Model Estimation and Prediction for a Water Management System

A water management model has been developed using identification techniques for predicting water table elevations. Data record near the Aurora site in the North Carolina coastal plains over a two-year period was used to develop and test the model. Rainfall and water table elevations were recorded continuously at this site and the observed water table elevations were compared to predicted day and end values. The identification of both linear and non-linear, difference equation model is described to represent the relationship between the three inputs (rainfall, potential evaporation and ditch water elevation) and the output (water table elevation

Stress day index models to predict corn and soybean yield response to water table management

Drainage and related agricultural water table management systems are being designed in humid regions of the United States using the water management simulation model, DRAINMOD. Since excessive and deficient soil-water conditions are stressful to most crops, crop yield is a useful measure of the effectiveness of the water management system design. Stress day index (SDI) models are presented which can be used to predict corn and soybean yield response to excessive and deficient soil-water conditions. The relative yield - SDI models developed herein and SDI models reported in the literature were tested using a comprehensive data base developed from corn and soybean yield studies conducted in eastern North Carolina over the past 35 years. / Le but de cette étude était triple. Premièrement, déterminer expérimentalement les facteurs de sensibilité culturale (CS) pour des cultures de maïs et de soja stressées par un excès d'eau dans le sol. Deuxièmement, développer des modèles d'indice de stress hydrique pour prédire le rendement de cultures de maïs et de soja soumises à des niveaux de nappe élevés, en se basant sur les facteurs CS déterminés expérimentalement. Troisièmement, tester à la fois les modèles SDI mentionnés dans la littérature, pour prédire le rendement cultural en cas de stress provoqué par un déficit hydrique. Le rendement prédît (calculé) est comparé au rendement mesuré sur les sites d'expérimentation

Comparison of models for subsurface drainage in flat and sloping lands

Solutions to the Boussinesq equation for predicting groundwater-table hydrographs in a drainage system included the numerical model SLOP that was based on the second Boussinesq approximation and provided accurate calculation of water table elevation at different positions of the horizontal X-axis. The semianalytical model SIDRA assumed constant water table shape during water table recession. Solutions were obtained for steady-state and transient drainage on flat soils and for drainage under steady-state recharge on sloping land. The 2 approaches provided similar results for flat lands with differences of less than 4 per cent in the calculated water table shape factors, and the implicit solutions in SIDRA showed good agreement wich SLOP for sloping lands. However SLOP numerical solutions were unstable when the streamlines could not be considered horizontal. / La plupart des modèles pour le drainage enterré des sols plats sont basés sur l'équation de Boussinesq. Cette étude compare un modèle semi-analytique SIDRA, se basant sur l'hypothèse d'une forme constante de la surface phréatique pendant la période de décrue, au modèle SLOP, qui est basé sur une solution numérique de l'équation de Boussinesq. Des solutions sont obtenues pour des épisodes de drainage à la fois en condition permanente et transitoire dans des terres plates et pour le drainage sous alimentation permanente dans des sols en pente