Infiltration of Water through Soil

Our Objective

 To study infiltration of water through soil  

The Theory

Infiltration is the process by which water on the surface enters the soil. Based on the type of soil, they show a difference in the time taken and amount of water allowed to pass through them.  

Sandy soils have particles of larger size. They cannot fit close together, so there are large spaces between them. These spaces are filled with air. Water can drain quickly through the spaces between the sand particles. So, sandy soils tend to be light, well aerated, and dry. 

Clayey soil has fine particles that are tightly packed together, leaving little space for air. The water can be held in the tiny gaps between the particles. They have good water holding capacity and hence it takes more time for the water to pass through. 

Silt soils have particles that are between the sizes of sand and clay, and so have an intermediate infiltration rate. Silt is usually found as a deposit in riverbeds.  

The water that infiltrates in upper layers of the ground are usually absorbed by the plants for photosynthesis and growth. The infiltration rate of soil influences the type of plants that can grow on them. Deserts have sandy soil with less vegetation as the surface run off water dries out very quickly and does not hold nutrients for long. The silty soils have moderate infiltration rate which enables them to retain water and nutrients long enough for plant roots to absorb. As infiltration is low in clay soils, it is harder for water to penetrate the soil. Such soils becomes waterlogged easily. Plants are usually grown in loamy soil which is a mixture of sand and clay. It has the right water holding capacity for the growth of plants. 

Surface water from any source (rain, pond, river, lake, spring, snow, human activities) may also continue to move further downwards through soil and gets stored as ground water.  

Learning Outcomes

  1. Students familiarise themselves with sand, silt, and clayey soil. 
  2. Students learn about infiltration of water through soil. 
  3. They understand the difference in infiltration rate of different soil type.