Groundwater Basin Research Articles

Laboratory observations of solute transport in groundwater basins

This paper introduces a method of groundwater pollution source identification obtained from laboratory by a physical instrument of Flow System Sand-Box Model. A Unit basin of a simple flow system and a Tóthian basin of a hierarchically nested flow structure are introduced as case studies. We add step-input solutes at recharge zones, separately or simultaneously, to obtain the breakthrough curves (BTCs) at each discharge zone. For the Unit basin, its BTC shows a gradual upward trend with a decreasing slope but with two more pronounced steps, which differs a lot from previous results of analytical and numerical solutions. These steps are caused by the settings of the current physical instrument as no solutes are input at the upper two discharge ports. For the Tóthian basin, internal steps may exist due to the late-time arrival of intermediate and regional groundwater flow systems. Although the Unit basin and Tóthian basin can both have internal steps in the BTCs, they are due to different reasons. By jointly solving solute mass balance equations with water mass balance equations, the circulation rate for each flow system is calculated, which quantitatively explains the phenomena encountered in the experiment and highlights the important contributions of intermediate and regional flow systems to the entire groundwater circulation. We indirectly obtain the pulse-input BTCs by deriving the step-input BTCs respective to time, which is also the residence time distribution (RTD) of the groundwater basin, that the groundwater pollution sources can be identified. The pulse-input BTC is characterized by peaks and sloping tails. The peaks correspond to the intermediate and regional groundwater flow systems. The sloping tails indicate the rate at which solutes are flushed out or contaminants fade away. By inputting tap water into the groundwater basin to purify the contaminations, we conduct self-purification experiments. The shapes of the solute-input curves and the self-purification curves are systematically symmetrical. As the self-purification experiment has less external interference, it is possible to use the self-purification curves to characterize and identify the groundwater flow system. This study proposes a physical method for identifying sources of groundwater contamination, and achieves a comprehensive understanding of the law of solute transport in groundwater basins, which could guide the prevention of non-point contamination at the basin scale.

Groundwater Recharge Assessment for Small Karstic Catchment Basins with Different Extents of Anthropogenic Development

Climate change and anthropogenic development considerably influence groundwater resource distribution and conditions. Catchment basin groundwater recharge—discharge computation reliability is needed for effective groundwater management policy formulation and implementation and also for resolving environmental challenges in such a watershed. This paper compares groundwater recharge patterns between urbanized and nearly natural small catchment basins of Israel’s Western Mountain Aquifer (WMA). The correlation between precipitation volumes and surface runoff shows that surface runoff volume constitutes 3–4% of the precipitation volume in the Natuf catchment and 1–2% in the Te’enim catchment. These assessments reflect the differences in the land use, outcrop lithology, topography and hydrodynamic properties of the WMA within the model basins. A groundwater recharge assessment based on water balance and water table fluctuation methods was performed for the mountainous karstic Te’enim and Natuf catchment basins for all the available data from 2000 to 2020. The water balance method provided reliable estimates. The groundwater recharge assessment considered land use classification and climate changes during this period. The average multiannual groundwater recharge values for the 2000–2021 period varied from 17.6 × 106–24.8 × 106 m3 to 24.5–29.2 × 106 m3 for the Te’enim and Natuf catchment basins, respectively. For the relatively dry period of the 2013/2014–2017/2018 hydrological years when detailed measurements of the surface runoff were available, the corresponding groundwater recharge volumes were 17.6 × 106 m3 and 24.5 × 106 m3. The corresponding local groundwater recharge coefficients constitute 0.46–0.57 for the mostly agricultural Te’enim basin and 0.29–0.32 for the urbanized Natuf basin. A significant difference in the groundwater recharge coefficients between the studied catchments is caused mostly by the differences in land use. It is suggested that applying such a groundwater recharge estimation for small hydrological sub-basins can improve one’s understanding of the groundwater recharge distribution within a major basin, enabling the application of an accurate regional hydrogeological model that may be extrapolated to other similar regions.

