Hydrogeological Situation Research Articles

Tiefgreifende Hangdeformation am südlichen Heinzenberg

AbstractGeotechnical assessment of the refilling of the LüscherseeA mass movement of several m/year towards the Nolla stream was detected at the southern Heinzenberg (Grisons, Switzerland) in the 19th century. Debris flows originating from the upper stream valley reached the Hinterrhein valley at irregular intervals, creating temporary dams, which raised the river > 10 m above normal levels. Since 1870, comprehensive mitigation strategies, including torrent control and drainage of the 3‐ha Lüschersee lake situated in the landslide area, have reduced the deformation velocity to approx. 4.3 cm/year and prevented further debris flows.Whether draining of the Lüschersee has influenced the slope deformation was debated back then and has not been conclusively resolved till this day. A potential use of the lake to store water for the local ski area makes the topic current.The integration of geological data with the results of numerical simulations shows that both the mechanical effect of the artificially raised riverbed and the subsequently reduced erosion have a positive influence on the slope, although the effects of changing the hydrogeological situation by refilling the Lüschersee remain uncertain. Therefore, the decision on refilling is dependent on a successful test filling accompanied by permanent GPS measurements.

Analysis and modeling of the hydrogeodynamic situation within the Stebnyk deposit of potassium salts

The purpose of the research was to determine the danger degree of saline waters breakthrough in the mine № 1 due to the self-flooding of mine № 2 by constructing digital models of the basic geological and hydrogeological elements, matching them with the stressed state of rocks within zones of the “Western” and “West” pit shafts and the seal of mines № 1 and № 2. Geophysical studies were carried out by the method of the natural pulsed electromagnetic field of the Earth (ENPEMF), which makes it possible to promptly assess the stress-strain state of rocks. In addition, the geological and hydrogeological situation of the study area was simulated to solve this problem. According to the results of the analysis of hydrogeological regime observations in the period from 2004 to 2017, long-term trends of changes in the groundwater level of the aquifer were established. Taking into account the filling of mines № 2 and drainage, the movement of groundwater from the research area towards the north – northwest is currently noted. There is a difference in groundwater levels up to 13 meters. Based on the results of interpretation of geophysical research data on the basis of which ENPEMF intensity maps were constructed, as well as taking into account geological and hydrogeological models, it was found that no significant anomalies of the field intensity corresponding to catastrophic stressstrain state were observed at present (including through additional hydraulic pressure to testify about the danger of a breakthrough reservoir water). Obviously, that obtained results do not raise any doubts about the further operation of mine № 1 at present. However, when the mine № 2 be completely flooded, it is advisable to check the regime hydrogeological observations of groundwater levels and the ENPEMF measurements to investigate possible changes in the stress-strain state of the rock mass.

To the issue of forecast assessment applicable for hydrogeological conditions of techno-ecosystem at Selidove mine group

The current hydrogeological state of Selidove mine group (named after D.S. Korotchenka, Selidivs’ka, № 2 Novogrodivs’ka and № 1-3 Novogrodivs’ka) is characterized by damaged geological environment, which was derived from coal extraction. According to the geological zoning the Selidove mine group can be classified as Donetsk hard-coal basin within Chervonoarmiqs’ka monocline damaged with tectonic framework.In this study the estimation of hydrogeological situation around the mine № 1-3 Novogrodivs’ka was performed. In undertaken the evaluation the flooding of mining galleries of № 2 Novogrodivs’ka, Selidivs’ka and, mine named after D.S. Korotchenka was taken into account. In terms of surveyor observation data the filtration of mining water from mine № 2 Novogrodivs’ka toward mine № 1 Novogrodivs’ka is possible through the nordic and south blocks, which divide the mining activities processes. The speed of flooding level change at mine № 2 Novogrodivs’ka is about 0.12 meters per day. Bearing this in mind the required time to reach the ground surface (absolute height) +185 meters is about 532 days starting from September 2019. Keeping in mind the volume of extracted underground space and the flooding factor 0.4, the common forecasted water income is about 65-130 m3 per year.In case there is a clear hydraulic connection between separate karst voids the common income of mining water from mining galleries of № 2 Novogrodivs’ka toward mine № 1 Novogrodivs’ka will be not more than 110-175 m3 per year (taking into account the value of income through the weathering zone and aquifer karst clamp).In order to maintain the safe working condition for employees and hydro safety at mine № 1-3 Novogrodivs’ka, it is required to implement the engineering and technical measures to pump the extra mining water (175m3) per year), which corresponds to water income from № 2 Novogrodivs’ka toward № 1 Novogrodivs’ka. It is ensured in case there is a perfect hydraulic connection between the karsts.

