Water and air flow parameters

In the previous chapter, some methods to be used for relatively static characteristics of the structural state were discussed. In this chapter attention will be paid to some methods that can be used to characterize the flow of water and air in soil. Direct measurement of flow rates is rather difficult from an experimental point of view. Besides, a very wide range of values can occur in any particular soil material because flow rates as such are a function of the pressure or concentration gradients in the system. It is therefore advisable to define flow rates as a function of defined pressure or concentration gradients. This aspect will be further discussed when dealing with the various methods. It should be pointed out that flow theory is thoroughly discussed in many recent soil physical textbooks.