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Permafrost thaw due to climate warming modifies hydrological processes by increasing hydrological connectivity between aquifers and surface water bodies and increasing groundwater storage. While previous studies have documented arctic river baseflow increases and changing wetland and lake distributions, the hydrogeological processes leading to these changes remain poorly understood. This study uses a coupled heat and groundwater flow numerical model with dynamic freezing and thawing processes and an improved set of boundary conditions to simulate the impacts of climate warming on permafrost distribution and groundwater discharge to surface water bodies. We show a spatial shift in groundwater discharge from upslope to downslope and a temporal shift with increasing groundwater discharge during the winter season due to the formation of a lateral supra-permafrost talik underlying the active layer. These insights into changing patterns of groundwater discharge help explain observed changes in arctic baseflow and wetland patterns and are important for northern water resources and ecosystem management.

MODFLOW is a modular hydrologic model developed by the United States Geological Service since 1984. The last version, MODFLOW 6, allows the use of finite volume (FV) general unstructured grid approach to solve the groundwater flow equations. The FV method entails constraints that are implicitly satisfied by a Voronoi discretization. In this paper, new versions of the freeware VORO2MESH and TOUGH2Viewer tools are presented for Voronoi grid generation for MODFLOW. Originally developed for the TOUGH family of codes, both software has been improved to also work with MODFLOW. VORO2MESH and TOUGH2Viewer have been applied to two case studies and the results have been compared with analytical solutions. Outcomes have demonstrated that VORO2MESH grids give simulation results very close to locally refined Grids created using the Quadtree approach; furthermore, the simulation activities are substantially enhanced using TOUGH2Viewer. • New pre and post processing tools for MODFLOW-compliant Voronoi grids are presented. • VORO2MESH allows the generation of unstructured MODFLOW-compliant Voronoi grids. • TOUGH2Viewer allows visualization of MODFLOW simulations performed on Voronoi grids. • TOUGH2Viewer allows the export of MODFLOW results to PARAVIEW. [ABSTRACT FROM AUTHOR]

An oil flow from the oil wells damaged during the 1991 Gulf War and the sea water used for extinguishing the resulting oil fire have contaminated the freshwater aquifers of Raudhatain and Umm Al-Aish water fields in north Kuwait. The numerical flow modelling of the aquifers was undertaken to create a calibrated and validated model that could be used in the future to explore a viable remediation strategy for the aquifers. The Environmental Visualization Software (EVS-pro) 3-D data presentation program was used to construct a conceptual model as a preliminary step. A 3-D numerical model was developed using the MODFLOW-SURFACT code that overcame the limitations of the classical MODFLOW. This model was able to combine both freshwater lenses in one model domain simulating the vadose zone together with the saturated zone. The model domain covered an area of 580 km2 encompassing the Al-Raudhatain and Umm Al-Aish basins. A steady-state model was developed first to study regional flow patterns in the aquifer. A transient model was developed subsequently to assess seasonal recharge on groundwater and investigate their effects on flow patterns. Analysis of the calibrated steady-state model output indicated that the model simulated the groundwater elevation and flow direction across the model domain to an acceptable level. The calibrated transient flow model is of significant importance to assess the vertical and lateral plume migration in the area and helps to come up with a plausible remediation strategy. [ABSTRACT FROM AUTHOR]

The sophisticated research and management problems of the Estonian water environment are considered by means of holistic modelling. The model elaborated is based on the computer code Visual MODFLOW Classic. The model encompasses the entire Estonian Artesian Basin (EAB) and the border districts of Russia and Latvia. It involves all main aquifers and aquitards on an area of 88,000 km2. The main hydrogeological and hydrological characteristics of the study area, including the time-dependent three-dimensional distribution of groundwater heads, the direction, velocity and rate of subsurface fluxes, itemised water budgets, volumes of hydrogeological units, and durations of groundwater exchange have been determined by modelling. The palaeohydrological situation during the last continental glaciation of the EAB was reconstructed and the principal problems of the sustainable management of water environment were elucidated. The model has been used to simulate the local and cumulative rates of the base flow. [ABSTRACT FROM AUTHOR]

