Evaluation of change in subsurface thermal environment due to groundwater flow in the Tokyo Lowland,Japan

Information on the distribution of subsurface temperature and hydraulic heads at 24 observation wells in and around the Tokyo Lowland, the eastern part of the Tokyo Metropolitan area, were examined to make clear the relationship between groundwater and the subsurface thermal environment in the urban area. Minimums in temperature–depth logs due to subsurface temperature increasing at shallow parts were recognized in 21 wells. This fact shows subsurface temperature is affected by ground surface warming in almost all of this area. Deeper than minimums, where the effects of surface warming became relatively small, regional variation is observed as follows: high temperatures are shown in the central part to the southern part, and low temperatures shown in the inland to eastern part. The high temperature area corresponds to an area where the lower boundary of groundwater flow is relatively shallow. This area corresponds also to an area with severe land subsidence resulting from excessive groundwater pumping. It is considered that this high temperature area is formed by the effects of upward groundwater flow affected by hydrogeological conditions and pumping. On the other hand, a comparison between past data (1956–1967) and present data (2001–2003) revealed widespread decreasing temperature in the inland area. This is explained by downward groundwater flow based on an analysis of temperature–depth logs. This fact suggests that subsurface temperature is not only increasing from the effects of surface warming but also decreasing from the effects of groundwater environment change due to pumping.     

Recent formations and their basal topography in and around Tokyo Bay,central Japan

This paper summarizes the subsurface geology of the recent (both $\text{Holocene}$ and latest $\text{Pleistocene}$ formations and the buried topography beneath them in and around Tokyo Bay, the type area of the late Quaternary in Japan. Buried abrasion platforms in the buried topography are classified into upper (ca. 0 to ?10 m high) and lower (ca. ?20 to ?40 m) platforms; upper and lower buried river terraces are also distinguished, and are correlated to the subaerial late Pleistocene terraces of Tc₁ and Tc₂, respectively. A buried valley system is elucidated, of which the trunk valley floor reaches ?70 m in Tokyo and emerges into a flat surface at the shelf edge in the entrance to Tokyo Bay. Approximate dates for these geomorphic surfaces are given. The height of sea level contemporaneous with the buried valley floor (ca. 20,000–15,000 yr BP) is estimated at about ?135 m. The recent formations are divided into two members, upper and lower, by a middle sand bed, in addition to the lowest buried valley floor gravel. The lower member, which is composed of brackish to marine deposits of complicated lithofacies, was accumulated in narrow drowned valleys during the early stage of the Yurakucho (Flandrian) transgression. The middle sand bed is the foreset bed of deltas, which was formed during a slight regression between ca. 11,000 and 10,000 yr BP. The upper member, which consists mainly of widespread homogeneous marine clay and deltaic sand, was accumulated in a wide bay and its embayments during the late stage of the Yurakucho transgression and the following stage of a relatively stable sea level.     

Multi-aquifer pumping test to determine cutoff wall length for groundwater flow control during site excavation in Tokyo, Japan

Multi-aquifer pumping tests, using a multi-screen pumping well and multi-level piezometers, were carried out for groundwater flow control in a large-scale excavation site in Tokyo, Japan. The site was underlain by multi-layered confined aquifers. In the tests, pumping was carried out using a multi-aquifer pumping well in which a screen depth was chosen arbitrarily. Changes in groundwater pressure heads in each aquifer were measured at each screen position of the multi-aquifer pumping well. Hydraulic conductivity (K) and specific storage (S _s) of not only aquifers, but also for low permeability layers between the aquifers, were estimated using the Cooper-Jacob method, and calibrated by a finite element method (FEM) groundwater model. Four different cutoff wall lengths were assumed for final excavation depth, and correlations among wall length, pumping discharge and drawdown at the back of the cutoff wall were obtained from simulations using the K and S _s parameters in the FEM model. Then, the most suitable wall length was selected based on the simulated correlations considering environmental condition, construction period and cost of the cutoff wall.     

Influence of groundwater flow on the estimation of subsurface thermal parameters

International Journal of Earth Sciences - We investigated the influence of groundwater flow on the thermal tests performed in borehole heat exchangers to infer the underground thermal properties....     

