Surface Water Infiltration Research Articles

Infiltration of surface water through subsidence failure assessment applying electric prospecting, case Aguascalientes Valley, Mexico

Abstract. Land subsidence is an anthropogenic hazard triggered by different causes, one of them is groundwater overexploitation over aquifer systems composed for granular compressible sedimentary fill. One of the effects of this phenomenon is the generation and reactivation of ground failures, becoming risk points for aquifer pollution through the fast infiltration of contaminated water. A system of failures and fractures has developed in the Aguascalientes valley since 1980's when groundwater overexploitation became intensive. Currently, the entire valley present regional subsidence and several ground failures have developed; many of them crossing surficial water flows and sewage pipes, thus, inducing filtering of domestic wastewater to the subsoil and increasing the environmental hazard for the aquifer system. In this work, we present the results of a study to assess the surficial water infiltrations through a subsidence related ground failure crossing a small stream, which carries domestic wastewater. Additionally, we investigate the acquisition method of Electrical Resistivity Tomography (ERT) and the electrode placement more suitable to detect the flow of contaminated water through the studied ground failure. To find out the potential leakage, we use electric geophysical methods, applying Schlumberger, Wenner and dipole-dipole arrangements with electrode separations from 2.5 to 10 m in order to explore a depth from 9 to 30 m. The obtained results showed that the Schlumberger configuration appears to be more helpful to detect changes in the stratigraphy toward depth, while dipole-dipole and Wenner are more suitable to detect lateral variations such as the vertical wastewater leakage in the first 6 to 8 m depth. Resulted resistivity models showed that in the first 10 m depth, the contaminant flow follow with a vertical path through the ground failure, then, the it becomes horizontal, flowing through the more permeable soil strata. Therefore, for the studied sites, the filtration of domestic wastewater through ground failure does not represent an immediate hazard to the aquifer system. Nevertheless, ground failures crossing damaged wastewater pipes or contaminated surficial water flows in Aguascalientes Valley, could induce the infiltration of polluted water to the near surface strata, favoring a potential aquifer pollution in a long term.

Application of 222Rn and microbial diversity to characterize groundwater/surface-water interactions in a riverside area (South Korea)

The interactions between groundwater and surface water under a river island in South Korea were investigated. Sampling was focused on the western part of the island, where a groundwater heat pump system with groundwater monitoring wells has been installed. A riverside area was selected for the system because a high specific capacity was expected. However, surface-water intrusion remains a major concern, as the efficiency of the system can be impaired by groundwater temperature changes following surface-water infiltration. A combination of radon (222Rn) concentrations and microbial diversity was analyzed, along with hydraulic data. A process for estimating residence time based on 222Rn data and flow direction was developed to identify relationships with microbial diversity. The spatial distribution of 222Rn concentration was affected by fluctuations of river water levels caused by surrounding dam discharge and seasonal effects. Groundwater flowmeter data supported observations on these distributions. The estimated residence times indicated that river-water infiltration into the study site affected the groundwater flow direction. The microbial diversity, based on cluster analyses after pyrosequencing, showed significant variation with river flow direction and rainfall events, which was in accordance with the 222Rn tracer results. The combination of frequent 222Rn concentration measurements with microbial data allows better characterization of the dynamic interactions between groundwater and surface water.

Identification of suitable sites and structures for artificial groundwater recharge for sustainable groundwater resource development and management

