Hayden Lake

This Process consists of two primary components, mapping and decision matrix. 

Mapping Component.  The mapping component is a geographic information system (GIS) based process where EWM location data (Global Positioning System points) can be input and viewed on an aerial ortho-photograph of the waterbody and polygons can be drawn around the locations to determine the area (acres) of a possible treatment site.  The input EWM points and drawn polygons are saved within the system to support future comparisons and can be printed out for use with grant or permit applications or other documentation.

The EWM location points must be obtained from a field inspection survey and a Field Data Worksheet is provided to guide that effort (see sidebar and link on this page).  The Data Worksheet lists equipment needed to perform these surveys which includes a GPS unit, an underwater view tube (necessary if the water surface is choppy during the survey) and a depth sounding device (could be an electronic “fish finder” or simple weighted rope).  A weed rake is also listed as this can be helpful in verifying the EWM presence if the water clarity is poor. 

The mapping component further consists of a limited access user map, which requires a password to use and which is where data are input and polygon boundaries are drawn; and a public access map which simply shows the input data (points and polygons) from all users.  Data and polygons input by all approved users are displayed on both maps.  Access to both of these maps is through the links displayed on this page.  The user access simply requires that a request be made with the process managers, Ms. Eckberg or Mr. Lamb (see sidebar this page).

Decision Matrix.  The decision matrix is an Excel spreadsheet-based program where potential EWM treatment areas are input, along with other waterbody and EWM infestation data (from the field survey) and appropriate treatment options, with associated costs, are output.  Again, the matrix outputs are intended to support treatment program decisions and are not treatment recommendations.  The matrix will assist its users in answering the question “How do we prioritize areas to be treated given known areas of milfoil infestation and limited funding available for treatment implementation?”   Matrix input criteria have been set up so that specific conditions are converted to numerical factors and calculations are made internally whose results relate to possible EWM control efforts. 

The input factors that are needed for this decision matrix are EWM infestation area, EWM infestation plant density and average water depth in the infested area.  The infestation area is obtained from the mapping component which, as stated above, is based on GPS points collected during a field survey.  The EWM plant density is also obtained during a field site survey and is divided into three density classes: light, medium and dense.  As indicated on the Field Data Worksheet, the definitions of these classes come from the apparent number of EWM plants (plant stems) seen within a 10 foot by 10 foot reference area.  It will be up to the surveyors to determine the average EWM density that is present within a larger infestation area.  Finally, the average water depth measured within the infestation area is input.

It should be noted that the decision matrix can be run even if only one or two of the input factors are actually input.  However, this will obviously reduce the accuracy of the output.