Using ARCGIS for groundwater flownets/direction

[DotLundberg]

Hello all,
Beginner user of ARCGIS. 
Background info: Created equipotential flow lines using the contour function in ARCGIS.  From here I am looking for a way to create groundwater flow paths based off of the created equipotential flow lines.  These lines were created using my research data of hydraulic head values and elevation of the groundwater system.  Help would be greatly appreciated.


Dot.

[DotLundberg]

Thank you for replying. I have been trying to use ArcHydro but have run into problems with that as well. When using ArcHydro I have discovered that instead of having a uniform direction, it shows that the groundwater will flow 360 degrees around a single well and this is for each well. This cant be possible so I am an stuck on how to approach this.

dot.

[DotLundberg]

Well they are technically piezometers so no pumping is going on. When I mean uniform, groundwater systems typically flow in few direction but as a collective. I am looking at the groundwater surfacewater relationship between stream and floodplain groundwater. So the direction of groundwater flow is usually two directions, losing stream or gaining stream for floodplains. I am trying to map out my hydraulic heads to show which of these relationships are present at the site. Hope that helps. The problem is I am encountering with using arc hydro is mixed results of directions, when it should be somewhat linear and flat since there is very little change if at all in topography, soils, and vegetation. Attached you will see photos. There are 3 of them. The first shows what I think should be the groundwater flow lines based off the equipotential lines that were created in ArcGIS using contours. The next two shows the output of using archydro with arrow spacing of 10 and 30. The other problem is that flow lines should cross the equpiotential lines at 90 degrees and never cross each other both which happen in the archydro. Maybe I am doing something wrong. I dont know. Thanks for the help, its much appreciated.

[DotLundberg]

Thank you again for your help in understanding ArcGIS.

In response to �??It looks like water is being injected at five discrete locations at the top and left (near points B1, B8, C7, D7, and F4)�?� : these piezometer locations are known to have higher groundwater elevations due to the spring season (recharge period) and soils that are more adapt to holding groundwater at its highest. Its location are offset to the beginning piezometers (approx. 1-3 for transect A-E) which are known to be a former gravel bar in groundwater seepage back into stream is much easier and the there is also about a 1meter difference almost immediately before the back piezometers, as there is a chute channel running in between. There is more storage at the back piezometers in which I thought might cause what you describe as injection sites. Adding additional piezometers would show similar patterns however I do not have piezometers that go back farther that can be used in the actual study.

You are correct that these maps were created based of piezometer head readings. I used IDW with standard settings to obtain the results you see, which you are correct from what I see about them causing individual mounds. Different groups (ranges) of the results were changed to offset this problem after they were created.  Everything calculated after that is based off these IDW. I guess I am not sure which interpolation you are suggestion since both have flaws. I read that IDW was best to use for groundwater systems but maybe that will not work for my site.

You are correct on that the hand version has flaws. I am constantly working on trying to fix problems with it. I was oversimplifying it in order to try to see a basic picture of what I think should be happening. I guess the main problem I would like to try and have fix is using an analysis that would not start at points of origin and would look at the site as a whole. I am mainly interested into what the floodplain section is doing as a whole, not individual piezometer points.

[DotLundberg]

As an update: so I took your advice and spent the day learning, reading, and trying out kriging. It seems to have worked out really well!  Below you will see the new version. I first used geostatistical analyst kriging in order to calculate the lag size, range, sill, and nugget. From there since I wanted to use my own masking I created, I took this information and ran the kriging in spatial analysts, interpolation, kriging.  It looks much smoother, easier to contour, and shows that is truly happening at the site. There are a few flaws in it around Piezometer A1, and H2 but these are very minor. I also have to see whats going on at A7. Other than that I wish the contours were smoother at B3, and then again between C1 and B1 but again, minor problems compared to what I was dealing with!  I cant thank you enough for your help. It is truly appreciated. Any other suggestions you might have now with the new version is welcomed. 🙂

[DotLundberg]

Bill,

Sorry to have to ask you for more advice but I am at a loss and so frustrated.  Brief update: from the previous image I had sent you that I was all excited with (lag size= 4.238, sill=0.034, range=46.62, and nugget 0.012) is now unable to be replicated. The previous image was using elevational values that were based off a benchmark of 10m, so values were between 9-7 meters but not true to mean sea level. Today I went in the field with gps to obtain correction elevations. I was able to convert all previous elevational ranges with the new current and accurate ones. Now values are between 36-38m.  Now I feel like the maps should still be similar in flow and appearance but they are different. The new values are just a relative to the old ones due to the natural of the conversion to the new ones from the old values. Its still the same field site just actual values. I must be missing something. Please see the image attached.  Is there an email I could reach you at that might be able to allow better communication? dotlundberg@gmail.com is mine. If you are willing, please send a reply there or on here. As always I very much appreciate your help. By the way the new values are lag size=4.238, sill=0.567, range=46.62, and nugget 0.633. I fear the new values for nugget and sill are the culprits. I calculated the lag size from natural neighbor as gis suggested. The new map is just plain ugly, and I want the previous map back!