Water quality characteristics of rivers in volcanic areas affected by discharge from hydroelectric power plant
Lin, X.; Shinozaki, M.; Maeda, S.; Kuroda, H.
PAWEES 2024, 2024年10月, ［査読有り］
Development of energy-saving irrigation and drainage systems for huge paddies rice field
Kuroda, H.; Yokoi, S.; Lin, X.; Maeda, S., ラスト(シニア)オーサー
PAWEES 2024, 2024年10月, ［査読有り］
Impact of nest size on deposition of detached filamentous algae within fish nests in an agricultural drainage canal: application of a 3D hydrodynamic model
Maeda, S.; Lin, X.; Kuroda, H., 筆頭著者
Proceedings of 15th International Symposium on Ecohydraulics and Fish Passage 2024, 2024年05月, ［査読有り］
Water depth and flow velocity characteristics of a portable fishway unit for salmon
Takahashi; N.; Nakata; K.; Sonoda; T.; Maeda; S., ラスト(シニア)オーサー, International Society of Paddy and Water Environment Engineering
Proceedings of 2023 Conference of International Society of Paddy and Water Environment Engineering, 2023年10月23日, ［査読有り］
Numerical experiment on the deposition process of detached filamentous algae on artificial fish nests introduced to an agricultural drainage canal
Maeda; S.; Miyashita; S.; Lin; X.; Kuroda; H., 筆頭著者, PAWEES
Proceedings of 2023 Conference of International Society of Paddy and Water Environment Engineering, 2023年10月23日, ［査読有り］
環境配慮工が導入された農業用水路と河川における流れの数値計算
吉成香貫花・前田滋哉・福田信二・黒田久雄, 責任著者, 農業農村工学会水文・水環境研究部会
応用水文, 2023年03月28日
〔主要な業績〕流れ・路床変動モデルを用いた魚巣における泥上げ効率の評価手法
前田滋哉・黒田久雄, 筆頭著者
土木学会論文集B1（水工学）, 2022年09月01日, ［査読有り］
曲がり桝における3次元流れの数値解析
姫野敦行・皆川明子・前田滋哉, ラスト(シニア)オーサー, 農業農村工学会 水文・水環境研究部会
応用水文, 2022年03月28日
付着藻類を考慮した魚巣・魚溜のある農業用排水路における路床変動の数値実験
前田滋哉・皆川明子・黒田久雄, 筆頭著者, 農業農村工学会水文・水環境研究部会
応用水文, 2021年03月27日
農業用排水路の急傾斜部に設置した可搬魚道における流れの数値計算
吉成香貫花・須藤真弥・前田滋哉・高橋直己, 責任著者, 農業農村工学会水文・水環境研究部会
応用水文, 2021年03月27日
水路急傾斜部に設置した可搬魚道における魚類遡上の調査
須藤真弥・前田滋哉・高橋直己, 責任著者, 農業農村工学会水文・水環境研究部会
応用水文, 2020年03月27日
タイ東北部農業主体地域を対象とした水資源・窒素負荷量推定モデルの構築
寺家谷勇希; 吉田貢士; Sritumboon SUPRANEE; Srisutham MALLIKA; 前田滋哉; 黒田久雄
農業農村工学論文集, 2019年11月14日, ［査読有り］
熱帯湿地における排水路水位の制御に伴うCO2放出量および火災リスクの低減効果
吉田貢士・大澤和敏・鈴木遥・水野広祐・前田滋哉・黒田久雄
土木学会論文集B1(水工学), 2019年11月06日, ［査読有り］
Field observation and numerical simulation of bed evolution in agricultural drainage canal with eco-friendly physical structures
Takagi, S; Maeda, S; Yoshida, K; Kuroda, H, 責任著者
Proceedings of 38th IAHR Congress, 2019年09月01日, ［査読有り］
温度変数に着目した水田・湿地の窒素除去速度推定方法の改良
林暁嵐・瀬田千夏・吉田貢士・前田滋哉・黒田久雄
農業農村工学論文集, 2019年08月08日, ［査読有り］
Ecohydraulic assessment of water abstraction for hydroelectric power generation in the Anegawa river, Japan
Maeda, S; Ishizaki, S; Minagawa, A; Kobayashi, H; Yoshida, K; Kuroda, H, 筆頭著者
Journal of Rainwater Catchment Systems, 2019年07月01日, ［査読有り］
農業用水取水の影響を受ける河川区間の魚類生息場評価
前田滋哉・小林佳奈・皆川明子・小林 久・吉田貢士・黒田久雄, 筆頭著者
応用水文, 2019年03月22日, ［査読有り］
サトウキビ栽培における渇水対策としての浅層地下水利用と生産ポテンシャル評価
吉田貢士; Desell Suanburi; 牧雅康; 前田滋哉; 黒田久雄, 土木学会
土木学会論文集G(環境), 2019年, ［査読有り］
Canal bed evolution and current velocity distribution in artificially-created nest and pool habitats in rural area
Maeda, S; Takagi, S; Yoshida, K; Kuroda, H, 筆頭著者
Proceedings of 12th International Symposium on Ecohydraulics, 2018年08月19日, ［査読有り］
〔主要な業績〕Turbulence and energetics of fish nest and pool structures in agricultural canalMaeda; S.; Yoshida; K. and Kuroda; H., 筆頭著者, Flow turbulence and fish energy expenditure were investigated in an artificial fish nest and fish pool introduced as resting habitats to an agricultural drainage canal in Japan. Instantaneous current velocity, water depth at various points, and water temperature in the canal were observed eight times during 2013–2015. Using the data, turbulence descriptors such as turbulent kinetic energy, degree of turbulence, and Reynolds shear stresses, as well as fish energy expenditure, were estimated at 15 monitoring sites. By categorizing these sites into three groups (fish nest, pool, and control), the hydraulic and energetic features of fish nests and pools were quantitatively analyzed. It was estimated that goby (Tridentiger brevispinis) expended significantly less energy in the fish nest and, to a lesser extent, pool than in the control environment, indicating that the two artificial refuges contributed to creating an energetically preferable fish habitat in the canal. The turbulence descriptors estimated in this study could provide realistic inputs to laboratory experiments on fish locomotion and lead to help improve the design of eco-friendly physical structures in agricultural canals., Springer Verlag
Paddy and Water Environment, accepted, 2018年04月04日,
［査読有り］ Effect of upstream discharge regulation on fish habitat in the Ane River, Japan
Ishizaki, S; Maeda, S; Minagawa, A; Noda, K; Kobayashi, H; Yoshida, K; Kuroda, H
Proceedings of the 37th IHAR World Congress, 2017年08月13日, ［査読有り］
急激な土地利用変化がジャカルタの大規模洪水リスクに及ぼす影響
吉田貢士,前田滋哉,黒田久雄
農業農村工学会 水文・水環境研究部会, 2017年03月24日, ［査読有り］
〔主要な業績〕A GIS-aided two-phase grey fuzzy optimization model for nonpoint source pollution control in a small watershedShigeya Maeda; Hisao Kuroda; Koshi Yoshida; Kenji Tanaka, A method for allocating allowable ranges of total nitrogen (TN) load to nonpoint (diffuse pollution) sources in a watershed has been developed by adopting the two-phase grey fuzzy optimization approach. Competing goals of water quality management authorities and TN load dischargers at nonpoint sources such as paddy field, upland crop field, and residential area are described with linear imprecise membership functions including interval numbers. TN load discharged from each cell of the nonpoint sources is assumed to be transported along with surface, subsurface, and river flow under the conventional first-order kinetic removal with respect to distance. The travel length of the load is estimated with a digital elevation model in a geographic information system (GIS). Uncertainty of river discharge and self-purification coefficients appearing in the TN transport model is also expressed with interval numbers. The GIS-aided grey fuzzy optimization model developed here is applied to the Seimei River watershed, Japan. By solving the optimization model, the allowable load represented by an interval number at each cell is procured, which would be a scientific base for effluent control regarding nonpoint sources in the area., SPRINGER HEIDELBERG
