[pftools] Water Budget Calculator Module(s)

[jaredwhite547]

Existing tools that calculate elements of the water budget are inadequate. Most do not account for variable depth layers, and none of them work with CLM.

We need to create modules that calculate elements of the water budget. These modules must account for variable depth layers, and work with CLM.

User Story: As a hydrologist, I want modules that can calculate various categories of the water budget so tools can help me figure out if the balance is closing, and use the data for additional analysis.