Feasibility prediction analysis of groundwater reservoir construction based on GMS and Monte Carlo analyses: a case study from the Dadougou Coal Mine, Shanxi Province, China

After years of mining, groundwater levels drop significantly. Reasonable use of coal mine goaf to build groundwater reservoirs has a large impact on solving the problem of water supplies around coal mines and is of great significance to regional water environmental protection. By investigating the hydrogeological conditions of the coal mines around Datong, Shanxi, the hydrogeological characteristics of the Dadougou mining area were analyzed, and the hydrogeological conceptual model and mathematical model were constructed and calibrated. Groundwater in the region was studied based on Groundwater Modeling System (GMS) simulation results combined with Monte Carlo analysis. The results show that the calibrated hydrogeological conceptual model can reflect the actual hydrogeological situation. It is mainly reflected in the fact that the simulated water level is consistent with the actual observed water level. From March to July, the water level continued to rise and reached its maximum in August, after which, the water level gradually fell. In the end, the water level in December was about 1.1 m higher than the water level in January this year, and the groundwater in the mining area was replenished. The water level change of the study area during the simulation period is greatly affected by the season, and the recharge conditions in the study area are conducive to the construction of an underground reservoir. According to the Monte Carlo analysis from the cumulative curve of calculated groundwater storage capacity, the cumulative frequency at more than 95% is greater than 1.15 × 106 m3, and the storage can thus be built underground.

3-D structure of the discharging zone of the Daginsky hydrothermal system (Sakhalin Island) according to the ground penetrating radar method and well logs

The paper presents the results of a comprehensive analysis of GPR data and geophysical well survey data (gamma-ray logging and self-polarization potentials) to study the 3-D spatial structure of the Daginsky hydrothermal system discharging zone (Sakhalin Island) and its hydrogeological situation. According to the GPR method, the paleo-valleys were identified, the morphology of which indicates the presence of runoff hollows, the accumulation of sandy-aleurite-clay sediments covered with peat formations. It can be concluded that the caprock in this area consists of a pack of water layers and permeable zones. Based on the data of geophysical studies in wells, three zones can be distinguished, each of which is characterized by the corresponding values of gamma activity and changes in the potentials of its own polarization. All this helps in identifying permeable thermally conductive zones. The data obtained are of practical importance.

Hydrogeochemical Model Supporting the Remediation Strategy of a Highly Contaminated Industrial Site

Delineation and understanding the geology and the hydrogeology of a contaminated site, considering its chemical and its biological aspects, are fundamental requirements for successful environmental remediation. The aim of this research is to provide some evidence about the effectiveness of a hydrogeochemical geodatabase to facilitate the integrated management, representation and analysis of heterogeneous data, enabling the appropriate selection, design and optimization of an effective remediation strategy. This study investigates a new technology for the remediation of a dense non-aqueous phase liquid aged source zone, with the aim of enhancing in situ bioremediation by coupling groundwater circulation wells with a continuous production system of electron donors. The technology was verified through a pilot test carried out at an industrial site highly contaminated by chlorinated aliphatic hydrocarbons. The multidisciplinary conceptual model confirmed a complex hydrogeological situation, with the occurrence of active residual sources in low permeability layers. The pilot test results clearly demonstrate a significant mobilization of contaminants from the low permeability zone, and the possibility of favoring the in situ natural attenuation mechanisms based upon biological reductive dechlorination. Different information related to the hydrogeochemical sphere must be integrated and taken into consideration when developing a reliable remediation strategy for contaminated sites.