PADDY AND WATER ENVIRONMENT, 2017年03月,
［査読有り］ UAVによる高解像度熱画と水塊・植生2層熱収支モデルを用いた水田内湛水深の空間分布推定
吉田貢士; 本間香貴; 牧雅康; 前田滋哉; 黒田久雄
応用水門, 2017年, ［査読有り］
Turbulence and energetic characteristics of water regions created by eco-friendly physical structures in an agricultural drainage canal
Maeda, S; Iida, M; Yoshida, K; Kuroda, H
E-proceedings of 12th International Conference on Hydroscience & Engineering, 2016年11月06日, ［査読有り］
NITROGEN LOAD INFLOW TO LARGE SCALE RESERVOIRS IN THE CITARUM RIVER BASIN, INDONESIA
Yuki Jikeya; Koshi Yoshida; Shigeya Maeda; Hisao Kuroda
Proceedings of the 16th World Lake Conference, 2016年11月, ［査読有り］
Rice harvested area estimation model for rain- fed paddy in Mekong river basinKenji Tanaka; Koshi Yoshida; Shigeya Maeda; Hisao Kuroda, In Mekong river basin, productivity of rice is still low and unstable because more than Surplus water stabilization 70% of paddy fields were classified as rain-fed paddy. In addition, future global climate change and land use change will make negative impact on rice production in this region. In order to analyze the stability of rice production quantitatively, it is important to consider the rice farming management such as strategy of rain-fed rice Water level yield stabilization. This management was defined as control their acreage under rice cultivation depended on rainfall amount. In drought year, farmers abandoned some paddies to cultivate rice and collect rain water from abandoned paddies to planted paddies. In this way, statistic data of rice yield was more stable than that of harvested area. In this study, rice production model was developed combined with distributed type water circulation model. This model consists of three sub models, harvested area estimation model used of FAO-33, yield estimation model used of Monteith equations and FAO-56 and rainfall runoff model used of TOPMODEL. Developed rice production model was applied to Mekong river basin. Mekong river basin was divided in 10km mesh grids, and model simulation was conducted in 10km resolution from 1986 to 1995. Simulation result of rice harvested area, yield and production were verified with the statistic data of northeast Thailand. As a result, rice harvested area, yield and production was good agreement with statistic data, and especially error in rice yield was improved by considering the strategy of rain-fed rice yield stabilization., Penerbit UTM Press
Jurnal Teknologi, 2016年,
［査読有り］ Contribution of ICT monitoring system in agricultural water management and environmental conservationYoshida, K; Tanaka, K; Hariya, R; Azechi, I; Iida, T; Maeda, S; Kuroda, H, Springer
Proc. of 2nd International Conference of Serviceology (ICServ 2014), 2014年09月14日,
［査読有り］ メコン川流域における栄養塩排出原単位および河川水中の栄養塩濃度の推定田中 健二・吉田 貢士・前田 滋哉・黒田 久雄, メコン川流域では，人口増加と急激な開発に伴う人間活動の様々な変化から，将来的な水質汚濁問題が懸念されている．そこで本研究では，メコン川本流・支流の水質環境を空間的に評価することを目的とし，水質観測データと空間統計データから栄養塩排出原単位を推定する線形モデルおよび河川流量を出力する水循環モデルを構築した．また，それらの出力を用いてメコン川の栄養塩濃度を推定した．栄養塩排出原単位については，メコン川流域の汚濁排水処理形態や営農状態などの特徴を表した値が推定された．また，河川流量の計算値は観測値の流況を良好に再現し，年平均の栄養塩濃度も実測値とよく一致した．, Japan Society of Civil Engineers
土木学会論文集G（環境）, 2014年,
［査読有り］ Optimal ecohydraulic design of fish habitat in canal under ambiguity in preference curveMaeda; S., 筆頭著者, A decision support model for ecohydraulic design of fish habitat in a canal is developed, aiming at ecological conservation. The model combines (1) the two-dimensional hydrodynamic simulation in a canal, (2) the HSI (Habitat Suitability Index)-based habitat evaluation, and (3) a GA (Genetic Algorithm)-based optimization framework. Designing fish habitat is defined as an optimization problem for arranging blocks on the bed in a section of the canal. The suitability of the canal section is evaluated with two hydraulic factors: water depth and current velocity. Using the computed values of the hydraulic variables and reported SI (Suitability Index) curves (or preference curves) for the two factors regarding spawning of Ayu (plecoglossus altivelis), the elemental HSI values are computed. In order to reduce the inherent effect of the ambiguity in the preference curves to the optimal block configurations, several patterns of preference curves on water velocity are assumed with slight modifications of the originally-reported one. A synthesized average HSI (SAHSI) value computed using the SIs and the associated weights is employed as a single objective function to be maximized in the optimization problem. The problem is then solved using the simulation-optimization procedure. The developed method is applied for optimal configurations of 30 blocks in a hypothetical canal section. The best block configuration is procured with the largest value, which demonstrates the applicability of the developed method for ecohydraulic design., TSINGHUA UNIV
Proceedings of 2013 IAHR World Congress, 2013年09月08日,
