An understanding of the fate of water arriving at the land surface via precipitation has a number of applications. Growing vegetation relies on water held within the soil, explored by roots in order for plant growth to be sustained. Water running off the soil surface not only creates the potential for soil erosion, but also transports sediments, nutrients and potential pollutants into surface waters. Deep percolation of water is of interest with respect to groundwater recharge, and the possible transport of potential pollutants from the land surface into groundwater. Evaporation from the land surface depends on weather variables as well as on the availability of water, and is an important mechanism for the dissipation of solar energy absorbed by the land surface. There are close links between the availability of water for evaporation and the temperature of the land surface, and the extent to which the land surface acts as a source of sensible heat and water vapour for the atmosphere.