Warunki kształtowania się odpływu w zlewni Czechówki

<p>W pracy przedstawiono charakterystykę hydrologiczną Czechówki, której zlewnia (80,1 km2) położona jest we wschodniej części Płaskowyżu Nałęczowskiego, subregionu Wyżyny Lubelskiej. Jest to teren o żywej rzeźbie lessowej, z typowymi wąwozami, stromymi zboczami i zrównaniami wierzchowinowymi. W środkowej części zlewni, w dnie doliny Czechówki, wybudowane zostały studnie głębinowe ujęcia „Sławinek”, oddane do eksploatacji w marcu 1961 r. W pierwszych latach jego funkcjonowania stwierdzano zanik przepływu rzeki w obszarze oddziaływania ujęcia. Od początku XXI w., przy zdecydowanie mniejszej eksploatacji wód podziemnych i wyższych opadach atmosferycznych, przepływ Czechówki utrzymywał się na całej długości rzeki. Celem pracy jest charakterystyka hydrologiczna Czechówki, a szczególnie zmian przepływu wynikających z narastającej antropopresji. Podstawę opracowania stanowiły zbierane od połowy XX w. dane hydrologiczne i hydrogeologiczne. W 2002 r. uruchomiono stacjonarne obserwacje wodowskazowe w przekroju zamykającym zlewnię o powierzchni 61 km2 przy Ogrodzie Botanicznym UMCS. Średni przepływ Czechówki w latach 2003–2017 wynosił 0,088 m3·s–1, a odpływ jednostkowy tylko 1,44 dm3·s–1·km2. Zasoby wodne Czechówki mają istotne znaczenie w zaopatrzeniu w wodę Lublina. Wielkość eksploatacji zasobów wody decyduje o charakterze równowagi hydrodynamicznej, o zasilaniu wodami podziemnymi dolin i koryt rzecznych, ewentualnie o ucieczce wody powierzchniowej do podziemia, a także o funkcjonowaniu źródeł i przepływie Czechówki.</p>

Guarding the long-term sustainability of groundwater resources by defining aquifer characteristics and inter-aquifer leakage using airborne EM technologies

The sustainable extraction of groundwater resources requires an understanding of aquifer integrity, geometry and quality, particularly where it is extracted from confined or multi-layered systems, and where shallow, unconfined aquifers are too saline for use either as a source of potable water or for irrigated agriculture or stock. In such situations, a major threat to the longterm sustainability of a groundwater resources is leakage of saline water from formations that overlie and/or underlie the target aquifers. From a hydrogeological perspective both situations demand information on the spatial variations in groundwater quality and information on surface water-groundwater interactions

Investigation of seawater intrusion in the Dibdibba Aquifer using 2D resistivity imaging in the area between Al-Zubair and Umm Qasr, southern Iraq