［査読有り］ Fuzzy comprehensive evaluation of water quality at monitoring points –Application to Lake Biwa-Maeda, S; Fujita, T; Kawachi, T, 筆頭著者, A method for comprehensively evaluating water quality at various points in a water body has been developed based on the fuzzy reasoning. Vagueness in borders of conventional water quality classes formed for each water quality index is quantified by introducing fuzzy sets associated with the classes and nonlinear membership functions. Mamdani method (or min-max-center of gravity method) is employed in the fuzzy reasoning in order to synthesize concentration data on multiple water quality indices. The evaluation method developed in this study can represent the state of water quality at each points with a real number ranging from 0 to 100. The applicability of the method is demonstrated with the series of monthly observed data from April 1980 to March 2010 at 49 monitoring points in Lake Biwa, Japan. Temporal and spatial variations of the synthesized water quality scores at the monitoring points are presented. The application of the fuzzy comprehensive evaluation method would lead to more rational comparison of synthesized water quality at MPs in the lake and to producing useful information in decision-making on water quality management in the water body., 日本雨水資源化システム学会
Journal of Rainwater Catchment Systems, 2013年,
［査読有り］ 〔主要な業績〕A simulation-optimization method for ecohydraulic design of fish habitat in a canalMaeda; S., 筆頭著者, A decision-support method for ecohydraulic design of a canal in rural engineering is developed using a GA (Genetic Algorithm)-based simulation-optimization technique. In order to demonstrate the ability of the method, a simple problem is presented aiming at searching for best configuration of blocks located for creating valuable fish habitat in a canal. The habitat condition is evaluated using a habitat suitability index (HSI) considering hydraulic factors such as water depth and velocity. The study area, a section of canal, is discretized into triangular finite elements with nodes, and the two-dimensional simulation of flow is conducted by the finite element method applied to the steady-state shallow water equations. The computed water depth and velocity at each node are then used to evaluate the weighted average HSI (AHSI) for the canal. In order to develop a robust method insensitive to uncertainty in these hydraulic parameters, a scenario-based stochastic optimization framework is adopted. The simulation part of the developed method comprises the numerical computation of canal flow at every scenario aiming at evaluation of the expected AHSI, whereas the optimization part includes rearrangement of blocks conducted by GA operators. The simulation and optimization process is iterated to maximize the expected AHSI in the canal section. The performance of the presented simulation-optimization method is demonstrated for a hypothetical ecohydraulic design of spawning area of Ayu (Plecoglossus altivelis) in a canal. The demonstrative example shows that the presented method can successfully specify the best block configuration in the canal section with the largest expected AHSI value. (C) 2013 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
Environmental Engineering, 2013年,
［査読有り］ Optimization model for cropping-plan placement in paddy fields considering agricultural profit and nitrogen load management in JapanShunsuke Chono; Shigeya Maeda; Toshihiko Kawachi; Chie Imagawa; Natsuki Buma; Junichiro Takeuchi, An optimization model for cropping-plan placement on field plots is presented for supporting decision-making on agricultural management by a farming organization. The mixed 0-1 programming technique is employed to select the next planting crop at each field plot in a holistic manner. Reduction of total nitrogen discharged from field plots to the downstream end of the drainage canals is expressed as an objective function of the model to balance an achievement of economic goal and environmental conservation. Some Japanese governmental policies on regulating rice cropping areas and on promoting production of particular upland field crops can be formulated in the model. A computational example of cropping-plan placement on field plots managed under integrated policies is given by operating the optimization model with various weights associated with the objectives. The procured trade-off curve and corresponding patterns of cropping-plan could be useful in the decision-making by the farming organization., SPRINGER HEIDELBERG
PADDY AND WATER ENVIRONMENT, 2012年06月,
［査読有り］ Optimization of block placement for ecohydraulic design of fish habitat in canal
Maeda, S, 筆頭著者
Proceedings of 9th international Symposium on Ecohydraulics 2012, 2012年, ［査読有り］
GA-based simulation-optimization approach for designing fish habitat in canalMaeda; S., 筆頭著者, A GA (Genetic Algorithm)-based simulation-optimization method is presented in order to search for best configurations of blocks located for creating valuable fish habitat in a canal. The habitat condition is evaluated by a habitat suitability index (HSI)-based method considering hydraulic factors such as water depth and velocity. The study area, a section of canal, is discretized into triangular finite elements with nodes, and the two-dimensional simulation of flow is conducted by the finite element method applied to the steady-state shallow water equations. The computed water depth and velocity at each node are then used to evaluate the comprehensive suitability defined as a habitat potential (HP) for the canal using the SI and HSI in the canal section. The simulation part of the developed method comprises the numerical computation of canal flow aiming at evaluation of the HP, whereas the optimization part includes rearrangement of blocks conducted by GA operators. The simulation and optimization are iterated in order to maximize the HP in the canal section. The applicability of the presented simulation-optimization method is demonstrated for a hypothetical ecohydraulic design of spawning area of Ayu (plecoglossus altivelis) in a canal. The demonstrative example shows that the presented method can derive better block placement in the canal section under some conditions on upstream discharge., IEEE