An integrated approach combining LISA, BI-LISA, and the modified COPK method to improve groundwater management in large-scale karst areas

Groundwater protection and sustainable utilization of wells in large-scale karst areas face many challenges due to the complexity of numerous groundwater basins and aquifers. Therefore, scientific evidence is needed for groundwater management in these areas. A method combining source vulnerability, spatial autocorrelation, and bivariate spatial autocorrelation is proposed for groundwater management research. Based on the COP method (composed of flow Concentration, Overlying layers, and Precipitation regime), the COPK method is modified by replacing the sinkhole distance with sinkhole density, and incorporating land use and karst network development. The modified COPK method is used to evaluate the vulnerability of nitrate in groundwater in large-scale karst areas. Guizhou Province in China, which is a typical karst region, was evaluated as a study area. Comparatively to the classical COP method, the revised vulnerability map shows more areas of high vulnerability, mainly in the middle of the study area. According to the receiver operating characteristic curve (ROC) analysis, the modified method had a higher accuracy than the classical COP algorithm. Based on the accurate vulnerability index, vulnerability was classified using the natural break method, and the spatial autocorrelation of vulnerability clustering characteristics was studied. The source vulnerability was divided into High-High (HH), High-Low (HL), Low-High (LH), Low-Low (LL), and Not Significant (NS) clusters. This result can clarify the vulnerability clustering of groundwater in specific areas, thereby helping to improve groundwater management accuracy and efficiency. In addition, bivariate spatial autocorrelation was used to study the nitrate content of wells and source vulnerability. The bivariate local Moran's index showed a spatial negative correlation between the two. Similarly, the BI-LISA map can be used to characterize the spatial aggregation of nitrate content and well vulnerability. This result can help groundwater managers develop reasonable measures to protect water wells.

Identification of non-conventional groundwater resources by means of machine learning in the Aconcagua basin, Chile

Study regionOur study region is the Aconcagua basin, central Chile. The catchment, home to over 500,000 people, currently experiences a multiyear drought that threatens water security. In this context, there is an impending need to explore unconventional groundwater resources, such as peripheral hard rock and deep aquifers. Study focusThe focus of this study is the application of machine learning techniques to identify areas of potentially untapped groundwater resources in the middle and upper reaches of the Aconcagua basin. New hydrological insights for the regionMachine learning classifiers accurately depict those areas known for their high groundwater potential, including the San Felipe, Putaendo, Panquehue, Catemu and Llay-Llay sectors. The Mesozoic sedimentary sequences and intrusive units of the coastal range, together with the Neogene units of the Andes range, are correctly identified as areas of very low hydrogeological interest. A major novelty of this study is the delineation of several new areas of potentially high groundwater prospect, namely, the geological domain associated with the Pocuro fault system, the Teatinos-Volcan-River fault system, and the Las Chilcas volcano-sedimentary sequence, in the Chacabuco Range. These findings are in line with the results of complementary studies, thus suggesting that machine learning applications may successfully underpin groundwater exploration across other groundwater basins in the coastal Andean region.

Improving mass change estimation in Panama with the GRACE/GFO gravity field using the variational mode decomposition

In this study, we aim to estimate the mass changes in Panama using the Gravity Recovery and Climate Experiment level-2 products, which are formed as spherical harmonic coefficients and limited by stripe noise. The empirical de-striping method and the temporal filter achieved by empirical mode decomposition can be used to reveal the signals but are still limited in signal reservation and noise reduction. To this end, we put forward a novel efficient strategy that uses the variational mode decomposition algorithm to filter the time series of each SHC separately. Based on the two reliable mascon products and in situ short-term groundwater observations, various comparisons in spatial, spectral, and temporal domains are implemented. In addition, the SNR (signal-to-noise ratio) index and the three-cornered hat method are adopted for assessment. The main results and conclusions are as follows: 1) Our filter outperforms the two previous methods with the best SNR (2.14) and the lowest Panama regional uncertainty (70 mm) for all available months. 2) Our estimate of the basin groundwater storage is closest to one of the groundwater observations with the maximum correlation coefficient (0.72, p<0.05). This result suggests that our method seems to detect small-scale mass signals that are undetectable in the two mascon products. Our work provides a reference for studying the mass change of small-scale basins in low latitudes.

