Are the groundwater levels falling in Puerto Rico between 1982 and 2017: comparing a karst aquifer with non-karst aquifers

Carbonate aquifers supply freshwater to about one-quarter of the world population. Their particular hydrodynamic behavior is a valuable property for groundwater extraction, on the downside, carbonate aquifers are vulnerable to overexploitation and pollution. Fractures, fissures, and typical karst features, such as&#160; conduits and vertical shafts, create high regional hydraulic conductivities and fast response times to hydrological events, complicating numerical modeling and management of carbonate aquifers in general. Here, we develop a new method to assess the vulnerability of Mediterranean karst aquifers concerning shifts in climate. Particularly, we are interested in 1) which types of karst aquifers are most vulnerable and 2) which factors have the highest impact on their climate vulnerability.Our approach is based on a vulnerability index, which is calculated from selected indicators of aquifer behavior that refer to land cover, soil types, wetlands, water demand, current change of groundwater levels, total water volume, run-off, water exploitation index, and freshwater production. First, we calculate vulnerability indices for all karst aquifers &#8211; as identified in the World Karst Aquifer Map by the World-wide Hydrogeological Mapping and Assessment Programme (WHYMAP WOKAM v1 database; Chen et al., 2017) &#8211; that have at least 90% of their area belonging to Mediterranean climate zones (Csa, Csb, and Csc). Then, we group these aquifers into classes representing different physical behaviors and morphological characteristics (e.g. highly karstified systems in mountainous areas).An evident approach to investigate various aquifers in terms of their vulnerability is the development of numerical flow models. The advantage is that the boundary conditions, such as average annual precipitation and temperature, can be modified to consider different climatic scenarios. Thus, the resulting impact on water volumes and the aquifer response can be simulated accordingly. However, this approach requires large amounts of data and high computational costs.Our method uses selected sets of karst aquifers representing different variations of Mediterranean climates (i.e. that are similar in terms of temperature and precipitation patterns). These aquifers are compared by analyzing and plotting regional climate variables versus previously calculated vulnerability indices. By identifying and comparing climate-vulnerability relations within aquifer sets, we can mimic changes in climate for individual aquifers in line with the RCP4.5 scenario until 2050. This approach, which relies on present-day observed conditions, allows us to predict the effect of a changing climate on the vulnerability of an aquifer class without the need to develop a complex numerical model.The results are visualized in the form of vulnerability maps and used to derive recommendations for the sustainable management of karst aquifers under Mediterranean climates.

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Sustainability of Water Resources in Karst Undermined by Tunneling: A Case Example

Sustainability ◽

10.3390/su14020732 ◽

2022 ◽

Vol 14 (2) ◽

pp. 732

Author(s):

Drago Dvanajščak ◽

Jože Ratej ◽

Vojkan Jovičić

Keyword(s):

Water Resources ◽

Karst Aquifer ◽

Karst Aquifers ◽

Groundwater Levels ◽

Karst Environment ◽

Railway Line ◽

Variable Porosity ◽

Site Investigations ◽

Limestone Rock

Water resources in karsts are scarce due to the high cavernosity in the otherwise low-permeability limestone rock mass. The highly variable porosity and transmissivity of karst aquifers are caused by a network of channels, caverns, and caves that typically act as water-bearing, connected vessels. Tunneling in a karst environment can severely deplete an aquifer and undermine the sustainability of water resources over the long term. A research study was carried out to elaborate and develop measures for the sustainable preservation of the water resources in a Slovenian karst, in which two approximately 7 km-long tunnels will be driven as part of the construction of the new Divača–Koper railway line. Hydrogeological site investigations were carried out with an aim to evaluate the transmissivity and spatial spreading of the karst aquifer along the route of the tunnels, including the observation of the long-term variation of the groundwater levels and trace experiments. The main findings, which are presented in this paper, were used to develop a methodology for the selection of adequate measures for tunnel construction with an aim of ensuring the sustainability of water resources in karst aquifers. The construction measures comprise limiting the inflows using injection grouting, obscuring the groundwater intake by undrained sections of the tunnel, and constructing bypasses around the tunnel to preserve the current groundwater flow regime. The presented methodology of dynamically accommodating the preventive measures to the actual hydrogeological conditions onsite is generally applicable for common cases in which the state of the karst aquifer could not be pre-determined with a sufficient accuracy of tens of meters to a meter. The spatially and temporally continuous hydrogeological investigations and decision-making charts to reduce the tunnelling’s impact on the karst aquifer are explained in detail in this paper.