Proceedings of SCIS-ISIS 2012, Kobe, Japan, November 20-24, 2012年,
［査読有り］ A Hydro-environmental Model Considering Nitrogen Dynamics in Surface Zone for Analysis of Groundwater Nitrate-nitrogen ContaminationImagawa Chie; Takeuchi Junichiro; Kawachi Toshihiko; Chono Shunsuke; Buma Natsuki; Maeda Shigeya, A cell-based distributed hydro-environmental model is developed which enables to analyze groundwater nitrate-nitrogen (N-N) contamination in rural areas, with well-coordinated incorporation of the water quality tank submodel for surface zone and the nitrate-nitrogen transport submodel for unconfined groundwater aquifer into the previously developed hydrologic model (Takeuchi et al., 2010). Cell-based building of all component submodels allows us to mesh the problem domain with unstructured cells of triangular shape, and therefore renders it possible to reflect in a refined fashion a variety of land-use practices in an analysis of the problem. The solutions based on reality, associated with groundwater flow and quality, can thus be obtained at a high (or field-plot-scale) resolution. It is also of great advantage that quantities of the hydro-environmental components of interest, such as surface water discharge, ground-water recharge, surface nitrogen discharge, and N-N leaching, can be obtained cell by cell or land-use by land-use. Application of the model to a real rural area having diverse terrains testifies to its satisfactory performance in a global sense. The simulated N-N concentrations of the groundwater vary in the ranges of the observed concentrations. The model also well reproduces the observed realities that the N-N concentration is high in upland areas such as alluvial fan and river terrace, while low in the lowland areas such as delta and valley floor, and is lowered in the irrigation season. It is thus considered that the model presently developed is useful for simulating and assessing the process and geographic distribution of groundwater N-N contamination in rural areas where fertilizing-induced groundwater contamination is a special concern., 日本雨水資源化システム学会
Journal of rainwater catchment systems = 雨水資源化システム学会誌, 2011年01月,
［査読有り］ A physically based FVM watershed model fully coupling surface and subsurface water flowsJunichiro Takeuchi; Toshihiko Kawachi; Chie Imagawa; Natsuki Buma; Koichi Unami; Shigeya Maeda, A sophisticated modeling approach for simulating-coupled surface and subsurface flows in a watershed is presented. The watershed model developed is a spatially distributed physically based model of composite dimension, consisting of 3-D variably saturated groundwater flow submodel, 2-D overland flow submodel and 1-D river flow submodel. The 3-D subsurface flow is represented by the complete Richards equation, while the 2-D and 1-D surface flows by the diffusive approximations of their complete dynamic equations. For piecewise integration of these equations, the finite volume method (FVM) is employed assuming unknown variables such as the water depth and the pressure head to be volume-averaged state ones. Problem plane geometry is meshed with the unstructured cells of triangular shape which conforms to external as well as internal irregular boundaries such as those between 1-D and 2-D flows. A cell size controlling scheme, referred to as quasi-adaptive meshing scheme, is introduced to keep the local discretization errors caused by topographic elevation gradient even over the entire-meshed geometry. Performance of the model is tested through its practical application to a rugged intermountain watershed. Tuning the values of the three key parameters ensures successful calibration of the model. Once the model is so calibrated, it could reproduce satisfactory runoff response to any rainfall event. Expansion and shrinkage of the contributing area importantly affecting the direct runoff, caused by the vicissitude of rainfall during its total duration, are well reproduced, like what the commonly accepted runoff theory argues. It is thus concluded that the model developed could serve as a powerful watershed simulator usable for investigating and assessing the hydrological aspect of a watershed., SPRINGER HEIDELBERG
PADDY AND WATER ENVIRONMENT, 2010年06月,
［査読有り］ A stochastic model for behaviour of fish ascending an agricultural drainage systemKoichi Unami; Kei Ishida; Toshihiko Kawachi; Shigeya Maeda; Junichiro Takeuchi, Adults of Carassius auratus grandoculis ascend from Lake Biwa, Japan, into riparian paddy fields via agricultural drainage systems for the purpose of spawning. However, land improvement works conducted in the second half of the twentieth century have brought about obstacles for passage of the fish, and several restoration projects to recover the migratory environment are being attempted. A continuous Markov process model is presented to scientifically support such a project, defining an ascending probability that quantitatively assesses the ability of an agricultural drainage system with hydraulic structures for the ascent of the fish. Computational methods are developed to numerically obtain flow fields of the agricultural drainage system and then the ascending probability in the entire spatio-temporal domain. The values of model parameters are deductively inferred, referring to results of field observations. From the computational results of the ascending probability in the agricultural drainage system, effects of hydraulic structures allowing ascent of the fish are clarified., SPRINGER HEIDELBERG
