An estimation method for evaluating groundwater velocity by means of the Single-Well Push-Pull (SWPP) test by Leap and Kaplan (1988) was applied to a confined aquifer at 100 m depth with a very slow groundwater movement. The SWPP test consists of a push phase, a drift phase, and a pull phase, and the groundwater velocity is evaluated based on the Breakthrough Curves obtained from the SWPP test. In this study, the accuracy of the SWPP test system was evaluated by performing a SWPP test without drift time four times in total. Also, four types of SWPP tests with different drift times from 10 to 1802 days were conducted to obtain an estimate of the regional groundwater velocity for a maximum of approximately five years. Furthermore, the stable isotope of water (delta O-18 and delta D) and uranine, which are known as conservative tracers, were used as tracers in the SWPP tests so as to evaluate their availabilities. The SWPP test results showed a higher reproducibility of the SWPP test using delta O-18 and delta D than that using uranine. The sorption of uranine in the aquifer was suggested based on the SWPP test results, indicating that the hydrological properties can be obtained by comparing the SWPP test results using delta O-18, delta D and uranine as tracers. The SWPP test yielded an actual groundwater velocity of 0.37 m/year, which is similar to approximately 0.1 m/year order of the estimated groundwater velocity based on the results of past studies. Moreover, setting the appropriate correction and drift time in the SWPP test played an important role in investigating the very slow groundwater flow in the aquifer. When a long-term drift time was set, the recovery rate of the tracer and the chaser of delta O-18 and delta D was decreased by diffusion in the aquifer's silt and clay layer.

Two single-well injection–extraction (“push–pull”) tracer tests were performed in a groundwater monitoring well located in the Horonobe coastal sedimentary basin, Japan. The aim of the experiment was to investigate the in situ behavior of groundwater constituents when different mineralized fluids intrude into the aquifer (e.g., through a dynamic saltwater–freshwater interface). Artificially produced brackish water was used as the test fluid in the first experiment and deionized water in the second. Results from mixing models strongly suggest rapid mobilization and demobilization of ions within the aquifer as a reaction to the intruding fluids. Hydraulic modeling of the conservative chloride ions yielded effective porosities of about 1 %. These results show that the transport of ions is dependent on the composition and mineralization of the fluid. The refreshening of an aquifer leads to increased mobilization of ions and, in addition, to an increase of dispersivity due to clay swelling. This has consequences not only for dynamic saltwater–freshwater systems (aquifers in coastal areas and aquifer storage and recovery systems), but also for all systems in which chemically altered fluids come into contact within an aquifer (as, for example, can occur during geothermal heat/energy generation, or during CO2 storage).

“Push–pull” tracer tests are a suitable tracer test method for hydrochemical characterization of an aquifer in a single-well setting (e.g. in deep geothermal systems). A known amount of selected solutes as conservative and reactive tracers is injected into the aquifer (“push”) and afterwards extracted (“pull”). In many cases, a so-called “chaser”, which is just original groundwater without any added solutes, is injected directly after the injection of the test solution. Its objective is to push the test solution out of the borehole into the aquifer and therefore to minimize the influence of the gravel pack on the shape of the breakthrough curve. The influence of the chaser on the tracer breakthrough curve is unknown so far. Also, the determination of the appropriate volume for the chaser is a difficult task if at all applied. A first experiment was conducted with the objective to compare three push–pull tests with similar injection volumes, two tests with and one without a chaser. Results show that the application of a chaser lowers the main peak concentration. However, it does not alter the tailing of the breakthrough curve nor does it have a negative influence on tracer mass recovery. In a second experiment, a new method was developed to determine the optimal chaser volume by testing seven different chaser injection volumes combined with temporal moment analysis. As a result, the application of a chaser is recommended, when reactions of injected solutes within the open well or the gravel pack should be avoided. If a chaser is used, the new method mentioned above can easily be used to determine the required chaser injection volume. The experiments were conducted at the Hamasato test site in Horonobe (Hokkaido, Japan).

