The recent research trends on water resources are investigated by classifying and comparing the themes of papers on water resource quality published in Japanese and international journals. The following research topics are considerably limited in Japan; 1) analyses on the runoff of toxic chemicals and groundwater quality, 2) models of package-type, models supported by GIS, and models for simulating the runoff of toxic chemicals, and 3) countermeasures and/or techniques for reducing the influence of non-point sources. The future research directions in this field are discussed and proposed with special reference to model, groundwater quality, risk management of toxic chemicals, influence of global warming, and integrated management of water quantity and quality.

View full abstract

This paper has developed an internet-based system for automatically displaying precipitation data obtained by a cost-effective meteorological observation equipment. Since the system can be accessed by mobile phones, observation data displayed on the internet web (WWW) site can be seen from the outdoors or even from the overseas. Establishing this kind of system is not so difficult for general users, because the cost is less expensive (about 100, 000 JPY) and no specific modification of the hardware and software is necessary. A problem for realizing this kind of system is the existing law system for precipitation data dissemination. According to the existing government's meteorological data dissemination policy, the private person or private company has no right to disseminate their own observation data to the general public. Finally this paper proposes the establishment of new legal system that is suitable for the modern Internet period.

View full abstract

Soil matric potential was observed using tensiometers in a tropical rain forest in Peninsular Malaysia. Undisturbed soil samples were also collected, and the relationships between volumetric water content (θ) and suction (ψ) of the soils were measured. The relationships between θ-ψ of soils with fitted curves generated by the van Genuchten model were excellent. The macro-and meso-porosity of the soil decreased with increases in soil depth. The capacity of water storage calculated by the difference of the saturated soil water content and residual water content in a 160-cm soil profile was 420mm. Although this humid tropics region has no distinct wet or dry seasons, the soil water storage showed both wet and dry conditions and the variation of the soil water storage corresponded to the fluctuation of rainfall. Soil water storage for the 160-cm profile ranged from 488 to 694mm of water with a mean of 565mm over a two-year. It should be considered the change of water storage when evapotranspiration of this basin is calculated using water balance method over only a period of one year. The variation of soil water storage to the rainfall in the upper soil (0∼80cm) was more remarkable and greater than the water storage in the lower soil (80∼160cm) throughout the year. The mean daily evapotranspiration rate calculated by the water balance of the 1.6-m of the soil profile ranged from 2.1 to 7.3mm day-1 with mean of 4.6mm day-1.

View full abstract

It is an important subject to evaluate adequately the storm runoff loading for the preservation of water quality environment in the stagnant water bodies. In this study, we analyzed the effects on the estimation of storm runoff loading using hourly observed data (rainfall, river flow and water quality) at two head works located in the middle of the Yahagi River basin, and applied simple regression models to estimate loading. Firstly, we observed closely relationships among rainfall, river flow, water quality concentration and loading. Secondly, by evaluating the difference between estimated and observed loading rate during the rainy period, we proposed conditions for upgrading the accuracy of loading estimation. Thirdly, we analyzed factors that affect storm runoff loading from the hydrologic aspects, and found relationships between the cumulative loading residual and the factors such as antecedent dry weather period. Finally, some conditions on the estimation for storm runoff loading are summarized which include the improvement in the application of the regression models to estimate loading.

View full abstract

The temporal variation of streamwater chemistry was observed in detail at three small headwater catchments where the hydrological processes are different in each during storm events having the same amount of rainfall in the same season. No abrupt changes in streamwater chemistry were observed in the catchments where the predominant hydrological pathway is the Matrix flow from the saturated ground water zone. In contrast, abrupt changes in streamwater chemistry were observed in the catchments where the predominant hydrological pathway is the Preferential flow from the soil pipe. The observed streamwater chemistry was analyzed using a model based on the end-members mixing concept. As a result, it was learned that the differences in the hydrological processes affect the streamwater chemistry of the catchments as follows; (1)In a catchment where the predominant hydrological pathway is the Matrix flow from the saturated groundwater zone, the chemistry of the groundwater component in a small saturated zone changes more easily for storm events having the same amount of rainfall, and this change affects the streamwater chemistry, (2)In a catchment where the predominant hydrological pathway is the Preferential flow, the hydrochemical process of the catchment is different from that of the catchment where the predominant hydrological pathway is the Matrix flow. This difference is because, in the former catchment dominated by Preferential flow, the end-member (of which chemistry is different from the groundwater chemistry of the saturated zone and the rainwater chemistry) mixes directly with the streamwater.

View full abstract

A simple method of pF measurement was developed by combining TDR-Tensiometer with TDR-Hygrometer. Using this method, we can measure the soil moisture characteristic curve over the wide range easily. This method was applied to the soil moisture characteristic curve of Toyoura sand. The experimental results were compared with those of the ordinary methods (e.g., suction and pressure plate methods), and its availability was discussed. As a result, the values measured by the TDR-Tensiometer were in good agreement with those of the ordinary methods, but the values measured by the TDR-Hygrometer were not satisfactory. Some problems to be overcome in the future were presented.

View full abstract