Data-driven approaches demonstrate legacy N accumulation in Upper Mississippi River Basin groundwater

Increases in nitrogen (N) fertilizer application, livestock densities, and human population over the last century have led to substantial increases in nitrate contamination. While increases in riverine N loads are well-documented, the total magnitude of N accumulation in groundwater remains unknown. Here we provide a first data-driven estimate of N mass accumulation in groundwater within the Upper Mississippi River Basin (UMRB), an area of intensive row-crop agriculture and the primary contributor to Gulf of Mexico hypoxia. Using approximately 49 000 groundwater nitrate well concentration values and a suite of geospatial predictors, we developed a Random Forest model to produce gridded predictions of depth-varying nitrate concentrations. Our results suggest that approximately 15 Tg of N (328 ± 167 kg-N ha−1) is currently stored in UMRB groundwater recharged over the last 50 years. For context, we compare these predictions to those from a lumped statistical model, which predicts accumulation of 387 ± 133 kg-N ha−1, as well as to a simple N mass balance model of the UMRB, which puts an upper bound on accumulation of approximately 1000 kg-N ha−1 (1967–2017). These findings highlight the importance of considering legacy N when forecasting future water quality, as N in the subsurface will continue to impair drinking water quality and elevate surface water N concentrations for decades to come.

Groundwater Facies in the South Parts of Tegal-Brebes Groundwater Basin

The southern part of the Tegal Brebes Groundwater Basin has various rock units originating from the volcanic activity of the Slamet Volcano. The groundwater interacts with these rocks and influences the hydrogeochemical process that may alter its chemical components. The objective of this research is to assess the relationship between groundwater chemistry facies and the rock aquifer. The finding of this research will help us better understand how hydrogeochemical processes work, perform thorough research, and determine the water quality. The groundwater characteristics are determined based on the chemical composition of the water taken from the citizen’s dug wells and springs. These samples were collected to represent a difference in rock’s formation, namely Linggopodo Formation, Tapak, and Slamet Undifferentiated Volcanic Rock. The analysis of the Piper diagram shows that all the samples fall into one facies: the calcium bicarbonate type (Ca-HCO3). The groundwater’s physical and chemical properties in the study area indicate that groundwater quality has not interacted much with lithology and is still greatly influenced by meteoric water. The groundwater facies are dominated by the Ca-HCO3, a characteristic of shallow groundwater and local water flow systems.

ANALYSIS OF CHANGES IN GROUNDWATER LEVELS IN QUATERNARY DEPOSITS IN THE SOUTH-EASTERN PART OF THE IRTYSH-OB ARTESIAN BASIN

Link for citation: Balobanenko A.A., Vasilyev D.I., Dutova E.M., Kuzevanov K.I. Analysis of changes in groundwater levels in quaternary deposits in the south-eastern part of the Irtysh-Ob artesian basin. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 202-213. In Rus. Relevance. The tasks of studying the level regime of groundwater are very closely related to the need to predict their resources under the influence of both natural and artificial factors in order to develop scientific foundations for the rational use of water resources and effective management of the groundwater regime in the study area. Purpose: to study changes in the level regime of groundwater for domestic and drinking purposes in Quaternary deposits in the south of the West Siberian artesian basin based on the results of long-term regime observations. Objects: groundwater of the Irtysh-Ob artesian basin of the II order, the southeastern part of the West Siberian artesian basin of the I order, most actively involved in the sphere of anthropogenic activity. The study area is confined to a province with stable seasonal freezing of the aeration zone, where the main groundwater recharge is carried out in the spring due to snowmelt. Methods. The methodology for conducting observations of groundwater levels was determined by the regulations of the former USSR Ministry of Geology, and then the Ministry of Natural Resources of the Russian Federation, this paper presents a statistical processing of time series of observations of groundwater levels and a comparison of the results obtained with the data on the water regime of surface watercourses and climatic characteristics of the study areas. Results. The leading influence of climatic conditions on the main regularities of the natural hydrodynamic regime of groundwater was revealed. A different degree of intensity of the influence of external factors is shown, expressed by the amplitude of the groundwater level, depending on the type of groundwater regime and the degree of moistening of the territory. Natural factors have the least effect on groundwater as they move away from draining ones and with increasing depth.

