| Author | Kazmi, H. A. |
| Call Number | AIT Diss. no.AE-91-03 |
| Subject(s) | Irrigation water--Quality
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| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. AE-91-03 |
| Abstract | In surface irrigation systems, considerable quantity of water percolates into the subsoil, creating shallow ground water table conditions. The percolating water could contain dissolved chemicals which are potential source of contamination of ground water. In this study the problem of ground water contamination due to surface irrigation has been formulated as a one-dimensional movement of water and solutes in the soil-water-plant system. A finite element model is developed for simulating the movement of water and solute through variably saturated nonhomogeneous porous media. The model parameters were physically measured by conducting independent experiments. The governing equations for one-dimentional transient density dependent flow and transient mass transport equation are solved using Galerkin's finite element method. Root water uptake model is modified to account for the effect of solute concentration on the extraction of soil water by growing plants and is implemented. Hysteresis is soil hydraulic properties and effect of velocity on hydrodynamic dispersion coefficient were incorporated. First order decay reactions, solute uptake by the plant roots and linear equilibrium adsorption/desorption are incorporated in transport equation. Outputs of the model include pressure head, water content, flux and concentration profiles, average concentration in ground water, moisture available in root zone and water table position. A mass balance computation scheme for water solute is included as a check on the accuracy of the numerical solution. Water and solute transport experiments were conducted on a large soil column under dynamic shallow water table conditions. The results generated from the experiments are compared with the predictions of the numerical model and discussed. The validity of the developed model is proved by comparing its results with available analytical and numerical solutions and experimental data. The model was applied to study the impacts of various alternative irrigation management strategies, stationary and dynamic water table, fluctuations in water table, soil type and soil layering on concentration in soil and ground water quality. The influence of geohydrologic parameters on water table behaviour and ground water quality are also presented. The long term effects of evaporation from the land surface, initial concentration in the ground water and quality of the irrigation water on soil salinity and ground water quality are also studied and presented. Resluts of the study showed that certain irrigation management pratices could reduce the normal rate of degradation of the ground water. An investigation into water table management practices revealed that its proper management helps in mitigating adverse impact of irrigation on ground water quality. It is also concluded that by following proper irrigation and water table management practices the solutes can be stored in a region in between root zone and water table for a considerable period, delaying their addition to the ground water |
| Year | 1991 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. AE-91-03 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Murty, V. V. N.; |
| Examination Committee(s) | Gupta, Ashim Das;Koga, Kiyoshi;Mino, Takashi;Tanji, Kenneth K.; |
| Scholarship Donor(s) | Government of Australia; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1991 |