Infiltration and Infiltration Capacity

What is Infiltration Capacity ?

When the water is flow on ground surface, a some part water seeps into the soil, This movement of water through soil is called Infiltration. This infiltrated water is used to increasing moisture content of soil up to field capacity and extra water moves downward and becomes a ground water.

Infiltration an Analogy

Relation between Rainfall Intensity and Infiltration Capacity,

If i > Fp      then,      F = Fp

If i < Fp      then,      F = i 

Where,

F = Actual infiltration rate

i  = Rainfall intensity

Fp = Infiltration Capacity 

which determine how much of falling rain will flow directly over the ground surface, and how much will enter the soil to be retained as net moisture storage for some period of time before being either passed downwards as percolation or returned to atmosphere by the process of evaporation.

Different models of infiltration as per low intensity rainfall and heavy intensity rainfall

Comparison between low intensity rainfall and heavy intensity rainfall model

In above infiltration model you can see there is no rainfall contribution to groundwater due to low intensity rainfall and other end there is rainfall contribution to groundwater due to heavy intensity rainfall.

Factors affecting on Infiltration Capacity :

• Rainfall Characteristics 
• Soil Characteristics 
• Surface Characteristics 
• Temperature 
• Water Characteristics 

Rainfall Characteristics:

As we know as the size of raindrop increases it reflects in increasing the force by which rain drop strike to the surface. This raindrop effects more in clayey surface as compared to sandy surface. The infiltration capacity of soil is high in beginning of storm and it decreases exponentially as the time passes. 

Soil Characteristics:  

As we know a dry soil can absorb more water than the soil whose pores are already full of water. A loose sandy soil have a large infiltration capacity than light clayey soil. A soil with good under drainage have high infiltration capacity.

Surface Characteristics:

As we know when the people and animal walk on the surface, the ground get compacted and compacted ground have less infiltration capacity. Also a vegetation cover tends to increases infiltration.   

Temperature:

The viscosity of water changes with temperature, Infiltration capacity will change with the temperature because infiltration capacity is lower in winter and higher in summer.

Water Characteristics:

Water infiltrating into the ground will have chances of many impurities both in solution and suspension, The turbidity of the water, especially the clay and colloid content is an important factor and such suspended particles block the fine pores in the soil and reduces the infiltration capacity of ground.