Remove ability to use different routing methods

[ekluzek]

There's some code fragments that aren't exercised to run with different RoutingMethod options. It's hardcoded to only one (1), so we might as well remove the fragments that aren't testing for other options.

Looking for it in the code:

src/riverroute/MOSART_physics_mod.F90:      if(Tctl%RoutingMethod == 1) then
src/riverroute/MOSART_physics_mod.F90:      else if(Tctl%RoutingMethod == 2) then
src/riverroute/MOSART_physics_mod.F90:      else if(Tctl%RoutingMethod == 3) then
src/riverroute/MOSART_physics_mod.F90:      else if(Tctl%RoutingMethod == 4) then
src/riverroute/RtmMod.F90:      Tctl%RoutingMethod = 1
src/riverroute/RunoffMod.F90:     integer  :: RoutingMethod    ! Flag for routing methods. 1 --> variable storage method from SWAT model; 2 --> Muskingum method?

We could leave the variable in place just in case it's added back again by a hydrologist. But, as the other methods aren't tested it makes sense to remove the options and update the comments that talk about it.

@swensosc @slevis-lmwg

[mvertens]

@ekluzek - I disagree that these variables should be kept in place. MOZART physics is not going to be developed further and these variables have not been exercised in years. Its confusing to have logic for code that is not planned to be developed.

[ekluzek]

The subject of this issue is the removal of these options as you did in #94. It's not about keeping them around.

[wwieder]

Hey, I sense some tension here that I wonder if we could address with more direct communication?

Separately, I think it's also worth noting that on the CESM side we want a functional implementation of MOSART that enables glacier to ocean communication with evolving ice sheets, which it seems like is accomplished in #94, and (nearly) ready for @slevis-lmwg to merge?

Beyond CESM3, however, we're aiming to move to mizuRoute. As such, I don't know that we need to create perfect MOSART code, just functional for CESM3. I'll defer to the SE team to settle on what this looks like.

[mvertens]

@ekluzek - sorry for misunderstanding this issue. I had it backwards.
@wwieder - I have been working with both the CESM and NorESM land ice groups to validate this implementation and I believe everyone has signed off on it.