Water runs down hill, it always has done and I believe it always will. But sometimes it can “push up” through the soil profile. Why is that?
Around the large rivers we have the flood meadows. With swollen rivers water can not escape from the minor streams and so rainfall is caught and held in the soil within the field. The surface “dries” (it is no longer raining) but as soon as you scratch down 150 mm your hole fills with water.
Going back to downward water movement; this you can affect. I talked in earlier Blogs this week about Structural Stability and Soil Texture.
We know that surface water is a problem for clay soils and getting it out of the “cultivation” zone is important. One solution to this problem is the installation of field drainage.
Land drains work by allowing water to flow into a pipe and away from a specific location. Thanks to perforations within the pipe and the essential use of surrounding aggregate, water flows naturally down the aggregate and into the perforations of the pipe. Once water enters the land drain, due to the effects of gravity and a gentle gradient on installation, the water flows to the designated disposal point.
The loose aggregate or shingles surrounding the pipe is brought up to within 300 mm of the soil surface and so provides a clear direction to travel for water flow. The large pore space, its high frequency, interconnectivity and ability not to denature under compaction all work to speed the removal of surface water from a field with a high clay content which would other wise take hours or days to remove if left unaided.