Jim Yeh Ph.D

Professor of Hydrology and Water Resources

The University of Arizona, Tucson

2007 Short Course - Hydraulic Tomography: A New Technology

Why learn new technologies? Traditional aquifer tests and analyses yield transmissivity estimates that are non-unique averages of heterogeneity over the cone of depression, which evolve with time and depend on the location of the observation well. On the other hand, the estimated storage coefficient is mainly influenced by the geology between the pumping and the observation well. These results suggest that ground water availability may have been either underestimated or overestimated and our current management strategies of groundwater resources as such are subject to great uncertainty

What is and why use hydraulic tomography? Hydraulic tomography (HT) is a sequential cross-hole hydraulic test followed by inversion of all the data to map the spatial distribution of aquifer hydraulic properties. Specifically, HT involves installation of multiple wells in an aquifer, which are partitioned into several intervals along the depth using packers. A sequential aquifer test at selected intervals is then conducted. During the test, water is injected or withdrawn (i.e., a pressure excitation) at a selected interval in a given well. Pressure responses of the subsurface are then monitored at other intervals at this well and other wells. This test produces a set of pressure excitation/response data of the subsurface. Once a test is completed, the pump is moved to another interval and the test is repeated to collect another set of data. The same procedure is then applied to the intervals at other wells. Afterward, the data sets from all tests are processed by a mathematical model to estimate the spatial distribution of hydraulic properties of the aquifer. These pairs of pumping and drawdown data sets at different locations make an inverse problem better posed since each pair cross-validates the others such that the estimates become less non-unique. In other words, predictions of ground water flow based on the HT estimates will be more accurate and less uncertain than those based on estimates from traditional site-characterization approaches and model calibrations.

click image to see animation

Is hydraulic tomography too costly? Hydraulic tomography can be applied to fully-screened wells, too, although the estimates will be at low resolutions. In effect, under this condition, often hydraulic tomography data may already exist, or it can be created using some existing sampling networks at little additional expenses.

More information Download the application and course schedule to get more details. See the short course webpage to learn more about this information-packed three-day seminar, held in Tucson, Arizona March 12-14, 2007.

THT_MPI: Transient Hydraulic Tomography using MPI

Interested in using my revolutionary new pumping test analysis method on your own pumping test data? Now you can. On my downloads page, you can obtain a parallel version of my transient hydraulic tomography inversion program, which is designed to run optimally on a Win32 PC cluster using MPI.

A New Aquifer Test Method: Hydraulic Tomography

Aquifers are heterogeneous at a multiplicity of scales. This is the rule rather than the exception. Traditional aquifer test analysis (i.e., Theis and Jacob methods), however, assumes aquifer homogeneity. If a pumping well taps into a high permeable zone and an observation well is installed in a low permeable zone, do you know what estimate you get from this type of test and analysis? Common sense tells you the analysis compares apples to oranges but you never question it. Let us show you that this analysis is indeed bogus(see Interpretation of Pumping Test Results). Even better, let's show you that with the same well facilities and costs, you can do better if you conduct pumping tests intelligently or using common sense (see hydraulic tomography section or presentation).

Some examples of hydraulic tomography - click graphics to see more

Estimated Ss distribution for 2D Ttransient HT

Estimated K distribution for 2D Ttransient HT

Exploiting Natural Stimuli for Large-scale Groundwater Basin Surveys

Tomographic surveys of the subsurface are the future. Expanding this new technology to basin-scale problems requires excitations that can affect a large extent of an aquifer. Naturally and frequently occurring stimuli (such as storms, precipitation, lightning, earthquakes, volcano activities, river-stage fluctuations, etc) are perfect excitations for this purpose. For example, cloud to ground direct lightning occurs frequently in many parts of the world, strikes different parts of a basin, contains enormous amount of energy, and transmits a broad-band of electric magnetic waves into the subsurface. If we can harvest these signals from the subsurface, we have naturally occurring large-scale EM surveys and we can see into the subsurface at great depths and over large areas. In other words, Mother Nature continuously sends out signals to lure us to unveil her mystery. Why do we ignore her? We will show you how we can exploit the natural stimuli for monitoring, charactering, and forecasting subsurface processes (see autonomic fusion of information). 'Seeing' into the subsurface is not a mission impossible.

View the posters and slide shows of my research group's latest presentations in topics of subsurface hydrology below

Posters

NAPL source zone characterization using tracer tomography

Numerical simulation of river stage tomography

Sequential Pumping Tests at a Well Field, Montalto Uffugo Scalo, Italy

Presentations

Interpretation of Pumping Test Results in heterogeneous media (comparing apples to oranges?) (pdf)

Hydraulic Tomography a powerful new aquifer test method (pdf),

Autonomic Fusion of information in the subsurface (including the use of natural stimuli) (pdf).


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