The Mar Piccolo basin is an internal sea basin located along the Ionian coast (Southern Italy), and it is surrounded primarily by fractured carbonate karstic environment. Because of the karstic features, the main continental water inflow is from groundwater discharge. The Mar Piccolo basin represents a peculiar and sensitive environment and a social emergency because of sea water and sediment pollution. This pollution appears to be caused by the overlapping effects of dangerous anthropogenic activities, including heavy industries and commercial and navy dockyards. The paper aims to define the contribution of subaerial and submarine coastal springs to the hydrological dynamic equilibrium of this internal sea basin. A general approach was defined, including a hydrogeological basin border assessment to detect inflowing springs, detailed geological and hydrogeological conceptualisation, in situ submarine and subaerial spring measurements, and flow numerical modelling. Multiple sources of data were obtained to define a relevant geodatabase, and it contained information on approximately 2000 wells, located in the study area (1600 km). The conceptualisation of the hydrogeological basin, which is 978 km wide, was supported by a 3D geological model that interpolated 716 stratigraphic logs. The variability in hydraulic conductivity was determined using hundreds of pumping tests. Five surveys were performed to acquire hydro-geochemical data and spring flow-yield measurements; the isotope groundwater age was assessed and used for model validation. The mean annual volume exchanged by the hydrogeological basin was assessed equal to 106.93 10 m. The numerical modelling permitted an assessment of the mean monthly yield of each spring outflow (surveyed or not), travel time, and main path flow. [ABSTRACT FROM AUTHOR]

Since last decade, the value per barrel of potable groundwater has outpaced the value of a barrel of oil in many areas of the world. Hence, proper assessment of groundwater potential and management practices are the needs of the day. Establishing relationship between remote sensing data and hydrologic phenomenon can maximize the efficiency of water resources development projects. Present study focuses on groundwater potential assessment in Salem district, Tamil Nadu to investigate groundwater resource potential. At the same, all thematic layers important from ground water occurrence and movement point of view were digitized and integrated in the GIS environment. The weights of different parameters/themes were computed using weighed index overlay analysis (WIOA), analytic hierarchy process (AHP) and fuzzy logic technique. Through this integrated GIS analysis, groundwater prospect map of the study area was prepared qualitatively. Field verification at observation wells was used to verify identified potential zones and depth of water measured at observation wells. Generated map from weighed overlay using AHP performed very well in predicting the groundwater surface and hence this methodology proves to be a promising tool for future. [ABSTRACT FROM AUTHOR]

In developing countries such as Syria, the lack of hydrological data affects groundwater resource assessment. Groundwater models provide the means to fill the gaps in the available data in order to improve the understanding of groundwater systems. The study area can be considered as the main recharge area of the eastern side of Barada and Awaj basin in the eastern part of Mt. Hermon. The withdrawal for agricultural and domestic purposes removes a considerable amount of water. The steady-state three-dimensional (3D) groundwater model (FEFLOW which is an advanced finite element groundwater flow and transport modeling tool), was used to quantify groundwater budget components by using all available data of hydrological year 2009-2010. The results obtained may be considered as an essential tool for groundwater management options in the study area. The calibrated model demonstrates a good agreement between the observed and simulated hydraulic head. The result of the sensitivity analysis shows that the model is highly sensitive to hydraulic conductivity changes and sensitive to a lesser extent to water recharge amount. Regarding the upper aquifer horizon, the water budget under steady-state condition indicates that the lateral groundwater inflow from the Jurassic aquifer into this horizon is the most important recharge component. The major discharge component from this aquifer horizon occurs at its eastern boundary toward the outside of the model domain. The model was able to produce a satisfying estimation of the preliminary water budget of the upper aquifer horizon which indicates a positive imbalance of 4.6 Mm³∙y-1. [ABSTRACT FROM AUTHOR]

