Groundwater Outflow Research Articles

Physical and chemical properties of natural and anthropogenic groundwater outflows in the cieszyn foothills

The purpose of this article is to present the hydrographic and hydrochemical properties of the waters of old adits, which drained excavations after exploitation of iron ores. For this research, both the natural springs and control object have been identified. These are located in the Cieszyn Foothills. It has been shown that adit water has a higher average electrolytic conductivity (> 600 µS/cm) than natural spring water (<300 µS/cm). The increase in conductivity is undoubtedly influenced by the air supply to the excavations, which accelerates the rock weathering process. However, the increase in water mineralisation has no effect on the hydrochemical type of water. Adit waters and spring waters represent the same bicarbonate calcium (HCO3− - Ca2+) hydrochemical type. Adit waters show a small variation in water temperature in the annual cycle (Cv < 8%) compared to a natural spring (Cv -18%). Changes in the water temperature in the adits and the spring show high synchronism (r> 0.7).

What is the worth of drain discharge and surface runoff data in hydrological simulations?

Quantitative analyses of empirical data requirements for hydrological simulations are rare. This study aims to analyze how a multi-objective optimization framework and information content computations aid in quantifying field-scale data worth in drainage studies. The results showed how a 1D numerical model and a differential evolution algorithm performed in describing the field water balance. The choice of the optimization target (subsurface drain discharge and surface runoff) impacted the simulation results more than parameter deviations. While the information content of surface runoff data was higher than that of drain discharge, drain discharge data contained more information on most of the soil parameters. Uncertainties related to groundwater outflow data, which were not used in the optimization, were higher than those of drain discharge and surface runoff. A central weighing optimization scheme with two data types produced the best but still incomplete description of the field hydrology. Despite the modest model performance, the results demonstrated how the choice of empirical data and optimization strategy can lead to uncertainties in drainage simulations and how the uncertainties can be assessed. Practically, a low amount of information and a parameter sensitivity analysis can lead to a biased description of uncertainty related to such hydrological variables which are not used in the optimization. Benefits of the modeling framework were shown when assessing (1) model structure adequacy with the Pareto front analysis, (2) information content of different data types regarding different parameters, and (3) uncertainties related to simulating hydrological variables based on optimization against a given data type.

Transformation Stages of the Cleaning Capacity of Agricultural Irrigation Fields by Wastewater from a Gas-Processing Plant

The dynamics of the cleaning capacity of agricultural fields irrigated with wastewater from a gas-processing plant is studied. It is shown that 5–7 irrigations at a rate of 480 m3/ha annually bring 2.98–4.17 t/ha of pollutants into the soil, and these pollutants are retained in the soils of the aeration zone and contribute to their salinization and alkalinization and, as a consequence, lead to a reduction in crop yields. In addition, calcium is carried from upper soil layers to deeper horizons, thereby forming a new geochemical barrier. Under conditions of a weak outflow of groundwater, we recorded a growth in its level, an accumulation of salts carried with wastewater, and an increase in the total mineralization of wastewater. It is established that the agricultural irrigation fields used for over 20 years undergo three transformation stages: adaptation stage (3–4 years); stable functioning of the geoecosystem utilizing industrial waste waters from the gas-processing plant (7–10 years), and the stage of the critical state of the geoecosystem due to the loss of the cleaning capacity by the soils and the necessity of soil-improving remediation activities.

Hydrogeochemical, isotopic and geophysical characterization of saline lake systems in semiarid regions: The Salada de Chiprana Lake, Northeastern Spain