Artificial recharge is the process of augmentation of the natural infiltration of precipitation or surface water into aquifers by some methods of construction, spreading of water or by artificially changing natural conditions. Upper Betwa watershed, has been taken under study is a semi-arid region, part of Obedullahganj block, Raisen district, M.P., India. The area is hard rock terrain with rugged topography and varying geology. Long term analysis of groundwater level conducted by CGWB, Bhopal has shown sharp decline in groundwater level from past one decade. To increase the groundwater potential of the area, action plan for artificial groundwater recharge has been developed using remote sensing and GIS techniques. Survey of India toposheet no's 55 E/8, 55 E/12, 55 F/5 & 55 F/9, GSI, 2002 resource map, LANDSAT 8, and SRTM (DEM) satellite data and NBSS&LUP soil map were processed in ArcGIS to prepare the various thematic layers viz. Geology, geomorphology, topography, soil, land use/land cover, slope, lineament, drainage and drainage density. Sub-watershed wise action plan of the area has been developed for the area using these thematic layers following the criteria given by NRSA, 1995. In the action plan, development of water harvesting structures (Check dam, Nala bund, Contour bund, Gully plug etc.) were proposed. These structures will provide a measure of artificial recharge in this hard rock terrain by collecting of the surface runoff and increasing the surface area of infiltration. Further, the developed action plan addresses identification of sites for groundwater recharge, through the anticipated artificial recharge structures. Thus, it is suggested that execution of the proposed sub-watershed wise action plan will help in development and management of groundwater resources of the area. Excavation of the proposed structures at their suitable sites identified will enhance the groundwater recharge potential of the area.

Groundwater study in Subang Industrial park and its recharge area as a suggestion for establishing recharge and discharge zones of Subang Groundwater Basin

This research was conducted in Subang Groundwater Basin, West-Java, related to the prohibition of groundwater extraction in the Subang Industrial Park (SIP) area. This is because the area is considered as the Recharge Zone of the groundwater basin. The purpose of this study is to determine whether SIP stands above the Recharge Zone or not, moreover, find out which part of the Basin that supplies groundwater aquifers of SIP. The method used in this study is applied of DRASTIC method using ArcGIS and conducting field research measuring the infiltration rate of soil formations at selected points in the Basin, geologic and hydrogeological mapping of Lakes. The results of this study indicate that the SIP is indeed built on a recharge area, the soil where the SIP is established, has ability to infiltrate rainwater. However, the results of more detailed observations of wellbore logs in this area, it is known that between the groundwater aquifer used in SIP and the infiltration zone of the ground surface is separated by impermeable clay layers. This ensures that there is no relationship between surface water infiltration and groundwater being extracted by factories in the areas. Therefore, it is certain that the recharge area originates from other areas in the Basin. Key words: aquifer, recharge area, Subang Groundwater Basin.

Root morphological characteristics and soil water infiltration capacity in semi-arid artificial grassland soils

Surface water infiltration is an important process to meet plant water needs and an important part of the hydrological cycle via groundwater recharge, with special relevance in semi-arid regions. This study evaluated the relationships between grassland plant root morphological characteristics and soil water infiltration rates (IR: initial, steady and average). For this purpose, five artificial homogeneous grasslands (Melilotus suaveolens, Medicago sativa, Panicum virgatum, Bromus inermis and Miscanthus sinensis) without irrigation or fertilization were studied in the Loess Plateau. The observed steady IR were significantly different between the 1-year grasslands: M. suaveolens >M. sativa >P. virgatum >B. inermis >M. sinensis. The root length density and root surface area were negatively correlated with the average, initial and steady IR at different soil depths (p < 0.05). However, the root volume did not significantly influence IR. The stepwise multiple regression determined that the main factors controlling IR were the root length density at the depth of 5−30 cm and root surface area at the depth of 10−20 cm. Our results provide insight into the influence of grassland root morphological characteristics on water infiltration in drylands and are of interest for soil water supply programs in forage production.

Pore-water chemistry and its influence on rock mechanical properties and hydrogeophysical processes in a mudstone slope in the southwestern Taiwan badlands

