In agricultural land use, it is necessary to ensure optimum soil moisture and optimum groundwater depth for the crops grown, as the water regime of the soil significantly affects the yield of the crops. Prolonged soil water deficit leads to agronomic drought. On the contrary, a long-term excess of water in the soil is referred to as waterlogging (causes – impermeable layers in the soil profile, high groundwater level, limitation of surface runoff from the land).
The main purpose of drainage is to modify the water and air regime of agricultural land by removing excess water from the soil. The drainage system consists of a detailed drainage system (DDS) which flows into a main drainage system (MDS). The MDS consists of open channels or covered pipes (up to 300 mm clearance) and other objects (steps, culverts, pumping stations, etc.). Although open channels are more suitable for MDS than covered pipes, the amount of piped MDS is currently still very high. This was due to the consolidation of land into larger production blocks, where this solution, unlike open channels, did not interfere with large-scale farming.
For open channels, the emphasis was on the fastest possible drainage and minimal impact on agricultural land. Therefore, the channels were built straight and unnaturally deep. Together with the intensification of agriculture, this had a negative impact on the runoff regime of the catchment (including the leaching of nutrients and pesticides from the soil into watercourses), on biodiversity (destruction of species dependent to permanently or temporarily waterlogged areas) and on the natural potential of the landscape.
Measures to eliminate the negative effects of drainage facilities
- Uncovering and subsequent revitalisation of blocked MDS
- Extending the channel alignment and mitigating the slope of open channels
- Leaving the channels to gradual siltation, scouring, disintegration of fortifications or overgrowth of vegetation
- Addition of runoff and channel water level control features or features that allow the use of the retention space of the surrounding soil.