This work analyses the feasibility and sustainability of closed-loop heat-exchangers, also known as Borehole Heat Exchangers (BHEs), in shallow geothermal areas. By circulating a carrier fluid in a closed-loop of pipes installed vertically in a deep well, there is no fluid exchange between the BHEs and hot thermal groundwater, but only heat transfer. The BHEs absorb heat when in contact with the warmer subsoil, and release it to buildings. It is designed that heating is provided through a free-heating system, avoiding the need to use a Ground Source Heat Pump system or other thermal energy device. An actual application of such technique in a public building located in an important thermal area in north–east Italy is analysed in terms of its thermal impact on underground and groundwater temperature. The test area is part of the so called Euganean Thermal Basin (ETB), which is the most important thermal district in northern Italy. The ETB is located in the eastern Po river plain and is one of the most important thermal and mud-therapeutic spas in the world. More than 250 hotels offer hospitality to more than 3 million tourists every year. Almost every hotel and spa owns a well to extract thermal water at a temperature in the range 60–87 °C from the fractured carbonatic bedrock found at a depth of about 50–200 m below ground level. To preserve this fundamental resource, the local legislation does not allow extracted thermal water to be used for purposes other than therapeutic ones. Several spas and thermal wells are present in the surroundings of the concerned building and it must be verified that heat extraction by the BHE-array during its operation does not hinder the temperature of thermal wells. The analysis is carried out using a finite elements analysis code (FEFlow 6.1), simulating mass and heat transfer inside porous media. Various array configurations are simulated and it is found that an array of 4 BHEs 240 m deep provide enough thermal energy to the building decreasing by less than 2 °C the temperature of the closest well's extracted water. A feasibility analysis of a more widespread District Heating scheme in the Euganean Thermal Basin area should therefore be carried out. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the impact of tunnel constructions on the steady-state groundwater head in the archaeological deposits at the Old Wharf (Bryggen) of Bergen. Water infiltration, permeabilities, and boundary conditions were deduced from available data and supplemented by leakage measurements into the existing railway tunnel located upstream of the Bryggen area. The pore water in the deposits at Bryggen has different origins viz . precipitation; leakage from drainage systems; infiltration of seawater; infiltration via the bedrock, and based on these observations, a 2D horizontal – and a 2D vertical numerical model were constructed where the seawater was the boundary at one side of the model and the groundwater divide at the other side. Given estimates of bedrock permeability and steady state infiltration rate, it was possible to calculate groundwater heads in the sediments at Bryggen that were consistent with observations, assuming that all the water percolating into the sediments flow through fractures in the bedrock. By this extreme assumption, a maximum sensitivity of the relation between groundwater flux in the bedrock and the groundwater level in the archaeological deposits was achieved. After simulation of the natural groundwater level (i.e. without any artificial extraction of water in the catchment), the impact of the water leakage into the existing tunnels was calculated. Given the relatively rough estimates of water leakage into the existing tunnels (4 L/day/meter of tunnel), the calculated decline of the groundwater head in the archaeological deposits was less than 1% of the natural groundwater level (<1 cm). If leakage rates were increased to one and two orders of magnitude, the steady state groundwater decline would be from 5% to more than 35% of the reference groundwater level (4–15 cm). The reason for these relatively robust groundwater conditions in the sediments are caused by the boundary conditions: Without any local water extraction in the deposits, the steady-state groundwater head at Bryggen will always be higher than the seawater level. A crucial point for these results was the leakage rates into the existing tunnels. Water discharge into tunnels and other subsurface constructions is the principal risk factor in this study and should be monitored before any new tunnels are constructed. [ABSTRACT FROM AUTHOR]

The aim of this paper is to solve the local pumping and recharging source identification problem by introducing a statistical technique, independent component analysis (ICA), into groundwater modelling. Such a problem suffers from limited observations in the field and is ill-posed. With the help of ICA, the observed head at monitoring wells is decomposed into a linear combination of head fluctuations caused by each source. The ill-posed problem is transferred into several independent well-posed ones. Moreover, the decomposed hourly head fluctuation, specially referred to as ‘characteristic pattern’, provides novel information on the type and distance of local sources. A hypothetical case to identify two local sources using two observation wells is presented, and the results show the accuracy and efficiency of the proposed method. The identified results are stable as long as the observation error is within a reasonable range. The characteristic pattern provides novel information, which can be widely used for source identification in the future.Editor D. Koutsoyiannis; Associate editor Xi Chen [ABSTRACT FROM PUBLISHER]

