The following text acts as a supplement to �The Watershed Treatment Model� documentation, and provides guidance for using the spreadsheet itself.� It outlines some general guidance for using the WTM and provides a description of each of the sheets in the spreadsheet.�
Overall Guidance
Although the WTM is a simple model, it requires significant data input.� In addition, the spreadsheet may appear overwhelming because all of the algorithms and data used by the Model are visible to the user.� In addition, no part of the spreadsheet is write protected, in order to allow for maximum flexibility.� These decisions put a great deal of responsibility on the user, and some guidelines need to be followed to prevent errors in algorithms.
Data Entry - Color Coding
In order to make data entry easier, cells are coded in four colors: green, blue, grey and purple.�
Model Structure
The WTM has eleven sheets for data entry, calculation or display.� Of these, six require some data entry.� Two sheets are invisible to the user, and are only for calculation.� The remaining three are solely for display purposes.
Data Entry Sheets
The six sheets that require data entry include: Primary Sources, Secondary Sources, Existing Management Practices, Future Management Practices, Future Land Use and New Development.
Primary Sources
This sheet requires basic land use information, and calculates surface runoff loads.� All of the cells on this sheet, with the exception of land uses that are not in the watershed, need to be filled out.� A description of the methodologies on this sheet is included in Chapter 6 of the model documentation.
Secondary Sources
This sheet calculates loads from secondary sources such as septic systems and SSOs.� It requires a variety of information, as indicated by the green cells.� Many of the secondary sources may not be present within your watershed.� A description of the methodologies on this sheet is included in Chapter 7 of the model documentation.� The loads at the bottom of this sheet represent �uncontrolled� loads from secondary sources.
Existing Management Practices
This sheet reflects programs currently in place to control loads from urban land.� Data regarding the extent of program implementation is required, as indicated by green cells.�� �A description of the methodologies on this sheet is included in Chapters 8 and 9 of the model documentation.� Two load reductions are presented at the bottom of this sheet.� The first is an �Undiscounted� load, which does not reflect treatability or practice discounts.� The actual load reductions are presented in the purple cells.
Future Management Practices
This sheet reflects the planned extent of programs to control loads from urban land. Please note that the data on this sheet reflect both current programs and programs that have not yet been implemented, unless a current program will be discontinued in the future.�� For example, if a lawn care education is in place currently, this program should appear in the Future Management Practices sheet as well. �(The model default is to continue existing programs).� The methodologies in this sheet are similar to those for existing management practices, and are also described in Chapters 8 and 9 of the model documentation.� Three load reductions are presented at the bottom of this sheet.� The first is an �Undiscounted� load reduction, which does not reflect treatability or practice discounts.� The second is a �Discounted� load reduction, which takes treatability and discount factors into account.� The third load, shaded purple, represents the net improvement of future programs over existing ones.
In this sheet, the user enters the projected future land use in the watershed.
New Development
This sheet calculates the loads from future development, based on future land use, as well as some additional secondary sources.� Note that the acres of land in this spreadsheet do not reflect new land use acres, but rather the change from current conditions.� The controls on new development are reflected by "program options" described in Chapter 11 of the model documentation.�
Calculation Sheets
Two of the sheets in the WTM, Discounts - Existing and Discounts - Future are primarily remnants of other assumptions input into the model, and are used to calculate loads after discounts and treatability are applied.� They also apply practices in series, as described in chapter 10 of the model documentation.
Display Sheets
Four sheets display final loads, both storm and non-storm for three points in time, and are called Existing Loads, Loads with Future Practices, Loads Including Growth, and Summary Sheet.� These sheets simply sum up the loading from other sheets, and partition them into storm and non-storm components of the annual load.
Comments
We are always striving to improve the WTM, and would appreciate any comments on technical content, or ways to make the Model more accessible.� Please send comments to Deb Caraco at: [email protected].