Land reclamation undertaken continuously in Tokyo Bay since the Edo era can be regarded as important for advancing civil engineering projects in Tokyo. Haneda airport D-runway extension work (hereafter D-runway construction) was completed in October 2010, with a new 2,500 m runway, operating a 24-h service, built in a sea area having a water depth of 15-20 m. Part of the island airport was constructed with a pier structure to provide flood control for the Tama River and preserve the environment. This report summarizes the marine geological survey, environmental assessment, and groundwater management for D-runway construction on the basis of previous reports. The main characteristics of construction are: marine drilling was carried out about every 500m in the sea area for the marine geological survey; the effects of construction on ocean currents, bottom sediments, and submarine topography were considered in the environment impact assessment of land reclamation; and, a new underground station was constructed with groundwater control provided by a deep-well dewatering system without building a sealing body for groundwater.

Land reclamation undertaken continuously in Tokyo Bay since the Edo era can be regarded as important for advancing civil engineering projects in Tokyo. Haneda airport D-runway extension work (hereafter D-runway construction) was completed in October 2010, with a new 2,500 m runway, operating a 24-h service, built in a sea area having a water depth of 15-20 m. Part of the island airport was constructed with a pier structure to provide flood control for the Tama River and preserve the environment. This report summarizes the marine geological survey, environmental assessment, and groundwater management for D-runway construction on the basis of previous reports. The main characteristics of construction are: marine drilling was carried out about every 500 m in the sea area for the marine geological survey; the effects of construction on ocean currents, bottom sediments, and submarine topography were considered in the environment impact assessment of land reclamation; and, a new underground station was constructed with groundwater control provided by a deep-well dewatering system without building a sealing body for groundwater.

While research focuses mainly on the intensively used shallower aquifers, only a little research has addressed groundwater movement in deeper aquifers. This is mainly because of the negligible relevance of deep groundwater for daily usage and the great efforts and high costs associated with its access. In the last few decades, the discussion about deep geological final repositories for radioactive waste has generated strong demand for the investigation and characterization of deep-lying aquifers. Other utilizations of the deeper underground have been added to the discussion: the use of geothermal energy, potential CO 2 storage, and sources of potable water as an alternative to the geogenic or anthropogenic contaminated shallow aquifers. As a consequence, the fast growing requirement for knowledge and understanding of these dynamic systems has spurred the research on deep groundwater systems and accordingly the development of suitable test methods, which currently show considerable limitations. This review provides an overview of the history of deep groundwater research. Deep groundwater flow and research in the main hydrogeological units is presented based on six projects and the methods used. The study focuses on Germany and two other locations in Europe.

深部の地下水流動の評価では、（1）流動を支配する要因、（2）検証対象となるデータ、および（3）空間・時間スケールが浅部の地下水流動と異なることを考慮することが重要と考え、浅部と深部を区分して評価するアプローチを提案した。本報は広域の地下水流動を対象として温度データを用い、流速の大小により流動場を定量的に区分する手法の提案を目的とした。地下温度分布を指標値として、関東平野を対象とした地下水流動・熱輸送解析を行った結果、上総層群上部層下面を境界として、上部を透水性の大きい帯水層、下部を透水性の小さい帯水層とした場合に最もよく地下温度分布を再現する結果が得られ、地下水流速の小さな深部の低流速域を抽出することが可能になった。

地下水資源の持続的な活用のため、保全と利用を両立した地下水管理が求められている。数値シミュレーションなどを活用した近年の地下水管理において、地下開発の影響範囲を評価するには、地下水盆や地下水賦存量の全容の把握が重要となる。しかし、地下水の基礎情報はいまだ十分でなく、全国規模でそれらの全容を明らかとした研究はない。本論では、地下水関連のデータベースを活用し、日本列島の三次元水文地質モデルを構築した。そして、構築した三次元水文地質モデルを用いて地下水賦存量を試算した。その結果、広範囲の地層の分布を明示することで地下水盆の全容の把握が可能となり、また、未利用水源の潜在性など、地下水資源の開発・保全にとって有用な情報の提供が可能と考えられた。

Submarine groundwater discharge (SGD) is considered to be the sustainable water resource, and also the important factor of the water cycle. Methods to evaluate the quantity of SGD can be divided into mathematical analysis and in-site survey, and in the case of wide area study, like the Japanese Islands, the macro evaluation by perennial water balance budget is suitable for the initial study. However, the evaluation of runoff using the River Discharge Year Book of Japan has several problems such as the uncertain accuracy of measurement, the existence of an inconsiderable area between the lowest flow gauge and river mouth, and unavailability of river flows in basins except for Class A rivers. In this paper, we calculated perennial water balances of 10 years in 204 regions on the Japanese Islands. It was the first time to make a distribution map of SGD in Japan. As there existed 144 regions where the flow data were insuff icient, the runoff in each area was estimated by the multiple linear regression analysis between the river flows and the recharges, divided by the geology of the basins where it was judged to be similar geologically by cluster analysis using area ratios of 43 geological classifications.

