The water-level fluctuations zones (WLFZs) are crucial transitional interfaces within river-reservoir systems, serving as hotspots for N2O emission. However, the comprehension of response patterns ...and mechanisms governing N2O emission under hydrological fluctuation remains limited, especially in karstic canyon reservoirs, which introduces significant uncertainty to N2O flux assessments. Soil samples were collected from the WLFZs of the Hongjiadu (HJD) Reservoir along the water flow direction from transition zone (T1 and T2) to lacustrine zone (T3, T4 and T5) at three elevations for each site. These soil columns were used to conduct simulation experiments under various water-filled pore space gradients (WFPSs) to investigate the potential N2O flux pattern and elucidate the underlying mechanism. Our results showed that nutrient distribution and N2O flux pattern differed significantly between two zones, with the highest N2O fluxes in the transition zone sites and lacustrine zone sites were found at 75 % and 95 % WFPS, respectively. Soil nutrient loss in lower elevation areas is influenced by prolonged impoundment durations. The higher N2O fluxes in the lacustrine zone can be attributed to increased nutrient levels resulting from anthropogenic activities. Furthermore, correlation analysis revealed that soil bulk density significantly impacted N2O fluxes across all sites, while NO3−and SOC facilitated N2O emissions in T1-T2 and T4-T5, respectively. It was evident that N2O production primarily contributed to nitrification in the transition zone and was constrained by the mineralization process, whereas denitrification dominated in the lacustrine zone. Notably, the annual N2O efflux from WLFZs accounted for 27 % of that from the water-air interface in HJD Reservoir, indicating a considerably lower contribution than anticipated. Nevertheless, this study highlights the significance of WLFZs as a vital potential source of N2O emission, particularly under the influence of anthropogenic activities and high WFPS gradient.
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•Topography and anthropogenic activities in WLFZs determine the nutrient levels.•N2O emission pattern in WLFZs of transition zone differed from lacustrine zone.•Nutrients and WFPSs dominated N2O production and emission from WLFZs.•WLFZs are significant N2O emissions source in karst river-reservoir systems.•The efflux from water-air interface is a major N2O contributor in karst reservoir.
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•Implications of future changes in climate on tropical karst groundwater resources were examined.•Climate projections were downscaled using SDSM.•Future conditions for two scenarios ...were simulated by MODFLOW model.•The results indicated variations of sustainability in groundwater recharge and spring discharge.•Tailored management strategies to ensure the sustainability of groundwater resource are presented.
Developing tailored management strategies to ensure the sustainability of groundwater resource under climatic and demographic changes is critical for tropical karst catchment, where relatively small watershed and highly porous soil make this natural resource highly susceptible and thus very sensitive to those changes. In this study, long term impacts of climate variability on groundwater recharge and discharge at Oemau spring, Rote Island, Indonesia were selected and investigated. Following calibration and validation of groundwater model using MODFLOW code, groundwater flow was simulated for the period of 2020–2090 under HadCM3 global climate model (GCM) scenarios, using input data of weather variables downscaled by Statistical Downscaling Model (SDSM). The reported analysis suggests that the sustainability of groundwater resources, which was evaluated by assessing the ability of the spring to supply water demand from irrigation requirement and domestic consumption, generally varies over the period and will be adversely affected by climate change during dry periods when the area is projected to variably experience supply shortage of around 29–67 L/s as a result of 5.24–23.63% decrease of rainfall, 2.48–24.57% reduction of recharge, and 2.53–22.80% decrease of spring discharge, under HadCM3 GCM scenarios. A subsequent comprehensive set of management strategies as palliative and adaptive efforts was proposed to be implemented by relevant stakeholders to assist the community dealing with water deficit during the dry periods. Three main adaptive strategies, namely socio-cultural, technical, and ecological measures, were proposed by incorporating physical and socio-economic characteristics of the area. This study presents a blueprint for assessing groundwater sustainability under climate change scenarios and developing tailored management strategies to cope with adverse impacts of climate change, which may become fundamental guidelines across other karst islands in the future.