Bedrock characteristics and its influence on hydrogeophysical processes in a Plio-Pleistocene mudstone slope were examined in southwestern Taiwan. Previous works carried out in this area indicated seasonal patterns of the bedrock physical properties and deterioration of the mechanical strength during weathering to generate extremely high rates of erosion during heavy rainfall, thereby forming badland topography. This area has a humid subtropical climate that is characterised by distinct dry and rainy seasons. During the rainy season, high rates of erosion of the weathered mudstone occur during rainfall events. To investigate impact of characteristics of bedrock physical properties on hillslope weathering and erosion processes in this area, we analysed the pore-water chemistry, specific surface area, and swelling of the mudstone of the studied slope and performed in situ monitoring of water content and pore-water electrical conductivity at 2.5–40 cm depths near the slope surface. The results indicate that the mudstone contains saline pore water, is categorized as dispersive, and has a dense fabric, thereby favouring the occurrence of rock mechanical breakdown due to chemical osmosis. The influence of rock mechanical properties and bedrock behaviour on the hydrogeophysical processes near the slope surface varies with the season. During the dry season, the water content of the mudstone near the slope surface decreases, causing desiccation cracks to form and concentrating salt on rock surfaces. Water contents at 40 cm depths increased within 1 h after rainfalls during the monitoring intervals of the dry season, suggesting that surface water infiltrates rapidly by gravity into networks of cracks during infrequent rain events. During the following rainy season, intense rainfall events moisten the slope surface layer and increase the volume of the mudstone by swelling caused by chemical osmosis. The swelling is associated with an enlargement of the pore size of the mudstone during the dilution of saline water by fresh rainwater, with the greatest amount of swelling occurring at or near the surface where salt is most concentrated. Water contents at 40 cm depths scarcely responded to rainfalls during the monitoring intervals of the rainy season, suggested that this swelling closes desiccation cracks and prevents surface water from migrating downwards into the slope. The resulting seasonal erosion occurs by slope surface wash caused by intense rain during the late rainy season. The newly exposed mudstone on the slope starts to become desiccated during the subsequent dry season, and a new cycle of weathering commences.

Potential infiltration and morphometry in the Arroyo Grande basin, Sucre Colombia

For areas that supply underground water sources, it is important to identify the conditions of circulation and infiltration of surface water as a fundamental contribution to the recharge, sustainability and protection of aquifers. A study of the potential infiltration capacity considering the geomorphological aspects in the Arroyo Grande basin, Sucre, Colombia is presented. The aquifers of the study area are at risk of water supply due to the intense extraction and contamination by urban discharges in the surface currents of the basin. Morphometric indicators were applied to study the forms and dynamics of currents; For the estimation of the potential infiltration, the curve number method (CN-SCS) was used; all analyzes were performed with GIS tools. The results described the drainage conditions of the surface, identified the areas with the highest Infiltration potential over the Morroa aquifer, and the factors that directly influence the water regulation process.

Water quality changes and organic matter removal using natural bank infiltration at a boreal lake in Finland

Managed aquifer recharge (MAR) refers to intentional infiltration of surface water to an aquifer for facilitating natural water treatment and storage. MAR is often used as a treatment to remove natural organic matter from water in drinking water production. The sustainability of MAR depends on how the aquifer capacity to remove organic matter will evolve over the long term. This report explores the behavior of MAR systems by using a natural lake–aquifer system as a surrogate. Natural infiltration of lake water to groundwater has been going on for millennia at the research site in Finland chosen for this study. According to the measurements, the mean concentration of total organic carbon (TOC) in lake water was 3.0 mg/L. Within the distance of 3 m from the lake bank (retention time 7–15 days), already 46% of TOC was removed. At greater distances along the flow paths within the aquifer, 80–90% of TOC was removed. The observed TOC removal in the aquifer was slightly higher than the reported values at MAR sites, indicating that MAR can be an effective solution to the problem of removing natural organic matter in the long term. Signs of accumulation of organic matter were not observed in the aquifer, which suggests that biodegradation was the main removal method, and the role of sorption was minor. Several processes had an impact on oxygen levels in the aquifer, which led to spatial and seasonal changes in the redox conditions and in the iron and manganese concentrations in groundwater.

