8. Redistribution and Drainage

We have considered how water inputs are modified by the process of interception and then partitioned between infiltration and runoff. Now, we will turn our attention to the fate of the infiltrated water. The process of continued movement of soil water after infiltration ends is called redistribution. In this chapter, we will focus on some fundamental aspects of the redistribution process such as:

• its rate decreases over time
• it influences the availability of water to plants
• it drives solute transport in soil

We will also examine the process of drainage, which is the loss of water from below the root zone or from the bottom of the soil profile. We will learn a relatively simple method for estimating drainage rates and will also think about artificial (or man-made) soil drainage systems and their impact on agriculture and the environment.