Fractures and fracture networks are key conduits for migration of hydrothermal fluids, water and contaminants in groundwater systems Modeling is widely used to understand the environmental risk ...associated with migration of pollutant for different hydrogeological conditions. In this paper, we proposed a conceptual and mathematical model of flow and transport phenomena in fractured rock systems, and applied in a arsenic contaminate site as a case study. The groundwater flow model and arsenic migration model in fissure-matrix dual system were established. The results show that the velocity of groundwater is positively correlated with inlet pressure, but not with the porosity of the fracture. When the velocity of groundwater is relatively high, arsenic is transported along with the current in a finger-like manner. The distribution of arsenic concentration on the fracture surface is heterogeneous and the phenomenon of diffusion from the fracture to the matrix is not obvious. Indeed, when the velocity of groundwater is relatively small, the arsenic moves forward slowly, the concentration distribution on the crack surface is relatively uniform, and the diffusion phenomenon from the crack to the matrix is more significant.
•This research presents a new approach by addressing the distinct features of cockpit karst.•The method addresses the limited field observation by employing remote sensing and GIS.•The paper proposes ...regional land use planning based on the source – pathway – target concept.•COCKPIT-PLUS is a viable approach for rapid land use planning with a limited dataset.
Karst groundwater is highly vulnerable to contamination, which urges better land use zoning. This paper proposes a new approach, called COCKPIT-PLUS, to minimize groundwater contamination within cockpit karst regions. The method employed four parameters: P (the existence of ponor/swallow hole), L (lineament density), U (sinking stream to an underground river), and S (distance to spring/pumping site). These parameters are essential for identifying contaminant pathways and transport from the surface to the karst groundwater/springs. COCKPIT-PLUS has been developed and validated in the Gunungsewu karst in Java, Indonesia. This research considers a cockpit as a single hydrological unit that uniquely recharges karst groundwater. We analyzed 2,811 cockpits and 81 other closed depressions to develop a land use planning map. The research used the time to first arrival (Ta), time to peak (Tp), and Qmax/min ratio parameters of two karst springs and two underground pumping sites for validation. Cockpits with ponors/swallow holes, sinking streams, high lineament density, and short distances to springs are vulnerable to groundwater and thus must be restricted areas for any land uses. The findings show that though the COCKPIT-PLUS uses a limited karst dataset, the proposed method seems reliable enough for a rapid land-use zoning approach in cockpit karst areas.
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Streamflow generation in mountain watersheds is strongly influenced by snow accumulation and melt as well as groundwater connectivity. In mountainous regions with limestone and dolomite geology, ...bedrock formations can host karst aquifers, which play a significant role in snowmelt–discharge dynamics. However, mapping complex karst features and the resulting surface‐groundwater exchanges at large scales remains infeasible. In this study, timeseries analysis of continuous discharge and specific conductance measurements were combined with gridded snowmelt predictions to characterize seasonal streamflow response and evaluate dominant watershed controls across 12 monitoring sites in a karstified 554 km2 watershed in northern Utah, USA. Immense surface water hydrologic variability across subcatchments, years and seasons was linked to geologic controls on groundwater dynamics. Unlike many mountain watersheds, the variability between subcatchments could not be well described by typical watershed properties, including elevation or surficial geology. To fill this gap, a conceptual framework was proposed to characterize subsurface controls on snowmelt–discharge dynamics in karst mountain watersheds in terms of conduit flow direction, aquifer storage capacity and connectivity. This framework requires only readily measured surface water and climatic data from nested monitoring sites and was applied to the study watershed to demonstrate its applicability for evaluating dominant controls and climate sensitivity.
Timeseries analysis of snowmelt, discharge and specific conductance in a karst mountain watershed reveals immense hydrologic variability across years, seasons and nested sites. We propose and apply a surface water timeseries‐based conceptual model to improve understanding of subsurface controls on melt–discharge dynamics in karst mountain watersheds in terms of conduit flow direction, aquifer storage capacity and connectivity.