Gas and liquid permeability in the variably saturated compacted loess used as an earthen final cover material in landfills

Landfill final covers are crucial to mitigating both the emission of landfill gases and surface water infiltration into solid wastes. Loess that is widely distributed in Northwest China has been transformed into earthen final cover (EFC), although not yet on a large scale. There remains a need for laboratory bench-testing in assessing the performance of this loess as an EFC material, particularly with respect to gas and liquid permeability. To evaluate gas and liquid permeability in the variably saturated loess at the laboratory scale, loess specimens with various resultant dry densities and post-compaction water contents were prepared. Laboratory tests were performed including constant gas pressure-gradient tests and wetting tests in a step-wise fashion to measure gas and liquid permeability as well as water retention behaviours. Large differences were found between intrinsic permeability to gas and liquid, and an empirical power relationship was proposed to characterize the measured intrinsic permeability to gas and liquid relative to the void ratio. The data of relative gas permeability as a function of liquid saturation plotted nearly along a single curve for all dry densities; this was also the case for the relative liquid permeability. Based on the regression results of water retention curves, the measured relative gas permeability values were well described by the van Genuchten–Mulaem (vG-M) model, and a certain difference between the relative liquid permeability evaluated by the vG-M model and the modified Childs and Collis-George equation. An unique relationship was found between the ratio of liquid to gas permeability and liquid saturation for all dry densities, in a range of residual liquid to gas saturation. An empirical model was proposed to efficiently describe gas and liquid permeability of the compacted loess at various liquid saturations and dry densities as well as the data of the loam from another experimental program.

Tracing sources of natural organic matter, trihalomethanes and metals in groundwater from a karst region.

Groundwater offers an important source for drinking water around the world; however, groundwater quality is under increasing pressure and is particularly vulnerable in karst areas. Total organic carbon (TOC) is significantly related to groundwater quality and when not removed by water treatment processes can give rise to the formation of disinfection by-products trihalomethanes (THMs) above the level of compliance. This study investigated the source of organic matter giving rise to the THM exceedances in a groundwater supply in a karst area. Results highlightedthatsource waterfor this groundwater supply was prone to surface water infiltration linked to rainfall events; was not accurately captured in the zone of contribution (ZoC); had inadequate treatment of natural organic matter (NOM) and suffered THM exceedances in 45% of sampling events. THMs were mostly represented by chloroform and caused by terrestrial delivered reprocessed organic matter. This work will support water managers tasked with decision-making.

Impact of heat advection on the thermal regime of roads built on permafrost

AbstractIn northern regions, transportation infrastructure can experience severe structural damages due to permafrost degradation. Water infiltration and subsurface water flow under an embankment affect the energy balance of roadways and underlying permafrost. However, the quantification of the processes controlling these changes and a detailed investigation of their thermal impacts remain largely unknown due to a lack of available long‐term embankment temperature data in permafrost regions. Here, we report observations of heat advection linked to surface water infiltration and subsurface flow based on a 9‐year (from 2009 to 2017) thermal monitoring at an experimental road test site built on ice‐rich permafrost conditions in southwestern Yukon, Canada. Our results show that snowmelt water infiltration in the spring rapidly increases temperature in the upper portion of the embankment. The earlier disappearance of snow deposited at the embankment slope increases the thawing period and the temperature gradient in the embankment compared with the natural ground. Infiltrated summer rainfall water lowered the near‐surface temperatures and subsequently warmed embankment fill materials down to 3.6‐m depth. Heat advection caused by the flow of subsurface water produced warming rates at depth in the embankment subgrade up to two orders of magnitude faster than by atmospheric warming (heat conduction). Subsurface water flow promoted permafrost thawing under the road embankment and led to an increase in active layer thickness. We conclude that the thermal stability of roadways along the Alaska Highway corridor is not maintainable in situations where water is flowing under the infrastructure unless mitigation techniques are used. Severe structural damages to the highway embankment are expected to occur in the next decade.

