To evaluate the water use of various trees in several different habitats, we measured leaf transpiration rate, stomatal conductance, and leaf and soil water potential to calculate leaf-specific hydraulic conductance and difference between soil and leaf water potentials. We also made P-V curve measurement to evaluate leaf water relations of these trees. Explicating leaf-specific hydraulic conductance, leaf water characteristics and transpiration rate together, we illustrated the manner of water use in several tall trees that compose their forest canopy. Although Fagus crenata Blume, a cool-temperate deciduous broad-leaved species, had higher leaf-specific hydraulic conductance, its leaf water potential at turgor loss point is higher indicating dehydration-postpone strategy. In Chamaecyparis obtusa Sieb. et Zucc., a temperate conifer, declines of leaf-specific hydraulic conductance and transpiration in dry period suggest occurrence of hydraulic disorder and stomatal regulation. Four warm-temperate evergreen species maintained low stomatal conductance even in wet period, and improved leaf dehydrate-tolerance by Osmo-regulation in dry period. Two tropical evergreen broad-leaved species have low leaf-specific hydraulic conductance, whereas Dipterocarpus sublamellatus Foxw., one emergent species, have higher leaf-specific hydraulic conductance compared to other two species, suggesting that it have a feed-water system overcome distant water transport.

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For an environment assessment related with the water pollution in the river basin, an analysis of each process such as pollutant release, distribution and exposure processes is needed to link in the significant scale. The purpose of this research is to build a hydrological river basin assessment model for an estimation of the water pollution distribution and an assessment of damage on fish population by using the distributed runoff model. A target area of the proposed simulation is the Yodo River basin including the Lake Biwa. The simulation is performed for an estimation of the distribution of Nonylphenol and Linear Alkylbenzene Sulfonate by physical-based model. Physiologically Based Pharmacokinetic model is used to estimate the accumulation of the chemical substance in fish body and the risk assessment of chemical substances is analyzed based on the simulated concentration of the chemical substances.

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Thermal environment in an urban river system can be significantly changed due to wastewater heat. If the stream temperature increases due to the wastewater heat, it is likely to damage the river ecosystem. On the contrary, the wastewater heat can be used effectively for heat energy. In this paper, the results of an intensive observation and dynamic simulation of water and heat transport in lower reaches of Ara River were reported.
Firstly, we clarified the actual state of the heat transport in lower reaches of the Ara River by the observation. It was found that Ara River receives a lot of heat from Sumida River and Shingashi River through the Iwabuchi gate. Secondly, stream temperature was reproduced using one-dimensional model which integrated water and heat transport process. Finally, wastewater impact on stream temperature in lower reaches of the Ara River was quantitatively evaluated using the dynamic simulation model. Consequently, it was found that wastewater increases stream temperature by 3 'C at the maximum in winter.

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In the Edo era, it was difficult for travelers in Tokai-do (the main road from Tokyo to Osaka) to pass through the Oi river because of the high water level and rapid flow. After the WWII, however, the river flow dramatically decreased due to hydropower dams developed throughout the river. As a result, the landscape of some parts in the downstream became called "river desert" because the wide river bed was covered by gravel without water. The aim of this study is to investigate flow regime changes from 1923 to 2000 to understand how much flow regime was changed in the past 80 years. It was found that before constructing the Shiogo Dam (before 1957), the normal, low, drought flow was 51.0, 29.4, 16.4 m³/s respectively. After constructing the Shiogo Dam (after 1963), the inflow of the dam were also reduced to 10.7, 5.2, 2.6 m³/s respectively. If people wish to restore the river flow regime in the Oi river, it will be not enough to remove the Shiogo Dam. An integrated river flow management is essential to restore the river flow regime in the past.

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Lake Okutama is an artificial lake formed by the Ogochi Dam that blocks the upstream of the Tama River. Analyzing the plankton data of 30 years (1974-2003) at the Ogochi Dam point, this paper characterized the water quality transition that can be divided into three patterns and three periods in terms of the increase of dominant plankton species. This paper revealed that the recent water pollution phenomenon is caused by the third pattern, which indicates an increase of cyanbacteria. After the enforcement of "selective withdrawal" in 1992, Anabana and the Microcystis became the dominant species in 1999. The selective withdrawal has changed the flow mechanism of the reservoir. It was considered that management of dam reservoir operation was related to the appearance of Anabaena and Microcystis, which cause the water pollution.