Subsurface thermal and hydrothermal characterization based on geothermal resources map, drill hole thermal gradients, Curie point depths and hypocenter distribution — Examples of Tohoku district, Japan

Subsurface thermal structure in Tohoku district are characterized by existing data such as geothermal resources maps, drill hole thermal gradients, Curie point depths and hypocenters distribution maps. The collected data are registered in a database system, then, compared in plan view, cross-section and bird's-eye pictures. The comparison indicates that subsurface temperatures extrapolated from drill hole thermal gradients are generally concordant to the Curie point depth, assumed to be 650 °C. Tohoku district is generally divided into 5 type areas; fore arc lowland, fore arc mountain country, Quaternary volcanic terrain, back arc lowland and back arc mountain country. The surface thermal manifestations in Quaternary volcanic terrain are mainly controlled by the magma chambers as heat sources, while, surface thermal features such as hot springs in non-volcanic areas are controlled by degrees of heat flows, and hydrothermal flows in permeable Cenozoic formations and along permeable fault zones.     

Assessment of groundwater pollution around Torbali,Izmir, Turkey

The Kuihe River is in Xuzhou, Jiangsu, China. It contains high concentrations of nitrogen. The water in the Kuihe River recharges the groundwater via riverbank filtration (RBF) along the Xucun and Huangqiao reaches, which are characterized by unsaturated and saturated percolations, respectively. The two sections were selected to study the effectiveness of RBF to the nitrogen removal from the infiltrating river water. The results showed that the RBF in the saturated percolation had the potential to remove the nitrogen through biochemical processes. The nitrogen-removal rates were more than 95% over the monitoring period. However, the RBF in the unsaturated percolation resulted mainly from the physical process and thus had no efficacy for nitrogen removal.     

Assessment of groundwater quality in and around Vedaraniyam,South India

Groundwater from 47 wells were analyzed on the basis of hydrochemical parameters like pH, electric conductivity, total dissolved solids, Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^?, CO₃ ^2?, HCO₃ ^?, NO₃ ^?, PO₄ ^3? and F^? in the Cauvery delta of Vedaraniyam coast. Further, water quality index (WQI), sodium percentage (Na %), sodium absorption ratio, residual sodium carbonate, permeability index and Kelley’s ratio were evaluated to understand the suitability of water for drinking and irrigation purposes. The result shows significant difference in the quality of water along the coastal stretch. The order of dominance of major ions is as follows: Na⁺ ≥ Mg²⁺ ≥ Ca²⁺ ≥ K⁺ and Cl^? ≥ HCO₃ ^? ≥ CO₃ ^2? ≥ PO₄ ^3? ≥ F^?. Na/Cl, Cl/HCO₃ ratio and Revelle index confirmed that 60–70 % of the samples were affected by saline water intrusion. WQI showed that 36 % of the samples were good for drinking and the remaining were poor and unsuitable for drinking purpose. The degradation of groundwater quality was found to be mainly due to over-exploitation, brackish aquaculture practice, fertilizer input from agriculture and also due to domestic sewage.     

Deep groundwater flow and geochemical processes in limestone aquifers: evidence from thermal waters in Derbyshire, England, UK

Thermal waters potentially provide information on geochemical processes acting deep within aquifers. New isotopic data on groundwater sulphate, inorganic carbon and strontium in thermal and non-thermal waters of a major limestone aquifer system in Derbyshire, England, UK, are used to constrain sulphate sources and groundwater evolution. Shallow groundwaters gain sulphate from oxidation of sulphide minerals and have relatively ¹³C-depleted dissolved inorganic carbon (DIC). Thermal waters have relatively high Sr/Ca and more ¹³C-enriched DIC as a result of increased water–rock interaction. In other respects, the thermal waters define two distinct groups. Thermal waters rising at Buxton have higher Mg, Mn and ⁸⁷Sr/⁸⁶Sr and lower Ca and SO₄, indicating flow from deep sandstone aquifers via a high permeability pathway in the limestone. By contrast, Matlock-type waters (97% of the thermal flux) have elevated sulphate concentrations derived from interaction with buried evaporites, with no chemical evidence for flow below the limestone. About 5% of the limestone area's groundwater flows to the Matlock group springs via deep regional flow and the remainder flows via local shallow paths to many non-thermal springs. Gypsum dissolution has produced significant tertiary porosity and tertiary permeability in the carbonate aquifer and this is an essential precursor to the development of karstic drainage.

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Resumen Las aguas termales potencialmente proporcionan información sobre procesos geoquímicos que actúan a profundidad en acuíferos. Nuevos datos isotópicos de sulfatos, carbón inorgánico y estroncio en aguas termales y no-termales de un acuífero importante de caliza en Derbyshire, Inglaterra se utilizan para delinear las fuentes de sulfato y la evolución de aguas subterráneas.Las aguas subterráneas no muy profundas adquieren sulfato a través de la oxidación de minerales de sulfuro y poseen carbón inorgánico disuelto (DIC) relativamente deplatado de ¹³C. Las aguas termales muestran un ratio Sr/Ca relativamente alto y poseen (DIC) más enriquecido en¹³C, como resultado de la mayor interacción de roca-agua. En otros aspectos, los aguas termales definen dos grupos distintivos. Las aguas termales que ascienden en Buxton tienen mas Mg, Mn y ⁸⁷Sr/⁸⁶Sr y menos Ca and SO₄, indicando flujo de acuíferos de areniscas profundas por un sendero de alta permeabilidad en la caliza.En contraste el tipo de agua - Matlock (97% del flujo termal) posee altas concentraciones de sulfato, derivado por interacción con evaporitas enterradas, sin evidencia química de flujo debajo de la caliza. Aproximadamente 5% del agua del área de la caliza se fluye al grupo de manantiales de Matlock a través de un flujo regional profundo y el resto fluye por senderos locales poco profundos a muchos de los manantiales no-termales. La disolución de yeso ha producido porosidad terciaria importante así como permeabilidad en el acuífero de carbonato y este es un precursor esencial del desarrollo de drenaje kárstico.

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Résumé Les eaux thermales peuvent apporter des informations sur les processus géochimiques dans les aquifères profonds. De nouvelles données isotopiques sur les sulfates présents dans les eaux souterraines, le carbone inorganique et le strontium dans les eaux thermales et non thermales d'un système aquifère calcaire majeur dans le Derbyshire, Angleterre, Royaume Uni, sont utilisées pour comprendre les sources de sulfates et l'évolution des eaux souterraines. Les eaux souterraines phréatique s'enrichissent en sulfate via l'oxydation des minéraux sulfatés et ont un Carbone Inorganique Dissous (DIC) relativement appauvri en¹³C. Les eaux thermales ont un rapport Sr/Ca relativement plus élevé et un DIC plus enrichi en¹³C, du fait de l'interaction accrue des eaux avec les roches. En d'autres mots, les eaux thermales définissent deux groupes distincts. Les eaux thermales remontant à Buxton ont un Mg, un Mn et un rapport ⁸⁷Sr/⁸⁶Sr plus hauts, mais un Ca et SO₄ plus faible, indiquant un écoulement à travers les zones perméables des aquifers gréseux. Par contraste, les eaux du type de Matlock (97% du flux thermique), possèdent des concentrations élevées en sulfates, provenant de l'interaction des eaux avec les évaporites enfouies, tandis qu'il n'existe aucune évidence chimique d'un écoulement sous les calcaires. Sur environ 5% de la surface des calcaires, les eaux souterraines alimentent des sources non-thermales. La dissolution du Gypse a produit une porosité tertiaire significative et une perméabilité dans les aquifères calcaires, et ceci est un précurseur essentiel au développement du drainage karstique.