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Isotopic content in high mountain karst aquifers as a proxy for climate change impact in Mediterranean zones: The Port del Comte karst aquifer (SE Pyrenees, Catalonia, Spain)

The Science of The Total Environment ◽

10.1016/j.scitotenv.2021.148036 ◽

2021 ◽

pp. 148036

Author(s):

J. Jódar ◽

I. Herms ◽

L.J. Lambán ◽

S. Martos-Rosillo ◽

C. Herrera-Lameli ◽

...

Keyword(s):

Climate Change ◽

Climate Change Impact ◽

Karst Aquifer ◽

High Mountain ◽

Karst Aquifers ◽

Change Impact

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Simulation of Regional Karst Aquifer System and Assessment of Groundwater Resources in Manatí-Vega Baja, Puerto Rico

Journal of Water Resource and Protection ◽

10.4236/jwarp.2015.712075 ◽

2015 ◽

Vol 07 (12) ◽

pp. 909-922 ◽

Cited By ~ 4

Author(s):

Balati Maihemuti ◽

Reza Ghasemizadeh ◽

Xue Yu ◽

Ingrid Padilla ◽

Akram N. Alshawabkeh

Keyword(s):

Puerto Rico ◽

Groundwater Resources ◽

Karst Aquifer ◽

Aquifer System ◽

Karst Aquifer System ◽

Vega Baja

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A comparison of emerging contaminant fingerprinting techniques to assess the impact of human wastewater on karst groundwater quality

10.5194/egusphere-egu21-7645 ◽

2021 ◽

Author(s):

Luka Vucinic ◽

David O'Connell ◽

Donata Dubber ◽

Patrice Behan ◽

Quentin Crowley ◽

...

Keyword(s):

Groundwater Quality ◽

Karst Aquifer ◽

Domestic Wastewater ◽

Wastewater Effluent ◽

Chemical Pollution ◽

Karst Aquifers ◽

Karst Springs ◽

Aquifer Systems ◽

Pollution Impacts ◽

The Impact

Lowland karst aquifers in Ireland are extremely complex to understand and are considered to be highly vulnerable to pollution (e.g. low-lying karst catchments exhibit a lot of surface water &#8211; groundwater interactions which makes them very susceptible to direct contamination). These aquifers are impacted by multiple contamination sources on land (in particular, rural sources from agriculture and on-site domestic wastewater effluent) which makes their protection and management challenging. Human wastewater effluent is identified as significant threat to groundwater quality in such lowland Irish karst environments, since approximately one-third of the population in Ireland is relying on decentralized wastewater treatment systems for the treatment of domestic wastewater. However, it is difficult to distinguish between human wastewater effluent and agricultural pollution impacts on karst aquifers using only traditional water quality parameters or any single environmental tracing method. Hence, the impact of microbial and chemical contaminants of human wastewater origin on groundwater quality must be assessed using a multiple-tracer approach, ideally targeting source-specific tracers. This paper presents an overview of the results obtained during the research conducted throughout the last several years at nine karst catchments in Ireland using a range of methodologies in order to determine and quantify domestic wastewater pollution impacts on karst springs. Microbial pollution was assessed using flow cytometric fingerprinting and faecal indicator bacteria, while chemical pollution impact assessment included the analysis of fluorescent whitening compounds (FWCs; well-known indicators of human contamination since their origin is mostly from laundry detergents), specific anion ratio signatures (Cl/Br), quantification and identification of microplastic particles using Fourier-transform infrared spectroscopy (FTIR), and faecal sterol and stanol profiles and ratios. A thorough analysis of the results obtained using a multiple-tracer approach has been conducted and methodologies have been evaluated in terms of applicability and sensitivity in a range of different karst catchments. The ability of these methodologies and techniques to determine and quantify human faecal pollution impacts on karst springs will be discussed. The results show a significant correlation between microplastic particle counts and detected FWCs signals at different springs, which helps to understand the contribution of household-derived contaminants to this environmental problem. Moreover, our results indicate that faecal sterols and stanols can be useful faecal source tracking method in karst aquifer systems despite the fact that concentrations of sterols and stanols of interest were usually low which makes the interpretation of results challenging.

