International awareness on water crisis has been rising through the World Summit on Sustainable Development (WSSD) in 2002, the Third World Water Forum (3WWF) in 2003, the International Year of Freshwater (2003) and the International Decade for Action: Water for Life (2005-2015) proclaimed by the UN resolutions, and the G8 Summit (2003) in Evian, France. In this context, the World Water Assessment Programme (WWAP) established in August 2000 under Japanese leadership is developing as the first UN System-wide programme on water resources while it has been highly appreciated by both developed and developing countries. The comparison between the WWAP and the Global International Waters Assessment (GIWA) led by UNEP has identified crucial factors in the success of WWAP, a UN water initiative. They are: 1) political leadership, 2) multilateral framework, 3) UN System-wide scheme, 4) governmental ownership and initiative, and 5) effective media strategy.

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Successful forestation using hardpan blasting in arid land having a hardpan layer requires selecting the most suitable tree species. Growth improvement by hardpan blasting is different among species; for example, the growth of Eucalyptus camaldulensis was improved, while that of Acacia aneura was not. It is hypothesized that the interspecies difference in growth improvement is attributable to the trees' ability to obtain water found deep in the soil at the blasted plot. The depth of the main water sources of the two species under hardpan blasting and nonblasting (i.e., natural) conditions was estimated by oxygen stable isotope analysis using branch water, soil water irrigated water and well water and by monitoring the volumetric water content at each depth. The main water source of both species at the nonblasted plot was the thin plow layer above the hardpan layer found at a depth of 20 cm. The plow layer was extremely dry during the dry season. However, soil below 100 cm at the blasted plot was wet condition, even during the dry season. The water source of E. camaldulensis was below 100 cm at the blasted plot, while that of A. aneura was above 100 cm. Therefore, E. camaldulensis could use the water found in the deeper soil, while A. aneura could not. It is suggested that the growth of the tree whose main water source is deep (>100 cm ) is improved by hardpan blasting.

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To clarify the effects of forest management on canopy interception, experiments to identify water storage capacity on branches of Japanese cedar and cypress were carried out and a model of tree form was developed to predict the effects of cutting branches and trees. The estimated storage capacity on a tree by the model is almost same as the calculated one using the experiment's result. Furthermore, the model was applied to estimate the storage capacity on trees in actual fields and the estimated values were compared with the calculated one in an experimental plot or reported one by other authors. As a result, it was found that those estimated values correspond reasonably to the calculated or reported values.

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Arsenic contamination of underground water has been a serious problem in Bangladesh. Various alternative technologies were introduced to supply safe drinking water since arsenic contamination was discovered. However, the technologies were not necessarily accepted by local residents. Many inhabitants carry water everyday from safe water sources which are sometimes far from their houses although they feel big burden in carrying water. Otherwise, they continue to drink arsenic contaminated water of the wells which are located close to their residences even though they know the water is arsenic contaminated. Regarding of this background, arsenic contamination of drinking water in Bangladesh is not thought that it is resolved simply by tackling improvement of arsenic removal technologies. It is important to recognize this arsenic contamination problem as a disaster which is deeply related with local social environment.
In this study, paying attention to the relation between the disaster and local social environment in Bangladesh, mitigation planning on arsenic contamination disaster is presented. The planning is composed of clarification of the issue, investigation of villages, and analysis of local residents' behavior and psychological background about their water selection. After conducting these processes, water utilization alternatives for residents to get safe water are designed, which are possibly acceptable for local residents.

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This study presents an application of the Particle Swarm Optimization (PSO) algorithm to the parameter optimization of rainfall-runoff models. Six global optimization algorithms, the shuffled complex evolution method (SCE-UA), modified SCE-UA, modified SCE-UA with initial value, PSO, modified PSO and modified PSO with initial value, were applied to parameter optimization on four kinds of series tank models. Performance comparison of there algorithms was evaluated and it can be concluded that SCE-UA and PSO show comparable performance in most cases. In addition, PSO is more effective than SCE-UA under the following conditions. 1) the model has large number of parameters, 2) the model has wide range of parameters, 3) calibration period is too short, 4) observation data contains large uncertainty. The modified PSO with initial value shows the most effective and stable performance.

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Though hydrological models often require solar radiation as input data, solar radiation observations are not so common as temperature and precipitation observations. Therefore, there are many methods for estimating the solar radiation including methods for estimating solar radiation from daily maximum and minimum temperatures. We investigated applicability and accuracy of this method to Japan using Japan Meteorological Agency measurement data, and obtained the following three conclusions. (1) When determining model parameters A and C based observed solar radiation data for each site, model estimation showed nearly no bias with RMSE = 4.40 MJ m^-2 day^-1. (2) When A and C cannot be determined due to absence of observed solar radiation data, assuming A = 0.76, C and C = 2.2 is recommended in Japan. (3) The accuracy based on the method is comparable to that substituting solar radiation data at an observation point ca. 200 km far from the site, indicating the method is useful when solar radiation data within ca. 200 km from the site are available.

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