Most of the athalassic saline and hypersaline lakes are located in arid and semiarid regions where water availability drives the hydrological dynamics of the lake itself and the associated ecosystems. This is the case of the Salada de Chiprana Lake, in the Ebro River basin (Spain). It is the only athalassic permanent hypersaline lake in Western Europe, and where rare and endangered bacterial mats exist. This work presents a robust hydrogeological conceptual model for the lake system. The model evaluates the contribution of groundwater discharge to the whole water budget and explains the hydrological behaviour of the lake system. The lake behaves as a flow-through system rather than a closed basin. About 40% of total water outflow from the lake occurs as groundwater, whereas evaporation accounts for the remaining 60%. The surface water inflows are variable, but the groundwater contribution seems almost constant, amounting to 13% of the average total water inflow and contributing 1.9% of salt income. The high water salinity of the lake is controlled by evaporation, by saline water inflows from irrigation return flows, and the by groundwater outflows. The role of groundwater should be taken into account when drafting the water and land planning, once the conditions for the conservation of the algal mats are defined. A major contribution of this study is the water balance in the Salada de Chiprana Lake, which is consistent with a robust hydrogeological conceptual model defined upon scarce hydrogeological, hydrochemical and isotopic data in the local context as conditioned by the regional behaviour. The water balance is a key tool to help to correctly manage this unique athalassic saline lake, and the approach used here can be extrapolated to other similar ecosystems around the world.

Numerical groundwater flow modeling of the Kombolcha catchment northern Ethiopia

Intensive groundwater extraction is a changing groundwater system. It is also the main challenge for future groundwater availability. In this study, numerical groundwater flow model was developed in Kombolcha catchment, Ethiopia by using MODFLOW-OWHM. To address this concern, the conceptual model was built by analyzing the hydrogeological data. The groundwater model was calibrated under the steady-state condition to produce the best match between the simulated and observed hydraulic head. The simulated outflow of the MODFLOW model was 358,221.09 m3/day which is nearly equal to 358,221.08 m3/day of groundwater inflow with a difference 0.01 m3/day and zero discrepancies. The subsurface inflow covers the most percentage (76%) in the budget and surface outflow contributes about 66% of the total groundwater outflow. The model result shows that the Kombolcha aquifer system is highly sensitive to change of hydraulic conductivity. Prediction of this aquifer behavior for increasing well withdrawal and decreasing recharge scenarios has been carried out. The effect of increasing withdrawal by 25, 50 and 100% results in a decline of groundwater level by 6.77, 12.15 and 24.37 m, respectively, whereas the effect of decreasing groundwater recharge by the same percentage of withdrawal results in a decline of groundwater level by 4.27, 6.34 and 11.25 m, respectively. This model can be as a tool to understand the aquifer system and sustainable utilization of groundwater resources.

МОДЕЛИРОВАНИЕ ВОДНО-СОЛЕВОГО БАЛАНСА РЕЧНОГО БАССЕЙНА С РАЗВИТЫМ ОРОШАЕМЫМ ЗЕМЛЕДЕЛИЕМ

The construction of a mathematical model of the water-salt balance for river basins with the predominant development of irrigated agriculture is considered. The structures of the water and salt balance of the irrigated territory and the balance of the main river bed within it are given. It has been established that if the inflow and outflow of water and salts dissolved in it are caused by its horizontal flows, then the evaporation and accumulation of water (salts) in the aeration zone and groundwater are caused by its vertical flows.This leads to the need to consider instead of the general equation of the water (salt) balance of the irrigated territory of its modifications for the distinguished three vertical zones, that is, “the surface of the territory – aeration zone – groundwater zone”. During the operation of the algorithm, the following are successively determined: elements of the water and salt balance of the irrigated territory and the riverbed; groundwater level as a result of the intake of salts with in-person flow of local tributaries; filtration losses from the channels and the lateral residue of the inflow; moisture content in the aeration zone after irrigation water and precipitation enters it; groundwater level after water from the aeration zone; moisture content in the aeration zone after the influx of groundwater into it; the outflow of groundwater into the riverbed and the final mineralization of water in the aeration zone.

Groundwater geochemical facie: implications of rock-water interaction at the Chamba city (HP), northwest Himalaya, India.

