Abstract of the proposal

A pumping test is a common tool used by hydrogeologists to determine aquifer hydraulic properties for various purposes such as design of groundwater supply and prediction of contaminant migration. Since the 1930s, many analytical and numerical models of transient flow to wells have been developed to interpret the test data. These models, however, focus mainly on single-phase water flow in saturated aquifers. On the basis of our research on tide-induced airflow in coastal aquifers and field experience of pumping tests, we speculate that groundwater pumping may generate negative air pressures in unconfined aquifers and that the air pressure can be significant under some circumstances. We hypothesize that airflow influences water level changes and consequently parameter estimation due to interaction between airflow and water level. We propose to investigate systematically and quantitatively airflow and its interaction with water flow in multilayered, semi-confined or unconfined aquifer systems under pumping conditions by combining theoretical studies, field pumping tests, and three-dimensional numerical modelling. Successful completion of this study will provide a better understanding of the fundamental processes of water release and water level change in response to pumping. A better understanding of the vacuum generated by pumping will also provide insights into the mechanism of the common engineering problem of ground collapse induced by extensive groundwater withdrawal.