The use of numerical groundwater model to improve effectiveness of subsurface drainage system in irrigated field

The research demonstrates that Three-Dimensional Variable-Density Groundwater Flow<br/>models such as the SEAWAT model can be effectively used for design of subsurface<br/>drainage systems for controlling salt concentration in the root zone on salt affected<br/>irrigated land. The SEAWAT model was used to optimize subsurface drainage design to<br/>ensure that the salt concentration of the groundwater at the base of the root zone does not<br/>exceed pre determined levels instead of the conventional approach of maintaining the<br/>groundwater at a predetermined water table level. The study was carried out on a<br/>conceptual uniform homogenous block of irrigated flat field of shallow water table depth<br/>of 0.5 m and salt concentration of 7200 mg/l with impermeable layer at 20 m deep and<br/>impermeable field boundaries. Using the model, spacings were designed to be used as<br/>design criteria for subsurface drainage system to maintain salt concentrations of 6000,<br/>5000 and 4000 mg/l at the base of the root zone and water table depth of 0.8 m from the<br/>soil surface. The results showed that over a wide range of irrigation water quality and<br/>aquifer hydraulic conductivity the optimum drain spacing using SEAWAT was,<br/>depending on irrigation water quality and aquifer hydraulic conductivity, wider by<br/>between 3 and 50 % and the amount of drain discharge reduced by 1 and 27 % than<br/>would be recommended using conventional design equations.<br/><br/>It was concluded that Three-Dimensional Variable-Density Groundwater Flow<br/>models are better for designing effective drainage systems than Conventional drain<br/>spacing design equations such as Hooghoudt.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2009

Author dc:creator

• Ampofo, Edward Akwasi

Advisors dc:contributor.advisor

• Tanton, Trevor W.
• Rycroft, David W.