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Showing posts from November, 2015

Integrated groundwater and surface water modeling: how to make use of the MODFLOW Listing file

Whatever version of MODFLOW you are using for groundwater modeling, knowing how to make use of the list file can help a lot to understand what you are actually doing.

As the official MODFLOW manual document describes:
"The Listing File is a key file to which model output is written. As MODFLOW runs, information is written to the Listing File, including much of the input data (as a record of the simulation) and calculated results."
And
"The Listing File includes a summary of the input data read for all packages. In addition, the Listing File optionally contains calculated head and drawdown controlled by layer and time step, and the overall volumetric budget controlled by time step. The Listing File also contains information about solver convergence and error messages. Output to other files can include head, drawdown, and cell-by-cell flow terms for use in calculations external to the model or in user-supplied applications such as plotting programs."
Therefore, the Li…

Spatial datasets operations: mask raster using region of interest

Climate change related studies usually involve spatial datasets extraction from a larger domain.
In this article, I will briefly discuss some potential issues and solutions.

In the most common scenario, we need to extract a raster file using a polygon based shapefile. And I will focus as an example.

In a typical desktop application such as ArcMap or ENVI, this is usually done with a tool called clip or extract using mask or ROI.

Before any analysis can be done, it is the best practice to project all datasets into the same projection.

If you are lucky enough, you may find that the polygon you will use actually matches up with the raster grid perfectly. But it rarely happens unless you created the shapefile using "fishnet" or other approaches.

What if luck is not with you? The algorithm within these tool usually will make the best estimate of the value based on the location. The nearest re-sample, but not limited to, will be used to calculate the value. But what about the outp…