Jump to content
GMS, SMS, and WMS User Forum
yacob

Infiltration issues with GSSHA

Recommended Posts

Hi. I am attempting to run a gssha model with infiltration (green ampt with soil moisture redistribution or "GAR"), however either one of two things are happening. My model crashes if I use Ksat and initial soil moisture that are too low. Conversely if I increase these parameters to the point where the model will run, all the water infiltrates and I get no runoff.

The crash error states "h NaN in main()- point 3, grid cell xxxxxx". Something interesting to note here is that the gridcell it says has crashed is actually outside of my watershed.

How I set up the index map:

I map shapefile to "soil type" coverage. In the "GIS to Feature objects wizard, I map USCS soil classification attribute in my shapefile to USCS soil type. Then I create an index map for gssha. The input coverage is my soils coverage and the coverage attribute is ID. I then set up the mapping tables and run the model.

The model runs fine without infiltration and I can get overland flow (ADE-PC) and stream flow routing(Diffusive Wave). I seems I have tried every conceivable combinations of infiltration parameter values and soil moistures. (within typical ranges of the wiki table) If I create a single soil type for the entire watershed it still fails. I have redrawn my shapefiles in case they may have been corrupted. I have lowered the timestep down to 1 sec. The highest initial moisture values it will take is .29 which, too me, is pretty low so no wonder its all infiltrating.

I'm not really sure what is causing cells outside of my grid to blow up. If it helps my gridcell resolution is 500m x 500m and I'm using WMS 8.1. Thanks in advance for the help.

Share this post


Link to post
Share on other sites

Hi. I am attempting to run a gssha model with infiltration (green ampt with soil moisture redistribution or "GAR"), however either one of two things are happening. My model crashes if I use Ksat and initial soil moisture that are too low. Conversely if I increase these parameters to the point where the model will run, all the water infiltrates and I get no runoff.

The crash error states "h NaN in main()- point 3, grid cell xxxxxx". Something interesting to note here is that the gridcell it says has crashed is actually outside of my watershed.

How I set up the index map:

I map shapefile to "soil type" coverage. In the "GIS to Feature objects wizard, I map USCS soil classification attribute in my shapefile to USCS soil type. Then I create an index map for gssha. The input coverage is my soils coverage and the coverage attribute is ID. I then set up the mapping tables and run the model.

The model runs fine without infiltration and I can get overland flow (ADE-PC) and stream flow routing(Diffusive Wave). I seems I have tried every conceivable combinations of infiltration parameter values and soil moistures. (within typical ranges of the wiki table) If I create a single soil type for the entire watershed it still fails. I have redrawn my shapefiles in case they may have been corrupted. I have lowered the timestep down to 1 sec. The highest initial moisture values it will take is .29 which, too me, is pretty low so no wonder its all infiltrating.

I'm not really sure what is causing cells outside of my grid to blow up. If it helps my gridcell resolution is 500m x 500m and I'm using WMS 8.1. Thanks in advance for the help.

I would turn on the contours for the created index map and see what values are getting mapped to it from the shape files. This may show where the problem is.

Cameron

Share this post


Link to post
Share on other sites

@ Cameron

If I use a text editor on the soils.idx file I find that all gridcells inside of my watershed are mapped to the correct uscs soil classification number. All cells outside of my watershed are zeros. The frustrating thing is it all looks normal. For some reason WMS doesnt show these grid cells that are mapped zero the lie outside of my water shed (which is where my model is blowing up). I have to look at the .idx file to see them all. In the mapping tables I only set up parameters for the possitive uscs classification integer.

@ Chris

Unfortunatley for me, I cannot disclose my model to the WMS tech support because it is classified. I'm am currently waiting for 8.3 to be approved for update and I hope that will help. I will also look at the tutorial.

Share this post


Link to post
Share on other sites

I think I have found a solution. Apparently it was a parameter issue. I was digging around on the gsshawiki and under primer -> capabilities -> infiltration I found that for green ampt inf "The initial moisture content must be less than or equal to the porosity and should be greater than the residual water content." I changed this in my mapping tables and was able to get a stable run. Some more testing is in order but I think I'm on the right track. I'll post if have anymore problems with this issue. Thank you all for your help and feedback.

Here is the link. Happy Modeling!

http://gsshawiki.com/gssha/Capabilities:Infiltration#Green_.26_Ampt_Infiltration

Share this post


Link to post
Share on other sites

Hello,

I'm using Green Ampt with soil moisture redistribution to assess infiltration for a long term simulation.

I would like to know if surface volumetric water content results are calculated assuming that the soil thickness is equal to the value inserted in SOIL_MOIST_DEPTH record ? Thank you.

Regards,

Fadoua

Share this post


Link to post
Share on other sites

Fadoua,

The following infiltration-related parameter maps are computed and can be read into WMS after GSSHA is run:

Cumulative infiltration depth
Infiltration rate
Surface soil moisture
I'm not sure whether this answers your question. Are you looking for the Cumulative infiltration depth values?
Chris

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×