Certain drainage criteria must be used to determine drainage need. A groundwater balance of the drainage area is the most accurate tool to calculate the volume of the water to be drained. Besides agricultural drainage criteria, technical drainage criteria (relating to minimization of the cost of installation and operation of system while maintaining the agricultural criteria), environmental criteria (relating to the minimization of the environmental damage), and economic drainage criteria (relating to the maximization of the net benefits i.e. the difference between benefits and costs, and damages) should also be taken into account.
Types of drainage system
Drainage is broadly divided into two types i.e., Surface and subsurface drainage. The excess surface or sub surface water of an agricultural field can be improved by applying the appropriate drainage method. Drainage system may consists of field drains system (internal) and main drainage system (external). Water of field is drained through field drainage and sent to main drainage for moving towards outlet. Field drainage system may be divided into surface drainage by gravity flow and subsurface drainage by gravity or pumped flow both divided into regular system and checked system (Figure 1).