Shigeya Maeda

Optimization model for cropping-plan placement in paddy fields considering agricultural profit and nitrogen load management in Japan

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.

A GIS-aided two-phase grey fuzzy optimization model for nonpoint source pollution control in a small watershed

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.

Contribution of ICT Monitoring System in Agricultural Water Management and Environmental Conservation

Recently, ICT based monitoring system is popularized in some agricultural areas. In such area, farmers can obtain their paddy conditions by using smart phone without going to the paddy. In this study, the effect of ICT based monitoring system on water and labor saving, and nutrient loads reduction was evaluated. Then, cost/benefit of monitoring system installation was compared. Finally, how to promote ICT systems in agricultural engineering field was discussed based on the characteristic of agricultural water management system.

Turbulence and energetics of fish nest and pool structures in agricultural canal

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.

GA-based simulation-optimization approach for designing fish habitat in canal

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.