1. Flow Anisotropy in the Red River Alluvial Aquifer Caddo Parish, Louisiana
By: John Hubbard
CE 394K

2. Problem
Can ArcView be used effectively to map the potentiometric surface in an anisotropic aquifer?
Can flow direction be determined using spatial analyst?

3. Study Area

4. Aquifers of Louisiana

5. Red River Alluvium Covers 2,120 sq. Miles of Louisiana
Composed of medium to fine-grained sand and silt.
Silt acts as retarding units with-in the alluvium

6. Wells Data from 69 USGS observation wells were obtained
Dates after 1990 were thrown out due to the construction of lock-and-dam.
1980 was selected as an average year with the most data available leaving 38 wells to be mapped

7. Well Data
The high, low elevations of the head in each well were sorted
The mean annual head elevation was calculated

8. Longitude and Latitude
Data about each well was obtained from the Louisiana Department of Transportation and Development
Longitude and Latitude were sorted in Excel and converted to decimal degrees

9. Plotting Well Data
The Elevation Table and Long/Lat Table were added to ArcView and joined by well number
The newly joined elevation table mapped using “Add Event Theme”
A decrease in head elevation can be seen from north to south

10. Spatial Analyst
The spatial analyst extension was then loaded and the “surface/interpolate grid” function was used
This produces a potentiometric map
However, this map shows no reference to the river or the edge of the alluvium

11. Spatial Analyst 2
The spatial Analyst was run again, however, this time the NHD file shp, was placed as a barrier
Again, this produces another potentiometric map

12. More Spatial Analyst
The Spatial Analyst was then used to calculate the the aspect of the potentiometric surface to approximate flow direction

13. Issues and Problems
Lack of data
No western border
River stage was not included
Aspect does not account for anisotropy