The present study describes geochemical facie and implications of rock-water interaction at the groundwater of Chamba city. The influence of rock dominance at the groundwater may be due to its flow and longtime rock-water interaction, whereas atmospheric precipitation dominance owing to high recharge and continuous outflow of groundwater that cause a short time interaction. The comparison among Ca2+ + Mg2+ versus Na+ + K+ and total cations indicated carbonate weathering as a main ionic source relative to silicate weathering, due to rich lithology and higher dissolution capacity of carbonate minerals. The chloro-alkaline indices (CAI-1 and CAI-2) and scatter plot of (Ca2+ + Mg2+) - (HCO3- + SO42-) versus (Na+ + K+) - Cl- (meq/L) inferred the presence of ion exchange process causing adsorption of Ca2+ and release of Na+. The Ca2+ - Mg2+ - Cl-, Na+ - HCO3-, and Ca2+ - Mg2+ - HCO3- types of groundwater suggested permanent and temporary hardness in the region. The Ca2+ and Na+ are observed as the dominant cations whereas HCO3- and SO42- as the dominant anions. The parameters like NH4+, NO3-, F-, and Br- are generated from different natural sources. The groundwater is found to be suitable for drinking purposes based on water quality index (14.24-61.13) and the Bureau of Indian Standards (BIS 2012) prescribed limit. The influence of carbonate minerals dissolution over TDS and salinity at groundwater of the city is also observed. The rock-water interaction confirmed mixing pattern of carbonate, silicate, and evaporites in the groundwater of the Chamba city.

Sustained post‐seismic effects on groundwater flow in fractured carbonate aquifers in Central Italy

AbstractA sustained increase in spring discharges was monitored after the 2016 Central Italy seismic sequence in the fractured carbonate aquifer of Valnerina–Sibillini Mts. The groundwater surplus recorded between August 2016 and November 2017 was determined to be between 400 and 500 × 106 m3. In fractured aquifers, the post‐seismic rise in spring discharges is generally attributed to an increase in bulk permeability caused by the fracture cleaning effect, which is induced by pore pressure propagation. In the studied aquifers, the large amount of additional discharge cannot only be attributed to the enhanced permeability, which was evaluated to be less than 20% after each main seismic event. A detailed analysis of the spring discharge hydrographs and of the water level at five gauging stations was carried out to determine the possible causes of this sudden increase in groundwater outflow. Taking into account the geological and structural framework, a conceptual model of a basin‐in‐series has been adopted to describe the complex hydrogeological setting, where the thrusts and extensional faults have clearly influenced the groundwater flow directions before and after the seismic sequence. The prevalent portion of the total post‐seismic discharge surplus not explained by the increase in permeability has been attributed to changes in the hydraulic gradient that caused seismogenic fault rupture and the disruption in the upgradient sector of the aquifer. The additional flow calculated through the breach of the pre‐existing hydrostructural barrier corresponds to approximately 470 × 106 m3. This value is consistent with the total discharge increase measured in the whole study area, validating the proposed conceptual model. Consequently, a shift in the piezometric divide of the hydrogeological system has been induced, causing a potentially permanent change that lowers the discharge amount of the eastern springs.

Insights into hydrological and hydrochemical processes in response to water replenishment for lakes in arid regions

Lakes in arid regions are ecologically valuable yet highly fragile due to intense evaporation. To provide an extra water supply for maintaining water balance in lakes, the Ecological Replenishment Water Program (ERWP) in northwest China has significantly changed the hydrological and hydrochemical conditions for these lakes. Descriptive statistics and water and mass balances, together with hydrogeochemical modeling were used in this study to gain an understanding of the impacts of water replenishment (irrigation and drainage water) on evolution for Shahu Lake. A virtual sample was introduced in NETPATH hydrogeochemical modeling to compute the net chemical reactions in the lake water. Variations in TDS indicated that the lake evolved to be saline during 2004–2012 (stage I) and then tended to be fresh during 2013–2014 (stage II). Results highlighted that groundwater outflow and chemical reactions were the overriding factors controlling chemical evolution in the lake system, which greatly depend on the replenishment activities. The salinity reduction from the virtual samples to the final samples were attributed to the precipitation of calcite and dolomite, dissolution of gypsum, Na-K and Na-Ca exchange, and the CO2 degassing in the lake system at an annual scale of 0.11 g/L in stage I and 0.15 g/L in stage II. The quality of replenishment water was as important as quantity for rehabilitating lakes, as it significantly determines the occurrence of chemical reactions in lake water. Findings from this paper can provide insight into the evolution of arid lakes in response to replenishment activities and can help contribute to better management of a valuable and fragile resource.

