The effect of fertilizer on chemical composition of groundwater was investigated from May 1991 to May 1994 in a farm land located West of Fukuoka city. It was ascertained that nitrate and dissolved oxygen concentrations in groundwater were greatly affected by the surface conditions of the farm land: paddy fields (April-August), vegetable fields (September-March), greenhouses (all seasons), fallow in farm land consolidation.
In the paddy fields, nitrate and dissolved oxygen concentrations decreased gradually from May, showing the minimum at the end of August. After the paddy fields were converted to vegetable fields, both concentrations began to increase, showing the maximum in March. This periodic variation of both concentrations is probably due to the change in the groundwater in view of the reduction or oxidizing conditions caused by the paddy field and vegetable field, respectively. In the land used for greenhouses, nitrate and dissolved oxygen concentrations in the groundwater were constant in high stage in all seasons. When the land was in consolidation, farming was stopped and the land was bare. During this period, since fertilizer was not used, the nitrate concentration was lower than that in the period the land had been used as vegetable field. On the other hand, the dissolved oxygen concentration was constant in high stage.

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Recently resistivity tomography techniques have been used as investigation method for civil engineering purpose. In this paper, the authors describe a new method to analysis the behavior of groundwater contaminant flow under saturated condition and to consider methods of determining the transport parameter such as longitudinal and transversal dispersion coefficients in the subsurface with the aid of conductivity probe method and resistivity tomography method. Resistivity between two electrodes was monitored using a multichanel cross borehole system. The experiments were conducted using pole-pole receiver electrode array. A two dimensional inversion tomography program was then used to simulate the apparent resistivity in laboratory experiments, and to estimate the salt water concentration.
The longitudinal and transverse dispersion parameters were determined using resistivity tomography method and they were compared with those from the conductivity method. The results from both methods were consequently compared with those from an FEM advection dispersion analysis. It will be shown that the result are mutually consitent.

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The fluvio lacustrine deposits of the Kathmandu Valley, Nepal are divided into four zones in terms of aquifer distribution. Deep confined aquifer in the south, GRI, medium depth interbedded aquifer, GRIT, shallow unconfined aquifer in the north, GRIII and an unconfined aquifer of thin sand and gravel deposit widely distributed on the surfaces of the terraces and other locations.
Surface sediment deposits of fine to medium grain size referred to as surface gravel deposits, supply considerable quantity of water for residents of the valley through“Dharas”(stone spouts) and wells at superficial depths. The discharge is reported to double during monsoon period. General quality of water from these sources is considered good with some exceptions.
For some years now, underground water source is believed to contribute about 40% of the city water supply. This is aggregated even further by pumping of the water in the private household with overdrafting going on for sometime. This overdrafting can be observed from the declining trend of the water levels in the tube wells. The total dynamic reserve of the valley is 12,730 m³/day. The average amount of infiltration from the rainfall is 17.2%.
The discharge from“Dharas”adds to 1380 m₃/day. Hence if the ground water is properly managed, overdrafting may not be necessary. Multipurpose projects specially in the northern zone should help induce artificial recharge. Otherwise, Kathmandu may face a potential disaster in the near future.

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The North-West area of the Northern Kanto groundwater basin is characterized by its complicated multi-aquifer structure and thus it is difficult to apply inverse analysis to estimate all parameters. Therefore, the aquifer parameter identification has been carried out by the combination of geostatistic kriging, trial-and-error identification method and inverse analysis. First, the initial aquifers' heads and prior transmissivities were estimated by geostatistic kriging. Second, the leakage factors of the confining layers were calibrated by a trial-and-error method which has been automatically carried out. Third, the storage coefficient was identified by trial-and-error method. Finally, the prescribed boundary flux intensities and transmissivity of the aquifers were estimated by an inverse analysis by means of Fletcher-Reeves conjugate gradient method. This sequential procedure seemed to be suitable for this practical case. Since the trial-and-error method and geostatistic kriging are widely well known, they will not be described in detail in this paper, but only briefly. This paper stresses on the use of combination of different parameter identification methods and mainly focuses on the utilization of the Fletcher-Reeves gradient method to solve a groundwater flow inverse analysis problem.

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Concentrations of major-elements, stable isotopes, tritium and bubble gas components including carbon and hydrogen isotope of methane were determined on water samples collected from rivers, springs, hot or mineral springs and drilled wells throughout the distribution areas of acidic rocks such as the Nohi-rhyolitic rocks, central Japan, and the Abukuma granodioritic rocks, northeast Japan. As a studied area, several types of aquifer lithologies were selected including the Nohi-rhyolitic welded tuff, Mino-sedimentary rocks and granitic rocks in the Nohi district, and including granodiorite, Takanuki-biotite schist and Yamizo sandstone in the Abukuma district.
Groundwater type was divided into ten groups. The change mechanisms in characteristics of water quality were identified in each hydrological groundwater flow systems, such as local flow system and regional flow system, and were clarified by the analysis of dissolved constituents and tritium concentration.
Stable isotope analysis indicates that both local and regional groundwaters of the two districts are originated in meteoric water. On the other hand, these have different residence time. Tritium concentration of the regional groundwaters are relatively low, which indicates that the residence time of those springs is longer than that of the water of local flow system. Regional groundwaters of the Abukuma district show lower tritium concentration, which was caused by the nature of fracture. In the Nohi rhyolitic area regional groundwater is easy to mix with local water by the occurence of cracks.
From water-mineral equilibrium consideration, it is concluded that the groundwater of relatively low salinity, high pH with sodium bicarbonate type (NR and AR groups) was formed by dissolution of surrounding acidic rocks with consuming carbon dioxide contained in soil, flowing through fracture zone.
Gero hot spring was formed by mixture of the Nohi regional groundwater with NaCl hydrothermal water related to the Yugamine rhyolitic rocks. Asahi village Agricultural Administration Bureau's well water which is NaCl type with high salinity reveals an original water and gas composition, which indicates the characteristics of water included in the Mino sedimentary rocks.
Inert gas composition indicates mixing of air saturated water with groundwaters included in the Mino sedimentary rocks. Yuya, Shitajima and Nigorigo waters have much contribution of air saturated water. Methane isotope ratios indicate that methanes in bubble gas were originated by mixture of thermogenic methane formed from kerogens with sedimentary methane in the Mino sedimentary rocks which is isotopically lighter. Bubble gas methane of Nigorigo has much contribution from volcanic or geothermal origin.
Gas analysis indicates that the depth of fracture system related to water with coexisting free gas extends to the Mino sedimentary rocks beneath the Nohi rhyolitic rock body. NR group groundwater without carbon dioxide bubble gas flow within the Nohi rhyolitic rock. AR group groundwater distributed in the Abukuma granodioritic rock body recharged in mountainous area about 10 km apart, flow through permeable fault, interrupted by impermeable fault such as Yujimata fault and flow upward to surface.

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