The 30-yr return levels of annual maximum daily precipitation at AMeDAS stations were estimated by applying regional frequency analysis with L-moments to each prefecture (sub-prefecture in case of Hokkaido). The results show that those estimated return values are highly close to ones estimated by the usual method with SLSC and stability. Moreover, by the verification based on the idealistic non-exceedance probability of the 30-yr return levels, estimated 30-yr return values by regional frequency analysis are likely to be closer to the idealistic values, and the efficiency of this method was confirmed.

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A series of small hydropower dams have been constructed along gorge sections of river in Japan. It is important to study hydraulic characteristics of flood flow associated with hydropower dams which will be usable for the future flood control management. At first, we show the effect of the gate operation of small hydropower dam on flood propagation speed and discharge hydrographs from observed results and unsteady 1D flow analysis which was developed so as to consider the effect of the gate operation. Secondary, storage functions of a gorge with a series of small hydropower dams are evaluated on the basis of the results of unsteady 1D flow analysis before and after the construction of a series of small hydropower dams.

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This paper first overviews the history of transboundary water dispute over the Euphrates and Tigris River Basin among Turkey, Syria and Iraq, and then discusses the possibility of the solution of this dispute. The dispute over the water resources of Euphrates and Tigris River has risen to the surface in the late 20th century as a result of the commencement of water resource development projects in each riparian state. Along with the development processes, the riparian states attempted to hold dialogues to reach agreement in the allocation manner of these rivers and they succeeded in establishing the Joint Technical Committee, but they have failed to achieve substantial agreements. As a potential driving force to settle this long-lasting dispute, this paper shed light in 'issue linkage approach', in which the issue in dispute is combined with other issues so as to induce compromise in the central issue. The history tells that the successful settlement in the Colorado River water dispute between the U.S. and Mexico in the mid 20th century was a perfect example of issue linkage approach. Reviewing available information sources, this paper revealed that three issues that may facilitate the negotiation on the water resources of the Euphrates and Tigris, namely energy security, border trade and ethnic problem.

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The Working Group II contribution to the Fourth Assessment Report (AR4/WG2) of the Intergovernmental Panel on Climate Change (IPCC) summarized the recent scientific findings on the revelation and future projection of climate change impacts, the adaptation for reducing the climate change impacts and vulnerability. We introduce the summary of observed results and future projection of climate change impacts on natural environment and human society reported by AR4/WG2. We focus on the observed results and future projection climate change impacts in Japan as well as the freshwater resources and management. Furthermore, we argue the future subjects on the research for the freshwater resources and managements in addition to the future tasks on the research for the climate change impacts assessment toward the Fifth Assessment Report of the IPCC (AR5).

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The report of the working group three of the IPCC 4^th Assessment Report (AR4) includes the summary for policy maker. The summary is not easily readable due to scientific jargons and conflicting political intents. The author explains the meaning and political background of the key 28 sentences of the summary to the non-experts of WG3.

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