Due to the greenhouse effect, the climatic change that may alter the water cycle regime is now becoming recognized. On the other hand, the groundwater environment is getting worse and people are discouraged, although groundwater plays an important role as base flow of river discharge and as water resources.
Recently, the term water cycle is frequently used in the water policies by governments that attempt to establish a sustainable water environment. The groundwater hydrologists and engineers, therefore, need to take actions.
In the present article, discussions are made on what the experts of groundwater hydrology should do in order to implement the proposed policies. Specifically emphasis is put on how the groundwater expert contributes as an interface between the targeting goals and the actual water environment.

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In the center part of Miyazaki City, urbanization is advanced. On the other hand, the observed unconfined groundwater level gradually falls though there is no falling tendency to precipitation. The fall of the groundwater level shows that the hydrological cycle has been changed due to urbanization. However, the relation between the change in the ground cover condition and the change of the groundwater level has not been clarified analytically.
In the present study, it was examined to prove the fall of the groundwater level in the center part of Miyazaki City, which originated in the change of the ground cover condition, by using the percent imperviousness of the area and by the modified tank model. The change of unconfined groundwater level was analyzed for the period from 1982 to 1996 when the percent imperviousness was measured. As a result, it was confirmed that fall of the unconfined groundwater level during the period can be explained by changing only percent imperviousness and using same tank parameter.

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Recently the word‘Water Cycle’has become a hot issue as a new approach to the environmental preservation. Some organization have already started discussing measures and taken actions to retrieve water cycle. When we discuss water cycle, it is often necessary to quantify and model it. Models of water cycle are usually the tank models with no consideration to hydrogeological conditions, which makes it easier to conduct a water balance simulation. However, we would not be able to have essential discussions on water cycle, if we just leave the hydrogeological conditions of a target groundwater basin. If these conditions are understood well enough and can be put into an equilibrium groundwater flow analysis model and the application is limited to dry season when the groundwater recharge, storage and flow are minimum, it will be a very convenient tool in solving water cycle problem. This paper presents the possibility of applying the groundwater flow analysis models to the evaluation of measures taken for water cycle retrieval.

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The groundwater quality of all the area in Kumamoto prefecture was investigated by Kumamoto prefectural government from 1989 to 1994. As a result, groundwater with high concentration of nitrate-nitrogen was found out in U-town located in north area of Kumamoto pref. The investigation points were classified into four groups based on a relation between concentrations of nitrate-nitrogen and nitrogen isotope values of nitrate from the result of investigation of groundwater quality in 1995 and 1996. Study of nitrogen supply in each group indicated that the pollution of group containing most of investigation points was caused by infiltration of chemical fertilizer. The soils of the lands used for greenhouses and vegetable fields contained a high concentration of nitrate-nitrogen and to deeper portion compared with other types of land use, from study of concentrations of three nitrogen forms in solution dissolved soils of several types of land use. The quantities of nitrogen infiltration from several nitrogen-sources in U-town were estimated. The livestock industry and fertilizer had a large quantity of nitrogen infiltration to underground. It was conjectured that groundwater pollution by nitrate-nitrogen in U-town was greatly affected by infiltration of chemical fertilizer into a field.

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Heat pulse method is an useful tool for measuring flow velocity including sap velocity in a wood stem. Sap velocity can be converted to transpiration rate and thus be an important component for evaluating groundwater recharge. Recently, a digital heat-pulse sensor was developed and widely utilized. In this study, properties of errors in measuring flow velocity by the digital heat-pulse sensor were investigated by laboratory experiments using a sand column and by field observation in a pine forest.
Laboratory experiments showed that the measured heat-pulse velocity was overestimated. A semi-theoretical correction method was proposed and applied to the result of field measurement. The corrected velocities agreed with the values measured by the Granier method with an error of ±4 cm/hr. This indicates that the correction method is effective to reduce the overestimation although random error induced by an instability of sensor output was not improved very well.

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