Hydrological processes commonly exhibit long-term persistence, also known as the 'Hurst phenomenon'. Here, we examine long-term precipitation and streamflow time series from the Elbe River Basin to quantify differences in the spectral properties and in the Hurst parameter estimates ( [ABSTRACT FROM AUTHOR]

The Heihe River Basin (HRB) is an inland watershed in northwest China with a total area of approximately 130,000 km2, stretching from the Qilian Mountains in the south to the oases and agricultural fields in the middle and further to the Gobi desert in the north bordering Mongolia. As part of a major ecohydrological research initiative to provide a stronger scientific underpinning for sustainable water management in arid ecosystems, a regional-scale integrated ecological and hydrological model is being developed, incorporating the knowledge based on the results of environmental isotope tracer analysis and the multiscale observation datasets. The first step in the model development effort is to construct and calibrate a groundwater flow model for the middle and lower HRB where the oases and vegetation along the Heihe river corridor are highly dependent on groundwater. In this study, the software tool 'Arc Hydro Groundwater' is used to build and visualize a hydrogeological data model for the HRB that links all relevant spatiotemporal hydrogeological data in a unified geodatabase within the ArcGIS environment. From the conceptual model, a regional-scale groundwater flow model has been developed using MODFLOW-2005. Critical considerations in developing the flow model include the representation of mountainous terrains and fluvial valleys by individual model layers, treatment of aquifer heterogeneities across multiple scales and selection of proper observation data and boundary conditions for model calibration. This paper discusses these issues in the context of the Heihe River Basin, but the results and insights from this study will have important implications for other large, regional groundwater modelling studies, especially in arid and semiarid inland river basins. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Water harvesting and artificial recharge have been a traditional solution to water scarcity problems in the arid and semi-arid Middle East for thousands of years. These techniques are increasingly being encouraged, and recently there has been renewed interest to find improved methods for water harvesting and artificial recharge in many arid countries. In this study, water balance calculations and groundwater modelling were utilized to investigate the performance and hydrological function of an improved water harvesting technique, referred to as the floodwater spreading system, in arid Iran. The recharge amount in the floodwater spreading system studied varied from a few hundred thousand cubic metres per month during drought periods to about 4.5 × 106m3per month during rainy periods. However, the gain through artificial recharge was diminished by excessive groundwater abstraction by numerous newly drilled pumping wells. Hence, the groundwater declined in spite of the artificial recharge. However, this research showed that, with balanced pumping, the floodwater spreading system could be an efficient way to increase groundwater resources in arid and semi-arid areas. Further research is needed to optimize the floodwater harvesting system to improve its management in view of the uncertain frequency and magnitude of inflow.Editor D. Koutsoyiannis; Associate editor S. Faye [ABSTRACT FROM AUTHOR]

The impact of climate change and Baltic Sea level rise on groundwater resources in a shallow, unconfined, low-lying coastal aquifer in Hanko, southern Finland, was assessed using the UZF1 model package coupled with the three-dimensional groundwater flow model MODFLOW to simulate flow from the unsaturated zone through the aquifer. The snow and PET models were used to calculate the surface water availability for infiltration from the precipitation data used in UZF1. Infiltration rate, flow in the unsaturated zone and groundwater recharge were then simulated using UZF1. The simulation data from climate and sea level rise scenarios were compared with present data. The results indicated changes in recharge pattern during 2071-2100, with recharge occurring earlier in winter and early spring. The seasonal impacts of climate change on groundwater recharge were more significant, with surface overflow resulting in flooding during winter and early spring and drought during summer. Rising sea level would cause some parts of the aquifer to be under sea level, compromising groundwater quality due to intrusion of sea water. This, together with increased groundwater recharge, would raise groundwater levels and consequently contribute more surface leakage and potential flooding in the low-lying aquifer. [ABSTRACT FROM AUTHOR]

