[Dhsvm-users] Re: Help interpretting end-of-model-run sediment statistics

[Voisin, Nathalie]

Brian, 

Responses are in line below

Best,
Nathalie




>#My specific questions are as follows:



>-the 'Basin Average Road Surface Erosion' and 'Average Road Surface Erosion' are negative numbers.  Does this reflect a lowering of the road surfaces?


YES, this is a mass loss.



>-the 'Average Road Surface Erosion (kg/hectare)' reads -3.66e+03.  Negative kilos/hectare seems like an obvious error.  Do these negative numbers indicate some error intrinsic in my roads network setup?


NO, this is a mass loss, so negative numbers.



>-the lower 'Storage' numbers: are these channel storage numbers?

The Upper Final Mass  Balance is for WATER
The lower Final Mass Balance is for SEDIMENTS 



>-the 'Mass Error' seems pretty large; what have other modelers seen in their models?


THIS is a mass error over your entire basin over your 8 months run. 6kgs mass error in 8 months .... it depends on the size of your basin.




>-in plotting my 'Sed.Stream.Flow' output, the mass of sediment (column 3) stays more or less constant at ~4000 most of the run.  It doesn't show any relationship to stream flow.  I've got plenty of graphics of this, but cannot attach them here.  Again, is this a problem intrinsic to the setup of my road net files?


The road erosion is transported via overland flow then in the ditch. It is usually captured into a culvert that redistributes the sediments/erosion in the hillslope where it can get trapped again. Looking at your results, that is happening. If your culvert transports the flow directly into the channel (pipe), this needs to be specified in the road network file, manually. The set up automatically diverts it to the grid cell where the culvert is presently.




>-Finally: the upper 'Storage' numbers: my 'Final Surface (mm) 56' Is there a sink or something I'm missing that's collecting water?


The storage you are referring to is not sediment but water. 
It looks like your water mass balance decreased during your run. Your sediment storage in the stream increased though.


Hope it helps,

Nathalie
__________________________________________________ 
Nathalie Voisin, Ph.D. 
Research Scientist 
Pacific Northwest National Laboratory 


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Today's Topics:

   1. Help interpretting end-of-model-run sediment	statistics
      (Huggett, Brian)


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Message: 1
Date: Thu, 17 Mar 2011 09:49:52 -0700
From: "Huggett, Brian" <BHuggett at parks.ca.gov>
Subject: [Dhsvm-users] Help interpretting end-of-model-run sediment
	statistics
To: "'dhsvm-users at u.washington.edu'" <dhsvm-users at u.washington.edu>
Message-ID:
	<17B89984CF865F4084CDE29D4A07F2DC01F156DC09 at MSHQEXCH3.parks.ca.gov>
Content-Type: text/plain; charset="us-ascii"

Greetings fellow modelers,

I'd like to request some help interpreting some of the sediment erosions statistics that are returned at the end of the model run.  I've recently created the necessary road.xxx.dat files using the .amls supplied.  This is my first couple of runs with the roads network and sediment options turned on, so I'm not sure what these numbers are telling me.

# this is the return from my most recent run - 8 months at a 1 hour time step

Final Mass Balance

Inflow, 930.82:
 Precip (mm): 930.823088

Outflow 1098.77:
 ET (mm): 647.281885
 SnowVaporFlux (mm): -0.026107
 CulvertToChannel (mm): 2.652700
 ChannelInt (mm): 445.255369

Storage:
 Initial Storage (mm): 218.714163
 End of Run Storage (mm): 50.514787
     Final SWQ (mm): 0.000000
     Final Soil Moisture (mm): -5.798025
     Final Surface (mm): 56.312811
     Final Road Surface (mm): 0.000000

Other:
 RoadInt (mm): 36.442913
 CulvertReturnFlow (mm): 30.185685
 Mass Error (mm): -0.254110
 Mass added to glacier (mm) 0.000000

Final Sediment Mass Balance

Basin Average Road Surface Erosion
 Road Surface Erosion (mm): -1.17e-03
 Road Surface Erosion (kg/hectare): -3.15e+01
Road Sediment to Hillslope (mm): 0.00e+00

Average Road Surface Erosion
 Road Surface Erosion (mm): -1.36e-01
 Road Surface Erosion (kg/hectare): -3.66e+03
Road Sediment to Hillslope (mm): 0.00e+00

Channel Erosion
Inflow 1.46e+04:
 DebrisInflow (kg): 0.000000e+00
 OverlandInflow (kg): 0.000000e+00
 OverroadInflow (kg): 1.460130e+04

Outflow 1.17e+03:
 SedimentOutflow (kg): 1.176784e+03
 CulvertReturnSedFlow (kg): 1.176784e+01
 CulvertSedToChannel (kg): 0.000000e+00

Storage:
 Initial Storage (kg): 7.032768e+05
 End of Run Storage (kg): 7.234422e+05
     Final Bed Storage (kg): 7.233632e+05
     Final Suspended Sediment (kg): 7.892342e+01

Mass Error (kg): 6.729135e+03

STARTING CLEANUP


END OF MODEL RUN

#My specific questions are as follows:

-the 'Basin Average Road Surface Erosion' and 'Average Road Surface Erosion' are negative numbers.  Does this reflect a lowering of the road surfaces?
-the 'Average Road Surface Erosion (kg/hectare)' reads -3.66e+03.  Negative kilos/hectare seems like an obvious error.  Do these negative numbers indicate some error intrinsic in my roads network setup?
-the lower 'Storage' numbers: are these channel storage numbers?
-the 'Mass Error' seems pretty large; what have other modelers seen in their models?
-in plotting my 'Sed.Stream.Flow' output, the mass of sediment (column 3) stays more or less constant at ~4000 most of the run.  It doesn't show any relationship to stream flow.  I've got plenty of graphics of this, but cannot attach them here.  Again, is this a problem intrinsic to the setup of my road net files?
-Finally: the upper 'Storage' numbers: my 'Final Surface (mm) 56' Is there a sink or something I'm missing that's collecting water?

Thanks for your time and attention, hope you can help.
As incentive for cross pollination: I've developed some great Gnuplot scripts to plow through most of the output files and would love to share them.  I've got scripts to plot the modeled vs (your) observed records, real-time scripts to watch the model data come in, and a couple to record outputs to animated .gifs (great gifts to advisors or funders!).  They are well commented to aid in modification as well.

Brian Huggett
Department of Forestry and Wildland Management
Humboldt State University
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