砂岩の間隙水を深度100mの岩石コア3本から遠心分離法で抽出した。合計63サンプルから、3段階のpF（低：2.3以下，中：2.3-3.9，高：3.9-4.3）で抽出し、各pFにおける主要な陽イオンと陰イオンについて水質分析を実施した。その結果、イオン濃度は、深度とpFによって変化することが示された。また、Ca2+濃度の深度方向分布は以下の3区間に分けられた。（1）Ca2+濃度がpFと無関係な区間、（2）Ca2+濃度がpFとともに増加する区間、（3）Ca2+濃度が中pFと高pFで等しくなる区間である。深部の間隙水は、地下水が滞留しているために化学的に平衡しているが、浅部の間隙水は地下水流速が大きいために周囲との化学変化に関与していると考えられる。これら3区間の境界深度は、風化砂岩と比較的固結した砂岩の地層境界と概ね一致しており、間隙水の水質と地層の岩石特性には関連があることを示している。

沿岸域の地下水が形成する塩淡境界は、地点によって多様な特徴を示す。よって、地下水流動解析でその形状を評価する場合、原位置データを取得しながら、解析結果との照合を繰り返す作業が求められるが、現実には困難である。本研究は、今後地球科学的知見が蓄積される幌延沿岸域で、地下水流動・塩淡境界解析のための初期モデルを構築し、海水準変動を考慮した試解析に基づいて、今後必要とされる調査項目の抽出を目的とした。試解析の結果、研究地の塩淡境界は、海水位が120m低下すると、深度約1000mの勇知層まで深部化する可能性があり、地下水サンプルを水質分析した結果の解釈には、海水準変動に伴う水質変化の履歴の評価が重要とした。幌延町は、沿岸域を対象とした地層処分基盤研究開発の対象地であり、数年内に深度1000mまでの水理地質構造が明らかになる。本研究の成果は、その時点で検証される。

沿岸域における塩淡境界は,流動する地下水による移流混合の影響が大きい浅部に比べて,化石海水の拡散混合が支配的な深部の評価が難しく,現地観測と数値解析を組み合わせた評価技術の高度化が求められるようになってきた(例えば,放射性廃棄物の地層処分事業).そのためには,塩淡境界の動的な形状変化の把握が重要となるが,これまでの観測事例は浅部を対象としたものが多く,深部の現象を捉えた事例はなかった.そこで本研究は,茨城県東海村の試験地における第四系と第三系の塩淡境界を深度200mまで動態観測した.試験地ではリング状トンネル構造物(大強度陽子加速器の一部)の建設に伴ってディープウェルによる揚水工事(日量約10,000m3)が行われ,塩水が浸入する状況下にあった.まず,静的条件下の塩淡境界解析を行い,自然状態の塩淡境界形状を推定するとともに集中的な観測研究を実施する位置(塩水化が進行すると考えられる領域)を決定した.続いて,揚水工事と並行して4孔の観測井を設け,水位,電気伝導度,温度を長期観測した.その結果,第四系と第三系の塩水浸入状況の違いについて次の知見を得た.(1)電気伝導度の測定結果によると,工事開始13-22ヶ月の問に,現海水が第四系に浸入したが,第三系には浸入しなかった.遮水層は浸入層下位の不透水層で,その透水性は浸入層の1/10-1/100であった.(2)揚水工事に伴う温度プロファイルの局所的な低温化と高温化が観察された.例えば,工事開始11-12ヶ月後に現海水浸入層が低温化し,18ヶ月後には第四系と第三系の地質境界付近などで低温化した.本試験地では,第四系への現海水浸入の他に,地層に含まれる塩水が複数深度から浸入した.(3)静的条件下の塩淡境界解析で,工事前の第四系と第三系の塩淡境界を推定した.塩淡境界の位置は観測結果と一致したが,第三系の塩分濃度評価は困難であった.静的条件下の塩淡境界解析は,浅部の形状が妥当であっても,深部まで含めた評価には不十分であることが分かった.