Groundwater fluxes in tidal marshes largely control key ecosystem functions and services, such as vegetation growth, soil carbon sequestration, and nutrient cycling. In tidal marshes restored on formerly embanked agricultural land, groundwater fluxes are often limited as compared to nearby natural marshes, as a result of historical agricultural soil compaction. To improve the functioning of restored tidal marshes, knowledge is needed on how much certain design options can optimize soil-groundwater interactions in future restoration projects. Based on measured data on soil properties and tidally induced groundwater dynamics, we calibrated and evaluated a 2D vertical model of a creek-marsh cross-section, accounting for both saturated and unsaturated groundwater flow and solute transport in a variably saturated groundwater flow model. We found that model simulations of common restoration practices such as soil amendments (increasing the depth of porous soil on top of the compact layer) and creek excavation (increasing the creek density) increase the soil aeration depth and time, the drainage depth and the solute flux, and decrease the residence time of solutes in the porewater. Our simulations indicate that increasing the depth to the compact layer from 20 cm to 40 cm, or increasing the creek density from 1 creek to 2 creeks along a 50 m marsh transect (while maintaining the total creek cross-sectional area), in both cases more than doubles the volume of water processed by the marsh soil. We discuss that this may stimulate nutrient cycling. As such, our study demonstrates that groundwater modelling can support the design of marsh restoration measures aiming to optimize groundwater fluxes and related ecosystem services. [Display omitted] • Historical soil compaction limits groundwater flow in restored tidal marshes • Seepage volumes were found to be 6 times less in restored marsh with compact subsoil • Creek excavation and soil amendments increase soil – groundwater interactions • Groundwater modelling is a useful tool to optimize tidal marsh restoration design [ABSTRACT FROM AUTHOR]

Hydrological models are useful tools to analyze present and future conditions of water quantity and quality. The integrated modelling of water and nutrients needs an adequate representation of the different discharge components. In common with many lowlands, groundwater contribution to the discharge in the North German lowlands is a key factor for a reasonable representation of the water balance, especially in low flow periods. Several studies revealed that the widely used Soil and Water Assessment Tool (SWAT) model performs poorly for low flow periods. This paper deals with the extension of the groundwater module of the SWAT model to enhance low flow representation. The current two-storage concept of SWAT was further developed to a three-storage concept. This was realized due to modification of the groundwater module by splitting the active groundwater storage into a fast and a slow contributing aquifer. The results of this study show that the groundwater module with three storages leads to a good prediction of the overall discharge especially for the recession limbs and the low flow periods. The improved performance is reflected in the signature measures for the mid-segment (percent bias −2.4% vs −15.9%) and the low segment (percent bias 14.8% vs 46.8%) of the flow duration curve. The three-storage groundwater module is more process oriented than the original version due to the introduction of a fast and a slow groundwater flow component. The three-storage version includes a modular approach, because groundwater storages can be activated or deactivated independently for subbasin and hydrological response unit level. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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Uneven distribution of domestic water in space and time is a major concern in many fast growing cities due to improper planning and lack of scientific approach. This problem is much severe where the maximum domestic water requirements are met from the groundwater resources. Optimising a single groundwater pumping scheme may be an easy task using simple linear programming technique but, if the number of pumping schemes and constraints are more, solutions for identifying such groundwater schemes are more difficult and laborious using conventional methods as the constraints varies in space and time. In this paper, a new technique was developed to identify new groundwater pumping schemes to meet the present and future domestic water requirements in space and time by integrating spatial optimisation technique with the groundwater model. The approach considers the possible optimum rate of groundwater pumping, minimising the cost of water supply scheme and having minimum impact on the downstream side groundwater table using high resolution satellite data (IKONOS), Geographical Information System (GIS) tools and optimisation techniques. Dehradun, which is one of the fast growing cities in India, was considered as a study area to demonstrate the proposed new technique. Domestic water demand for next two decades (up to 2,031) was forecasted and compared with the existing supplies. Nearly 48 additional groundwater pumping schemes were identified to cater the present and future demands. Its impact on the groundwater table was also studied using groundwater modelling technique. [ABSTRACT FROM AUTHOR]