Special Field Configurations

Although WEPS 1.0 is designed to simulate rectangular field shapes, special field configurations such as circles or strip cropping can be simulated. By manipulating the field shape to represent a field with the same area and rotating the field along, with any barriers, many field shapes can be approximated.

Circular Fields. A circular field can be simulated by selecting a field shape 'Circle' in the Simulation Region Information panel. Note that the circle is approximated within WEPS as a square field with an area equal to that specified in the Simulation Region Information panel. The Field View panel displays an approximate inscribed circle within the simulated rectangular field (Fig. 1.11 ). When a circular field is selected, the field described in the Simulation Region Information panel has an area equal to that of the simulated rectangular field. For such fields, barriers should be added and the field rotated to best simulate the actual field configuration.

Irregular Field Shapes. Half circles can also be simulated by selecting 'Half Circle' in Simulation Region Information panel. A half circle is approximated within WEPS as a rectangular field with an area equal to that specified in the Simulation Region Information panel. The Field View panel displays an approximate inscribed half circle within the simulated rectangular field (Fig. 1.13). To simulate an irregular field shape such as a field along a stream, select the shape in Simulation Region Information panel that most represents the shape of the actual field with the same area.

Strip Cropping. Fields managed for wind erosion control by strip cropping in WEPS 1.0 are simulated as linear strips, with each strip of unique management as an individual rectangular field and the erosion losses for each unique strip multiplied by the number of those strips. A tract of land where strips are installed ideally will have strips with long side perpendicular to prevailing winds. They will also be of equal width across the field, thus allowing for the shortest width of the field along the most erosive winds. The field will be resized down to the strip width that a producer agrees with, or to other widths for demonstration purposes. We can change the field size by just typing in the field dimensions. See the Interface Reference section "How To Guide: Barriers" for more details on adding and modifying field barriers. Figure 1.13 illustrates a field layout for simulating strip cropping or grass barriers.

Tillage Direction. WEPS 1.0 only allows tillage in one direction, typically parallel to the field border (e.g., Northwest/Southeast for a field oriented in that direction). Observing the effects that tillage direction may have for a particular simulation may illustrate the need to alter tillage directions in the actual field to control wind erosion. Multiple tillage directions for an individual field, such as the operator tilling parallel to each border of the field in a spiraling pattern, or a circular tillage pattern on circular fields, cannot be directly simulated with WEPS 1.0. However, wind erosion on fields with tillage parallel to each border can be estimated by averaging outputs from two runs. Each run should be made with tillage direction perpendicular to each other and the results averaged.