Impact of river reconstruction on groundwater flow during bank filtration assessed by transient three-dimensional modelling of flow and heat transport

Bank filtration (BF) is an established indirect water-treatment technology. The quality of water gained via BF depends on the subsurface capture zone, the mixing ratio (river water versus ambient groundwater), spatial and temporal distribution of subsurface travel times, and subsurface temperature patterns. Surface-water infiltration into the adjacent aquifer is determined by the local hydraulic gradient and riverbed permeability, which could be altered by natural clogging, scouring and artificial decolmation processes. The seasonal behaviour of a BF system in Germany, and its development during and about 6 months after decolmation (canal reconstruction), was observed with a long-term monitoring programme. To quantify the spatial and temporal variation in the BF system, a transient flow and heat transport model was implemented and two model scenarios, ‘with’ and ‘without’ canal reconstruction, were generated. Overall, the simulated water heads and temperatures matched those observed. Increased hydraulic connection between the canal and aquifer caused by the canal reconstruction led to an increase of ~23% in the already high share of BF water abstracted by the nearby waterworks. Subsurface travel-time distribution substantially shifted towards shorter travel times. Flow paths with travel times <200 days increased by ~10% and those with <300 days by 15%. Generally, the periodic temperature signal, and the summer and winter temperature extrema, increased and penetrated deeper into the aquifer. The joint hydrological and thermal effects caused by the canal reconstruction might increase the potential of biodegradable compounds to further penetrate into the aquifer, also by potentially affecting the redox zonation in the aquifer.

Potential groundwater recharge in north-western India vs spaceborne GRACE gravity anomaly based monsoonal groundwater storage change for evaluation of groundwater potential and sustainability

The north-western part of India has been affected by severe ground water depletion. In this study, an attempt has been made to assess potential ground water recharge of North West (NW) India and its comparison with Gravity Recovery and Climate Experiment (GRACE) gravity anomaly based monsoonal groundwater storage change. An assessment of potential groundwater recharge was done in terms of terrain suitability for groundwater recharge and average monsoonal recharge. Terrain suitability was assessed based on hydrogeology and terrain parameters which were then integrated with the spatial variability in monsoonal recharge (expressed as the surface water column available for underground infiltration). The average monsoonal groundwater storage (GWS) change was derived from GRACE terrestrial water storage (TWS) change. An evaluation of potential groundwater recharge vs. terrain suitability for groundwater recharge and potential groundwater recharge vs. monsoonal GRACE GWS change shows that there is high terrain suitability but low potential groundwater recharge in the north-western part of NW India essentially due to very low precipitation. In the north-western part, terrain suitability is high primarily due to the presence of sandy alluvium, deeper sandy loam soil and flat terrain. The remaining alluvial plains, lithologically covered by unconsolidated sediments with loamy-silty-sand or clayey-loamy-silty-sand soils, show moderate terrain suitability. Rainfall induced surface water infiltration capacity is high in Upper Ganga drainage basin and in major parts of Narmada drainage basin but low to very low in Luni-Ghaggar drainage basin and in major parts of Yamuna and Chambal drainage basins. The average monsoonal GRACE GWS change is low in the north-western part of NW India which is in agreement with potential groundwater recharge scenario. The comparison between precipitation, terrain infiltration potential and GRACE gravity based average groundwater storage observations enables to evaluate prospective and vulnerable areas in terms of groundwater availability and sustainability in NW India.

Improvement of Internal Stability of Alluvial Clay from Famagusta Bay, Cyprus, Using Copolymer of Butyl Acrylate and Styrene

ABSTRACT The internal stability of alluvial clays may be significantly compromised during a heavy rainfall due to infiltration of surface water causing sudden inundation, softening, and loss of erosion resistance or mechanical strength. Most of the available stabilization methods for clay soils employ pozzolanic or other cementitious binders, creating a chemically bound clay-admixture matrix. These admixtures commonly require a curing period after placement and compaction. Alternatively, aqueous polymers can be used in diluted form without any need for a curing period. Aqueous polymers can form agglomerations of clay particles enclosed in a matrix of polymer chains, held together by electrostatic and hydrogen bonding, improving erosion resistance. In this research, an aqueous polymer, namely, copolymer of butyl acrylate and styrene (CBAS), is mixed with alluvial clay sampled from Famagusta Bay, Cyprus, and the clay stability test is performed as a basis for assessing the degree of improvement on erosion resistance. A time-dependent approach for the evaluation of test results is followed to increase the accuracy of the analysis of the actual behavior observed during the test. A significant improvement in the erosion resistance is observed in treated test specimens. The mode of collapse of specimens during the clay soil stability test when aqueous polymer is used also changed from being gradual cracking and slaking to explosive. The swelling behavior and the effect of drying on the erosion resistance are also observed in the testing program. X-ray diffraction analysis and Fourier transform infrared spectroscopy are performed for observation of the effect of CBAS on microstructural interactions, such as electrostatic bonding and changes in soil fabric.