Groundwater level (GWL) is a significant indicator for quantifying groundwater availability. Currently, hydrologists worldwide are actively engaged in modelling and predicting GWL. In karst regions, ...GWL exhibit varying responses to rainfall events across different locations and the impact of rainfall events on GWL within the same location also varies. Despite incorporating rainfall as an input variable, most existing data‐driven GWL prediction models inadequately account for the spatio‐temporal heterogeneity of karst water areas. Therefore, this study proposes a new analysis method to investigate the response patterns of GWL to rainfall events in karst regions with typical spatio‐temporal variations, known as the sensitivity analysis of rainfall‐GWL response. The method introduces the rainfall response coefficient to describe the response characteristics of GWL to rainfall. Through the rainfall response coefficient, the rainfall response variable (RR) is calculated and incorporates it as an input in the RR‐long short‐term memory (LSTM) GWL prediction model. The effectiveness of proposed method was validated by GWL prediction in karst aquifers located in Jinan City, China, renowned for its spatial–temporal heterogeneity in karst development. Through the analysis and validation conducted by integrating geographical multi‐feature, the study revealed a significant improvement in the accuracy of the RR‐LSTM model after integrating RR as a variable, particularly during significant rainfall events. These findings affirm that the method proposed in this study is highly effective in karst regions characterized by anisotropic karst features.
We proposed a new method to investigate the response of GWLs to rainfall to greater reveal geographical patterns in karst regions with typical spatio‐temporal variation. This method extracts and corrects rainfall‐GWL response sequences and develops the idea of rainfall response coefficient and rainfall response variable. By integrating the findings into LSTM model, we conducted comparative experiments to evaluate model performance by considering geographical multi‐feature, demonstrating that the new method significantly improved model performance especially during significant rainfall events.
The Sichuan Basin is a typical superimposed oil- and gas-bearing basin with abundant hydrocarbon resources in deeply buried marine carbonate rocks. The petrological characteristics, origin, ...diagenetic evolution and controlling factors of the high-quality Sinian Dengying dolomite reservoirs were investigated based on outcrop and core observations in addition to data from various analyses, including thin section, casting thin section, scanning electron microscopy, cathodoluminescence, carbon and oxygen isotope, major and trace elements, and X-ray diffraction analyses. The main lithologies of the Dengying reservoirs are microbial dolomite, crystalline dolomite, granular dolomite and karst breccia dolomite. The reservoir spaces include microbial pores, interparticle dissolution pores, intraparticle dissolution pores, intercrystalline pores, karst caves and fractures. Three models to explain the origin of Dengying dolomites are proposed: (1) syngenetic microbial dolomitization, (2) penecontemporaneous reflux dolomitization and (3) burial dolomitization. Development of the high-quality Dengying dolomite reservoirs in the central Sichuan paleo-uplift was essentially controlled by two factors: sedimentation and supergene karstification. High-quality reservoirs were developed mainly in algal mound and grain-shoal sediments deposited on the platform margin and intraplatform margin. Affected by the multistage Tongwan movement, long-term weathered crust karstification resulted in the formation of a large number of dissolution-enlarged pores and caves in the Dengying reservoirs. Multistage fractures, especially the unfilled tectonic fractures that formed during the late Yanshanian–Himalayan period, connected the relatively isolated pores and karst caves and effectively improved the permeability of the reservoirs. The results of this study provide a deeper understanding of the origin and preservation mechanism of deeply buried paleocarbonate reservoirs and can also effectively guide future exploration in the Sinian Dengying Formation of the Sichuan Basin.