Is the Vegetation Succession a Threat for Rare and Protected Species in a Sand Quarry? Case Study of the Kuźnica Warężyńska Sand Quarry (Southern Poland)

The work focuses on analyzing and reason of occurrences of rare and protected species by European and Polish low. These species are growing in the areas of former sand exploitations quarry and have different ecological requirements. The origin of such quarries is strictly connected strictly connection with development of coal mining in the Silesian Upland (Southern Poland). From the end of exploitation the processes of spontaneous vegetation ecosystems have been observed. The research was conducted in Southern Poland in the area of the Kuznica Warężyńska sand quarry with an area of approximately 8 km2, exploited in the years 1972 - 2003. In results of work has been confirmed by 2 types of habitats which are included in I Annex Council Directive 92/43/EEC on the Conservation of natural habitats and of wild fauna and flora forms in zone of groundwater outflow. They are 7140-transition mires and quaking bogs and 7230 - alkaline fens. In these communities, numerous population of 22 protects spiecies as Dactylorhiza maculata, D. majalis, Epipactis atrorubens, E. helleborine, E. palustris, Malaxis monophyllos, Lycopodiella inundata, Pinguicula vulgaris, including Liparis loeselii found in Annex II of the Habitats Directive occur. These are early-successional species, whose numbers in next successions phases decrease or after several years completely disappear. The analyzed flora differs in terms of life forms, ecological requirements related to the habitat mosaics. The fragments of sand quarry that were where are not reclaimed can play important role in nature conservation not only in local level but even on supra-regional scale. Hence, this object is a place for many rare, threatened with extinction species and plant communities as substitute habitats. The conservation of such species and plant communities in sand quarry needed active protection. It consists in maintaining the initial stages of succession and preventing the formation of the forest.

Charakterystyka hydrologiczna zlewni rzeki Ciemięgi

&lt;p&gt;Na podstawie materiałów zbieranych w latach 1956–2017 przez pracowników Zakładu Hydrologii UMCS w pracy przedstawiono warunki tworzenia się zasobów wód podziemnych, spływu powierzchniowego, wydajności źródeł, odpływu i bilansu wodnego w zlewni Ciemięgi położonej w północnej części Wyżyny Lubelskiej. Analizę hydrologiczną oparto na dobowych stanach i przepływach z lat 1981–2017. Zasoby wodne zlewni zmieniały się w cyklu wieloletnim, z wyraźnie zaznaczonym rytmem sezonowym. Średni roczny przepływ wyniósł 0,53 m&lt;sup&gt;3&lt;/sup&gt;∙s&lt;sup&gt;-1&lt;/sup&gt;, co odpowiada odpływowi jednostkowemu 3,46 dm&lt;sup&gt;3&lt;/sup&gt;∙s&lt;sup&gt;-1&lt;/sup&gt;∙km&lt;sup&gt;2 &lt;/sup&gt;i warstwie odpływu 109 mm. Wysokie zasilanie podziemne, kształtowane przez dopływ wody z kilku źródeł o wydajnościach 10–80 dm&lt;sup&gt;3&lt;/sup&gt;∙s&lt;sup&gt;-1&lt;/sup&gt;, warunkuje wyrównanie przepływów w dolnym biegu rzeki. Spływ powierzchniowy (mimo znacznych spadków terenu) pojawia się stosunkowo rzadko, najwyższe wartości osiągając w okresie spływu wód roztopowych po zamarzniętym gruncie. Wielkość odpływu ze zlewni Ciemięgi utrzymuje się poniżej średniej dla Wyżyny Lubelskiej i Polski.&lt;/p&gt;

Numerical simulation and field test of grouting in Nong'an pilot project of in-situ conversion of oil shale

