The regional distribution, annual change and controlling 'factors of chloride concentration were investigated on deep groundwater of Musashino Plateau, west Saitama Prefecture. The published city water examination data were used as the basic data of this study, and especially chloride concentration was studied among water components.
The relations between the annual change of chloride concentration and the change of groundwater level were classified into four patterns, by which the investigated area was divided into four groups. Relatively, in the westward area, the chloride concentration was low and showed a small annual change. On the other hand, in the eastward area, it was high and had a tendency to increase even when the water level was recovering after the restriction of groundwater pumping.
It will be considered that the geological condition represented by gravel percentage has an influence on the regional distribution of chloride concentration. That is, the concentration is lower where there is a larger gravel percentage in the covering layer, but it is higher where there is a larger gravel percentage in the pumping layer.
Synthesizing the above results with a cell-model experiment and simulation results, we conclude that the annual change and regional feature of chloride concentration are indirectly influenced by the size of the recharge area and the volume of water leaked through the confining layer, and are directly caused by the downward seepage of polluted shallow groundwater and the squeezing out of pore water from the confining layer.

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This study presents the results from experiment on the groundwater flow in a borehole in porous media. A laser-Doppler velocimeter is employed for measuring the velocity in the hole. The groundwater flow in the porous media around the hole is demonstrated using the observed stream line in the tracer experiment. The measured velocity distributions in the streamwise direction agree well with the theoretical solution presented by Sano (1983). It is experimentally found that (I) the streamwise velocity at the center of the hole is three times larger than the seepage velocity in the porous media before the hole bored, (ii) the streamwise velocity distribution in the hole is a parabolic type, and (iii) the fluid in the vicinity of the upstream side of the hole is sucked into the hole and flows out to the downstream side in a symmetrical stream line. It can be said that these experimental findings will be useful in the in-situ measurement of groundwater velocity using a single borehole.

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A groundwater investigation performed before and after filling the reservoir to study the characteristics of groundwater quality at the rock fill dam two years form initial filling.
The results were as follows:
(1) Variation in groundwater quality before and after filling the reservoir became smaller than that of initial filling due to seepage from the reservoir into the rock for two years.
(2) Small variation in groundwater quality could be expressed clearly by the principal component analysis basd on the water quality.
(3) When the variation in groundwater quality is large, we can estimate the flow routes of seepage by electric conductivity of groundwater.
(4) In this area, investigating groundwater quality after 3 or 4 months froms the start of filling is effective for clarifing the variation in groundwater quality.

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Groundwater contamination by pesticides or herbicides is getting one of the most serious environmental problems. This study focuses on water contamination by pentachloronitrobenzene (PCNB) on the northern foot of Mt. Asama, Gumma Prefecture, where cabbage patch is intensively distributed and a great amount of PCNB is applied. The area is composed of volcanic ashes, lavas and pyroclastic materials whose permeabilities are very large. Waters of river, groundwater and spring were sampled through April to October in 1987 and PCNB, PCA, PCTA, and other major elements were analyzed. Water quality is determined mainly by geologic formation and secondary by land use or agricultural activities. Groundwater as well as river water is contaminated by PCNB. The maximum values in river water and groundwater are 1.4 μg/l and 7.9 μg/l, respectively. Even spring water above cabbage patch area is also contaminated, which indicates PCNB is carried through atomosphere. PCA and PCTA, the principal degradation products of PCNB, are detected proportionally to PCNB and their rations to PCNB are relatively higher in September and October than in summer.

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