Research on eogenetic karsts has mostly focused on oceanic settings but rarely targeted lacustrine settings. This study describes an eogenetic karst formed in a saline lacustrine setting in the upper ...4th member of the Shahejie Formation (Es4s), Dongying Depression, China. Limestones were deposited on a landmass-attached carbonate platform characterized by boundstones and grainstones interbedded with micrites. Tectonic uplift at the end of Es4s caused the karstification in a saline lake shore setting over approximately 2 Ma. During the exposure period, pervasive macroporosity developed in intervals within the top 20 m below the unconformity. Caves formed along the periphery of the platform, and they are mainly at 0.2–1.3 m in height and are filled with wackestone sediments without turbulent flow features. The caves are interpreted as the result of mixing dissolution on the margin of a mixing zone of saline lake-water and fresh-water. Sponge-like intervals occur in interior areas and range from 0.5 to 2.5 m in height, and they present a spongy porosity with pyrite crusts, pervasive pyrite framboid disseminations and occasional cements. The sponge-like dissolution pores are analogous to the Swiss-cheese texture forming in modern and fossil mixing zones and are probably caused by microbially-mediated dissolution in a mixing zone where mixing rate is limited because of reduced circulation in saline lake phreatic water. A small number of sub-vertical conduits (turbulent flow paths) and pervasive fissures are generated due to dissolution by meteoric water. The dissolution effects are strongly influenced by primary lithofacies. Spongy dissolution and caves develop almost in boundstone and grainstone layers, which is probably because they maintained a high permeability after shallow burial and thus become the preferential diffuse flow paths. According to this model, the boundstone and grainstone intervals that developed along the periphery of the platform could be favorable reservoirs for future petroleum exploration.
•The paleokarst was an eogenetic karst forming in a saline lake shore setting.•Mixing corrosion and microbially-mediated dissolution are the main causes of caves and spongy pores.•Boundstone and grainstone layers maintained a high permeability after shallow burial and became favorable to form macro-pores.•High-quality karst reservoirs developed in both the highs and transition zones of the platform.
Plant adaptability in karst regions Liu, Chunni; Huang, Yang; Wu, Feng ...
Journal of plant research,
09/2021, Letnik:
134, Številka:
5
Journal Article
Recenzirano
Karst ecosystems are formed by dissolution of soluble rocks, usually with conspicuous landscape features, such as sharp peaks, steep slopes and deep valleys. The plants in karst regions develop ...special adaptability. Here, we reviewed the research progresses on plant adaptability in karst regions, including drought, high temperature and light, high-calcium stresses responses and the strategies of water utilization for plants, soil nutrients impact, human interference and geographical traits on karst plants. Drought, high temperature and light change their physiological and morphological structures to adapt to karst environments. High-calcium and soil nutrients can transfer surplus nutrients to special parts of plants to avoid damage of high nutrient concentration. Therefore, karst plants can make better use of limited water. Human interference also affects geographical distribution of karst plants and their growing environment. All of these aspects may be analyzed to provide guidance and suggestions for related research on plant adaptability mechanisms.
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•An improved COPK method is proposed for the covered karst groundwater vulnerability assessment, which is modified from the widely used COP method according to the unique ...hydrogeological features in northern China.•The COPK method is used in the Baotu Spring basin in Jinan City as a typical representative.•Most of the study area exhibits moderate to low karst groundwater vulnerability.•The nitrate concentration in karst groundwater demonstrated that the improved COPK method has much better performance than the original COP method.
Karst in China is characterized by a wide distribution, diverse forms, well-developed features, and excellent preservation, making it a representative example on a global scale. The semi-arid karst in northern China, widely distributed in many provinces, has unique hydrogeological features, including covered karst, weak karst development, thick aquifers, highly interconnected fissure network, and numerous karst springs, making it difficult to directly apply the COP method which is widely used in karst groundwater vulnerability assessment in this area. Additionally, the quality of the karst groundwater in many northern China cities is facing a threat in recent years, making it urgent to evaluate the vulnerability of the karst groundwater. This study aims to develop an improved COPK method for the covered karst groundwater vulnerability assessment modified from the widely used COP method, and to use it in the Baotu Spring basin in Jinan City, as a typical representative of the covered karst area in northern China. The assessment result by the improved COPK method shows that most of the study area exhibits moderate to low karst groundwater vulnerability, and the area with very high to high vulnerability is situated in the Middle Ordovician-Upper Cambrian Chaomidian Formation limestone exposed area. The above results by the improved COPK method are more consistent with the hydrogeological conditions than those by the original COP method. A comparison of nitrate contamination map to the groundwater vulnerability map reveals the more efficient performance of the improved COPK method compared to the original COP method in vulnerability assessment of the typical covered karst areas in northern China. This paper can provide a reference for karst groundwater vulnerability assessment of covered karst areas in northern China, as well as other countries and regions with similar hydrogeological conditions, which can provide valuable support for groundwater pollution control efforts.
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