The Design Document page provides a description of the algorithms, implementation and planned testing including unit, verification, validation and performance testing. Please read Step 1.3 Performance Expectations that explains feature documentation requirements from the performance group point of view.
Design Document
In the table below 4.Equ means Equations and Algorithms, 5.Ver means Verification, 6.Perf - Performance, 7. Val - Validation, 
- competed, 
- in progress, 
- not done
Overview table for the owner and an approver of this feature
1.Description | Lake water storage in ELM |
| 2.Owner | Michael Brunke |
| 3.Created | 30 August 2021 |
| 4.Equ | |
| 5.Ver | |
| 6.Perf | |
| 7.Val | |
| 8.Approver | |
| 9.Approved Date |
Title: Some descriptive title
Requirements and Design
E3SM BGC Group
Date: 30 August 2021
Summary
The purpose of this section is to summarize what capability is to be added to the E3SM through this design process. It should be clear what new code will do that the current code does not. Summarizing the primary challenges with respect to software design and implementation is also appropriate for this section. Finally, this statement should contain general statement with regard to what is “success.”
Requirements
Requirement: Eliminate negative runoffs in ELM
Date last modified: 30 August 2021
Contributors: Michael Brunke
ELM generates negative runoffs, especially in the tri-grid configuration. This is coming from the QRGWL, the combined runoff from glaciers, wetlands, and lakes. This goes negative periodically to maintain these features. Figure 1 shows that most of the grid cells generating negative total runoff (blue in panel (a)) occur in areas with lake fraction > ~5%.
Algorithmic Formulations
Design solution: Add lake water storage
Date last modified: 31 August 2021
Contributors: Michael Brunke
The negative contribution to runoff from lakes comes about from assuming a constant lake water storage. Therefore, the water needed to maintain that needs to be taken from the total runoff. If there is excessive evaporation, this can result in negative runoff. To counter this when this feature is turned on, what would go to QRGWL goes to change the lake water storage (WSLAKE): DWSLAKE = ((QIN - EVAP - QRGWL - QSNOWCP) - DWSNO - DWSOI) * dt. If WSLAKE is too low (<5000 mm), QRGWL is set to 0, while the excess water is removed by QRGWL if WSLAKE >= 5000 mm.
Design and Implementation
Implementation: Verification of lake water storage
Date last modified: 30 August 2021
Contributors: Michael Brunke
Figure 1b shows the total runoff from a test run including lake water storage. The negative runoff from the grid cells with lakes is eliminated. The only negative runoff left is from grid cells containing glaciers.
Planned Verification and Unit Testing
Verification and Unit Testing: short-desciption-of-testing-here
Date last modified:
Contributors: (add your name to this list if it does not appear)
How will XXX be tested? i.e. how will be we know when we have met requirement XXX. Will these unit tests be included in the ongoing going forward?
Planned Validation Testing
Validation Testing: short-desciption-of-testing-here
Date last modified:
Contributors: (add your name to this list if it does not appear)
How will XXX be tested? What observational or other dataset will be used? i.e. how will be we know when we have met requirement XXX. Will these unit tests be included in the ongoing going forward?
Planned Performance Testing
Performance Testing: short-desciption-of-testing-here
Date last modified:
Contributors: (add your name to this list if it does not appear)
How will XXX be tested? i.e. how will be we know when we have met requirement XXX. Will these unit tests be included in the ongoing going forward?