Combining spectral analysis and geochemical tracers to investigate surface water–groundwater interactions: A case study in an intensive agricultural setting (southern Guatemala)

An increase in the frequency of severe hydrological events has highlighted the importance of sustainable water management in intensive agricultural regions. In a warming climate, improved understanding and stewardship of water resources are needed to guarantee water supply, ensure food security, and build resilience against extreme events. In this study, we evaluate a framework that combines spectral analysis and geochemical tracers as a potential tool for (1) gaining valuable insights into surface water (SW)–groundwater (GW) interactions, and (2) providing guidance for improved water management in an intensive agricultural basin in southern Guatemala. The framework proves to be useful in revealing important water dynamics, exposing key feedback mechanisms for water availability and quality. With the use of power density functions and hydrochemistry (T, pH, EC, and major ions), two specific interaction regimes (influent and effluent) were identified and delimited for the main watercourse. These segments are estimated to interact at high rates with the shallow aquifer in the river channel proximities and would lose influence towards the basin flanks. Furthermore, the δ2H and δ18O values indicate that regional groundwater flow systems play an essential role in the basin groundwater recharge. Lastly, we established three influence zones that depict the spatial extent of the SW-GW interactions within the basin. With these zones, we provide recommendations that will allow for further investigation and application into better water management strategies regulating groundwater development and land use activities within the agricultural context of the area.

Determination of Potential Groundwater in Van Province Basin using GIS-based MCDM, AHP and Fuzzy-AHP Methods

Changes in the climate put extreme pressure on the use of groundwater resources. As the worldwide demand for consumption in agriculture, industry and other fields increases, so does the need for modeling and evaluation of the efficiency of groundwater potential and quality. Today, it has gained great importance in groundwater exploration due to the rapid increase in methods based on multi-criteria decision-making studies (such as GIS, AHP, F-AHP, ELECTRE methods) and providing first-hand information about the source for subsequent developments. In the light of this information, this study was carried out in order to model and evaluate the groundwater potential and quality of Van. In order to evaluate the groundwater potential of the Van province basin, remote sensing data with AHP and Fuzzy AHP methods, which are GIS-based MCDM programs, were used. With the help of ArcMap 10.2 program, eight thematic maps were created such as rainfall, slope, soil texture, land use/land cover, geology, geomorphology, drainage density, drainage density and fault density. These thematic parameters were graded and weighted according to their effects on the groundwater potential. Then, five different groundwater recharge potential regions were classified as very good (8%), good (17%), moderate (43.37%), poor (23.03%) and very poor (9.6%). The evidence obtained by validating the results is in line with the flow calculation studies showing that groundwater flows from the south to the northeast, the central part, and the north to the southwest of the basin. The evidence obtained by validating the results is consistent with the flow calculation values showing that the groundwater basin flows from south to northeast, center and north to southwest of the study area. The validation shows that the method applied for the study area gives a significant and reliable result

Hydrogeochemical characteristics of groundwater in Baleendah - Soreang, South Bandung, West Java Province

The Baleendah – Soreang area is part of the southern part of the Bandung Soreang Groundwater Basin, constructed by volcanic activity. Regional development in the Baleendah – Soreang area can decrease groundwater quality, influenced by natural and anthropogenic factors. Groundwater hydrogeochemical analysis is important in environmental management studies. This study aims to determine groundwater’s physical properties and hydrogeochemical facies in this area. The groundwater hydrochemistry analysis, determined by analysis of Stiff diagrams and Piper diagrams, shows that the groundwater in the area is classified as freshwater and has intermediate groundwater flow. In addition, the groundwater quality is affected by some anthropogenic activities.

Groundwater Quality Variations in Multiple Aquifers: A Comprehensive Evaluation for Public Health and Agricultural Use

