Partial Differential Equation Model for Spatially Distributed Statistics of Contaminant Particles in Localy One-Dimensional Open Channel Networks

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Controlling wasteloads from point and nonpoint sources to river system by GIS-aided Epsilon Robust Optimization model

A stochastic multiobjective programming model, an var epsilon-RO (Epsilon Robust Optimization) model as a simulation–optimization model with an embedding approach, is developed for river water quality management under hydro-environmental uncertainty. The model is a hybrid of the var epsilon-constraint method and the robust optimization framework, which depresses the high sensitivity of the model to the input data uncertainties by introducing a plausible set of scenarios. Possible pollutant sources (all kinds of point and nonpoint pollutant sources excepting forests) are treated as controllable. The finite element method is employed for approximations to COD (Chemical Oxygen Demand) and DO (Dissolved Oxygen) transport equations with convection and dispersion terms. Realizations for the in-stream COD–DO interactive events, thus described in discrete forms, are embedded as equality constraints in the model. Controlling wasteloads from a variety of sources is implemented by seeking noninferior solutions (management alternatives) that maximize total COD load to the stream while minimizing COD load deviations and in-stream water quality violations. Demonstrative operation of the model is made with its application to the Yasu River, Japan. It is shown that there is indeed an alternative management strategy to improve in-stream water quality as a whole while increasing the total allowable load to the stream. The var epsilon-RO model developed could thus be a viable alternative to the conventional river water quality management models

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

Case study: Hydraulic modeling of runoff processes in Ghanaian inland valleys

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