Electrical resistivity surveying for delineating seawater intrusion was performed in the Dibdibba aquifer in the area between the cities of Al-Zubair–Safwan and Al-Zubair–Umm Qasr in the vicinity of Khor AL-Zubair Channel, Basrah governorate, southern Iraq. Fourteen 2D resistivity profiles with a total length of 14 km were collected in the study area. The resistivity sections were compared with lithological data extracted from 11 boreholes. Thirty-nine groundwater samples were collected within the area and analyzed for chemical constituents; internal hydrogeological reports and unpublished studies were also evaluated. Results reveal the existence of three major resistivity layers, ranging from 0.1 to 130 Ωm at various depths and locations. The first layer has very low electrical resistivity (0.1–5 Ωm) representing a layer saturated with saltwater intruded from Khor AL-Zubair Channel. The second layer shows resistivity in the range of 5–130 Ωm, attributed to a transition zone and an unaffected zone saturated with brackish groundwater. The last resistivity layer (< 3 Ωm) represents coarse-grain sediments saturated with saline groundwater. Furthermore, a hard clay bed (Jojab) appears with a resistivity of 3–7 Ωm in all 2D imaging lines within a depth of 20–28 m. Electrical conductivity (EC) measurements from seven wells collected in 2014 and 2016 show a positive EC difference increasing landward with an average increase of 1927 µS/cm. In addition, six chemical relationships (Na/Cl, [Ca + Mg]/[HCO3 + SO4], SO4/HCO3, SO4/Cl, Mg/Ca and Cl/[HCO3 + CO3]) are used to detect the source of salinity in groundwater. This study proves that extensive use of high-resolution 2D imaging sections, alongside lithological and hydrogeological data, can serve as a useful tool to delineate the boundaries between aquifers, identify hydraulic boundaries between groundwater with different salinities and allocate hard clay layers between the upper and lower Dibdibba aquifer. In general, the combination of 2D imaging and hydrochemistry enables conceptualization of the hydrogeological situation in the subsurface and characterization of the salinity source, here seawater intrusion, in the study area. There have been no studies published so far on the characteristics of saltwater intrusion in the study area, and this study is considered to be important for monitoring and studying the intrusion and regression of seawater.

Conditions for the Sustainable Development of Underground Transport in the Ljubljana Basin

In Ljubljana, the capital of Slovenia, surface road traffic prevails and there is a strong need to free urban areas and use underground space for public transport. As a result of excessive use of combustion engines, the concentration of particulate matter and CO2 emissions in Ljubljana is high and is of public concern. For this purpose, several studies have been made in which sustainable development of underground transport has been considered as an alternative for rail, inter-rail and city traffic. The city of Ljubljana lies on quite a diverse geological substratum, consisting of alluvial and lacustrine deposits. A complex hydrogeological situation comprising a high water table and perched water supply zones located within the urban environment presents a particular challenge for underground construction. For this reason, a research study concerning the sustainable development of underground traffic in the Ljubljana Basin was carried out. The results of the study presented in the paper highlight the possible technological conditions for the development of underground transport with a particular emphasis on sustainability and environmental impact.

Application of remote sensing, GIS and MCA techniques for delineating groundwater prospect zones in Kashipur block, Purulia district, West Bengal

Demand of groundwater resources has increased manifold with population expansion as well as with the advent of modern civilization. Assessment, planning and management of groundwater resource are becoming crucial and extremely urgent in recent time. The study area belongs to Kashipur block, Purulia district, West Bengal. The area is characterized with dry climate and hard rock terrain. The objective of this study is to delineate groundwater potential zone for the assessment of groundwater availability using remote sensing, GIS and MCA techniques. Different thematic layers such as hydrogeomorphology, slope and lineament density maps have been transformed to raster data in TNT mips pro2012. To assign weights and ranks to different input factor maps, multi-influencing factor (MIF) technique has been used. The weights assigned to each factor have been computed statistically. Weighted index overlay modeling technique was used to develop a groundwater potential zone map with three weighted and scored parameters. Finally, the study area has been categorized into four distinct groundwater potential zones—excellent 1.5% (6.45 sq. km), good 53% (227.9 sq. km), moderate 45% (193.5 sq. km.) and poor ~ 0.5% (2.15 sq. km). The outcome of the present study will help local authorities, researchers, decision makers and planners in formulating proper planning and management of groundwater resources in different hydrogeological situations.

