Institute of Karst Geology

Guilin, China

Institute of Karst Geology

Guilin, China
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Chang Y.,Nanjing University | Wu J.,Nanjing University | Jiang G.,Institute of Karst Geology | Jiang G.,International Karst Research Center Auspices of UNESCO | And 2 more authors.
Journal of Hydrology | Year: 2017

Conceptual models often suffer from the over-parameterization problem due to limited available data for the calibration. This leads to the problem of parameter nonuniqueness and equifinality, which may bring much uncertainty of the simulation result. How to find out the appropriate model structure supported by the available data to simulate the catchment is still a big challenge in the hydrological research. In this paper, we adopt a multi-model framework to identify the dominant hydrological process and appropriate model structure of a karst spring, located in Guilin city, China. For this catchment, the spring discharge is the only available data for the model calibration. This framework starts with a relative complex conceptual model according to the perception of the catchment and then this complex is simplified into several different models by gradually removing the model component. The multi-objective approach is used to compare the performance of these different models and the regional sensitivity analysis (RSA) is used to investigate the parameter identifiability. The results show this karst spring is mainly controlled by two different hydrological processes and one of the processes is threshold-driven which is consistent with the fieldwork investigation. However, the appropriate model structure to simulate the discharge of this spring is much simpler than the actual aquifer structure and hydrological processes understanding from the fieldwork investigation. A simple linear reservoir with two different outlets is enough to simulate this spring discharge. The detail runoff process in the catchment is not needed in the conceptual model to simulate the spring discharge. More complex model should need more other additional data to avoid serious deterioration of model predictions. © 2017 Elsevier B.V.

Deng Y.,Institute of Karst Geology | Deng Y.,Hubei University | Jiang Z.,Institute of Karst Geology | Kuo Y.-M.,Hubei University | Zhou X.,Institute of Karst Geology
Carbonates and Evaporites | Year: 2017

The effects of vegetation on epikarst water are unclear due to the lack of understanding of the effects of canopy interception on epikarst water properties. In this study, throughfall (T), stemflow (S), borehole (B) and epikarst (E) spring water (PTSBE profile) from two different vegetation canopies, forest and shrub, from July to October 2015 in Southwest China, were sampled to investigate the effects of canopy interception on epikarst water chemistry and its response to precipitation. Significant difference in pH, EC, and DO concentrations exists among precipitation, throughfall, stemflow and epikarst water. Stemflow is an acidic input and throughfall is a less acidic input to the epikarst zone. The mean δ18O value of precipitation is −7.45‰, and the mean δ18O values of throughfall in forest and shrub are −7.11 and −7.37‰, respectively. The results indicate that precipitation becomes acid and nutrient enrichment after canopy interception. The canopy also alters hydrologic cycle processes and enhances the precipitation solute input to the epikarst zone. Our study suggests that precise interpretation of the mechanisms of carbonate rock dissolution and deposition requires the use of throughfall and stemflow. © 2017 Springer-Verlag GmbH Germany

Guo F.,Chang'an University | Guo F.,Institute of Karst Geology | Wang W.,Chang'an 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.

Guo F.,Institute of Karst Geology | Guo F.,The International Research Center on Karst under the Auspices of UNESCO | Jiang G.,Institute of Karst Geology | Jiang G.,The International Research Center on Karst under the Auspices of UNESCO | And 3 more authors.
Environmental Earth Sciences | Year: 2013

