Spacing of tile drains to relieve waterlogged land

Introduction:
Tile drainage is a widely used method to manage waterlogged land, especially in agriculture. It involves the installation of a network of underground pipes or tiles, which provide an outlet for excess water to drain away. The spacing of these drains plays a crucial role in effectively relieving waterlogged conditions.

Factors affecting the spacing of tile drains:

1. Depth of drain below the ground surface:
- The depth of the drain below the ground surface affects the efficiency of drainage.
- As the depth of the drain increases, it allows for a greater volume of water to be drained away.
- Therefore, a deeper drain requires a wider spacing between drains as it can cover a larger area.

2. Depth of impervious strata from the drain:
- An impervious strata or layer hinders the movement of water downwards, resulting in water accumulation above it.
- The depth of this impervious layer from the drain is crucial in determining the spacing of the drains.
- If the impervious layer is closer to the drain, the drains need to be spaced closer together to effectively drain the waterlogged area.

3. Discharge per unit length in the drain:
- The discharge per unit length refers to the amount of water that can flow through the drain in a given length.
- A drain with a higher discharge can effectively drain a larger area.
- To maintain a consistent drainage capacity and prevent waterlogging, the drains should be spaced closer together when the discharge per unit length is lower.

4. Coefficient of permeability of the soil to be drained:
- The coefficient of permeability of the soil determines the rate at which water can flow through it.
- Soils with higher permeability allow water to drain more quickly, requiring wider spacing between drains.
- Conversely, soils with lower permeability necessitate closer spacing to ensure effective drainage.

Conclusion:
The spacing of tile drains to relieve waterlogged land is inversely proportional to the discharge per unit length in the drain. This means that as the discharge per unit length decreases, the spacing between drains needs to be reduced to maintain effective drainage. Other factors such as the depth of the drain below the ground surface, depth of impervious strata from the drain, and coefficient of permeability of the soil also influence the spacing of tile drains. It is important to consider all these factors to design an efficient drainage system that effectively relieves waterlogged conditions.