Albania is situated in the western part of Balkan Peninsula, on the eastern coast of the Adriatic and the Ionian Sea, which is one of the most water−rich regions of the world. The karst landscape in ...Albania covers about 2750 km
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consisting of nearly 24% of the countries territory. Karstic aquifers are the richest in the country. The total renewable karst water resources represent about 80% of the groundwater resources of Albania and nearly 80% of the population of the cities, including the capital Tirana, are supplied by karst water, and important resource is used for the production of the electricity. The sustainable management of karst water resource is difficult due to the high heterogeneity of karst aquifers in terms of type and development of hydraulic porosity, flow velocities, hydraulic head, recharge type and quantity, karst water quality, as well as to the high vulnerability to the human impact.
•Studied karst systems are hydraulically linked to the hosting karst aquifers.•The greatest event sensitivity observed during autumn and snowless winter periods.•A typical water year with a snowmelt ...spring flood showed ambiguous CCF response.•Flat topography and shallow vadose zone contribute to complex baseflow interaction.•Matrix-conduit gradient inversion occurs during high flow events.
In Estonia, karst aquifers supply roughly a third of annually abstracted domestic groundwater. Karst systems recharged by allogenic humic-rich streams originating from mire-dominated watersheds are common in Lower Estonia (lowlands). This study aimed to characterize the hydrology and hydraulics of two binary lowland karst systems: Salajõe (SKS) and Tuhala karst system (TKS), and their interaction with the hosting karst aquifer. High-resolution water level, discharge, specific conductance time series data combined with tracer test results were analyzed to assess the two systems. The temporal effect of evapotranspiration, snow deposition and snowmelt floods contributed to the variability in recharge event sensitivity of studied watersheds and aquifers, resulting in time-varying CCF strength between precipitation and discharge. The greatest event sensitivity was observed during the autumn and snowless winter seasons. The celerity and solute transport were the greatest in the preferential flow paths of both karst systems, however, solute transport characteristics varied significantly because of differences in structure and maturity of karst porosity. While the dilute allogenic recharge flushed the karst systems occasionally, the contribution of high-SEC groundwater baseflow was significant. During flood events, the matrix-conduit hydraulic gradient could be inverted, resulting in dilute floodwater being pushed into the hosting aquifer from the karst system.
Carbonate strata are widely distributed in China, which can be found in more than 30 provinces and cities, covering about 1/3 of the country’s territorial area. Affected by different geological and ...climatic conditions, carbonate strata in China geographically present different karst landscapes and groundwater resources. Specifically, northern China is dominated by large karst springs, while southern China is characterized by underground rivers. By determining the distribution range of carbonate strata in China, this paper pointed out the locations of large karst springs in the north and underground rivers in the south, analyzed the distribution characteristics of carbonate rocks in the north and south, the degree of karst development as well as their geological and climate genesis, and discussed the differences between karsts in northern and southern China in terms of occurrence forms of karst water and groundwater systems.
Abstract
The karst cavern is common undesirable geological body in limestone areas, which can bring great safety hazards to the construction and operation of tunnels, bridges and highways. Transient ...electromagnetic method (TEM) can effectively detect hidden karst structures based on the difference in electrical property between the karst cavern and the surroundings. Traditionally, 1D inversion is commonly used for the interpretation of TEM data due to its high efficiency. However, this may lead to artifacts due to 2D or 3D effects in practical surveys. In this study, we present a Gaussian-Newton approach to 3D inversion of TEM data for karst cavern detection. The numerical test on synthetic TEM data demonstrates that 3D inversion can effectively delineate the location and geometry of concealed karst cavern compared to the 1D inversion results.
•A coupled conceptual hydrological model (K-XAJ) for simulating the rainfall-runoff processes in karst-dominated areas.•The proposed K-XAJ model satisfactorily simulated the rainfall-runoff ...processes.•The peak flow predicted by the K-XAJ model was larger than that by the Xinanjiang (XAJ) model.•The interflow routed by the K-XAJ model was significantly smaller than that by the XAJ model.•The magnitude of groundwater predicted by the K-XAJ model was greater.
