| 1. |
Daoluang Honglikith, Masayoshi Harada, Kazuaki Hiramatsu, Toshinori Tabata, Akinori Ozaki, Water Quality Improvement via Anoxification Recovery Using Underwater LED Irradiation, International Conference of PAWEES 2021 Taiwan, 2021.10. |
| 2. |
Sai Hong Anh, Toshinori Tabata, Kazuaki Hiramatsu, Le Viet Son, Masayoshi Harada, Assessment of Floodwater Impact on Residential Areas in the Floodplain Areas along the Day River System in the case of Emergency Solution to Protect Hanoi Capital, 7th JASID (The Japan Society For International Development) Western Japan Research Meeting, 2020.08. |
| 3. |
Takuma Kobayashi, Masayoshi Harada, Kazuaki Hiramatsu and Toshinori Tabata, Seasonal Changes in Phytoplankton characteristics in a Hyper-eutrophic Water Area under Nitrogen Limitation, Integrated Land & Water Management and Climate Change in Vietnam and Japan, 2019.11. |
| 4. |
Misaki Kawara, Masayoshi Harada, Kazuaki Hiramatsu and Toshinori Tabata, Experimental Suppression of Phytoplankton Growth Employing Bactericidal Effects of Copper Ions under Eutrophic Conditions, Integrated Land & Water Management and Climate Change in Vietnam and Japan, 2019.06. |
| 5. |
Makoto Fukui, Kazuaki Hiramatsu, Shinji Fukuda, Dario Pineda, Toshinori Tabata and Masayoshi Harada, Development of long-term rainfall-runoff model and scenario analyses for water-saving effect in rice farming in the Ibague Watershed, Colombia, Integrated Land & Water Management and Climate Change in Vietnam and Japan, 2019.11. |
| 6. |
Toshinori Tabata, Akihiro Fukuda, Kazuaki Hiramatsu and Masayoshi Harada, Applicability of a Three-Dimensional Dissolved Oxygen Model, Integrated Land & Water Management and Climate Change in Vietnam and Japan, 2019.11. |
| 7. |
Sai Hong Anh, Toshinori Tabata, Kazuaki Hiramatsu and Masayoshi Harada, Evaluation of Flood Mitigation Function of the Van Coc Lake in a Catastrophic Flood Event of the Red River, Northern Vietnam, Integrated Land & Water Management and Climate Change in Vietnam and Japan, 2019.11. |
| 8. |
Akihiro Fukuda, Toshinori Tabata, Kazuaki Hiramatsu and Masayoshi Harada, Salinity Analysis for Tracking the Behavior of Large Freshwater Discharge into Hakata Bay Due to Heavy Rainfall Using a Three-Dimensional σ-Coordinate Model, Integrated Land & Water Management and Climate Change in Vietnam and Japan, 2019.11. |
| 9. |
Sai Hong Anh, Toshinori Tabata, Kazuaki Hiramatsu and Masayoshi Harada, Scenario analyses for the emergency solution to protect Hanoi Capital from flood disaster of the Red River, 令和元年度農業農村工学会大会講演会, 2019.09. |
| 10. |
Kunihiko Hamagami, Satsuki Yamaki, Masayoshi Harada, Akinori Ozaki,
Toshinori Tabata and Kazuaki Hiramatsu, Stratification and Movement Characteristics of Algae in a Small Reservoir, International Association for Hydro-Environment Engineering and Research (IAHR) World Congress, 2019.09. |
| 11. |
Toshinori Tabata, Mitsuhiro Inoue, Kazuaki Hiramatsu and Masayoshi Harada, Hydraulic Analysis of Sediment Transportation in Yamada Weir Located in Chikugo River, Japan, International Association for Hydro-Environment Engineering and Research (IAHR) World Congress, 2019.09. |
| 12. |
Akihiro Fukuda, Toshinori Tabata, Yuri Honda, Kazuaki Hiramatsu, Harada Masayoshi, Simulation of large freshwater behavior in Hakata Bay due to torrential rain using nested two-dimensional model, 21st Congress of International Association for Hydro-Environment Engineering and Research-Asia Pacific Division: Multi-Perspective Water for Sustainable Development, IAHR-APD 2018, 2018.09, In this study, a numerical simulation consisting of a two-dimensional model of Hakata Bay, Kyushu Island. Japan, was conducted to analyze the impact oflarge river discharges due to torrential rain. Since Fukuoka city, one of the largest cities in Japan, surrounds Hakata Bay, the bay has a very complex environment, including an artificial island (Island City) in its eastern region and small bay (Imazu Bay) where tideland is spread with rich ecosystems in its western region. Tank models were applied to calculate the discharges of the 38 rivers that flow into Hakata Bay, and a two-way nesting technique, "edge nesting," was developed and applied in the model to capture the influence of complex geographical features, such as the Island City area and the Imazu Bay area, which were nested with a high-resolution mesh. The model accurately reproduced the observed tidal current and salinity data. To simulate the behavior oflarge river discharges, a historical simulation period including a torrential rain event (163.5 mm/d) was input into the model. The results showed that after the rain event, low-salinity water covered the entire inner part of Hakata Bay, and freshwater covered the entire area of the tidal flats and flowed out from the mouth of Imazu Bay. The behavior of this large mass of fresh water was remarkably different from usual discharge river flow. These results indicate that the environment in the bay can be significantly changed by torrential rain events.. |