PADDY AND WATER ENVIRONMENT, 2010年06月,
［査読有り］ A refined hydro-environmental watershed model with field-plot-scale resolutionJunichiro Takeuchi; Chie Imagawa; Toshihiko Kawachi; Koichi Unami; Shigeya Maeda; Tomoki Izumi, A distributed hydro-environmental model is developed that achieves detailed analysis of the movement of water at a field-plot-scale resolution in a mesoscale watershed including lowland areas where, especially for agricultures, it is an essential need to get rid of redundant groundwater by drainage facilities such as rivers, canals and/or underdrains. For this, the problem geometry is meshed with unstructured cells of triangular shape. Profile of a column cell is zoned into two: surface zone and groundwater zone in which water movement is represented by combined tank and soil moisture sub-models, and well-defined two-dimensional unconfined shallow groundwater flow sub-model, respectively. The top-two sub-models serve to evaluate evapotranspiration, infiltration, soil water content, lateral surface water flow, and vertical percolation. The vertical percolation so evaluated is given as longitudinal recharge to the bottom sub-model for computing groundwater flow. Surface water-groundwater interactions through beds and stream-banks of perennial and ephemeral canals are considered by treating the canal courses as internal boundaries in the groundwater flow model. The finite volume method (FVM) that allows of unstructured mesh and produces conservative solutions is employed for groundwater flow computation. The model developed is applied to an actual watershed which includes a low-lying paddy area to quantify the hydrological impact of land-use management practices over a period of 29 years in which the farmland consolidation project was implemented and part of the paddy fields were converted to upland crop fields and housing lands. From the results obtained, it is concluded that the model presently developed lends itself to water-as well as land-use management practices., SPRINGER HEIDELBERG
PADDY AND WATER ENVIRONMENT, 2010年06月,
［査読有り］ Infiltration Process in Rainfed Rice Field Soil of Ghanaian Inland ValleyUNAMI Koichi; IZUMI Tomoki; IMAGAWA Chie; KAWACHI Toshihiko; MAEDA Shigeya; TAKEUCHI Junichiro, Soils of rainfed rice fields have unique characteristics. Inland valleys are extensively found in West African savannas, and their hydromorphic valley bottoms are intensively used for rainfed rice-culture during rainy seasons when become wetlands. Data of rainfall and soil moisture are perennially collected in a study site located in Northern Region of Ghana. The soil of the site is classified as Dystric Planosols. The soil moisture retention curve at a depth of the soil is identified from observed volumetric water content and matric head. Since the soil is variably saturated, it is important to clarify abruptly changing hydraulic properties of the soil near saturation. A bimodal model including eight empirical parameters turns out to be suitable for this purpose. The vertically one-dimensional Richards equation is considered to reproduce infiltration process of rainwater into the soil. The saturated water content, one of the empirical parameters, and saturated hydraulic conductivity are assumed to be functions of the depth of soil. Then, the finite element method is applied for solving the Richards equation to simulate the process. The simulation results are in good accordance with actually observed data. The physically-based model serves as a tool for comprehending formulation process of the wetlands at early stages of rainy seasons., 日本雨水資源化システム学会
J Rainwater Catchment Syst, 2010年01月,
［査読有り］ Optimal allocation of maximum allowable discharged total nitrogen load among field plots in agricultural watershed前田 滋哉; 吉川 和樹; 竹内 潤一郎; 河地 利彦; 長野 峻介; 宇波 耕一, A multiobjective optimization model is developed for controlling TN (Total Nitrogen) load discharged from field plots in an agricultural watershed. In optimization, maximizations of allowable TN discharge per unit area and total yield of rice are intended while complying with an effluent limitation standard prescribed for river water quality management. The discharge from a field plot is separated into two components, i.e., direct runoff and baseflow. As discharged TN from a plot travels with these components toward an outlet of the watershed, the amount of TN is assumed to decrease due to distance-related self-purification occurring in subsurface zone, drainage canal and river. Locations of field plots and traveling routes of TN are identified or predicted by a GIS (Geographic Information System) with a digital elevation model and by field surveys. The model developed is applied to an agricultural watershed bordering with Lake Biwa in Shiga Prefecture, Japan. The result demonstrates that the optimal allocation of maximum allowable discharged TN load among field plots is helpful in prioritizing plots where fertilization should be reduced., 公益社団法人 農業農村工学会
Transactions of the Japanese Society of Irrigation, Drainage and Rural Engineering, 2010年,
