contaminants could happen in the cave, such as Mn, Ba, and Hg. Source


Jiang G.-H.,Institute of Karst Geology | Yu S.,Institute of Karst Geology | Chang Y.,Nanjing University
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2011

Some kinds of runoff were identified in a karst hydrological system by observation and monitoring in field during rain storm events at YAJI hydro-geological site, Guilin, China. Runoff includes many forms such as epikarst springs, slope return flow, overland flow and soil interflow in a depression. The runoff aroused by rainfall has different residence time and hydrochemistry. A multi sensor for pH and specific electrical conductivity together with calcium and bicarbonate concentration were used to determine the chemical composition of stream water, spring, drop water and stored water in rock holes. The results are quite different among these kinds of karst water, indicating that the chemical items of water can be used for tracing the sources of spring. Calcite dissolution in pure water with different pCO2 was calculated by PHREEQC. We get a line of Ca2+ concentrations at different pCO2. The dots representing different water in the system were near the theoretical line of Ca2+ concentration VS pCO2 in CaCO3-H2O-CO2 (g) system. It showed that the chemical character of runoff was controlled by pCO2. Runoff was classified into two groups according to its hydrochemistry based on difference of pCO2 in atmosphere and soil. The two groups were end numbers of spring water in flood. It showed that event water controlled by atmosphere but not soil air occupied about 70% when storm by end-number method. Source


Zhang F.,Chinese Academy of Geological Sciences | Zhang F.,Institute of Karst Geology | Song Y.,Chinese Academy of Geological Sciences | Song Y.,Non ferrous Metal Geological Survey Center | And 3 more authors.
Acta Geologica Sinica | Year: 2012

Coal mining subsidence is a universal environmental-geological problem in mining areas. By selecting the Shen-Dong coal mining subsidence area as the research field, this paper studies the changes in precipitation infiltration recharge in the circumstances of coal mining subsidence by means of field geological investigation and laboratory simulation experiments, which is expected to provide a scientific basis for eco-environmental restoration in the mining area. The results indicate that at the unstable stage of subsidence, three types of subsidence in the Shen-Dong mining area have positive effects on the precipitation infiltration recharge, and the type of full-thickness bedrock subsidence has the greatest influence. In the stable stage of subsidence, the precipitation infiltration process after long-term drought and the moisture migration in the aeration zone undergo three different stages: evaporation-infiltration before precipitation, infiltration-upward infiltration-infiltration during precipitation and evaporation-infiltration after precipitation. During a heavy rainfall infiltration process, the wetting front movement in fine sand, coarse sand and dualistic structure of fine-coarse sand consists of two stages: the stage of wetting front movement during precipitation, in which the wetting front movement distance has linear relationship with the depth, and the stage of wetting front movement after precipitation, in which the wetting front movement distance has the power function relationship with the depth. The wetting front movement velocity is influenced by the rainfall amount and the lithology in the aeration zone. However, as the depth increases, the movement velocity will decay exponentially. Source

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