Understanding Waterlogging Due to Obstruction

Waterlogging occurs when the soil pores in the root zone become saturated with water, leading to poor aeration and affecting plant growth. Several factors can contribute to waterlogging. The question specifically asks for the factor that causes waterlogging due to obstruction.

Analysis of Factors Causing Waterlogging

Let's look at the given options and see how they relate to waterlogging, particularly in the context of an obstruction:

• Inadequate Natural Drainage: This refers to a situation where the natural ability of the land to drain water is insufficient. While it leads to waterlogging, it's a general lack of drainage capacity, not necessarily caused by a specific physical obstruction blocking water flow.
• Flat Topography: Land with a flat surface has very little slope, which hinders the natural runoff of surface water and the lateral flow of groundwater. This can lead to waterlogging, but like inadequate natural drainage, it's a landscape characteristic, not a specific obstruction.
• Impervious Obstruction: An impervious material is one that water cannot pass through easily. An impervious layer or structure underground or on the surface acts as a physical barrier that blocks the downward or lateral movement of water. This blockage, or obstruction, causes water to accumulate above it, leading directly to waterlogging. Examples include a hardpan layer in the soil, bedrock near the surface, or even constructed barriers like roads or foundations if drainage is not properly planned.
• Over and Intensive Irrigation: Applying excessive amounts of irrigation water to a field can saturate the soil and lead to waterlogging, especially if drainage is poor. While this is a common cause of waterlogging, it is due to the excessive *input* of water rather than a physical *obstruction* blocking its removal.

Conclusion on Obstruction and Waterlogging

Based on the analysis, the factor that specifically causes waterlogging because of a physical barrier or blockage (an obstruction) is an impervious obstruction. This impervious layer stops water from draining away, causing it to build up in the soil profile.