In-situ recovery of oil from oil shale using the convection heating method requires a hydraulic fracturing process to provide transportable channels for thermal carriers and shale oil and gas released by oil-shale pyrolysis. However, flowing groundwater could enter the reaction zone through fissures generated by hydraulic fracturing, causing significant heat loss and blocking the generation and outflow of oil and gas during the heating process of the in-situ conversion of oil shale. Therefore, a continuous water-stop is indispensable. This study optimized the layout of grouting wells in a hexagonal pattern and carried out a series of grouting diffusion simulations according to the hydrogeological data of the Nong'an oil shale stratum. Moreover, a field test was conducted at the site of the Nong'an pilot project of oil shale in-situ processing. The simulation result indicates that the production wells should be kept open during the grouting process, as numerous local high-velocity zones of groundwater between the grouting wells could restrict the expansion and intersection of grouting. An optimized open pattern grouting method for the Nong'an pilot project was proposed, and a well-spacing of 3 m was determined to be appropriate. Finally, in the field grouting test, the fine grout intersection without local high-velocity zones was verified through water pressure tests and according to the initial and ultimate outflow of groundwater in the production well of the field test, which corresponded to the simulation result. Hence, the authenticity of the grouting method determined by numerical simulation has been verified.

Are catchments leaky?

AbstractCatchments, generally understood as the drainage areas of low‐order streams, are often regarded as closed hydrologic entities; that is, precipitation (P) minus evapotranspiration (ET) over a catchment equates stream outflow (Q r). Here, we review evidence that catchments can be leaky due to groundwater outflow or inflow across topographic divides, based on catchment mass balance across a continent and several site‐based studies across the globe. It appears that a catchment is more likely to be leaky with the combination of the following factors: small catchment size, positioned at either the high or low end of a steep regional topographic and climatic gradient, underlain by deep permeable substrates that extend beyond the study catchment, and in drier climate or dry seasons and droughts. Catchment leakage has hydrological, geochemical, and ecological implications. Thus, catchments are best framed as semiclosed hydrologic units perched on top of a larger, regional hydrogeological system with no real boundaries regarding the movement of water and solutes.This article is categorized under: Science of Water &gt; Hydrological Processes Water and Life &gt; Nature of Freshwater Ecosystems

Impacts of supplementary drainage on the water balance of a poorly drained agricultural field

In northern clay soils, field drainage is needed to ensure suitable moisture conditions for crop growth and farming operations. Supplementary drainage installations improve the efficiency of old drainage systems, but the hydrological impacts of the drainage procedures are not comprehensively understood or quantified. The objective was to simulate the hydrological behavior of a clay field section and to quantify the effects of a supplementary drainage on the water balance of the field section. The study site, in southern Finland, was originally subsurface drained in 1952 with 32 m drain spacing. Supplementary drainage was installed in 2014, decreasing the drain spacing to 10.7 m. Simulations were carried out with a dual-permeability hydrological model and two model parametrizations describing the field hydrology (1) before and (2) after the supplementary drainage installation. The parameterizations were used for simulations of a nine-year period to quantify the hydrological impacts of the supplementary drainage. For the periods without snow on the ground, the modified Nash-Sutcliffe efficiency for daily drain discharge and topsoil layer runoff values ranged from 0.43 to 0.53 and from 0.44 to 0.53, respectively. During the original drainage setup scenario, the average annual drain discharge was lower (7.8% of precipitation) than topsoil layer runoff and groundwater outflow (10.3% and 26.4%, respectively). For the supplementary drainage scenario, most of the water outflow was through drain discharge and groundwater outflow (20.4% and 21.9%, respectively). The supplementary drainage installation increased the average annual drain discharge by a factor of 2.6, while the annual average topsoil layer runoff and groundwater outflow decreased by 75% and 18%, respectively. The supplementary drainage setup was found to expedite the drying of the field section in spring by 8 days on average compared to the original drainage setup.