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Review: Groundwater flow and transport modeling of karst aquifers, with particular reference to the North Coast Limestone aquifer system of Puerto Rico

Hydrogeology Journal ◽

10.1007/s10040-012-0897-4 ◽

2012 ◽

Vol 20 (8) ◽

pp. 1441-1461 ◽

Cited By ~ 119

Author(s):

Reza Ghasemizadeh ◽

Ferdinand Hellweger ◽

Christoph Butscher ◽

Ingrid Padilla ◽

Dorothy Vesper ◽

...

Keyword(s):

Puerto Rico ◽

Groundwater Flow ◽

Transport Modeling ◽

North Coast ◽

Karst Aquifers ◽

Limestone Aquifer ◽

Aquifer System ◽

Flow And Transport ◽

The North ◽

Groundwater Flow And Transport

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Borehole-based study of CO2-rich air transport in the vadose zone of a Mediterranean karst system (Malaga, southern Spain)

10.5194/egusphere-egu2020-7483 ◽

2020 ◽

Author(s):

Lucía Ojeda ◽

José Benavente ◽

Iñaki Vadillo ◽

Cristina Liñán ◽

Enrique P. Sanchez-Cañete

Keyword(s):

Vadose Zone ◽

Karst Aquifer ◽

Field Measurements ◽

Temporal Variations ◽

Groundwater Levels ◽

Sources And Sinks ◽

Global Carbon Budget ◽

Vertical Heterogeneity ◽

Test Linking ◽

Karst Systems

The characterization of CO2 transport, and other C compounds (CH4, DIC, organic matter, etc.), in the vadose zone of a karst aquifer is key in order to quantify sources and sinks of carbon. In karst environments, most of the studies are focused on the dynamics of CO2 in caves, but only a few studies are related to field measurements of the CO2 content in boreholes, which provides direct insights about the vadose zone. Located at the east of the Nerja Cave (Malaga, Andalusia), one of the most important tourist caves in Spain, the vadose zone was accessed by 9 boreholes drilled into the vadose zone of a Triassic carbonate aquifer, with depths ranging between 15 and 30 m. The karst network in the study area is characterized by a great vertical heterogeneity, with significant cavities and voids at specific intervals. Groundwater levels at different altitudes are a consequence of this heterogeneity. Similarly, CO2 distribution and transport are clearly determined by the complex karst network.Our study aims to identify significant horizontal gradients of CO2 in the karst vadose air, both spatial and temporally. We present monthly measurements of CO2 concentration, relative humidity, air temperature and 222Rn inside boreholes. In addition, we present CO2 results from an 18 hours-atmospheric air injection test. Linking them to the geophysical knowledge of voids in the study area, the results allow us to identify lateral fluxes of CO2-rich air in the vadose zone and how these fluxes are favoured by the incidence of the main karst discontinuity orientations. We observe different ventilation patterns: &#160;in spring the vadose air seems to be stored in specific orientations, while in summer there is a lower convective ventilation. The results contribute to explain the temporal variations of the chemical composition of recharge water in karst systems, as well as to support studies on the global carbon budget.