Rainfall-runoff processes in the karst dominated regions are of great importance. However, not all areas in a karst-dominated river basin are covered by typical limestone and both limestone and soil cover may exist. This study proposes a coupled conceptual hydrological model for simulating the rainfall-runoff processes in karst-dominated areas. The model, named as K-XAJ, couples the traditional Xinanjiang (XAJ) model and a two reservoir-based karst model for simulating runoff in both the karst area and the non-karst area in the Lijiang River basin. Simulated results demonstrated that the proposed K-XAJ model satisfactorily simulated the rainfall-runoff processes. Compared with the traditional XAJ model, the K-XAJ model produced better forecasts. The peak flow predicted by the K-XAJ model was larger than that by the XAJ model, but the interflow routed by the K-XAJ model was significantly smaller than that by the XAJ model. The magnitude of groundwater predicted by the K-XAJ model was greater. This study thus provides a new way to simulate rainfall-runoff processes in karst areas.
•Shallow epikarst fissure soil (EFS) has good hydraulic connectivity.•Soil structure controls water infiltration and retention time in the epikarst.•Vertical hydraulic connectivity of EFS is ...different from surface soil.•The hydrological path of EFS in rocky desertification areas is complex.
Epikarst fissures filled with soil (EFS) are important factors controlling karst hydrological processes and ecological hydrological functions. The EFS are common in karst rocky desertification areas, and it is important to understand the hydraulic properties and hydrological characteristics of EFS for vegetation restoration. In this study, we analysed the soil moisture content dynamics of surface soil and EFS in a rocky desertification environment to explore the influencing factors of soil moisture variation. A typical epikarst fissure was selected as the sample site in the rocky desertification area of the Karst Plateau Gorge (Beipanjiang catchment, Guizhou Province) in Southwest China, and surface soil was used as the control site. From May 12, 2018 to January 10, 2020, soil moisture content data for the EFS profile (20, 80, 140, 200, and 260 cm) and the surface soil profile (20 and 40 cm) were monitored synchronously at 30-min intervals. Simultaneously, soil samples were collected to measure the physical properties. The results show that the difference in vegetation cover and soil physical properties is the main reason for the difference in soil water dynamics between the shallow EFS and surface soil. The shallow EFS hydraulic connectivity is better, and the mean values of total porosity and saturated hydraulic conductivity of shallow EFS are 15.6% and 69.5% higher than those of the surface soil, respectively. The seasonal variations in soil moisture in the shallow EFS are obvious, the soil moisture rainfall response and dry-wet alternation are fast, the seasonal variations in soil moisture in the surface soil are relatively stable, and the soil water retention time is long. In the EFS profile, the hydraulic connectivity of the shallow soil (0–40 cm) are obviously better than those in the middle and lower layers (40–280 cm), which affected the response speed and retention time of soil water at different depths. In conclusion, the vertical hydraulic connectivity of the EFS profile is quite different and is shown to be significantly different from the surface soil hydrology. These results are helpful for understanding the ecohydrological process of epikarst.
•Subsurface runoff dominates the runoff components in karst hillslope.•Thinner soils decrease surface runoff and increase subsurface runoff.•Bedrock topography controlled subsurface runoff generation ...in the thinner soils.•Thinner soils had a higher contribution of new water than that in the thick soils.
