Research - Category I: Hydrology, Climatology & Hydraulics

Soil Water Monitoring Using Geophysical Techniques: Development and Applications in Agriculture and Water Resources Management
(Funded 1999-2000)

Principal Investigator: Yoram Rubin
Civil and Environmental Engineering
UC Berkeley
(510) 642-2282
rubin@ce.berkeley.edu

Executive Summary:
Monitoring of soil water content in the subsurface over large areas is a vital component of productive agriculture and effective water resources management. The information obtained from monitoring is critical for optimizing crop yields, achieving high irrigation efficiencies, planning irrigation scheduling, and minimizing lost yield due to waterlogging and salinization. Such water content monitoring is also important for addressing issues of water quantity and quality that are important in managing the environmental impacts of irrigated agriculture and for protecting functional ecosystems. Leaching of agrochemicals and salts into the groundwater and downstream ecosystems, for example, can be minimized if irrigation water infiltrates only to the bottom of the root zone. High resolution, continuous water content distributions allow one to design optimal irrigation and chemical application programs that make possible such "prevention at the source," and most importantly, to save huge amounts of water.

Conventional sampling techniques require expensive and invasive drilling, and at the same time, provide only point measurements. The soil properties which control water movement greatly vary over space and time. Consequently, point measurements generate large uncertainties when used for estimating water contents at the scales of space and time required for detailed site characterization in a dynamic environment. No current technique can provide the areal soil water content distribution quickly, reliably, and at low cost.

The purpose of the proposed research is to systematically develop and test geophysical techniques such as ground penetrating radar (GPR) and electromagnetic induction (EM) for providing large-scale, detailed, three-dimensional maps of soil water content. Preliminary studies of GPR and EM indicate they can efficiently provide high-resolution data about the subsurface over large areas.

The proposed study will answer fundamental questions regarding the applicability of GPR and EM methods, as well as practical ones such as optimal data acquisition modes and optimal interpretation.