The amount of water in the soil is the limiting factor that determines the yield of agricultural crops. Learning how to manage this water is therefore a crucial task for modern agriculture. One of the effective technical tools for influencing the groundwater level on the plot is a subsurface drainage system.
The drainage system in the field in front of you consists of a pipe made of burnt clay 5 to 10 cm wide and laid at a depth of about one metre. The total length of the drainage system laid on our plot is 290 km (on an area of 333.14 ha of drainage). This system is capable of removing up to 3 litres of water per second from the field for every hectare of land drained, i.e., in our case up to 1 m3/s. Up to 86 400 m3 of water can then be drained per day. Normally, however, it is 3 to 6 times less.
If we can prevent the drainage water from flowing out (e.g., by installing small gates) and raise the level in the drainage system to the chosen level, we can achieve a similar effect as if we were to reduce the depth at which the system is installed or the depth of the trench. The drainage water then seeps (infiltrates) from the drain vertically and horizontally into the surrounding soil profile or even deeper, thereby increasing the amount of water retained in the soil. If the water level is at a greater depth than the drainage, the drainage has practically no effect on the groundwater flow.
In order to operate the drainage structure in a controlled manner - i.e., to divert water when there is an undesirable excess and to retain it when there is a shortage - the drainage pipes must be kept clean. If there is a large amount of sediment clogging (e.g., at the drainage outlet or inspection well), we use a "hydro cleaner" for maintenance, which uses water pressure to flush the sediment out of the pipe.
