Drainage of Agricultural Lands

In this course, the role of drainage in agricultural water management will be treated. Worldwide, about the same percentages of agricultural lands are irrigated (17%) and drained (13%). Irrigation is needed when the natural rainfall is not sufficient to satisfy the crop water requirements and/or drainage is needed to remove excess rainfall and irrigation water or salts brought in by the irrigation water. As the global demand for food continues to increase and this increase mainly has to come from existing agricultural lands, there is urgent to invest in irrigation and drainage systems. Global climate change may further exacerbate the pressure on supply and demand for water through changing temperatures and long-term variation in annual precipitation amounts and regional distribution patterns. In addition to the changing climate, cropping patterns are diversifying and field irrigation methods are changing. In light of all these changes in water demand, supply and use, the role of (subsurface) drainage has changed from a single-purpose measure for controlling waterlogging and/or salinity to an essential element of integrated water management under multiple land use scenarios. Although the total area under irrigation continues to grow, very little is being invested in drainage systems to sustain the investments in irrigation. This is due in part to drainage being at the end of the pipeline where it has to clean up the “mess” that other activities leave behind: i.e. salts brought in by irrigation water, residues of fertilizers and pesticides, etc. However, to move towards more sustainability, drainage has to be given its appropriate role in agricultural water management.
In this course, the role of drainage in agricultural water management will be treated in five modalities:

• drainage, concepts and benefits;
• drainage, soil and water;
• drainage, salinity and alkalinity;
• drainage, design and implementation;
• drainage, part of agricultural water management.
  The course is offered as an online course. Students will do five E-learning modules on the above-mentioned drainage modalities. At the end of this block, students will make an individual exam to assess their knowledge on these issues.

After successful completion of this course students are expected to be able to:

• Understand the need of drainage in agricultural lands
• Classify the components of a drainage system
• Formulate the requirements for water table and salinity control in agricultural lands
• Analyse the soil and hydrological factors that influence the functioning of an agricultural drainage system
• Design drainage interventions, which special emphasis on the design of subsurface drainage systems
• Develop drainage practices to optimize agricultural water management
• Assess the expected performance of the proposed interventions and analyse these for the multiple dimensions of technology, management/governance and water user perspectives

Assumed Knowledge:
WRM10306 Irrigation and Water Management;
HWM21806 Hydraulics and Hydrometry;
WRM21312 Design in Land and Water Management 2 and SLM20306 Land and Water Engineering.