     

Relationship between groundwater flow estimated by soil temperature and slope failures caused by heavy rainfall, Shikoku Island, southwestern Japan

Most of the slope failure disasters in a humid area such as that of Japan are caused by heavy rain. However, even for the case of heavy rainfall that occurs once in every 10 years, total area of slope failures seldom exceeds 10% of a watershed. From this background, we focused on the vein-like groundwater flows that increase pore-water pressure, and clarified the relationship between distributions of slope failures and groundwater veins. In this study, a 1-m-depth ground temperature survey and water-chemistry analyses at springs and boreholes were conducted in Zentoku area of Shikoku Island, southwestern Japan, to grasp the distribution of groundwater veins and their sources. Subsequently, slope-stability was analyzed to investigate the relationship between groundwater veins and slope failures at study sites. These results lead to the following conclusions: The slope failures appear to concentrate around shallow groundwater veins and groundwater veins rising from deep layers. This means that slope failures caused by these groundwater veins in addition to rainfall. Two types of groundwater originate in the deep layers: one has short storage time as indicated by the fact that dissolved substances are low; the other is stored for a lengthy period as noted by a high concentration of dissolved substances. By combining the results of stability analyses and distribution of groundwater veins, it is suggested that prediction of zones with high potential for slope failure can be more accurate.     

Sustainable groundwater resources, Heretaunga Plains, Hawke's Bay, New Zealand

 The Heretaunga Plains, Hawke's Bay, New Zealand, is underlain by Quaternary fluvial, estuarine-lagoonal, and marine deposits infilling a subsiding syncline. Within the depositional sequence, river-channel gravels form one of the most important aquifer systems in New Zealand. An interconnected unconfined–confined aquifer system contains groundwater recharged from the Ngaruroro River bed at the inland margin of the plain, 20 km from the coast. At the coast, gravel aquifers extend to a depth of 250 m. In 1994–95, 66 Mm³ of high quality groundwater was abstracted for city and rural water supply, agriculture, industry, and horticulture. Use of groundwater, particularly for irrigation, has increased in the last 5 years. Concern as to the sustainability of the groundwater resource led to a research programme (1991–96). This paper presents the results and recommends specific monitoring and research work to refine the groundwater balance, and define and maintain the sustainable yield of the aquifer system. Three critical management factors are identified. These are (1) to ensure maintenance of consistent, unimpeded groundwater recharge from the Ngaruroro River; (2) to specifically monitor groundwater levels and quality at the margins of the aquifer system, where transmissivity is <5000 m²/d and summer groundwater levels indicate that abstraction exceeds recharge; (3) to review groundwater-quality programs to ensure that areas where contamination vulnerability is identified as being highest are covered by regular monitoring. Received, January 1998 / Revised, August 1998, March 1999 / Accepted, April 1999     

Subsurface temperature variations and heat flow in the Anambra Basin,Nigeria

Data from sixteen deep walls drilled for oil exploration purposes in the Anambra Basin of southeastern Nigeria indicate large variations in temperature gradients and heat flow within the basin. Geothermal gradients vary between 25 and 49 ± 1°C km⁻¹, while heat flow estimates are in the range 48 to 76 ± 3 mW m⁻². The highest geothermal gradients and heat flow values were computed for the wells located in the southwestern part of the basin north of Onitsha and Asaba. This part of the basin coincides with zones of thick, low conductivity sediments, low ground surface elevation, and hydraulic discharge zones. The general direction of increase in geothermal gradient, originally projected as south to north by earlier workers dealing with the Niger Delta data and the very limited well data from the Anambra Basin, is inconsistent with the results of the present study.The distribution of subsurface temperatures, geothermal gradients and heat flow is found to be directly related to the basin hydrodynamics - higher geothermal gradients and heat flow in areas of low hydraulic head distribution. Hydrocarbon metamorphism and migration appear to have been greatly influenced by the movements of circulating meteoric waters. A higher level of organic maturity of sediments should be expected in the southwestern zone, where the thermal anomaly exists. However, owing to hydrodynamic activities, tertiary migration would have taken place leaving many traces of residual hydrocarbons. The several cases of fluorescence noticed in wells in the southwestern zone of the Anambra Basin are taken as evidence that this process may indeed have taken place in the geological past of the basin.     

