Migration of chemical substances in gas system of soil should be considered to purify soil polluted by harmful chemical substances. Fick's law has been applied to gas system as the only theory of this migration in the country. However Fick's law must be employed for the binary gas system and is not appropriate to multi-component gas system. These are a few models or concept for multi-component gas system, for example Stefan - Maxwell equations and Dusty Gas Model. Then this article has concluded the application of Fick's law, the assumption and derivation of Stefan - Maxwell and Dusty Gas Model.

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In the downstream area of the Echi-gawa river, groundwater is dominantly utilized for industrial water and irrigation in the Shiga Prefecture. The Echi-gawa alluvial fan is the main recharge area of the groundwater along the Echi-gawa river. To understand the groundwater flow system in this area, the relation between water temperature and groundwater flow is investigated with shallow and deep wells.
The shallow groundwater temperature of constant temperature layer has a difference of approx.0.8°C with 15.5°C in right bank, 16.3°C in left bank of the river. Vertical direction of groundwater flow was belting in the apex alluvial fan and fluvial terraceII. The deep groundwater temperature indicated that was 15.0∼15.5°C in the entire basin of right bank and rose in temperature along the depth in the left bank as surface layer is 16.0°C, middle layer is 16.5°C, deep layer is 17.5°C.
The estimated horizontal velocity of groundwater was that right bank is 4×10^-3cms^-1, left bank is 3×10^-3cms^-1 in the shallow layer and left bank is 7.4×10^-5cms^-1 in the deep layer. Furthermore, at the center of fan in the left bank, calculated vertical velocity of the deep layer is 2.4×10^-7cms^-1 in April, 8×10^-7cms^-1 in June.

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Water table provides important information for the evaluation of groundwater resource. Recently, the estimation of water table in wide area is required for effective evaluation of groundwater resources. However, evaluation process is met with difficulties due to technical and economic constraints. Regression analysis for the prediction of groundwater levels based on geomorphologic and geologic conditions is considered as a reliable tool for the estimation of water table of wide area. Data of groundwater levels were extracted from the public database of geotechnical information. It was observed that changes in groundwater level depend on climate conditions. It was also observed and confirmed that there exist variations of groundwater levels according to geomorphologic and geologic conditions. The objective variable of the regression analysis was groundwater level. And the explanatory variables were elevation and the dummy variable consisting of group number. The constructed regression formula was significant according to the determination coefficients and analysis of the variance. Therefore, combining the regression formula and mesh map, the statistical method to estimate the water table based on geomorphologic and geologic condition for the whole country could be established.

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For assessing the safety of geological disposal of high-level radioactive waste, it is important to understand groundwater flow as a driving force of mass transport. Authors have been carrying out the surface hydrological investigation in the Horonobe area, Hokkaido. Results of groundwater-level observations, and relationship between distributions of groundwater-level and geological structures suggest that constructions of underground facilities have no effect on shallow groundwater-level fluctuations, and that water infiltrate from ground surface into shallow underground in the snow covered season, and that water infiltrate into deeper underground along faults. In the future, it is necessary to be modeling and quantitatively assess the water infiltration and recharge based on directly and/or indirectly observed data of evapotranspiration and soil moisture content by weighing lysimeter and soil moisture meter, and tensiometer.

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