Page 283 - Modern Spatiotemporal Geostatistics

264 Modern Spatiotemporal Geostatistics — Chapter 12

EXAMPLE 12.22: Computerized hydrogeologic systems are used to integrate
and simplify the process of ground-water flow and transport modeling by bring-
ing together all of the tools needed to complete a successful study (e.g.,
DoD-GMS, 1997). Below we present an approach based on Figure 12.19 that
uses modern spatiotemporal geostatistics techniques to study the hydrogeo-
logic properties of real sites. In the first step of the approach (initial site
characterization), the concern focuses on: (la) the development of general
knowledge bases (ground-water flow equations, statistical moments of the hy-
drologic variables, etc.); (Ib) the acquisition and storage of specificatory knowl-
edge bases (borehole data display, stratigraphy representation, hard and soft
attribute data, etc.); and (Ic) the establishment of an adequate space/time ge-
ometry (coordinates, metric, local patches, etc.). The second step (site model
conceptualization) focuses on: (2a) the scanned regional map; (2b) import-
ing from CIS objects consisting of points, arcs, and polygons organized into
coverages; and (2c) assigning attributes to the CIS objects (e.g., for a drain
arc, the conduction of the drain is assigned to the arc and the elevation of the
drain is assigned to the endpoints of the arc). In the third step (physical grid
generation): (3a) an appropriate physical grid is constructed dividing the area
into cells on the basis of the conceptual model of the site (e.g., the grid may
be refined around the wells or other points in which a large gradient in head
is expected and the grid cells outside the model domain are inactivated); and
(3b) the CIS objects and attribute data of the specificatory knowledge bases
of the first step above are overlaid on the conceptual model and all stresses
(wells, rivers, drains, heads, etc.), recharge, and hydraulic conductivity zones
are inherited by the grid cells in the appropriate format for use as inputs in BME
codes. In the fourth step (geostatistical modeling and knowledge integration
in space/time): (4a) the physical grid-based BME equations are solved within
each grid cell subject to the constraints of the previous first three steps (which
integrate the knowledge bases collected in these steps), thus leading to (4b)
a complete characterization of the hydrogeologic variables of interest in terms
of multivariate pdf, space/time maps, etc. Finally, in the fifth step (graph-
ical visualization of the results), the solutions (hydraulic heads, contaminant
concentrations, etc.) are plotted in the form of space/time maps.
By way of summary, we may conclude that modern geostatisticians and
CIS analysts can benefit a great deal from mutual interaction. In addition
to the powerful logical concepts and sophisticated mathematical techniques of
modern spatiotemporal geostatistics, the methodology can provide a valuable
guide to the new realities of CIS, some of which have been described above.
CIS, in turn, offers a highly efficient network of computerized technologies
for representing and visualizing space/time data. Therefore, we should expect
that a mathematically rigorous and physically meaningful integration of the
theoretical and computational models of modern spatiotemporal geostatistics
with the versatility and flexibility of CIS technologies will be a main topic of
future research in our field.