Determining the stability of slopes in the conditions of transport infrastructure objects construction

The article is devoted to the stability determining of the slopes, near which are being carried out works on the construction of the foundation of an automobile overpass. The methods of determining the landslide pressure on the retaining structures, accounting for the technological vibration load on the base, which occurs when the sheet pile is submerged into soil base during the excavation are considered. The analysis of the options for usage the strength undrained characteristics of the soil base under vibration influence on them is made. The risk of construction works near the slope is estimated with the forecasting of the safety coefficients and limiting slip surfaces obtained by the finite element method implemented in the PLAXIS geotechnical software. Many factors of influence on the safety of the slope were taken into account: the staging of construction, the change in the hydrogeological situation, the application of technological and vibrational loads. Based on the results obtained, possible types of work to increase the stability of the slope are presented, and conclusions are drawn on the need for additional studies in the field of undrained properties in case of vibrational loads.

ВОДНІ ДЖЕРЕЛА ВОЛИНСЬКОЇ ОБЛАСТІ В СТРУКТУРІ САКРАЛЬНОГО ЛАНДШАФТУ

The sacred landscape is a natural anthropogenic system which is associated with certain life symbols, myths, important dates, and religious feelings. It is of extreme importance to a person or a group of people and is paid special attention. Water has been one of the main sacred symbols in society both in the past and present. In the religious rituals around the world, water has always been given the key role. In Ukraine, among all water sources, springs are often considered sacred. This is due to the legends about the healing power of spring water and the miracles observed in it (connected with religious objects or saints). Sacred springs constitute a special type of water sources. They are used in different rituals, for example, when asking for rain or in the rituals to end a drought. The studies of the hydrogeological situation in Volyn region show that in the process of springs’ formation, the aquifers of the Neopleistocene, Holocene and Cretaceous deposits play an important role. The groundwater in the given area belongs to the hydrocarbonic class (with the calcium group mainly of the first or second type). The springs of Volyn region are often formed in the valleys of rivers, and ravines. They are supplied by groundwater. This is due to the physical and geographical characteristics of the region. The peculiarities of the springs in the structure of the sacred landscape are described. The water in these springs is usually transparent, of good quality, and is safe to drink. The sacred landscape is regarded as a complex system, where not only natural and anthropogenic but also spiritual components interact with each other. Their function is to convey historical information to future generations. The study describes the spatial, temporal, and morphological structure within the sacred landscape. The spatial structure of the sacred landscape contains the following components: – landscape structure. It consists of the integral system formations, which are the result of the development of area unities; – spring. It is the nucleus or the centre of the sacred landscape. It has a spiritual, cultural, healing, aesthetic value for a certain group of people; – abiotic components include hydrogeological, geomorphological, microclimatic characteristics of the sacred landscape; – flora and fauna; – anthropogenic and technological component. It includes a certain infrastructure within the sacred landscape (for example, a paved road leading to the spring, a well, a chapel, a church); – human. Due to the fact that the springs’ aquifer is usually close to the surface and the water is not pumped, springs require environmental and sanitary care due to the possibility of siltation, drying up, and pollution. That is why this subsystem also plays an important role in landscape functioning. The most famous water sources in Volyn region, which are also used as pilgrimage and worship destinations, are the following: the spring between the Bug river and its right tributary Luha (not far from Budiatychi in Ivanychivsk raion), the spring in Stara Lishnia village (Ivanychivsk raion), the spring in Laskiv village in Volodymyr-Volynsk raion, the spring in Kivertsi raion (7 km away from Sylne village). In order to preserve the water springs within the sacred landscape in Volyn region, it is necessary to monitor the ecological situation, to take measures that will ensure not only their conservation but also will improve their aesthetic, ecological, sanitary condition.