Characteristics and Genesis of Loess High Slope on the West Side of Shuiliandong Colliery in Binxian County

The loess high-slope on the west side of water curtain cave colliery is an old landslide debris back-wall. There is an old landslide debris deposit at bottom of the slope. Surface water can infiltrate into the slope through loess uprightness joints and cranny. The groundwater flow gradually causes the formation of water cavities in the upper slope region. The slope further has loess stratification, obliquity (from 5° to 10°) and paleosols place. Surface water infiltrates into paleosols and induce water cavity exit with the top water cavity transfixion. The paleosols ideally prevents water. The loess stratification leans to ravine. The slope is unstable and will fail under the action of precipitations.

Stress-Dependent Pore Deformation Effects on Multiphase Flow Properties of Porous Media

Relative permeability and capillary pressure are the governing parameters that characterize multiphase fluid flow in porous media for diverse natural and industrial applications, including surface water infiltration into the ground, CO2 sequestration, and hydrocarbon enhanced recovery. Although the drastic effects of deformation of porous media on single-phase fluid flow have been well established, the stress dependency of flow in multiphase systems is not yet fully explored. Here, stress-dependent relative permeability and capillary pressure are studied in a water-wet carbonate specimen both analytically using fractal and poroelasticity theory and experimentally on the micro-scale and macro-scales by means of X-ray computed micro-tomography and isothermal isotropic triaxial core flooding cell, respectively. Our core flooding program using water/N2 phases shows a systematic decrease in the irreducible water saturation and gas relative permeability in response to an increase in effective stress. Intuitively, a leftward shift of the intersection point of water/gas relative permeability curves is interpreted as an increased affinity of the rock to the gas phase. Using a micro-scale proxy model, we identify a leftward shift in pore size distribution and closure of micro-channels to be responsible for the abovementioned observations. These findings prove the crucial impact of effective stress-induced pore deformation on multiphase flow properties of rock, which are missing from the current characterizations of multiphase flow mechanisms in porous media.

Detioracja kamiennych obiektów budowlanych - główne czynniki i procesy

Deterioration of stone buildings – main factors and processes. A b s t r a c t. The condition of stone building objects is determined by many physicochemical factors and destructive processes. All stone materials are subject to natural aging, losing many of their primordial properties. The destructive processes and decline of the stone quality are termed the “deterioration” (Latin: deterior – worse). This definition is close to that of rock weathering. However, weathering and deterioration are two different concepts.Weathering is a large-scale process related to large rock masses located in a geological environment. By contrast, deterioration refers to processes destroying a stone material, which has already been treated with stonework. The most known field of research for the deterioration processes are all historical old monuments. It is assumed that the deterioration reaches such a depth as those influenced by changes that take place on the stone object surface during the adsorption of solar radiation and deep penetration of oxygen and carbonated water, coming from infiltration of atmospheric precipitation or surface water. The most prominent factors of deterioration are caused by temperature changes, crystallization pressure of salts dissolved in water, gaseous pollutants and dust contained in the air, wind, hail and snow action, adsorption of acidic chemical substances, and dust particles, activity of microorganisms, fungi and lichens living on surfaces of monuments.

