The characteristics of groundwater flow in the western Tokachi plain is clarified as follows: (a) Groundwater temperature in the piedmont area is less than average and greater than average in the central plain, indicating the recharge and discharge areas, respectively. (b) Groundwater flow velocities estimated from groundwater temperatures are consistent with those from hydraulic analyses. (c) The origin of groundwater in the western Tokachi plain and hot spring from Tokachigawa spa is meteoric. (d) The groundwater flow estimated from the stable isotopic ratiosδD andδ¹⁸O supports the results obtained from groundwater temperature. (e) δand δ¹⁸O variations in the Tokachi plain agree with the regional groundwater flow system model, in that deeper aquifers are expected to have lighter isotopic ratios because of the altitude isotope effect, including recharge occurred on Mt. Daisetsuzan or the Hidaka mountains. (f) The eastern geological block of the Tokachi central fault forms the eastern impermeable boundary of the Tokachi artesian basin. (g) Three-dimensional thermal advection-dispersion analysis shows that the Tokachigawa spa is formed as the convergence of groundwater flow in the western Tokachi plain, although the influence of special heat source cannot be ignored.

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In order to keep contaminated groundwater by chlorinated organic compounds from flowing out to outside of the facilities, permeable treatment wall using zero-valent iron had installed in the groundwater contaminated site. Monitoring of remediational effect and prediction of durability of the treatment wall were carried out. Reactivity of iron powder is measured by batch experiments. Durability of treatment wall was predicted by the reaction model proposed by Shimomura et al. (1998) using estimated parameters from the column experiment using groundwater sampled in the field.
The permeable groundwater treatment wall consists of block-style reactive zones installed in a zigzag disposition. Each reactive zone is approximately 0.6m in thickness,3.0 to 6.0m in length, and 7.0m in depth, and focuses to clean up the contaminated groundwater that passed through the first aquifer which consists of boulder gravel layer.
Effectivity of remediation has been confirmed through the monitoring. Concentration of the treatment water is verified under the Environmental Quality Standards of groundwater by the results of groundwater monitoring at monitoring wells installed to up- and downgradient sides of the treatment wall.
It is predicted that the durability of the treatment wall is enough to prevent from flowing out of contaminated groundwater which concentration exceeds Environmental Quality Standards of groundwater approximately for 17000 days (about 47 years), even in case that the groundwater velocity is ten times of the measured average groundwater velocity on the site. As the results of this predictive calculation, if the remediation of contaminant source will be carried out in case of scraping, enlarging, or rebuilding of the facilities in 47 years, it is possible to remediate at a low cost without disturbing the site operations.

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In planning the management of groundwater resources in desert areas, the temporal variation and spatial distribution of actual evaporation must be evaluated accurately because evaporation is important as not only a main component of the loss of water resources but also as a factor affecting rainfall amount. In this study, an energy balance model for the estimation of actual evaporation from bare soil surfaces is developed. The model does not require observations of soil moisture and can estimate simultaneously an index of soil moisture conditions using several meteorological elements and soil characteristics as inputs. The model was applied to field observation data from three different bare land sites. In all cases, the estimated evaporation rate was found to agree very well with the observed result. The behavior of the estimated effective-evaporation zone was compatible with the soil moisture conditions of the surface soil layer for each site.

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Interphase mass transfer is an important process that dominates overall transport processes in multi-fluid system in porous media. This process plays a key role during the volatilization of non-aqueous phase liquids (NAPLs) in porous media that usually takes place during the remediation process of volatile organic compounds (VOCs) using soil vapor extraction (SVE) technique. Previously, interphase mass transfer coefficient was usually lumped together with interfacial area between air and liquid because of inaccessibility to quantify the interfacial area due to the heterogeneous nature of the pore structure of the media and the morphology of the fluid distribution. An effort was made to estimate the air-liquid interfacial area in three glass beads media using surfactant adsorption concept and was found decreasing with increasing liquid saturation. A series of one-dimensional NAPL volatilization experiments were carried out in a horizontal column for the same three-glass beads media using Toluene as the contaminant. Experiments were conducted for NAPL saturation range of 13.8∼71% and a pore gas velocity of 0.1∼2 cm/s and lumped mass transfer coefficients were evaluated. Actual vapor phase mass transfer coefficients were calculated using corresponding air-liquid interfacial area for a specific NAPL saturation and was characterized in dimensionless form for all the porous media used in the study. Results showed that the vapor phase mass transfer coefficient increases with increasing pore gas velocity and grain size but decreases with increasing NAPL saturation.

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