Hydrological processes in the critical zone are closely related to the soil–bedrock structures. However, the effect of soil thickness on the rainfall-runoff relationship on the hillslope with complex topography remains unclear. Surface runoff, lateral subsurface runoff from soil–epikarst interface, and epikarst runoff from the epikarst–bedrock interface were monitored on two adjacent plots with deep and shallow (66.0 vs. 35.4 cm) soil thicknesses from June 2019 to December 2020 in the karst region of southwest China. During the monitoring period, surface and subsurface runoff account for 20% and 37% of the total runoff in the deep-soil plot (DSP), and 3% and 43% in the shallow-soil plot (SSP). This demonstrates that runoff from the soil-epikarst system is predominant compared to the relatively small contribution of surface runoff. In the SSP, the surface topography wetness index (TWI) was highly coupled with bedrock TWI, and the bedrock TWI had a significant negative linear relationship (p < 0.01) with subsurface runoff. Moreover, isotope hydrogen-separation results showed that subsurface and epikarst runoff were dominated by pre-event water, but a higher contribution of event water was observed in the SSP than in the DSP. These findings supported the hypothesis that rainwater could infiltrate the epikarst more easily in shallow soil slopes. Rainfall and surface runoff exhibited a linear relationship in the dry season and a non-linear relationship in the rainy season, indicating the occurrence of threshold rainfall–runoff behavior. The rainfall amount threshold for surface runoff was higher in DSP (44.7 mm) than in SSP (39.5 mm), and the corresponding variation of rainfall intensity interpretation was greater (54% vs. 38%). For subsurface runoff, the rainfall amount threshold was higher in the DSP than in the SSP (91.0 vs 79.4 mm), and the corresponding variation of soil moisture interpretation was higher (56% vs. 20%). This demonstrated that runoff can be better predicted at deeper soil hillslopes by rainfall and antecedent soil moisture. Accordingly, this study emphasizes the importance of evaluating the spatial heterogeneity of soil thickness in hydrological process research.
•A physically-based distributed Karst-Liuxihe model (KL) was improved and simplified effectively.•The rainfall-runoff generation and confluence algorithms were improved.•Better flood simulation ...results showed that the simplified and improved model is successful.•The simplified KL model requires less hydrogeological data when modeling in karst basins.
The karst trough valley basin in Zhongliang of Chongqing is one of the most developed karst areas in Southwest China, with unique topographic features such as karst troughs and valleys that are prone to flash floods. Accurate simulation of flood processes in these areas using hydrological models can provide references for predicting future local runoff evolution trends. The main challenge for hydrological modelling in karst areas lies in building a model with limited hydrogeological data. In this study, the Karst-Liuxihe (KL) model was simplified and improved to simulate karst flood processes in the Zhongliang karst trough valley. The KL model consists of multiple, complex structures; a large amount of data is needed to model karst areas. To overcome the modelling data requirements, we modified the model structure and its parameters to propose a simplified KL (SKL) model. Additionally, we improved the runoff generation and confluence algorithms. Compared with the simulation results for 22 flood processes obtained by using the KL model, the results for this SKL model were better with less modelling data. For example, the mean value of the Akaike information criterion (AIC) index decreasing rate was 35%, and the process relative error and the peak flow relative error decreased by 10%, indicating that the technique of simplifying and improving the KL model is effective and that the simplified SKL model can quantitatively depict karst floods in karst trough valley areas.
When tunnels are excavated in karst areas, the existence of karst caves in the surrounding rock usually results in the collapse failure of tunnels. Tunnel collapse has always been a challenging issue ...because it seriously threatens the safety of tunnel builders. To investigate the collapse of a deep tunnel under a karst cave, we constructed the collapse mechanisms of the rectangular and circular tunnels under a karst cave, and obtained the expressions of the collapse failure in tunnel considering seismic force and seepage force by means of the variational principle and limit analysis theory. Compared with previous results and numerical solutions, it is found that the results in this paper are consistent with those results and numerical solutions, which indicates that the proposed method in this work is rational. According to the analytical solutions, the shape of the collapsing blocks of the deep rectangular and circular tunnels under a karst cave are drawn, and the effects of different parameters, especially the vertical seismic coefficient kv, on the collapsing blocks are analyzed. The findings in this paper indicate that the range of collapsing blocks decreases with increased kv. The two formulas for calculating the critical height between the tunnel and the karst cave are given by derivation.
Due to insufficient research on the collapsing range of karst rectangular and circular tunnels:•We constructed a new failure mechanism of rectangular and circular tunnels under a karst cave.•The effect of seismic force is considered in this paper.•The expressions of the collapsing block of deep tunnels under a karst cave can be obtained.•The influence of various parameters on the collapsing range is demonstrated.