Carbonate Beach Sand of Abaiang Atoll, Kiribati: Geochemistry, Biogenic Sources, and Properties

Sandy beaches are critical resources for low-lying Pacific atoll communities, providing protection during storms, and land area for many coastal villages. Information on the nature of atoll beach sediment, its geochemistry and composition, can help to establish priorities to effectively protect the sources of Pacific island beach sediment. To understand sand sources, this study evaluated its physical characteristics including grain-size, geochemistry and composition, from windward and leeward beach profiles around Abaiang Atoll, Kiribati. Beach sand was &gt;99% carbonate, averaging 37% coral fragments, 30% mollusc shells, 12% foraminifera, and 20% calcareous algae. Significant differences were found between reef and lagoonal sites in proportions of coral and mollusc fragments and foraminifera tests, with lagoon beaches having higher mollusc and coral proportions and lower foraminifera relative to reef beaches. This is attributed to high foraminiferal productivity offshore of reef beaches, and taphonomic durability of coral fragments in longshore drift into the lagoon. Mean sediment diameter increased from the upper to lower beaches at all sites, but fine sediment was lacking, attributed to its dissolution by rainfall and groundwater outflow. Geochemical analysis showed a mean of 84% Ca-Mg carbonates, of which 80% was calcium carbonate. There was no significant difference in the mean calcium percentage or calcium carbonate composition of the sediment between lagoon and reef beach sediment sources. Magnesium and magnesium carbonate content were significantly higher at reef sites relative to lagoon sites, attributed to higher proportions of foraminifera. Sediment-producing near shore habitats are critical to village protection through provision of beach sand, and this study shows the need to better conserve and manage coral reefs and habitats such as lagoon seagrass beds, to ensure continued atoll beach sand supply.

Prediction of groundwater levels from lake levels and climate data using ann approach

There are many environmental concerns relating to the quality and quantity of surface and groundwater. It is very important to estimate the quantity of water by using readily available climate data for managing water resources of the natural environment. As a case study an artificial neural network (ANN) methodology is developed for estimating the groundwater levels (upper Floridan aquifer levels) as a function of monthly averaged precipitation, evaporation, and measured levels of Magnolia and Brooklyn Lakes in north-central Florida. Groundwater and surface water are highly interactive in the region due to the characteristics of the geological structure, which consists of a sandy surficial aquifer, and a highly transmissive limestone confined aquifer known as the Floridan aquifer system (FAS), which are separated by a leaky clayey confining unit. In a lake groundwater system that is typical of many karst lakes in Florida, a large part of the groundwater outflow occurs by means of vertical leakage through the underlying confining unit to a deeper highly transmissive upper Floridan aquifer. This provides a direct hydraulic connection between the lakes and the aquifer, which creates fast and dynamic surface water / groundwater interaction. Relationships among lake levels, groundwater levels, rainfall, and evapotranspiration were determined using ANN-based models and multiple-linear regression (MLR) and multiple-nonlinear regression (MNLR) models. All the models were fitted to the monthly data series and their performances were compared. ANN-based models performed better than MLR and MNLR models in predicting groundwater levels.

Groundwater–lakewater interactions: an evaluation of the impacts of climate change and increased abstractions on groundwater contribution to the Volta Lake, Ghana

A 3D steady state groundwater flow model has been calibrated for the Afram Plains portion of the Southern Voltaian Sedimentary Basin. The model was based on data of hydraulic parameters of the aquifer in the area, and regional groundwater recharge estimates conducted by various researchers using a variety of methods. Model calibration was conducted using hydraulic head data of 43 boreholes in the area. Although the groundwater system in the area appears to receive some amount of recharge from the Volta Lake, the net groundwater outflow into the lake currently outstrips the volumes received from the Lake. The net effect, as suggested by the calibrated model is that groundwater outflows into the Volta Lake amount to approximately 465 m3/day (169,725 m3/year). However, with increasing groundwater abstractions at a rate of 2.5%, consistent with annual population projections, a reversal of flow is predicted by 2030 if groundwater recharge remains at the 2015 rates. This would lead to a net lake discharge of approximately 9755 m3/day into the aquifer system to sustain abstraction rates by 2050. This is predicted to increase further if there is a reduction in groundwater recharge as suggested by regional hydroclimatological data. A 25% reduction in groundwater recharge rate by 2050 will induce a net lake discharge of approximately 11,000 m3/day into the aquifer system to sustain abstractions for domestic consumption. Lateral outward/environmental flows will reduce from 5200 m3/day to 2700 m3/day under the 2015 recharge conditions, and 1300 m3/day under conditions of reduced recharge by 2050. Groundwater in the area does not appear to hold promise for commercial abstraction for irrigation purposes, especially under climate change conditions.