| 13. |
Toshinori Tabata, Kodai Nakashima, Kazuaki Hiramatsu, Harada Masayoshi, Investigation of the effects of human activities using multi-box ecosystem model in the Ariake sea, Japan, 21st Congress of International Association for Hydro-Environment Engineering and Research-Asia Pacific Division: Multi-Perspective Water for Sustainable Development, IAHR-APD 2018, 2018.09, In this research, the effect of human activities has been investigated in the Ariake Sea located in Kyushu Island. Japan. The Ariake Sea has been suffering from environmental degradation for more than a decade with unstable fisheries productivity. Therefore, it is important to understand the change of environmental characteristics in the Ariake Sea quantitatively. Moreover, it is concerned that the fertilizer applied for the aquaculture is effecting to the ecosystem in the sea. Also, since nutrient loading from rivers are so high that red tide or anoxic water mass occurs every year, it is significant to evaluate the effect of nutrient load to the sea. Therefore, in order to characterize the coastal environment and investigate the effect of human activities, Muti-Box Ecosystem model have constructed to simulate the water quality items in the Ariake Sea. The sea was divided into 12 boxes. Each box is comprised of three layers which is water, oxidative bottom and reductive bottom layer. Simulation period was set from 1st January 2000 to 31st December 2012. The model reproduced the water quality items well. Then, the model calculated with two different scenarios about the fertilizer application to the aquaculture and nutrient load from the river. The result showed that the fertilizer for the aquaculture has no effect to the coastal ecosystem and coastal environment would improve if the nutrient load reduced by half.. |
| 14. |
Asari Takada, Kazuaki Hiramatsu, Trieu Anh Ngoc, Harada Masayoshi, Toshinori Tabata, Development of a mesh-based distributed runoff model incorporated with tank models of several land utilizations in a Southeast Asian watershed, 21st Congress of International Association for Hydro-Environment Engineering and Research-Asia Pacific Division: Multi-Perspective Water for Sustainable Development, IAHR-APD 2018, 2018.09, We propose a new long-term rainfall-runoff model for a Southeast Asian watershed. To reflect the impact of land use changes associated with rural development, and the nonuniformity of rainfall in tropical regions, a mesh-based distributed runoff model was constructed. Four tank models (paddy, upland field, urban, and forest) were incorporated into each mesh element, to capture the outflow from different land uses. Each mesh element was connected to the river network to reproduce the rainfall-runoff flow processes. By incorporating a watershed groundwater tank, we improved the representation of the baseflow component which is important in long-term runoff analysis. To shorten the calculation time and improve the application to other watersheds, we introduced an inflow/outflow matrix that defines the direction of rainwater flow between adjacent mesh elements. The model was applied to the Dau Tieng watershed in Southern Vietnam, with an area of 2,700 km
2
. The model was run for the period 1999-2009, and the calculated discharge was compared with the observed values, and a good model fit was achieved. As the model represents the flow processes from rainfall to river discharge with highly versatile tank models, it can be applied to watersheds where hydrological data for model verification are scarce, which is a common issue for many developing countries in Southeast Asia.. |
| 15. |