Understanding hydrological and hydrochemical processes is crucial for the effective management and protection of groundwater resources. This study conducted a comprehensive investigation into hydrochemical processes and variations in groundwater quality across five distinct aquifers in Phra Nakhon Si Ayutthaya, Thailand: Bangkok (BKK), Phra Pradaeng (PPD), Nakhon Luang (NKL), Nonthaburi (NTB), and Sam Khok (SK). Utilizing various diagrams, the findings revealed that high levels of sodium and salinity in shallow aquifers (BKK and PPD) were found which can impede soil permeability and have potential consequences on crop yields. The presence of four distinct types of groundwater—Na-Cl, Na-HCO3, Ca-Cl, and Ca-HCO3—suggests the influence of rock weathering, mineral dissolution, and ion exchange reactions with the surrounding geological formations, controlling the chemistry in the groundwater basin. The research also highlights concerns regarding groundwater quality, particularly elevated concentrations of heavy metals (e.g., Zn, Hg, Pd, Fe, and Mn) exceeding safe drinking water guidelines established by the World Health Organization (WHO) in certain samples. The evaluation of water suitability for consumption and irrigation using the Water Quality Index (WQI) and Wilcox diagram reveals a predominance of “poor” or “unsuitable” categorizations. Untreated sewage discharge and fertilizer usage were identified as the primary anthropogenic activities affecting hydrochemical processes in groundwater. These findings emphasize the need for continuous monitoring, appropriate management, and remediation efforts to mitigate potential hazards.

Evaluation of Seasonal a Spatial Variation of Groundwater Quality by Determining Factors Associated with Water Quality Using Multivariate Analytical Methods, Erbil Central Sub-Basin

The study area is located in the northern Iraqi province of Erbil, covering a total area of about 1400 Km2 (3.5% of Iraq). The Erbil basin is mostly covered by Quaternary sediments, with only a few outcrops of Miocene–Pliocene formations in the east and northeast of Sharabot-Dedawan highlands, Avanah Mountain in the west and southwest in narrow strips, and Damirdagh in the north. The lithology of sediments ranges from clay, silt, sand, and gravel (sandstone, clay stone, and conglomerate). Erbil Basin, also known as Dashty Hawler Basin, Erbil provinces is the largest groundwater reservoir, with a surface area of 3200 Km2 and a depth of approximately 800 meters. Erbil Basin, one of the Middle East's most important groundwater basins, is bounded on the north by the Greater Zab River and on the south by the Lesser Zab River. Thirty water samples (27 samples of groundwater wells, and 3 samples of wastewater channels) were collected during May (Water surplus period) and September (Water deficit period) 2020 in Erbil central sub-basin and analyzed. Physical analyses include temperature (T), pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD5), Chemical oxygen demand (COD), Dissolved oxygen (DO), Total Suspension sediments (TSS), whereas the geochemical analysis included concentration determination of the major, minor and trace elements. This article aims to evaluate the pollution in groundwater of the Erbil central sub-basin due to different kinds of wastewater, the samples of water in the study area were collected from different locations and sources, deep wells, and waste. all chemical, physical, and trace elements parameters are presented in this work, the pollution has been founded in the study area due to waste water by Kahrez (old groundwater distribution in Erbil basin), cesspools, and septic tanks.

A Spatiotemporal Characterization of Water Resource Conditions and Demands as Influenced by the Hydrogeologic Framework of the Willcox Groundwater Basin, Southeastern Arizona, USA

In the Willcox Groundwater Basin (WGB), increasing rates of agricultural groundwater withdrawal have led to significant regional groundwater level decline, threatening the basin’s long-term water resource security. Updated characterization of the basin’s water resource conditions and agricultural water demand is critically important for informing groundwater resource management efforts. We developed the hydrogeologic framework of the WGB and linked groundwater level data with land cover classification data to provide a spatiotemporal assessment of water resource conditions and agricultural development in the WGB. A correlation analysis evaluated the degree of association between the basin’s mean annual depth-to-groundwater and agricultural land cover extent. Results of this study indicate that between 2008 and 2021, agricultural land cover in the WGB increased by 29%. The average rate of groundwater level change in the basin’s measured wells was calculated at −13.8 m between 2006 and 2021. We found a strong correlation between the basin’s mean annual measured depth-to-groundwater and the annual agricultural land cover extent, further reinforcing the understanding of agricultural water use in the basin as a principal driver of groundwater level decline. The methodological framework employed proved a simple and effective way to assess groundwater resources as influenced by geology and land use. The outcomes of this study provide critical information toward improved water resources management by providing an integrated understanding of local hydrogeology, groundwater level variability, and changes in agricultural land cover in arid inland basins such as those found in Arizona, USA.