Hydrogeological modelling in the geotechnical forecast

Underground development project activities for structures located below existing level of groundwater can cause changes in hydro-geological conditions on the construction site and adjacent territories and lead to development of unfavourable engineering-geological processes. Article presents results of hydrogeological forecast at the construction site with foundation pit enclosed in diaphragm wall. To recreate existing hydrogeological conditions and to create accurate model, inverse problem was solved with a multivariate selection of the filtration parameters of the modeled system in such way that there was a satisfactory alignment of modeled groundwater levels and groundwater levels marked during well-drilling, and analytical data, acquired during analysis and compilation of existing hydrogeological data. Upon solution of inverse problem to replicate existing hydrogeological conditions on the model, a series of forecasting tasks was undertaken to assess the impact of planned construction on hydrogeological situation of the construction site and adjacent territories. Construction was modelled in a multi-variant setting for a completely impermeable diaphragm wall and a permeable diaphragm wall with coefficient of filtration of 0.005 m/day. It is advisable to provide a comprehensive hydrogeological and geotechnical forecast at the design stage as it helps to predict how changes in hydrogeological regime affect deformation behaviour of surrounding buildings.

Geoelectrical investigations on coastal aquifers to assess the saline water intrusion in Nghi Son, Thanh Hoa

This paper presents the results of geoelectrical investigations for delineation of the aquifers and determination the hydrogeological situation of the water bearing in Nghi Son economic zone. Following the geophysical investigations and the stratification of geological formation, the boundary between fresh and saline water is determined in study area. The geoelectrical measurements indicate that the saline water intrusion within the Pleistocene aquifer occurs along the coastline of the Northeast part of Nghi Son economic zone. The values of formation resistivity below 20 Ωm imply that the water bearing is brackish or saline water. The geophysical results are corresponding to borehole nearby profiles. The geoelectrical methods have proved to be appropriate tools to investigate 2D geological structure in the coastal areas that have low resistivity of subsurface.

Storm water injection in Bahrain: pilot studies

Kingdom of Bahrain often suffers from urban flooding problems despite being a desertic country. An attempt has been made in this contribution to study the efficacy of the storm water injection systems not only in tackling urban flooding problems but also in augmenting the depleting ground water resources of the country. Two pilot studies were carried out in a centrally located area, one in a relatively open area and another in a densely populated location. A set of one recharge well and one observation well of about 40 m depth and 30 m apart was drilled in each site. Storm water was injected into the recharge wells after allowing it to pass through a specially designed natural filter system. Ground water levels were monitored at the observation wells on monthly basis and water samples were collected periodically during and after the rainfall events for chemical analysis. Initial results showed that the volume of storm water injected is proportional to the volume of storm water generated in an area. However, in the long run, the injection well having favourable hydrogeological situation and lesser silts in the storm water performed better in terms of total recharge despite having lesser volume of storm water available. Ground water quality for some parameters such as lead and cadmium remained an issue of concern, but could be controlled through construction of stricter filter system. Dilution of the injected storm water with the host ground water too significantly reduced the risks of contamination. The injection well located in the open area performed better than that of the densely populated area despite having lesser volume of storm water available. Site selection of the recharge wells, therefore, plays a vital role in the efficacy of a storm water injection system.

A Velocity-Oriented Approach for Modflow

When considering three-dimensional groundwater flow, the hydrogeological community widely uses the MODFLOW model based on the head-oriented approach (HOA). However, a great deal of hydrogeological situations requires an extremely accurate assessment of the Darcy velocity in three dimensions. Despite the good numerical approximation of the piezometric head offered by MODFLOW, it does not guarantee sufficient accuracy in estimating all three components of the flow velocity. As an alternative, this article presents the MODFLOW-based velocity-oriented approach (VOA), which can approximate the three components of the groundwater velocity with high accuracy. The article gives comprehensive theoretical background and a comparison of the HOA and VOA approaches. Importantly, the authors show how the VOA equations with the VOA boundary conditions can be implemented and solved with MODFLOW. Recently, the VOA has become a basis for new version of MODFLOW. The two approaches are effectively combined and compared using Visual MODFLOW for a simple case of river–aquifer interaction.

