Nash Cascade based surface runoff

[ajkhattak]

Added a new scheme for the surface runoff that is based on Nash Cascade approach. The CFE will now support two schemes for surface runoff: 1) GIUH-based scheme, and 2) NASH_CASCADE-based scheme. Also, with these changes we will have now one Nash cascade model for the surface and one for the subsurface lateral flow. The two Nash models are slight different and hence implemented differently, but the hope is to merge them later. The changes in this PR don't change results of the existing tests.

Additions

• Added Nash Cascade model for surface runoff

Removals

• None

Changes

• BMI variable name change GIUH_RUNOFF to SURFACE_RUNOFF
• The model requires a new parameter surface_runoff_scheme as an input in the config file

Testing

1. All existing tests passed

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (link if applicable)
• Passes all existing automated tests
• New functions are documented (with a description, list of inputs, and expected output)
• Reviewers requested with the Reviewers tool ➡️

[hellkite500]

This is not a string copy, and these comments should probably reflect that. This is a copy of the pointer so that the beginning of the string isn't lost. The following loop will set value = copy, and then changes , to \0 so that strtod converts the right bytes for the ordinate value. I think the full string copy is misleading, that would require something like strcpy or some other allocation of a buffer and copy of the string values. This is just a reference copy.

[ajkhattak]

good catch. it has been there for a while but probably nobody caught it. I agree we are just copying one pointer to another, and not a full string copy, to preserve the original pointer to giuh_ordinates. I will update the comment to help clearly explain it, please have a look afterward.