Walkthrough 2: DOWNSTREAM_ID Help

[baps]

New user to Raven - apologies if this is a silly question!

In my Raven_errors.txt file I consistently get the following errors:
ADVISORY : CModel::InitializeBasinFlows: one or more subbasin reference discharges were autogenerated from annual average runoff
ADVISORY : CModel::InitializeBasinFlows: one or more subbasin initial outflows were autogenerated from annual average runoff

I'm wondering if this could be related to the values I provided for the subbasin DOWNSTREAM_IDs.

The Walkthrough 2 Manual states:
"Modify the Nith.rvh file from a text editor after gathering the input files. From the map above, specify the proper subbasin outlet IDs; note that the most downstream subbasin (subbasin 43, which empties outside the modeled domain) should be assigned a DOWNSTREAM_ID of -1. Just to test Raven’s errorchecking skills, first temporarily set this ID to 36, and attempt to run the model – note that
RavenErrors.txt should reflect that there was a circular reference, since 36 empties into 39 empties backinto subbasin 43. Raven requires that the stream network is a branching network, and all flows are noncyclical. Change the outflow index back to ‐1 and re‐run the model, then click Gather Output to examine the output files."


My question is, what value should subbasins 30, 36, and 39 have? And what about the basin names.

Here is an example of my Nith.rvh file at the moment:
:SubBasins
:Attributes NAME DOWNSTREAM_ID PROFILE REACH_LENGTH GAUGED
:Units none none none km none
30 Sub30 -1 sub30profile 0 0
36 Sub36 -1 sub36profile 37.0 1
39 Sub39 -1 sub39profile 42.7 0
43 Sub43 -1 sub43profile 35.4 1
:EndSubBasins

Any help would be much appreciated!

[rchlumsk]

Hi there

Please ask any questions you have as a new user, no worries there. In the 'Raven Walkthrough 2.pdf' file, the map shows that the subbasins are one linear connection, i.e. 30 -> 36 -> 39 -> 43. Thus, the subbasin connections would look like this in the rvh file (where -1 indicates an outlet that flows outside of the model domain).

Code: Select all

:SubBasins
  :Attributes   NAME  DOWNSTREAM_ID       PROFILE REACH_LENGTH  GAUGED
  :Units        none           none          none           km    none
  30            Sub30             36 sub30profile            0       0
  36            Sub36             39 sub36profile         37.0       1
  39            Sub39             43 sub39profile         42.7       0
  43            Sub43             -1 sub43profile         35.4       1
:EndSubBasins

The tutorial is asking you to play with the connections and test Raven's error checking, for example to make a circular reference, such as: 30 -> 36 -> 39 -> 43 -> 30. This would cause an error to be raised in Raven. Note that in your setup an error is not raised as each subbasin with the -1 downstream ID simply flows outside of the model, and each subbasin is then essentially independent of one another.

The ADVISORY lines you see are not errors, simply notes produced in Raven_errors.txt letting you know that the refernece discharges were autogenerated, and the initial flows in each subbasin were also autogenerated. In the rvp file you will see an :AvgAnnualRunoff line that provides the average annual runoff, which Raven uses to initialize those values and flows. This is part of a normal model run and typically you would use a warm-up period in your simulation before using the results so that these initializations don't impact your model usage.

Hope that helps!
Rob

[baps]

That was immensely helpful.
Thank you so much, Rob!

Ben