Harada Masayoshi, Tran Tuan Thach, Kazuaki Hiramatsu, Toshinori Tabata, Biochemical characteristics of water quality dynamics near the bottom sediment under anaerobic state in the organically polluted reservoir, 21st Congress of International Association for Hydro-Environment Engineering and Research-Asia Pacific Division: Multi-Perspective Water for Sustainable Development, IAHR-APD 2018, 2018.09, Anoxic conditions, occurring in enclosed water bodies from an overabundance of organic matter, cause further deterioration of the aquatic environment through nutrient elution and hydrogen sulfide production. The quantises of biochemical reactions under anaerobic states, such as denitnfication, iron reduction and sulfate reduction are important research topics when considering conservation and improvement of water quality environment. This study involved regular observations for two years in the reservoir, in which overabundant organic matter was prominent due to humic acid, to evaluate the water quality dynamic near the bottom during long-term anoxic periods. Based on the temporal changes of dissolved oxygen, nitrate-nitrogen, ammonia-nitrogen, phosphate-phosphorus, sulfide, total iron ions, and sulfate, this study focused specifically on the influence of the redox state of the sediment surface during the early stage of thermal stratification on the anaerobic biochemical reactions. As a result, nitrate-nitrogen started to decrease to zero due to denitnfication as soon as the anoxic state occurred, and then both ammonia-nitrogen and phosphate-phosphorus increased linearly with time due to iron reduction after nitrate-nitrogen had decreased to zero. Sulfide began to increase linearly due to sulfate reduction as soon as nitrate-nitrogen disappeared. Also, the initial redox state of sediment impacted on the change characteristics of phosphate-phosphorus, ammonia-nitrogen and sulfide in the points of increasing timings, duration, and rates. It was concluded that our results would provide important finding about the mechanisms of aqueous environmental deterioration due to organic pollution as well as beneficial information for the modification of water quality prediction model.. |
| 16. |
Toshinori Tabata, Wataru Hayashi, Emi Otsubo, Kazuaki Hiramatsu, Masayoshi Harada, Appropriate Water Quality Environment for Protecting the Coastal Ecosystem in the Ariake Sea, Japan, 37th World Congress of the International Association for Hydro-Environment Engineering and Research (IAHR), 2017.08. |
| 17. |
Sai Hong Anh, Toshinori Tabata, Kazuaki Hiramatsu, Masayoshi Harada, Le Viet Son, Impact of Flood to Residential Areas in Van Coc Lake, Hanoi Vietnam, 2017 Annual Conference of the Japanese Society of Irrigation, Drainage and Rural Engineering, 2017.08. |
| 18. |
Vu Thi Hoai Thu, Toshinori Tabata, Kazuaki Hiramatsu, Trieu Anh Ngoc, Masayoshi Harada, Effects of tides and upstream flow on inundation of Can Gio mangrove forest, Vietnam, 2016 Annual Conference of the Japanese Society of Irrigation, Drainage and Rural Engineering, 2016.08. |
| 19. |
Hoang Quang Duong, Takayoshi Nishioka, Masayoshi Harada, Kazuaki Hiramatsu, Toshinori Tabata, Water Quality Dynamic above the Bottom Sediment under an Anaerobic State in an Organic Polluted Reservoir, 2016 Annual Conference of the Japanese Society of Irrigation, Drainage and Rural Engineering, 2016.08. |
| 20. |
田畑 俊範, 大坪 えみ, 平松 和昭, 原田 昌佳, Assessment of the Bivalve Production with Water Quality in the Ariake Sea using Artifitial Neural Network
, 9th Vietnamese – Japanese Student’s Scientific Exchange Meeting, 2016.09, The purpose of the present study is a close examination of the relation between water environment quality factors and bivalve catch volumes in the Ariake Sea, and a quantitative assessment of the effect of changes over time in the water environment on fishery stock. To this end, we focused on hierarchical neural network modeling to build a bivalve catch volume estimation model based on the related factors of organic contamination and eutrophication. The model showed a good result for estimating Asari clams (see Fig.1). Furthermore, we used this model in a sensitivity analysis to assess the effect of changes in the marine environment of the Ariake Sea on bivalve catch volumes. Results suggested that the primary cause of reduced catch volumes for the Asari clam (Ruditapes philippinarum) in recent years are increased transparency and excessive COD reduction in the Kumamoto Prefecture coastal waters as shown in Fig.2 and Fig.3, respectively. On the other hand, this report does not as yet have a clear conclusion as to the reasons behind the trends of increased water transparency and reduced COD in the Ariake Sea at the Kumamoto Prefecture coast. These changes in water quality are a subject for future investigation.. |
