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

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The first table in Design Document gives overview of this document, from this info the Design Documents Overview page is automatically created.

In the overview table below 4.Equ means Equations and Algorithms, 5.Ver means Verification, 6.Perf - Performance, 7. Val - Validation

Equations: Document the equations that are being solved and describe algorithms
Verification Plans: Define tests that will be run to show that implementation is correct and robust. Involve unit tests to cover range of inputs as well as benchmarks.
Performance expectations: Explain the expected performance impact from this development
Validation Plans: Document what process-based, stand-alone component, and coupled model runs will be performed, and with what metrics will be used to assess validity

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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

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Table of Contents

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: Implementation of lake water storage

Date last modified: 1 September 2021
Contributors: Michael Brunke

The above formulation will be added to LakeHydrologyMod.F90 and included in the ELM water budget calculations. WSLAKE will also be added to ELM output and restarts. It will also be exchanged with CIME for its water budget calculations.

Planned Verification and Unit Testing

Verification and Unit Testing: 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.

Figure 2 (below) shows that the addition of this feature has minimal impact on the total discharge in MOSART.

Unit testing will be performed by running the E3SM land developer suite.

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: Performance testing with lake water storage

Date last modified: 31 August 2021
Contributors: Michael Brunke

This feature should have a minimal impact on the performance of the model. This will be verified from the model's timing tables.

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