The long‐term legacy of subvolcanic intrusions on fluid migration in sedimentary basins: The Cerro Alquitrán case study, northern Neuquén Basin, Argentina

AbstractCooling subvolcanic igneous intrusions are known to have a substantial impact on fluid flow in the shallow Earth's crust, for example activation of geothermal systems, circulation of mineralized fluids in ore deposits, fast maturation of organic matter in sedimentary rocks and the potential release of large volumes of greenhouse gases, which have triggered mass extinctions during the Earth's history. However, the long‐term post‐cooling legacy of subvolcanic intrusions on fluid flow received much less attention. Here we describe a demonstrative geological example in the Andean foothills, Argentina, showing that igneous intrusions have long‐term effects on fluid flow after their emplacement and cooling. The case study is a ca. 11‐million‐year‐old, eroded subvolcanic conduit, at the rims of which large volumes of bitumen are naturally seeping out on the Earth's surface. This contribution highlights that intense syn‐emplacement fracturing of the magma has created high‐permeability pathways that affect the regional fluid circulations, even millions of years after cooling. Our observations reveal how extinct subvolcanic intrusions have long‐term consequences on subsurface fluid circulations, which need to be accounted for in the exploration of geothermal energy, drinkable groundwater, hydrocarbons and CO2 sequestration in volcanic basins and regions hosting ancient shallow magma intrusions.

Groundwater vulnerability assessment for drinking water suitability using Fuzzy Shannon Entropy model in a semi-arid river basin

Groundwater protection against geogenic and anthropogenic diffuse pollutants are of preeminent importance for convoying groundwater-dependent hydro-aquatic ecosystems and safeguarding human health by securing a safe and sustainable water security plan. Mapping groundwater vulnerability to pollution represents a topical area of research where traditional models suffer from inherent prejudices. A novel approach to identify groundwater vulnerable zones is thus presented in this study by combining Fuzzy Shannon Entropy (FSE) with a decision support algorithm to replace DRASTIC, GOD and other related methods. We proposed a contemporary “FSE-GVI″ framework for assessing aquifer vulnerability, which for the first time expands and redesigns the seven original geological and hydrogeological parameters with geochemical and anthropogenic factors. Applying such technique weights of 13 geo-environmental and hydrogeological factors (slope, soil, pH, recharge), and anthropogenic factors (land use land cover, population density, groundwater based schemes for irrigation) has been optimized. The computed map has been categorized into very high (10.82%), high (23.20%), moderate (29.29%), low (25.02%) and very low (11.64%).The groundwater of the river basin is rated on a scale of excellent, good, poor, very poor and unfit for consumption. The model is compared to 74 groundwater quality data, and the findings demonstrate an excellent correlation between water quality index (r = 0.84), Total dissolve solids (70%), iron (72%), hardness (85%) and alkalinity levels (75%).The findings of the research reveals 27.3 % of the sampling sites (villages) under poor water quality and 23.21% of very high vulnerable zone which requires competent planning, development, managerial technique to safeguard groundwater resources.

Measuring basin-scale aquifer storage change and mapping specific yield in Albuquerque, New Mexico, USA, with repeat microgravity data

Study RegionThe groundwater basin underlying the City of Albuquerque, New Mexico, USA. Study FocusThe study focuses on changes in groundwater storage and how those changes relate to groundwater-level changes. Groundwater storage change was measured using repeat microgravity at 35 stations from 2016 to 2021. Usually, storage is monitored by converting groundwater-level changes to storage changes using the aquifer storage coefficient, a difficult property to measure. With gravity, storage change can be measured directly. The storage coefficient, or specific yield in an unconfined aquifer, was estimated using the gravity method at individual sites, and a map created showing how this property varies over the region. New Hydrological Insights for the RegionFor the first time, a map of specific yield was produced based on interpolated maps of gravity-derived storage change and groundwater-level change, allowing inference of this property over a broad region even without collocated monitoring wells and gravity stations. Gravity data indicate aquifer drawdown and recovery mainly occurs in the central part of the basin where pumping is greatest. This spatial distribution is not captured by the more widely spaced monitoring well network. Because the aquifer is recovering from historically greater-magnitude pumping, net-neutral storage change (inflow=outflow) occurs when pumping from the central part of the well field is about 1.54 × 107 cubic meters (12,500 acre-feet) per year.