［査読有り］ Optimization approaches to nonpoint pollutant source control in watershedsShigeya Maeda; Toshihiko Kawachi; Koichi Unami; Junichiro Takeuchi, © 2010 by Nova Science Publishers, Inc. Application of optimization theory to a problem of nonpoint source (NPS) pollution control is effective in producing alternatives for water quality management in a watershed. In this chapter, two kinds of watershed management models, inter-subwatershed and intrawatershed management models, are proposed depending on the method of treating NPS loading at a watershed level. The inter-subwatershed management model lumps NPS-born pollutant loads together for each of the component subwatersheds of a large-scale watershed. In contrast, the intra-watershed management model handles NPSs within a small watershed in a distributed manner with, e.g., square-cell-based or field-plot-based definition of NPSs. In this topic, an ε-RO (Epsilon Robust Optimization) model, a hybrid of the ε-constraint method and the robust optimization framework, is presented as an inter-subwatershed management model for allocating maximum allowable COD (Chemical Oxygen Demand) loads among point sources (PSs) and NPSs in a river watershed. Discretized COD and DO (Dissolved Oxygen) transport equations with convection and dispersion terms in the river are embodied as equality constraints of the ε-RO model. The model can proactively control uncertainties inherent in the input data, producing highly-effective management alternatives for river water quality conservation. Additionally, as an example of the intra-watershed management model, a bi-objective linear programming model is presented that has environmental and economic goals. Surface and subsurface transport of total nitrogen in a watershed is expressed by following the distance-related first-order kinetics. With the aid of a GIS (Geographic Information System), these management models for river water quality management are applied to actual watersheds in Japan. The optimal distributions of maximum allowable loads in watersheds, obtained from the optimization models, would be helpful in taking measures for water quality conservation, such as enhancement of wastewater treatment capacity in industrial plants and sewage works, reduction of nitrogen fertilizer application, and planning of cropland retirement.
Watersheds: Management, Restoration and Environmental Impact, 2010年01月01日
Fuzzy optimization model for integrated management of total nitrogen loads from distributed point and nonpoint sources in watershedShigeya Maeda; Toshihiko Kawachi; Koichi Unami; Junichiro Takeuchi; Tomoki Izumi; Syunsuke Chono, A fuzzy optimization model is developed to allocate allowable total nitrogen (T-N) loads to distributed nonpoint sources (NPSs) and point sources (PSs) in a watershed for river water quality management using the linear programing technique. The watershed is divided into uniform grid cells on which T-N loads issuing from NPSs such as paddy fields, upland crop fields and cities are controlled. A geographic information system integrated with the digital elevation model facilitates computation of route lengths of surface and subsurface flows from cells to a river running through the watershed. The T-N loads discharged from their sources are assumed to decay, subject to distance-related first-order kinetics. As management goals, maximizations of total allowable NPS loads, total allowable PS loads and total yield of rice are considered from environmental and economic viewpoints. A prime constraint is an effluent limitation standard for the aggregate amount of loads that arrive at the downstream end of the river. The fuzzy sets theory helps appropriately describe vague attitudes of decision-makers (i.e., stake-holders and management authorities) in terms of constraints and conflicting goals. An application of the fuzzy optimization model, developed as an improvement over our last nonfuzzy model, to a real watershed in Shiga prefecture, Japan, demonstrates that the fuzzy model embodies our last model, and is capable of creating management alternatives for T-N load allocation in a more practical and flexible manner., SPRINGER HEIDELBERG
PADDY AND WATER ENVIRONMENT, 2009年09月,
［査読有り］ Case Study: Hydraulic Modeling of Runoff Processes in Ghanaian Inland ValleysKoichi Unami; Toshihiko Kawachi; Gordana Kranjac-Berisavljevic; Felix Kofi Abagale; Shigeya Maeda; Junichiro Takeuchi, The inland valleys of West Africa are strategic in terms of food security and poverty alleviation, but scientific studies on hydrologic processes happening in these environments have not been well documented. Modeling approaches presented in this paper are an attempt to better comprehend hydraulic phenomena occurring in inland valleys. An inland valley situated in the Northern Region of Ghana is set as the study site. The inland valley comprises well-drained uplands and hydromorphic valley bottoms. There are several earthen dams across the valley bottoms, which are at the same time seasonal wetlands cultivated to rice during the rainy season. A finite volume model for the shallow water equations is developed to numerically simulate surface runoff flows in the valley bottoms during flood events. Innovation is necessitated to handle a series of different hydraulic phenomena. Flux-splitting and data reconstruction techniques are used to achieve stable computation in the complex topography of the valley bottoms. Standard problems of oblique hydraulic jump and dam break flows are used to test the accuracy of the numerical model. The Manning's roughness coefficient is determined from calibration in another Ghanaian watershed located in the Eastern Region. Using actually observed time series data of rainfall intensity, surface flows during the rainfall events are simulated in the computational domain representing the valley bottoms of the study area. Observed data of water levels in the dams are compared to predictions, and discrepancies between them are examined from the hydrological point of view. In the case of a hypothetical flood event, cascading collapses of the dams and flooding of cultivated fields are reproduced., ASCE-AMER SOC CIVIL ENGINEERS
