トウホク タイ ニ オケル デントウテキ カンガイ ノ レキシ オヨビ コウゾウ キノウ ソシテ チケイテキ セイリツ ヨウイン ニ カンスル ケンキュウ

京都大学0048新制・課程博士博士(農学)甲第10876号農博第1382号新制||農||887(附属図書館)学位論文||H16||N3887(農学部図書室)UT51-2004-G723京都大学大学院農学研究科地域環境科学専攻(主査)教授 小林 愼太郎, 教授 三野 徹, 教授 河地 利彦学位規則第4条第1項該当Doctor of Agricultural ScienceKyoto UniversityDA

Economic Feasibility of Diversified Farming System in the Flood-Prone Mekong Delta: Simulation for Dike Area in An Giang Province, Vietnam

A simulation of crop choice was performed to examine the feasibility of introducing diversified farming systems, coexisting with seasonal floods, as an alternative to triple rice cropping system in the flood-prone Mekong Delta in Vietnam. A combination of 1.78 to 1.88 ha of double rice cropping and 0.12 to 0.22 ha of upland cropping can achieve an equivalent income or profit from 2 ha of triple rice cropping. Farmers evaluated the full-dike system positively in terms of both economic aspects and living conditions. Some farmers recognized that full flood control might have worsened the natural environment and reduced soil fertility resulting in declining rice yields. To establish a smart flood control system as an adaptation strategy against expected climate change, the following measures must be undertaken: (1) sensitize farmers to the increasing climatic risk in the near future and long-term adverse effects of intensive triple rice cropping; (2) offer alternative environmentally sound and economically profitable farming systems; and (3) develop institutional design for well-coordinated gate and pumping operations both at dike units and in canal network systems

Characteristics of the Annual Maximum and Minimum Water Temperatures in Tonle Sap Lake, Cambodia from 2000 to 2019

The Tonle Sap Lake contains unique hydrological environments and ecosystems. Although water temperature is an important consideration in lake management, information on the water temperature of the lake is limited. Thus, we investigated the characteristics of the daytime water temperatures of the Tonle Sap Lake from 2000 to 2019 using MOD11A1, a Moderate Resolution Imaging Spectroradiometers (MODIS) product. Moreover, the relationship between water temperature fluctuations and hydrological–meteorological conditions was analyzed. The maximum and minimum daytime water temperatures were recorded in May (30.7 °C) and January (24.6 °C), respectively, each a month after the maximum and minimum air temperatures were recorded. The annual maximum, average, and minimum water levels showed a downward trend (−0.14, −0.08, and −0.01 m/y, respectively). The annual maximum water temperature increased at a rate of 0.17 °C/decade, whereas the annual minimum water temperature decreased at a rate of 0.91 °C/decade. The annual maximum daytime water temperature had a strong negative correlation with water level change (flood pulse) and a weaker correlation with air temperature. The annual minimum daytime water temperature presented the strongest positive correlation with water level change (flood pulse) in the previous year. However, there was no correlation between the annual minimum daytime water temperature and air temperature. These results indicate that water temperature in the Tonle Sap Lake is mainly affected by water level fluctuations, which are mainly driven by flood pulses

An Integrated Hydrological-Hydraulic Model for Simulating Surface Water Flows of a Shallow Lake Surrounded by Large Floodplains

An integrated hydrological-hydraulic model employing the 2-D local inertial equation as the core is established for effective numerical simulation of surface water flows in a great lake and its floodplain. The model is a cascade of validated hydrological and hydraulic sub-models. The model was applied to simulating the surface water flows of the Tonle Sap Lake and its floodplain in Cambodia using the roughness coefficient value calibrated comparing with a remote-sensing data set. The resulting model reasonably handles backwater flows during the rainy season and simulates the propagations of wet and dry interfaces without numerical instability, owing to a proper setting of time step supported by a novel numerical stability analysis. Sensitivity analysis of the surface water dynamics focusing on the setting of roughness coefficient and the backwater effect was also carried out. Overall, utilizing the 2-D local inertial equation in the assessment of lake water dynamics is a new modelling approach, which turns out to be an efficient simulation tool