Regional Analysis of Tracer Tests in the Karstic Basin of the Gacka River (Croatian Dinaric Karst)

Tracer testing is the only method in karst hydrogeology that can definitively determine whether a particular site belongs to a watershed of a particular karst spring. Therefore, it is an essential technique for delineating groundwater basins in karst areas. The availability of tracer test results is often limited due to the complicated and relatively expensive application of this approach, especially for large regional watersheds. The Croatian part of the Dinaric karst region extends for several hundred kilometers along the Adriatic coast and consists almost entirely of highly karstified carbonate rocks. The groundwater basins in these areas almost never match the surface morphology of the terrain. In practice, all available results of previous surveys are often used to define watersheds, regardless of the methodology and age of their implementation. This is also true for the earlier delineations of the Gacka River watershed, a regional karst basin in the Croatian Dinaric karst. However, tracer testing methods, especially the accuracy of tracer determination and monitoring, have improved significantly during this time. In order to assess the reliability of past tracing results in this significant karst basin, we reviewed reports of previous tracer tests. More recent tests, in particular the most recent multitracer injection test with continuous tracer detection on the major springs, produced high-quality data that allowed us to assess the reliability of the findings from prior research. A number of large karst springs with partially overlapping subcatchments feed the Gacka River. After discarding unreliable tracing data, we reevaluated the subcatchments of the main springs as well as the characteristics of the regional groundwater flow patterns throughout the basin, which is particularly important for water quality protection measures of the springs. The Gacka River basin is used as a case study to emphasize the importance of thoroughly assessing the reliability of previous tracing data before using them in regional analyses.

Quantifying basin-scale changes in groundwater storage using GRACE and one-way coupled hydrological and groundwater flow model in the data-scarce Bandung groundwater Basin, Indonesia

Assessing basin-scale groundwater storage changes is often difficult when groundwater table data are scarce. In this study, we quantify the groundwater storage changes by using the Wflow_sbm hydrological model coupled with the MODLOW groundwater model in the data-scarce area of the Bandung groundwater basin, Indonesia. The soil moisture storage change calculated by Wflow_sbm plus the groundwater storage change calculated by MODFLOW is compared to the water storage change estimated by the GRACE satellite between 2005 and 2015. The calculated cross-correlation coefficient is 0.502, and 62.1% of the simulated water storage change falls within GRACE's estimated uncertainty bounds. The important context in the water storage comparison are GRACE temporally local time-lags, data gaps in GRACE datasets, and differences in model seasonal performance and analyzed domain characteristics. The two latter factors highlight the importance of considering local groundwater-related information over large-scale global datasets in basin-scale groundwater storage change assessment. Based on the groundwater flow model, the current predicament of groundwater abstraction in the Bandung groundwater basin is highly unsustainable for future groundwater uses. On average, the groundwater storage in the study area is dwindling at the rate of 87 million m3/year between 2005 and 2018, dominantly a consequence of groundwater abstraction, whose effect is rippled to further impact the whole groundwater flow regime. Agreed by the situation shown by the limited data, the simulated groundwater table drawdown, spatially, is found to be locally and non-uniformly distributed. The capability of a one-way coupled hydrological and groundwater model to investigate basin-scale groundwater storage change, with comparable estimates to the GRACE dataset, unravel the opportunity of using such methods to estimate the behavior of future groundwater storage dynamics under the changing anthropogenic and climatic factors in catchment-scale studies.

Aquifer Geometry Identification and Determination of Aquifer Storage and Recovery (ASR) in Bandung

Groundwater basins in Bandung city are included in the category of vulnerable areas to damage. It is interpreted that the Bandung area has damaged groundwater conditions. Geological conditions and soil in Bandung and its surroundings consist of alluvial layers of the eruption of Mount Tangkuban Perahu. The type of material in the north is generally a type of andosol. In the south and east of Bandung consists of a distribution of alluvial species with clay deposits and andosol soil types scattered in the central and western parts. This research was conducted to determine the hydrogeological and environmental conditions, groundwater level, pisometrics, aquifer characteristics, and water balance in the ASR Aquifer Storage and Recovery (ASR) wellbore. The research resulted in providing clean water that continues to be developed because of its effectiveness as a solution to overcome the groundwater crisis and groundwater level decline in the manufacture of ASR wells.