Three-dimensional analysis of groundwater flow in neogene rocks at the Rokkasho low-level radioactive waste disposal center, Japan

As a preliminary step for predicting groundwater flow in a plateau 30–50 m above sea level, a model for three-dimensional analysis of groundwater flow was formulated and its validity was verified. The plateau consists of Neogene sedimentary rocks and a Quaternary deposit. Most of the groundwater originates in precipitation, with the groundwater table lying in the Quaternary deposit. Steady-state analysis was conducted by using the finite element method. The results of pore-water pressure measurement and water examination were useful in verifying the validity of the model. In constructing the model, reducing the hydraulic conductivity according to the depth on the basis of the results of the actual measurement was important.     

Abiki oscillations in Sakitsu Bay,west Kyushu,Japan

Sakitsu and Yokaku bays in Amakusa in west Kyushu, Japan, experienced inundation damage in the February 2009 meteotsunami (Abiki) event. The oscillation characteristics of both bays are investigated by taking field measurements and conducting numerical experiments with regard to flood mitigation with the aim to reduce the flood impact during Abiki events. A continuous wavelet transform and bandpass filtering both of the pressure and water level indicated that a sequence of pressure disturbances, as small as 1.0 hPa, caused the large amplified oscillation within Sakitsu Bay. When a sequence of ocean long waves entered the bay, a surf beat evolved in the early stages. Subsequently, the sea level began to undergo large amplitude oscillations, and there was a secondary peak of oscillation with a period of around 24 min, as seen in both field measurements and numerical experiments. A surf beat with the period of 12 min formed in Yokaku Bay owing to the continuous incidence of ocean waves with period of 12 min, but its wave period was almost half of that of the natural period of the bay. This surf beat may have entered Sakitsu Bay with natural period of 11.8 min and caused large water-level fluctuations.     

Stable isotopic and geochemical data for inferring sources of recharge and groundwater flow on the volcanic island of Rishiri,Japan

An isotopic and chemical study was conducted on precipitation, spring water, streams, groundwater wells and submarine groundwater discharge (SGD) to constrain the recharge areas and flow paths of SGD. The isotopic values of precipitation were used to determine the local meteoric water lines (LMWLs) of Rishiri Island. The d-excess values of precipitation showed seasonal variation, with lows of 2.5‰ in the summer and highs of 24.2‰ in the winter. The d-excess values of spring water, streams, groundwater wells and SGD ranged from 12.5‰ to 23.0‰, indicating that the resulting waters were a mix of two seasons of precipitation. The isotopic composition of the groundwater wells sampled along the coast and SGD showed more negative values than that of the spring water sampled along the coast. This indicated that SGD recharged at high altitudes and flowed into the sea. The isotopic and chemical composition of SGD indicated unidirectional flow from land to sea.     

Accidents due to oxygen deficiency and methane gas blow-off in Tokyo area,Japan

The groundwater leve in the Tokyo area had declined to about 60 m below the surface because of excess withdrawal of groundwater from various aquifers. Many construction workers died due to oxygen deficiency at construction sites from 1960 to 1980, the period of decreasing groundwater level. The compressed air in pneumatic foundation construction sites passed easily through the aquifer, and the oxygen in it was consumed by ferrous ions oxidizing to ferric ions. During periods of high barometric pressure, atmospheric air penetrates into the strata and it is deoxygenated there. Suffocation occurred not only at construction sites in underground excavations, but also in residences in Tokyo. Such acidents have become less frequent with recovery of the pore-water pressure in aquifers, which has accompanied the recovery of the groundwater level since 1972.With the recovery of the pore-water pressure and the groundwater level in the aquifer, fires and explosions resulting from gushes of methane have occurred in Tokyo lowlands since 1973. These blow-off gases are classified into two types: Kameido and Asakusa.The gas of the Kameido type originates from the Kazusa Group and migrates into upper alluvial deposits or Pleistocene sediments because of the recovery of pore-water pressure in the Kazusa Group. The gas of the Asakusa type formed from the air that penetrated the aquifers during the period of low groundwater level. Methane was produced by the depletion of oxygen accumulated in alluvial deposits and Pleistocene sediments. This gas blows off through wells in alluvial deposits and Pleistocene sediments at times of low barometric pressure. Accidents of the Asakusa type will not happen when the groundwater level and pore-water pressure in alluvial and Pleistocene sediments is restored to previous levels.     

