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鞠智城の貯水池と韓国の古代山城の集水遺構を、立地、構造、機能的側面に分けて比較、分析した。鞠智城の貯水池は、韓国古代山城の集水遺構と立地＋構造＋機能的な面で親縁性が高いことが確認された。そして、築造技術的には百済、立地と構造的には百済・高句麗と類似しているといえる。

The purpose of this study is to develop and apply the carbon dioxide (CO2) measurement technique and to elucidate the CO2 concentration dynamics in the reservoir of freshwater regions, where the photosynthetic rate is high and the short-term changes are affected by the inflowing river. To clarify the CO2 concentration dynamics in the surface water, pH, dissolved oxygen (DO) and electric conductivity (EC) has been continuously and monthly measured in Sengari reservoir from 2016 to 2018.The total alkalinity (TA) highly correlated with the electric conductivity, and a linear equation that converts EC to TA was obtained for Sengari reservoir. The values of CO2 partial pressure (pCO2) were calculated using the “CO2SYS” by CDIAC that uses pH and TA. DO and pCO2 fluctuated with high correlation (R2= 0.90). This suggests that CO2 dynamics can be measured in freshwater using this method. DO and pCO2 records at the Sengari reservoir during the summer stratification period, when the photosynthetic rate was high, indicated prominent diurnal variations corresponding to the changes in solar radiation. In summer, surface water CO2 fluctuation had large diurnal change by photosynthesis, and atmospheric CO2 is absorbed to surface water. In the autumn, CO2 in surface water is released to the atmosphere.

長年，国内外の様々な地域で水環境の調査・研究を続けてきたが，最近は，年に1～2回，海外で調査する機会を作るように努め，その結果を継続して報告してきた。特に，アジア地域に力を入れ，マレーシア，インドネシア，中国，韓国と調査してきたが，2019年7月にAOGSがシンガポールで開催された際，シンガポール島全域の調査を行う機会を得たので，その概要を報告する。調査を行ったシンガポール島は，63の島からなるシンガポール共和国最大（東京23区程度）の島で，高度に都市化され，人口密度も高い（世界第2位）。高低差のない国土であるため水資源に乏しく，多数の貯水池と隣国マレーシアから購入した水に頼っている。河川は，勾配がなく緩やかなため，停滞しているところが多く濁っていて水質が悪いと思われたが，実際にサンプリングして分析したところ，水質が悪いのは汽水域など特別な場所に限られ，予想以上に良好な地点が多かった。汚水処理施設の充実と考えられる。人口密度が高く都市化はしているものの，居住空間としては，高層住宅を活かすことで公園や緑地が広くとられており，水辺空間も整備されていて，貴重な自然環境を保全する努力が見られ，学ぶ点が多かった。, Singapore Island, which was surveyed, is the largest island in the Republic of Singapore （about 23 wards in Tokyo） consisting of 63 islands, highly urbanized, and has a high population density （the second largest in the world）. Since it is a land with no difference in elevation, it lacks water resources and relies on many reservoirs and water purchased from neighboring Malaysia. Since the river has no slope and is gradual, it seems that there are many stagnant places and it is cloudy and the water quality is poor, but when actually sampled and analyzed, the poor water quality is found in special places such as brackish water areas. It was limited, and there were many better points than expected.Although the city is densely populated and urbanized, by utilizing high-rise housing as a residential area, there are many green spaces and a waterside space, and efforts to preserve the precious natural environment were seen, and there were many points to learn.

By the heavy rain in the northern part of Kyushu in July 2017, many rivers in the Chikugo River sys-tem were flooded and caused serious damage. In the Sata River located in the middle basin of the Chikugo River system, a large amount of driftwood flowed into the Terauchi dam due to the intensive flood. If driftwood had flowed into the downstream and had been clogged by the bridge piers, the Sata River might have overflowed in wide area near the bridges. Actually, there was little damage in the down-stream area because Terauchi dam had effects of flood control and driftwood trapping. In this study, the quantitative estimating method was developed by using the image processing software, Image J, to esti-mate driftwood volume and sizes over the reservoir area. In addition, the influence of driftwood trapping by the Terauchi dam on the downstream flood damage reduction was estimated by using two-dimensional hydraulic TELEMAC-2D model.