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As the serious floods due to typhoon or concentrated heavy rainfall have been happened at many areas in the world, the total control system for the whole river basin is getting significant. The distributed runoff model can be provided through newly arranged mesh data and GIS technologies. From the viewpoint of real-time flood prediction to prepare the necessary countermeasures or actions, the system should keep the quick response and high accuracy against abnormal rainfall events with new methodologies.In this research artificial intelligence is used to develop a distributed flood forecast system capable of real-time simulation of river flood levels at all locations within a watershed. Parameter calibration of a distributed rainfall-runoff model (Hydro-BEAM) is carried out using a particle filter, and real-time modeling of river discharge is enabled through the use of a State-Space Neural Network. Optimal training of the neural network is carried out using Optimal Brain Damage, which systematically reduces weak links in the network to allow for improved forecast efficiency and accuracy. An application is made for the Nagara River watershed to demonstrate the effectiveness of the system.

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The establishment of technologies for large-scale afforestation in arid lands for carbon fixation is expected. This technology is one of the countermeasures for reduction of carbon dioxide that is the main cause gas of global warming. Arid lands can provide only small amount of water for plant growth, so highly effective water use is required. The objective of this study is the establishment of a method to estimate the amount of water required for tree growth on the basis of nutrion flow in a tree. Therefore, detailed examination on the effects of various factors on the behavior of nutrions is necessary. In this report, the behavior of nutrions in a sap was examined by changing pressure for sap extraction, height of a tree, distance from tree bottom, and time in a day for Eucalyptus camaldulensis, one of the typical species in the research area near Leonora, Western Australia. As results, the pressure for extraction of a sap from a tree had remarkable influence on the nutrion concentration which approached a value with increased pressure. The daily variation in the nutrion concentration was also found to exist. Effects of other factors on the behaviors of nutrions in a sap were not found.

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This paper describes an ecological classification of tropical monsoon forests in northern Thailand and reviews published hydro-meteorological studies conducted at each forest type. As a result of summarizing current status of knowledge, we found that basic hydro-meteorological aspects, i.e. seasonal variation in energy partitioning throughout a year with normal climatological condition, at most of the forest types in the region has been already studied. Also, we found a clear contrast in evapotranspiration in the dry season between forest types. The contrast might be one of notable characteristics of hydro-meteorology in tropical monsoon forests in the region. Inter-annual variations in both rainfall and its seasonal distribution might be significantly large in this region, leading to occasional severe droughts and irregular ecological rhythms of trees. Recent findings from several study sites imply that the variations in rainfall result in phenological and physiological responses of the studied forest ecosystems. These responses in turn may affect the exchanges of energy, water vapour, and carbon between forest ecosystems in the region and the atmosphere. Such effects of temporal variations in rainfall on the tropical monsoon forests have been poorly understood thus far. We, therefore, stress the necessity of further efforts to examine the ecological and hydro-meteorological responses of all tropical monsoon forests to the inter-annual variation in rainfall and its seasonal distribution.

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In order to restore river ecosystem, it is necessary to manage the sediment dynamics in rivers. Therefore, the forming process of microhabitat in a riffle was focused on, and sediment dynamics in it was analyzed.
In this study, the following three analyses were carried out in consideration of hierarchical structure of spatial scales. Firstly, it was analyzed how riffle shape was determined by the condition of a gravel bar that depends on the sediment condition. Next, it was investigated how the distribution of depth and velocity was in each riffle shape. Finally, the relationship between microhabitat condition on riffle bed and hydraulic condition was analyzed.
Consequently, the following characteristics were clarified. Riffles can be classified into three types; Convergence, Long, and Wide type. The shape is determined by the amount of sediment which determines the development of gravel bar. Each riffle has its original bed slope, cross-sectional shape and hydraulic condition. Moreover, thickness of the open work gravel on a riffle bed tends to be thick in a riffle that discharge is large. Therefore, the thickness of the surface layer is largest in a convergence type riffle that has the most diverse hydraulic condition. In terms of micro habitat in a riffle, the area with thick surface layer locates downstream side of a riffle. And also, the surface layer at both sides of riffle is thinner than that on a thalweg. Moreover it was clarified that it takes a few weeks to develop the gravel structure in a riffle after flood.

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