Vadose Zone Hydrology and Groundwater Recharge

Abstract

The rate of recharge (i.e., renewal) of groundwater is a key factor regulating sustainable use of groundwater resources. Hydrological processes in the vadose zone have two important roles: one is to partition the precipitation input into groundwater recharge and evapotranspiration, and the other is to damp down the temporal variability of the recharge flux. Infiltration is the first process after precipitation and is controlled by atmospheric (e.g., rainfall intensity) and soil conditions (e.g., infiltration capacity). Bare soil evaporation and transpiration are the processes of loss of infiltrated water. The rate of bare soil evaporation is sensitive to moisture status in surface soils as well as to atmospheric conditions. Transpiration rate is not very sensitive to these conditions and is capable of taking up water from deeper depths. The temporal and spatial characteristics of the groundwater recharge process change drastically depending on climatic conditions (i.e., humid or arid). Climate change and human activity can affect the rate and temporal variation pattern of groundwater recharge. Proper understanding of vadose zone hydrology is fundamentally important in increasing and improving our knowledge for wise use of groundwater during changes in climate and society.