The research demonstrates that Three-Dimensional Variable-Density Groundwater Flow models such as the SEAWAT model can be effectively used for design of subsurface drainage systems for controlling salt concentration in the root zone on salt affected irrigated land. The SEAWAT model was used to optimize subsurface drainage design to ensure that the salt concentration of the groundwater at the base of the root zone does not exceed pre determined levels instead of the conventional approach of maintaining the groundwater at a predetermined water table level. The study was carried out on a conceptual uniform homogenous block of irrigated flat field of shallow water table depth of 0.5 m and salt concentration of 7200 mg/l with impermeable layer at 20 m deep and impermeable field boundaries. Using the model, spacings were designed to be used as design criteria for subsurface drainage system to maintain salt concentrations of 6000, 5000 and 4000 mg/l at the base of the root zone and water table depth of 0.8 m from the soil surface. The results showed that over a wide range of irrigation water quality and aquifer hydraulic conductivity the optimum drain spacing using SEAWAT was, depending on irrigation water quality and aquifer hydraulic conductivity, wider by between 3 and 50 % and the amount of drain discharge reduced by 1 and 27 % than would be recommended using conventional design equations. It was concluded that Three-Dimensional Variable-Density Groundwater Flow models are better for designing effective drainage systems than Conventional drain spacing design equations such as Hooghoudt.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:518563 |
| Date | January 2009 |
| Creators | Ampofo, Edward Akwasi |
| Contributors | Tanton, Trevor ; Rycroft, David |
| Publisher | University of Southampton |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://eprints.soton.ac.uk/146869/ |
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