An Introduction to the Mechanics of Model Integration

 

QUALHYMO has a Comprehensive Suite of Capabilities

The stand-alone QUALHYMO calculation engine has a comprehensive suite of analytical capabilities, of which the “Water Balance Model” decision support interface currently uses only a portion. This article introduces the concept of “exposed features” and the potential to access additional features and capabilities over time.

The purpose in merging the Water Balance Model for British Columbia and QUALHYMO was to provide consistent delivery of reliable results, and manage data so that users and reviewers can compare multiple development and land use scenarios.

Exposed Features

Features of QUALHYMO that are “exposed” in the Water Balance Model powered by QUALHYMO comprise a limited set of QUALHYMO capabilities that are called upon by a user of the Water Balance Model (WBM) interface. Additional QUALHYMO features and capabilities fall into four categories:

• Category One: This encompasses QUALHYMO sub-routines that are called by the WBM User Interface, but not all of the capabilities are used; some may be added in future by altering the WBM User Interface.
• Category Two: This encompasses QUALHYMO subroutines that are not called by the WBM User Interface, yet have a series of capabilities that are available but are quite different that anything that the WBM User Interface is now accessing. Again these can be enabled as and when the WBM User Interface is adapted to incorporate them.
• Category Three: This encompasses capabilities within the QUALHYMO code that are not turned on; or are accessible to a user with minor code revision and recompiling of the code, and
• Category Four: This encompasses new QUALHYMO capabilities that have not yet been implemented, and may require substantial code writing and debugging.

The Water Balance Model powered by QUALHYMO user can access features and capabilities in Category One, but will be unaware of features and capabilities pertaining to the three other categories.

What is Visible versus What is Not:

On the matter of QUALHYMO sub-routines that have been enabled within the Water Balance Model powered by QUALHYMO, not all of the features available within those particular sub-routines have been exposed to the user. This means the WBM user is unaware that there is a data structure for model input; and that there are other capabilities that are not displayed.

An example that illustrates what the foregoing statement means pertains to the sediment buildup and wash-off from the watershed and the treatment processes within the storage pond and low impact development system components. Looking ahead, to make this feature visible to the WBM user would be a matter of programming the capability to enter the additional information in the interface, building the handoff routines to fill in the data file created for QUALHYMO, and then accessing the output and summarizing the results.

Rolling 3-Year Plan:

The stand-alone QUALHYMO user can easily access all Category One and Category Two features and capabilities, and may even be aware of the difference between Category One and Category Two.

Regarding Category Three, an example of a feature that is currently embedded in the code but not activated is a table of weekly snow pack depth in a watershed.  Looking ahead, many other features only need a revised READ statement and a data spot in the input file to activate them. This aspect is part of the ongoing enhancement of the QUALHYMO engine.

Finally, Category Four represents another level of capability that could be added over time as wish-list items on the Rolling 3-Year Plan are progressively implemented.  Potential examples include adding plant uptake and transpiration losses to the soil moisture reservoir, or adding a time variable rainfall interception to reflect various tree conditions.

Application of QUALHYMO Commands:

The QUALHYMO commands listed below are incorporated in the WBM User Interface, but the total capability of each has been intentionally limited. Looking ahead, it would be relatively simple to expand the capabilities as when there is a confirmed need.

• PULL POND SPAN allows extraction of pond specific calculation results for selected time periods to examine in detail the operation of a pond.
• CALC POND STATS allows users to develop statistics on calculated pond (storage) systems
• GENERATE subroutine calculates watershed discharge based on two alternative methods of estimating runoff; only one method is currently enabled in the WBM User Interface; the other may be enabled in the future.

Capabilities of Stand-Alone QUALHYMO:

Under Category Two, the stand-alone QUALHYMO includes specific capabilities that are not being called by any part of the WBM User Interface. Major sub-routines that can be accessed only via the stand-alone QUALHYMO include:

• PULL SERIES SPAN allows the user to select and extract the detailed flow from operation of a system over a specified time period
• STORE  –  allows the input of flow data that is either from recording gauge stations or calculated by other means
• PRINT SPAN – allows selection of specific short periods for examination of calculated runoff and water quality
• REACH – allows examination of routing of flows and quality parameters though a stream reach; this may be the routine that would be upgraded to include the erosion analysis in future
• CALIBRATE – compares two hydrographs such as recorded and calculate; this allows modification of parameters to allow the calculated hydrograph to match (“calibrate”) the other. This applies to the pollutants as well.
• POLLUTANT SERIES  – allows input of sediment and first order pollutants
• SPLIT SERIES  – allows diversion works to divide the hydrographs into separate streams or conveyance systems
• FILTERED REMOVAL  – allows the evaluation of water quality improvement systems that would operate like sand filters.

QUALHYMO was originally developed in 1983 by Dr. Charles Rowney et al during the creation of a methodology for analysis of stormwater detention ponds for water quality control, funded by a grant from the Ministry of Environment. QUALHYMO incorporates some of the concepts developed in the predecessor HYMO and OTTHYMO models. QUALHYMO is distinct from those predecessor models in its ability to simulate the generation and routing of pollutants, snowmelt, soil freeze-thaw and in-stream erosion, and in its orientation towards continuous simulation.