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A ConvLSTM Conjunction Model for Groundwater Level Forecasting in a Karst Aquifer Considering Connectivity Characteristics

Water ◽

10.3390/w13192759 ◽

2021 ◽

Vol 13 (19) ◽

pp. 2759

Author(s):

Fei Guo ◽

Jing Yang ◽

Hu Li ◽

Gang Li ◽

Zhuo Zhang

Keyword(s):

Neural Network ◽

Groundwater Level ◽

Short Term Memory ◽

Karst Aquifer ◽

Structural Features ◽

Spatial Distance ◽

Series Data ◽

Karst Aquifers ◽

The Real ◽

Hydrogeological Characteristics

Groundwater is an important water resource, and groundwater level (GWL) forecasting is a useful tool for supporting the sustainable management of water resources. Existing studies have shown that GWLs can be accurately predicted by combining an artificial neural network model with meteorological and hydrological factors. However, GWL data are typically geographic spatiotemporal series data, and current studies have considered only the spatial distance factor when predicting GWLs. In karst aquifers, the GWL is affected by the developmental degree of the karst, topographic factors, structural features, and other factors; considering only the spatial distance is not enough, and the real spatial connectivity characteristics need to be considered. Thus, in this paper, we proposed a new method for forecasting GWLs in karst aquifers while considering connectivity characteristics using a neural network prediction model. The connectivity of a karst aquifer was analyzed by a multidimensional feature clustering method based on the distance index and hydrogeological characteristics recorded at observation wells, and a convolutional long short-term memory (ConvLSTM) conjunction model was constructed. The proposed approach was validated through GWL simulations and predictions in karst aquifers in Jinan, China, and four experiments were conducted for comparison. The experimental results show that the proposed method provided the most consistent results with the measured observation well data among the analyzed methods. These findings demonstrate that the proposed method, which considers connectivity characteristics in karst aquifers, has a higher simulation accuracy than other methods. This method is therefore effective and provides a new idea for the real-time prediction of the GWLs of karst aquifers.

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Calibration of a semi-distributed lumped karst system model and analysis of its sensitivity to climate conditions: the example of the Qachqouch karst spring (Lebanon)

10.5194/hess-2020-90 ◽

2020 ◽

Author(s):

Emmanuel Dubois ◽

Joanna Doummar ◽

Séverin Pistre ◽

Marie Larocque

Keyword(s):

Time Series ◽

Karst Aquifer ◽

Regulatory Function ◽

Karst Aquifers ◽

Karst Spring ◽

Flow Rates ◽

Lumped Model ◽

Climate Conditions ◽

Time Series Analyses ◽

Spring Flow

Abstract. Flow in complex karst aquifers is challenging to conceptualize, therefore to model for better management practices, especially in poorly investigated areas, in semi-arid climates, and under changing climatic conditions. The objective of this work is to propose a calibration approach based on time-series analyses for a karst aquifer and to assess the impact of changing climate conditions on the spring discharge. Based on more than three years of high-resolution continuous monitoring, a semi-distributed lumped model was calibrated and validated for the Qachqouch karst spring, north of Beirut (Lebanon). Time-series analyses and decomposition of spring hydrographs revealed that the system has a high regulatory function, with considerable storage capacity providing stable flow (minimum flow of 0.2 m3/s) during the dry season, and with flow rates exceeding 10 m3/s during the wet season, similar to other karst aquifers in the region. Based on this detailed understanding of the hydrodynamics of the system, the model geometry and parameters were validated. Three linear reservoirs were implemented to reproduce the combined contribution of the different flow components of the system. A satisfactory simulation (Nash–Sutcliffe coefficient = 0.72) of measured spring flow rates was obtained after calibration. Climate change conditions (+1 to +3 °C warming, −10 to −30 % less precipitation annually, and intensification of rain events) were added to a baseline climatic year to produce scenarios of expected spring flow responses. Results show that the Qachqouch karst aquifer is sensitive to decreasing rainfall, which is associated with more pronounced recessions, with flow rates decreasing by 34 % and 1-month longer dry periods. Because of the limited influence of snow on the spring flow rate, a warming climate has less impact on spring flow conditions than a reduction in precipitation. Although the model shows that increasing rainfall intensity induces larger floods, recessions and shorter low flow periods, the real impact of high-intensity precipitation events remains uncertain, since the model does not account for complex unsaturated and epikarst processes. This work shows that calibrating a semi-distributed lumped model using time series analysis can be an efficient approach to improve simulations of complex karst aquifers, thus providing useful models for long-term sustainable water management.

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