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The structure of the project groundwater system is defined with relative ease once the database has been completed. Data is recovered from the database using GIS querying techniques and this data is used to create maps describing multiple aspects of the groundwater system.
KOT-ECI has developed a procedure (STRATMOD®) to produce a three-dimensional model of the stratigraphy of the groundwater system. When completed, this model is used to illustrate the horizontal and vertical distribution of hydrogeologic units (aquifer, aquitard, aquiclude, and bedrock).
The project groundwater system can be thought of as a box whose surface extent is determined by the project boundaries and whose vertical extent is established by the bedrock surface. A stack map is developed to define the box contents. The figure below is an example of a simple stack map. The top map is the surface layer and the bottom map is the bedrock layer. The two intermediate maps are layers indicating conditions at a given elevation.
Depending on the complexity of the site stratigraphy, layers are constructed at a vertical interval of 5 to 20 feet of elevation. Five-foot intervals are used in very complex situations while 20 feet or greater intervals are used where there is little variation in the stratigraphy.
The stratigraphic model is composed of the series of layers extending from the surface to the bedrock. A typical model may have 50 to 100 layers. Other examples of the stratigraphic model may be viewed by clicking on the following buttons:
Once the stratigraphic model has been completed it becomes the conceptual model that is used to build a preliminary groundwater flow model of the project site.
Although the groundwater flow model will supply more definitive answers to common questions, the stratigraphic model can be used to make preliminary estimates of the total volume of water and the extractable volume of water in the project area. Additionally, the model provides a three dimensional picture of the location of the aquifer material. In many cases there is enough information available to estimate the values of the components of a water budget as shown below. Values of these components are relatively large and this exercise is generally used to provide a rough estimate of the accuracy of the stratigraphic model.
As mentioned above, the structure of the project groundwater system is defined with relative ease once the database has been completed. This also is true for developing maps characterizing other attributes of a shallow aquifer system. As with the development of a stratigraphic model, data is recovered from the database using GIS querying techniques and these data are used to create maps describing multiple aspects of the groundwater system. Additional types of maps traditionally produced as part of a study to characterize an aquifer system may be viewed by clicking below: