Abstract: Soil water infiltration is a main approach of groundwater recharge for the unconfined aquifers. Research on the mechanism of soil water transport has transferred from perspectives of qualitative to quantitative, and from homogenous to heterogeneous. Preferential flow is a prevalent phenomenon of groundwater recharge, which indicates that soil water infiltrates into the unconfined aquifers in the way of shortcut flow. Research on preferential flow is an important and difficult topic, with dyeing tracing, x ray microtomography and ground penetrating radar as main methods. Many of methods, e.g., tracing, groundwater level fluctuation, lysimeters, zero flux plane and numerical model, for the evaluation of groundwater recharge, are used in different conditions, therefore, we advise that the groundwater recharge is evaluated using several methods together by comparison and verification to improve assessment reliability.

Key words: unconfined groundwater, soil water, preferential flow, infiltration, recharge