JOURNAL OF HYDRAULIC ENGINEERING-ASCE, 2009年07月,
［査読有り］ A distributed hydro-environmental watershed model with three-zoned cell profilingJunichiro Takeuchi; Toshihiko Kawachi; Koichi Unami; Shigeya Maeda; Tomoki Izumi, A cell-based distributed watershed model is developed which enables us to simulate the hydrological and hydraulic aspects of the watershed in a refined fashion. With three-zoned cell profiling, the model is composed of three sub-models; tank model for a surface water zone, soil moisture model for a surface soil zone, and unconfined shallow groundwater flow model for a subsurface zone. Inclusion of the soil moisture sub-model modified to reroute the infiltration, routed from the tank sub-model, into the return flow and the groundwater recharge features the model. The groundwater flow sub-model, numerically approximated by use of the finite volume method and the implicit time-marching scheme, considers a network of on-farm drainage canals as internal boundaries, which is an essential need for modeling the watershed including farmlands. Cascade-linking of the three sub-models in a cell and assembling of all the cells over the entire watershed domain provides the global equations system to be solved. Applicability of the model is demonstrated with its practical application to a real watershed in that paddy and upland crop fields take great part of the land-use practice. It is then indicated in a quantified manner that rice farming significantly contribute as a major groundwater recharger in an irrigation period to fostering and conservation of regional water resources. Along with appropriately profiling a cell, the model is so versatile and tough that it can be applied without difficulty to a watershed of diverse terrains and land-uses and the computations can stably be carried out. It is thus concluded that the model presently developed could be a powerful "watershed simulator'' to investigate and assess the time-varying hydro-environmental properties of a watershed while separating and integrating the hydrological and hydraulic components of particular importance., SPRINGER HEIDELBERG
PADDY AND WATER ENVIRONMENT, 2009年03月,
［査読有り］ Dynamics of Nonpoint Source Pollutant Loadings from Agricultural Watershed : A Case Study in Paddy-farming Area with 122 Drainage Water Outfalls Exactly IdentifiableChono Shunsuke; Maeda Shigeya; Kawachi Toshihiko; Unami Koichi; Takeuchi Junichiro, Paddy farming is the cause of water pollution in many parts of the Asian monsoon district. As a primary study for strategically managing river water quality on a watershed scale, the dynamics of nonpoint source pollutant loadings from paddy farming area are examined for a selected agricultural watershed where a river runs through and rice paddies take greater part of the farmland. A total of 122 outfalls at which drainage (irrigation runoff) waters enter the river are exactly identifiable along the whole course of the river. Results of the detailed surveys of drainage waters, conducted at typical stages in an indigenous calendar of paddy farming practice (CPFP) in an irrigation season as well as at a few stages in the off-season, are analyzed. Major findings are as follows. (1) Any of the COD_<Mn>, NO_3-N, T-N and T-P loadings totalized over all the outfalls is maximized in puddling and transplanting with basal fertilizer application. (2) The concentrations of NO_3-N and T-N, averaged over all the outfalls, are rather low during the irrigation period of mid April to early September. Nevertheless the loading amounts of them remain high during the same period, relatively closely correlating with the amount of outfall discharge. (3) Topdressing the paddies in the booting stage of rice causes a distinguishable extra load of NO_3-N. (4) The dynamics of the COD_<Mn> and T-P loadings are totally different from those of the NO_3-N and T-N loadings, taking straightforward declines from their maximums or being significantly restricted by their concentrations rather than by outfall discharges., 日本雨水資源化システム学会
Journal of rainwater catchment systems = 雨水資源化システム学会誌, 2009年
An Inverse Method to Estimate Soil Hydraulic Properties in Saturated-unsaturated Groundwater Flow ModelIZUMI Tomoki; TAKEUCHI Junichiro; KAWACHI Toshihiko; UNAMI Koichi; MAEDA Shigeya, An alternative approach to the inverse problems encountered prior to the computations of saturated-unsaturated groundwater flow is addressed. The soil hydraulic properties (i.e., the relative hydraulic conductivity K_r and the volumetric water content θ) which are the a priori unknown parameters in the Richards equation governing the flow are interpolated by an assembly of the piecewise cubic spline functions expressed in terms of the pressure head. This free-form parameterization approach provides high flexibility and degrees of freedom in identifying the functional form of the parameters, compared with the conventional approaches in that the functions are of specific shape as in the van Genuchten model of a fixed functional