Effects of different boundary conditions on the simulation of groundwater flow in a multi-layered coastal aquifer system (Taranto Gulf, southern Italy)

The evaluation of the accuracy or reasonableness of numerical models of groundwater flow is a complex task, due to the uncertainties in hydrodynamic properties and boundary conditions and the scarcity of good-quality field data. To assess model reliability, different calibration techniques are joined to evaluate the effects of different kinds of boundary conditions on the groundwater flow in a coastal multi-layered aquifer in southern Italy. In particular, both direct and indirect approaches for inverse modeling were joined through the calibration of one of the most uncertain parameters, namely the hydraulic conductivity of the karst deep hydrostratigraphic unit. The methodology proposed here, and applied to a real case study, confirmed that the selection of boundary conditions is among the most critical and difficult aspects of the characterization of a groundwater system for conceptual analysis or numerical simulation. The practical tests conducted in this study show that incorrect specification of boundary conditions prevents an acceptable match between the model response to the hydraulic stresses and the behavior of the natural system. Such effects have a negative impact on the applicability of numerical modeling to simulate groundwater dynamics in complex hydrogeological situations. This is particularly important for management of the aquifer system investigated in this work, which represents the only available freshwater resource of the study area, and is threatened by overexploitation and saltwater intrusion.

Using artificial neural network and multivariate analysis techniques to evaluate road operating conditions

Regional paved roads are low volume roads with a prevalence of heavy traffic. In the world, these roads concern about 80% of the total road network; however, the traffic that affects these roads is about 20%. Since regional roads are characterized by weak demand, budget for their management/maintenance is very low. This produces considerable difficulties in the choice of strategies for maintenance planning and scheduling. For this reason, the recurring topics of research in this field deal with typical roads issues and aim to develop low cost tools and methods. The study proposes a decision support system to evaluate regional paved roads operating condition in relation to the hydrogeological situation. In particular, the system allows to evaluate in a quick and easy manner, the operating conditions of the road, through low-cost tools (i.e. using low economic resources). This is very useful in the case of LVRs because administrations for these roads have a limited budget. The procedure is developed on a regional paved roads network based on more than 80 roads located in Southern Italy. Data is collected by direct surveys in the field and is integrated with cartography and information available in road agency records. From data analysis, obtained using two different techniques, an easy and quick use procedure is made. In particular, Model 1 is built through multivariate analysis and Model 2 using the artificial neural network (ANN) technique. The results show the validity of the two models in Regional paved roads operating conditions estimation in relation to hydrogeological situations of sites. Both models show good reliability. In particular, the first model (Model 1) is characterized by a high level of significance (p < 0.01) and by a coefficient of determination equal to 0.82. Comparative tests between the second model (Model 2) on which standard tests cannot be performed for obvious reasons, and the first model (Model 1). The results show that the ANN model (model 2), characterized by lower residual, simulates more accurately than the second (Model 1).

FROM FLOOD TO DROUGHT – CHANGES OF HYDROGEOLOGICAL SITUATION IN POLAND BETWEEN 2010–2015

Hydrogeological and hydrological situation is primarily conditioned by climate and natural features, however, land use and catchment management are also important. Both droughts and low groundwater levels, as well as floods and flooding have been occurring in Poland in the past and they will certainly be repeated in the future. Undertaking measures aimed at effective mitigation of effects of such extreme events is possible. Nevertheless, this requires reliable and verifiable hydrogeological forecasting. In order to meet these expectations, the Polish Hydrogeological Survey undertakes cyclic assessments of hydrogeological situation in Poland on a national scale and carries out projections of its changes. This paper presents results of an analysis of hydrogeological situation in Poland between 2010–2015, during which a transition from high groundwater levels in 2010 and 2011 (related to flood events in 2010) to low levels (related to the drought in 2015) were observed. To present the spatio-temporal changes of hydrogeological situation in years 2010–2015 the authors analyze extreme groundwater levels in the considered period based on data from the national groundwater monitoring network of the Polish Geological Institute - National Research Institute.