Time-lapse transient electromagnetic monitoring of a water infiltration experiment: An application to the Central Avra Valley recharge basin, Tucson, Arizona

摘要

Recharge flux is one of the most difficult components of the water balance to measure. However, quantitative estimates of this flux are critical for water resource planning in semi-arid and arid areas. Land based geophysical techniques offer significant advantages for recharge monitoring. Specifically, because they do not require boreholes, they are typically inexpensive and can be used to monitor large areas. Electrical and electromagnetic methods may be useful for monitoring recharge because of their dependence on the electrical conductivity of sediments and therefore on the volumetric water content of a porous medium. In this study, we examine time domain electromagnetic (TEM) methods for monitoring water infiltration into an initially dry soil and subsequent drainage of the wetting front with time at a recharge basin near Tucson, Arizona. Results suggest an impermeable clay layer at approximately 30m depth and a subsequent buildup of water in the subsurface to the west of the site.