Here is how the tool works:

1. A mask of all the tile drained fields is generated based on that drainage table.

Mask of tile drained field

2. The largest point of exiting flow accumulation and the mask must be between 20 and 100 acres. It is found along those fields that are likely to be tile drained.

Note: This is our best guess of where a tile outlet may exist. However, field verification will be needed, and local knowledge of the area could be valuable.

3. Next, the watershed is delineated using that outlet as a pour point, and then a check is done to make sure a minimum of 10 acres of upstream drainage falls within that current field.

Watershed with 10 acres of upstream drainage

4. The points along those fields are buffered out 100 meters. From those points, areas within 1 meter of elevation are checked for the two following conditions:

4.1 The area makes up at least a half a percent of the drainage area to that point.

4.2 The main hydric percent is less than 90.

5. If suitable, a square is drawn that is approximately 0.5% the size of the drainage area. This gives you an idea of the actual size that your bioreactor would be.

100 meter buffered area