Karst terrains are generally regarded as a fragile and vulnerable environment. China's karst is mainly developed in pre-Triassic, old-phase, hard, compact carbonate rock. The lack of soil cover in bare karst land can enhance desertification. Its underground drainage system can aggravate both drought and flooding problems; the interconnected surface and subsurface conditions allow for easy contamination by pollutants. Moreover, karst terrains quite often suffer from a series of engineering problems, such as water infiltrating into mines or transportation tunnels, leakage from reservoirs, and failure of building foundations. As resources and energy exploitation intensified in recent years, karst areas in Southwest China faced some severe geo environmental problems. In order to find out how the problems action and evolution in recent years, field and laboratory investigations were conducted in Guangxi autonomous region, Guizhou, Yunnan, Guangdong, Hunan, Hubei provinces, and Chongqing municipality. About 100 experts from the Provincial Geological Survey and graduate students took part in this project. Several symposiums were held during those 3 years. Besides the in situ survey, data were collected from hydrogeological survey results since 2000 when the new round of land resources investigation began. After analyzing these data, rock desertification, drought and flooding, and contamination and engineering geological environmental problems were considered the most prevalent problems in karst areas in Southwestern China. The status of each problem is elaborated upon in this paper and should be considered for future sustainable development. © 2012 Springer-Verlag Berlin Heidelberg.

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.

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.

Meng Y.,Institute of Karst Geology | Ji F.,Chengdu University of Technology | Jia L.,Institute of Karst Geology | Jiang X.-Z.,Institute of Karst Geology | Lei M.-T.,Institute of Karst Geology
Environmental Earth Sciences | Year: 2014

The paper deals with a frequent and known problem of suffusion type of sinkhole formation in soil, due to water level oscillations above karstified bedrock. The authors measured groundwater pressure oscillations caused by pumping groundwater from the excavated tunnel to determine the reliable indicators for prediction of sudden soil collapse based on risk assessment. The statistical analysis was performed to determine suspicious values, which reliably predict the soil collapse. The results of analysis of monitored values indicate very good time correlation coefficients with the failures. The work comprises the following main parts: (1) survey of the geologic environment; (2) monitoring of hydrodynamic conditions; and (3) acquisition of a forecasting criterion based on the statistical analysis of anomalous monitoring data. From this research, it might be concluded that the appearance time of sinkholes and the abnormal values were strongly linearly dependent with a correlation coefficient of over 99 %. This conclusion will be a contribution to estimate the risk of karst collapse in a similar environment. © 2013 Springer-Verlag Berlin Heidelberg.

Guo F.,Institute of Karst Geology | Guo F.,The International Research Center on Karst under the Auspices of UNESCO | Yuan D.,Institute of Karst Geology | Yuan D.,The International Research Center on Karst under the Auspices of UNESCO | And 2 more authors.
Acta Carsologica | Year: 2010

Approximately 33% of China is karstic. The most extensive karst areas are in southwestern China and cover approximately 540,000 km 2. Southwestern China hosts some of the most typical karst landforms in the world and has important high-quality karst water resources. Due to the rapid development of China, karst waters are threatened by various types of contamination. Detail field and laboratory investigations in five provinces including several cities in southwestern China were conducted in 2008 and 2009. Eighty-three springs and underground rivers were surveyed and water samples collected from each for laboratory analyses for major ions. Four main types of karst aquifer contamination were identified based on contaminant sources: Rural and agricultural pollution, pollution from urban development and industry, pollution from mining, and accidental groundwater pollution. Several representative instances for each type of contamination and their impacts on the environment are discussed in more detail. Contamination countermeasures of karst waters and a framework for overall management of karst water resources in southwestern China are provided.

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.

PubMed | Institute of Karst Geology
Type: Journal Article | Journal: Water environment research : a research publication of the Water Environment Federation | Year: 2015

Changes of groundwater flow and quality were investigated in a subtropical karst aquifer to determine the driving mechanism. Decreases in groundwater flow are more distinct in discharge zones than those in recharge and runoff zones. Long-term measurement of the represented regional groundwater outlet reveals that groundwater discharge decrease by nearly 50% during the dry season. The hydrochemistry of groundwater in the runoff and discharge zones is of poorer quality than in the recharge zone. Indications of intensive land resource exploitation and changes in land use patterns were attributed to changes in groundwater conditions since 1990, but the influence of climate change was likely from 2001, because the water temperature exhibited increasing trends at a mean rate of 0.02 C/yr even though groundwater depth was high in the aquifer. These conclusions imply the need for further groundwater monitoring and reevaluation to understand the resilience of aquifer during urbanization and development.

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