form. In addition, the approach is field-oriented in a point that the solution of the inverse problem can be achieved having only recourse to the observed time-series data of pressure head which are relatively easily in situ available. To find the shapes of such spline functions best expressing head-dependency of the soil hydraulic properties, a simulation-optimization algorithm with the aid of the Levenberg-Marquardt method is developed which serves to iteratively solve an optimization problem of minimizing errors between the observed (or measured) and computed values of the pressure head, in combination with the embedded simulation module for solving forward problems. Validity of the approach is examined with its application to different two soil types which are characterized by less and more sensitive changes of the relative hydraulic conductivity near saturation, respectively. The results show that the approach developed could be a viable alternative to the conventional fixed functional form approaches., 日本雨水資源化システム学会
J Rainwater Catchment Syst, 2008年01月,
［査読有り］ Model-based Optimal Design of Land Use Arrangement for Environmentally Sound Watershed ManagementTakeuchi Junichiro; Izumi Tomoki; Kawachi Toshihiko; Unami Koichi; Maeda Shigeya, In Japan, more and more paddy fields, left fallow mainly by nationwide rice production control policy, have recently been changed to upland crop fields or artificial wetlands. Since such change or diversification of land use probably has an impact on the water quality environment of the whole neighborhood, it must strategically be implemented in the context of land use arrangement for environmentally sound watershed management. Of great importance is then to make effective use of self-purification functions fulfilled by paddy fields or wetlands. The present study is associated with development of a simulation-optimization model for designing an optimal land use on a watershed scale. The model is composed of a hydro-environmental subsurface watershed simulation model, represented by coupled 3-D Richards and advection-dispersion equations, and a GA (Genetic Algorithm)-aided optimization part. An optimization problem is formulated which, with the most use of self-purification, minimizes the objective function expressed in terms of a weighted total of discharged nutrient from a watershed and residual nutrient within the watershed, taking the location of paddy fields in fallow, changed to upland crop fields or wetlands, as a decision variable. An example problem for a small watershed of an irrigation tank is solved that requires deciding the optimal locations of paddy fields that can be changed to other land use categories. The results show that the model developed could be a powerful tool for making tactics to combat the environmental impact resulting from land use diversification., 日本雨水資源化システム学会
Journal of rainwater catchment systems = 雨水資源化システム学会誌, 2008年
Fuzzy optimization model for allocating allowable discharged T-N load to point and nonpoint sources
Maeda, S; Kawachi, T
Proceedings of 32nd IAHR Congress, 2007年, ［査読有り］
Optimal management of agricultural wastewaters for improving river water quality
Maeda, S; Kawachi, T, 筆頭著者
Proceedings of Pawees 2005 International Conference, 2005年, ［査読有り］
Evaluation of river water quality management level based on COD-loads optimally allocated to point and nonpoint sources
Maeda, S; Kawachi, T, 筆頭著者
Proceedings of XXXI IAHR Congress, 2005年, ［査読有り］
Integrated management of river water quality under uncertainty using optimization model
Maeda, S; Kawachi, T
Proceedings of XXX IAHR Congress, THEME B, 2003年, ［査読有り］
Management of water quality environment under uncertainty – Mathematical modeling and computational optimization -
Kawachi, T; Unami, K; Maeda, S; Takeuchi, J
Proceedings of the International Conference on Water and Environment (WE-2003), 2003年, ［査読有り］
Optimization model for allocation of pollutant loads from non-point sources in watershed using GISKumar; A.; Maeda; S. and Kawachi; T., A method is developed to optimize the allocation of pollutant loads from non-point sources in a watershed by combining the application of optimization theory and GIS technique. The study area is modeled as a watershed with land use map and digital elevation model by ArcView GIS. Using calculated values of flow length from each land management unit (LMU), in the study area, to the outlet and area of each LMU, and assumed value of watershed-wide self-purification coefficient, a linear programming model is formulated. The objective function maximizes total allowable discharged pollutant loads from LMUs in the study area subject to the constraints of effluent limitation at the outlet of the watershed, i.e., study area, relation among mean effluents from different LMUs, and minimum limit of effluent in each LMU. Optimization is carried out at different weight values depending on decision-maker's preference order of LMU type with respect to mean load discharged from unit area. The developed model is applied to a subcatchment of Yasu river basin in Shiga prefecture, Japan, which demonstrates the model's ability to determine optimum allocations of discharged loads of total nitrogen from different types of LMUs in the sub-catchment., WORLD SCIENTIFIC PUBL CO PTE LTD
Proceedings of the 13th IAHR-APD Congress, Advances in Hydraulics and Water Engineering,, 2002年,
［査読有り］ Decision support model for managing river water quality under uncertainty
Maeda, S; Kawachi, T; Okumura, H, 筆頭著者
Proceedings of 4th International Conference on Hydroinformatics, 2000年, ［査読有り］