A groundwater flow model for the Wolin Island area, including glaciotectonic deformation

Abstract During the construction of mathematical models for mapping hydrogeological conditions it is necessary to apply simplifications, both in the geological structure and in hydrogeological parameters used. The present note discusses problems surrounding the mapping of glaciotectonic disturbances that occur in the northern part of Wolin Island (northwest Poland). For this part of the island, a direct outflow of groundwater towards the Baltic Sea basin has been determined on the basis of geophysical survey results. An important feature in the hydrogeological conditions here is the isolation of groundwater from both the Baltic Sea and Szczecin Lagoon by clay with a Cretaceous xenolith. Such a geological structure explains the presence of perched water at considerable heights in zones close to the cliffs, without any significant hydraulic connection with surrounding reservoirs. Hydrogeological conditions of Wolin Island have been modelled using the Visual MODFLOW package v.4.2. In the vertical section, these conditions can be simplified to one aquifer (Pleistocene-Holocene), in which two aquifers can be distinguished. In a large part of the island, these remain in mutual hydraulic contact: layer I – upper, with an unconfined aquifer, and layer II – lower, with a confined aquifer, locally an unconfined one. The schematisation of hydrogeological conditions adopted here has allowed to reproduce present groundwater dynamics in the study area.

Application of pollution indices for the spatiotemporal assessment of negative impact of a municipal landfill on groundwater (Tychy, southern Poland)

Risk assessment plays an essential role in the protection of groundwater resources, especially in the regions of potential contamination sources. The present research was aimed at assessing the risk of groundwater contamination in the vicinity of the Tychy-Urbanowice municipal landfill systems (southern Poland), using the contamination index tool. Groundwater samples from the Quaternary Aquifer were collected from 22 piezometers located near the former landfill site (currently closed) and the new sealed landfill site during a monitoring period from 1995 to 2015. Extremely high values (1700) of the groundwater contamination index were observed in a piezometer that captures water beneath the abandoned landfill. Very high index values (154 or 216) were also noticed in piezometers located in the groundwater outflow from the landfill site. Results of interpolation for individual piezometers, which capture only the upper or lower part of an aquifer, are unrepresentative. The interpolation for the mean values of the contamination index increased the groundwater risk assessment.

Quantitative reconstruction of early Holocene and last glacial climate on the Balkan Peninsula using coupled hydrological and isotope mass balance modelling

We investigate the modern hydrology of Lake Ohrid (Macedonia/Albania) using a combined hydrological and isotope-based modelling approach and present a new evaluation of contemporary water balance and palaeoclimate estimates. The combined model is able to estimate hydrological components that cannot be directly measured, and indicates that sublacustrine spring inflow is in the order of 50% higher than previous estimates and groundwater outflow comprises approximately a third of overall water outflow. In combination with sediment core oxygen isotope data, we used the combined model to quantitatively reconstruct past climate, in particular precipitation, during the early Holocene and last glacial period. Calculated precipitation in the early Holocene was higher than the value for present day and was approximately 44% lower than present during the last glacial, assuming the majority of precipitation fell as snow. The estimated amount of precipitation in the last glacial would have been high enough to provide refugial conditions at Lake Ohrid and to support the continuous existence of arboreal vegetation in the catchment. The improved understanding of the modern isotope hydrology of Lake Ohrid is fundamental for explaining the systematics of past isotope variation and providing context for extended sediment records from the lake, which will provide longer-term palaeoclimate reconstructions covering multiple glacial-interglacial cycles.