Long-term water quality data with high temporal resolution, together with hydrological data, are essential in developing hydrogeochemical and diffuse pollution modeling. An in situ flow injection potentiometry (FIP) system to monitor the stream water quality (chloride, sodium and potassium) every 15 minutes for two weeks was developed and tested in the laboratory and in a small forested catchment in Gozyo City, Nara Prefecture, Japan. The system resolves main hurdles that prevent long-term monitoring, except the problem of samples freezing in winter. Frequent calibration with three standards was adopted to compensate for the temperature dependency of ion-selective electrodes. The results of monitoring stream water quality in this catchment in 2004 showed clear differences in the concentration of the ions of chloride, potassium, and sodium depending on discharge: chloride showed the simple washout of accumulated atmospheric input, potassium implied the washout from the stock in the shallow soil layer, and sodium indicated the effect of ion exchange and chemical weathering.

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The management of suburban pine (Pinus densiflora) forests in Japan has been almost abandoned, causing invasion of understory plants and secondary succession from the shade-intolerant tree forest to the shade-tolerant tree forest. The water sources for pine and co-occurring plants were identified by comparing isotopic signatures of rain, soil, ground, and sap waters. We obtained clear evidence that there was niche separation of water source: preexisting pines took up deep soil water and/or groundwater, while invading oaks (Quercus myrsinaefolia) absorbed shallow soil water and understory (mainly Pleioblastus chino) utilized soil water in intermediate depth zone. A fact that water source separation can occur under not only arid climate but also relatively humid climate would be important for addressing interactions between ecosystem and hydrological cycle.

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The overwinter water loss due to evaporation at a field in the upper reaches of the Yellow River in Inner Mongolia, China, was evaluated. It was estimated that the field was irrigated by impounding more than 230 mm of water in late autumn, but only about 20 mm remained in the upper 100 cm of soil when corn was planted in the next spring. Although precipitation of about 40 mm occurred during the period, about 170 mm was lost by evaporation and more than 80 mm percolated into the aquifer when irrigation was practiced. On the other hand, Wang et al. (2006) estimated in the same field that about 80 mm moved upward by capillary rise into the root zone in spring and early summer of little rain. Consequently, only about 100 mm out of the irrigation water of more than 230 mm was utilized for growing corn in this field. Furthermore, a considerable part of the evaporation of about 170 mm must have been occurred because of the application of autumn irrigation.
The results obtained in this study may be applicable to the site in the alluvial valley of the upper Yellow River where the depth of the water table is in the range of about -1 m to -2 m.

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We aimed to clarify diurnal and seasonal changes of the photochemical reflectance index (PRI) in a temperate Japanese cypress forest and evaluate PRI as an indicator of canopy photosynthetic light-use efficiency (LUE). PRI and LUE were calculated from canopy-scale, ground-based measurements. PRI was high in the mature-leave phase from summer to autumn, and low both in the expanding phase during spring and in the red-brown-leave phase during winter. PRI decreased under excess light on clear days in spring and summer, whereas did not decrease under moderate light and temperature in autumn, and showed low values all day in winter. Such seasonal and diurnal patterns were considered to be related with how Japanese cypress leaves dissipated thermal energy against light, affected by the phenology. When we removed the effect of strong light dependence of the LUE and selected the data during clear sky, PRI was almost linearly related to LUE throughout the season.

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The Dead Sea is hydrologically considered a very important place due its location at the lowest point on the Earth at an elevation of 416.3m below sea level, and being the saltiest lake (332kg/m³) in the world. The continuous decrease in the Dead Sea water level is causing serious environmental problems in the region. The most important is reduction of the Dead Sea area, and its effects on the surrounding groundwater resources. This paper assessed the Dead Sea area changes by studying the relationship between human activities, represented by evaporation pond surface area, and the Dead Sea surface area, in order to determine the boundary conditions of the Dead Sea groundwater basin for possible groundwater resources assessment. In this study, it is found that the Dead Sea surface area has shrunk by 30.4% during the period 1973 to 2004, and the evaporation pond surface area has increased by more than 600%. The continuous expansion of evaporation ponds for industrial works in both Jordan and Israel is accelerating the evaporation rate of the Dead Sea. In the last few years, the average drop of the Dead Sea water level has been 1 m/year. About 47% of this drop results from the industrial works.

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Ten sediment cores, collected from Ise Bay, were used to determine the annual sedimentation amount in the bay using ²¹⁰Pb method. A general increasing trend in annual sedimentation amount over the last century was found, and was prominent after 1950. Sedimentation amount in 2000 is ∼2 million tons, which is ∼2.5 times of that in 1900. The increase rate of annual sedimentation amount is similar to the increase rate of the populations in the catchment (Aichi, Gifu and Mie). The generally increasing trend in annual sedimentation amount might be related to the improvement of river discharge regime. It is speculated that the particles from the dredging and reclamation contributed significantly to the abrupt increase in annual sedimentation amount after 1950.

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I estimated the difference of observed air temperature at surface observation stations at the time of equipment renewal from JMA-80 to JMA-95 surface meteorological observation equipments. The following facts are obtained: 1) the difference in extreme air temperatures caused by the equipment renewal is estimated from the difference in extreme air temperatures of the surface observation data and the AMeDAS observation data before and after the renewal; 2) significant jumps in monthly mean maximum and minimum temperatures are estimated at the time of the equipment renewal and its magnitudes are +0.14±0.04 and -0.04±0.01 degrees Celsius (Ave.±S.D.), respectively; 3) significant jump of +0.18±0.04 degrees Celsius (Ave.±S.D.) in monthly mean temperature range is detected, and the jump in monthly mean maximum temperature contributes to seventy percent of the magnitude;

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