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Accueil du site → Doctorat → États-Unis → 1993 → DRAINMOD-S : A water management model for irrigated arid lands

North Carolina State University (1993)

DRAINMOD-S : A water management model for irrigated arid lands

Kandil, Hesham Mohamed

Titre : DRAINMOD-S : A water management model for irrigated arid lands

Auteur : Kandil, Hesham Mohamed

Université de soutenance : North Carolina State University

Grade : Doctor of Philosophy (PhD) 1993

Résumé
A simplified water-balance approach (DRAINMOD) was used to solve fluid flow in poorly drained soils. Results from DRAINMOD were used to obtain solutions for solute transport in drained, shallow water-table soils, and to compare the results with solutions based upon Richards’ equation. Transient soil water flux rates computed with DRAINMOD (water-balance model) were used as input to a Petrov-Galerkin advective-dispersive transport model to simulate solute transport in unsaturated soils. Sample simulations showed good agreement between a Richards’-equation-based transport model and a water-balance-based transport model. DRAINMOD was modified to include the effect of irrigation water quality and drainage on soil salinity and drainage water quality. The modified model (DRAINMOD-S) includes an explicit solution of the advective dispersive equation to predict solute transport. The solute transport part of DRAINMOD-S was tested against the more complex Petrov-Galerkin advective-dispersive model. The reliability of DRAINMOD-S for artificially drained arid soils was also evaluated using field data collected from the Zankalon Pilot Area in Egypt. The reliability of the model was evaluated by comparing the observed and simulated water table depths midway between drains, daily lateral discharges, and salt concentrations in the soil profile and drain effluent. Simulation results were in good agreement with the observed values. An algorithm to quantify the effects of stresses due to soil salinity on crop yields was incorporated into DRAINMOD-S. The overall crop function in the model includes the effects of stresses caused by excessive soil water conditions (water logging), soil water-deficits, salinity, and planting delays. The objective function of these simulations was crop yield. The yields of individual in a crop rotation of (bean, cotton, maize, soybean, and wheat) were simulated for 19 years. Results showed that, the third strategy provided the best soil water and salinity conditions during the growing seasons for cotton, maize, soybean and wheat while maintaining a suitable salinity level in the root zone. Optimum drain spacings were dependent on irrigation strategy and were determined for each crop. Results are also presented on the effect of drain depth on bean and maize yields for different drain spacings. DRAINMOD-S is a useful tool for design and evaluation of irrigation and drainage systems in irrigated arid lands. (Abstract shortened by UMI.)

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