Characterization of bottom sediments from Osaka Bay,Japan

The physical, chemical, and dewatering characteristics of 19 bottom sediments from Osaka Bay, Japan, have been analyzed to aid in the development of sediments in the coastal bay area. The sediments in the east near Osaka Port were highly polluted from the influence of human activities and were difficult to dewater. These sediments were composed of fine particles, low in pH, zetapotential, and initial settling rate, and were high in ignition loss, metal concentrations, compression volume, specific resistance, cake water content, and drying index. However, the sediments near Akashi Channel showed the reverse where they are affected by strong tidal current. A correlation analysis has been made of all the parameters. There are significant relationships between all the dewatering parameters. Therefore, sediments difficult to dewater by gravity settling are also difficult to dewater by vacuum filtration and solar evaporation. Sediments containing fine particles and pollutants are difficult to dewater. Several forms of pollutants can occur in the sediments.     

Geochemical assessment of groundwater around Macherla-Karempudi area,Guntur district,Andhra Pradesh

Groundwater in Palnad sub-basin is alkaline in nature and Na⁺-Cl⁻-HCO₃⁻ type around Macherla-Karempudi area in Guntur district, Andhra Pradesh. Total dissolved solids (TDS) show strong positive correlation with Cl⁻, Na⁺, Ca²⁺ and Mg²⁺, and positive correlation with SO₄²⁻, K⁺ and HCO₃⁻. Calcareous Narji Formation is the dominant aquifer lithology, and water-rock interaction controls the groundwater chemistry of the area. Chloro-alkaline indices (CAI) are positive at Miriyala, Adigopula, Mutukuru, Macherla and Durgi suggesting replacement of Na⁺ and K⁺ ions from water by Mg⁺⁺ and Ca⁺⁺ ions from country rock through base exchange reactions. Negative CAI values are recorded at Terala, Rayavaram and Nehrunagar, which indicate exchange of Na⁺ and K⁺ from the rock as cation-anion exchange reaction (chloro-alkaline disequilibrium). TDS range from 91 to 7100 ppm (Avg. 835 ppm) and exceed the prescribed limit of drinking water around Mutukuru, Durgi, Rayavaram, Khambampadu and Ammanizamalmadaka areas. Scanty rainfall and insufficient groundwater recharge are the prime factors responsible for high salinity in the area. Fluoride content ranges from <1 to 3.8 ppm and contaminated areas were identified around Macherla (1 sq km; 3.8ppm), Mandadi (1 sq km, 2.1ppm) and Adigopula (2 sq km, <1 to 3.7 ppm). The % Na⁺ content varies from 17 to 85 with the mean value of 57, and eighty (80) samples showed higher %Na⁺ in comparison to the prescribed limit of 60 for irrigation water. Sodium Adsorption Ratio (SAR) and % Na⁺ in relation to total salt concentration indicate that groundwater (51%) mostly falls under doubtful to poor quality for irrigation purpose. Groundwater of Adigopula village is fluoride contaminated and remedial measures are suggested to improve the water quality.     

Numerical simulation of groundwater flow for a coastal plain in Japan: data collection and model calibration

Using a three-dimensional finite element model, this study characterizes groundwater flow in a costal plain of the Seto Inland Sea, Japan. The model characterization involved taking field data describing the aquifer system and translating this information into input variables that the model code uses to solve governing equations of flow. Geological geometry and the number of aquifers have been analyzed based on a large amount of geological, hydrogeological and topographical data. Results of study demonstrate a high correlation between the ground surface elevation and the groundwater level in the shallow coastal aquifer. For calibrating the numerical groundwater model, the groundwater flow was simulated in steady state. In addition, the groundwater level and trend in the transient state has also been elucidated. The numerical result provides excellent visual representations of groundwater flow, presenting resource managers and decision makers with a clear understanding of the nature of the types of groundwater flow pathways. Results build a base for further analysis under different future scenarios.