Sediment production and soil water infiltration under different simulated rainfall characteristics

ABSTRACT The study was carried out to evaluate sediment production, water infiltration and surface runoff in an Ultisol under simulated rainfalls with similar erosivity, but different combinations of intensity (Int) and duration (Dur). The rainfalls were applied after soil tillage in the period from August to September 2017, in Seropédica, RJ State, Brazil. Using a computer program, the treatments were defined from the erosivity calculated for a rainfall with intensity of 60 mm h-1 and duration of 60 min, resulting in the other combinations of Int and Dur: 44.5 mm h-1 and 106 min; 53.5 mm h-1 and 78 min; 66.9 mm h-1 and 48 min; and 76.5 mm h-1 and 38 min, in a completely randomized design with five repetitions. Sediment production varied from 2.17 to 6.11 g m-2, respectively, in the treatments with Int 53.5 mm h-1 and Dur 78 min and Int 44.5 mm h-1 and Dur 106 min. Stable infiltration rate (mm h-1) were 21.6, 37.7, 31.4, 29.5, and 22.4, respectively, in the treatments Int 44.5 mm h-1 and Dur 106 min; Int 53.5 mm h-1 and Dur 78 min; Int 60.4 mm h-1 and Dur 60 min; Int 66.9 mm h-1 and Dur 48 min; and Int 76.5 mm h-1 and Dur 38 min. The different combinations of intensity and duration of rainfalls with similar erosivity change sediment production, but do not significantly influence surface runoff and water infiltration in the soil.

Hydro-climate characteristics of the karst system of Wintimdouine cave (Western High Atlas, Morocco): monitoring and implications for paleoclimate research

The cave of Wintimdouine, located in a semi-arid context in Morocco, comprises the longest-known underground river in Africa. This cave system faces many challenges related to anthropogenic and climate forcing. Therefore, it has become necessary to understand the functioning of the aquifer system of Wintimdouine and how the regional climate affects its environment. Herein, we used different approaches based on a 4-year monitoring to shed light on the hydro-chemical behavior and stable isotopes contents of water samples, climate settings inside the cave, and moisture trajectory analyses. Chemical analyses show that groundwater is dominated by bicarbonate and calcite with an excellent chemical quality of cave water, suggesting an active recharge of the aquifer system which constitutes the main drinking source in the region. The stable isotope composition is consistent among rainwater, cave water and groundwater samples outside the cave. The evaporation effect is not significant, probably due to the rapid infiltration of surface water to the epikarst and vadose zone, which is favored by the abundance of exo-karstic forms above the cave. The cave monitoring indicates that periods of increased drip water flow induce an increase of temperature and humidity inside the cave, mainly during the spring–summer season. The high relative humidity and the relatively stable temperature favor the carbonate deposition under equilibrium conditions with drip water inside the cave. Furthermore, the moisture trajectory analysis confirms that the predominant air masses reach Wintimdouine cave from the North Atlantic Ocean, consistent with the mean deuterium-excess value of rainwater samples and the NAO-related westerly winds. Hence, we highlight the potential of Wintimdouine speleothem δ18O as a proxy of past climate variability at a regional scale.

Sprinkling infiltration as an artificial groundwater recharge method – Long-term effects on boreal forest soil, tree growth and understory vegetation

The artificial recharge of groundwater by infiltrating surface water through forest soil has been introduced as a groundwater producing practice in Finland. As a result, the forest soil, as well as the whole ecosystem, is subjected to extremely high inputs of carbon and nutrient rich lake water.The effects of sprinkling infiltration on forest soil, tree growth and understory vegetation and their respective recovery were studied on a forested esker in central Finland. The Scots pine-dominated experimental plots were sprinkled with lake water in 1998–2001 and sampled after a 12–15-year recovery period. Soil pH and base cation concentration, as well as the rate of net N mineralization were significantly higher at the plots that had been infiltrated. The concentrations of base cations calcium and magnesium were thousands of times higher in the infiltrated soil than in the untreated soil. In addition, sprinkling infiltration had favored early-successional herbs, grasses and forbs and negatively affected late successional, slow-growing mosses and lichens. Sprinkling infiltration had significantly increased tree radial growth.Sprinkling infiltration is an environment altering soil treatment method which, based on the findings of this study, can have long-term effects on tree growth, soil processes and understory vegetation.