Describing the Field and Barriers

One of the first tasks in beginning a new simulation is to describe the simulated field and any barriers that are present. This section describes the WEPS procedures for specifying the field geometries and barrier properties.

Field View

The Field View panel (Fig. 1.3) is located in the center of the WEPS1.0 main screen. It is designed to give the user a view of the field size, shape, and orientation (green). The placement of any barriers present is also displayed in red. A yellow bar on the side of the field in the Field View panel indicates which side of the field has been selected for barrier placement using the radio button in the Wind Barrier Information panel. This is useful for selecting field barrier placement when the field is oriented at angles close to 45 degrees. A red barrier shaded with yellow, as shown for the south barrier in Figure 1.3, indicates a selected barrier that has already been placed on the field border. Note that if the ratio of length to width of the field or barriers is too great to display to scale, this will be indicated within the panel, and an approximation of the field or barrier shape will be displayed. This panel is for viewing only and is not editable.

When a full, half, or quarter circle field is simulated (Fig. 1.4), it is approximated within WEPS as a square or rectangular field with an area equal to that specified in the Simulation Region Information panel. The Field View panel displays an approximate inscribed a circle (or half or quarter) within the simulated rectangular field When a non-rectangular field is selected, the field described in the Simulation Region Information panel has an area equal to that of the simulated rectangular field.

Simulation Run Information

Customer information for a simulation run is entered by using the upper left panel of the WEPS1.0 main screen (Fig. 1.5), which is labeled 'Simulation Run Information'.

The Client Name and as the Farm, Tract, and Field Number for the simulation run can be entered by typing the information in the appropriate boxes in the panel. These four items (Client Name and Farm, Tract, and Field No.) are for informational purposes only and do not affect the results of a WEPS simulation.

The run-length mode can potentially affect results. Note that there are three options for run-
length mode. An 'NRCS mode' specification indicates that the number of cycles is fixed. This option is locked for official NRCS field use. Other users can specify a simulation run start date and end date or enter the number of management rotation cycles in the 'Simulation Run Information' panel of the main screen. The length of run is controlled through the 'Run' tab on the 'Configuration' panel (see the discussion on 'Configuration' for more details).

Wind Barrier Information

The Wind Barrier Information panel (Fig. 1.6) is used to add barriers to the field borders. Note that WEPS1.0 only allows barriers on the borders of the field, not within the field. The barrier location is labeled for the side of the field on which the barrier is to be placed, such as 'N' for north, 'S' for south, 'E' for east, and 'W' for west. If the field is rotated, the location is labeled for the direction closest to one of the four cardinal directions. The barrier type can be selected from the drop-down list in the panel by clicking the down arrow to the right of the barrier type to bring up the list of available barriers and clicking on the appropriate barrier. Once a barrier type is selected, the barrier properties may be viewed and edited by clicking the 'Edit Selected Barrier' button at the bottom of the panel. This displays a separate panel where one may enter the barrier width, height, and porosity in the appropriate spaces. Note that the area of the barrier is displayed but cannot be edited. If barrier properties are modified, it will be noted in the type list with a '<mod>' designation before the type name. To remove a barrier from the field, click the radio button to select it (notice the barrier will be 'highlighted' when selected), then select the barrier type 'None' to remove it. To 'deselect' all barrier locations, click each enabled radio button to the off position. See the "WEPS How To Guide" for Barriers for further explanations on how to use barriers within WEPS and how to modify the barrier database. The Wind Barrier Information panel is not the best way to simulate the effects of strip cropping, but it may be useful in strip cropping designs that include barriers along the strips. See the "WEPS How To Guide" for Strip Cropping for a detailed description of simulating strip cropping with WEPS.

Simulation Region Information

The Simulation Region Information panel is shown in Figure 1.7. To describe the simulation region, the field dimensions are entered. For example, the X-Length and Y-Length are entered for a rectangle. Note that the area of the region will be displayed. To orient the field, simply type in the angle in degrees of deviation from north for the north/south field border and click 'Enter'. Note that the field will only rotate in a range of ±45 degrees. By rotating and adjusting the field length and width, the user should be able to obtain the desired field size and orientation for a field.

Other field shapes can be specified by clicking the down arrow to the right of the 'Shape' box to display a list of valid field shapes. Figure 1.8 illustrates the panel entry for a circular field. To describe a circular field, either the radius or the area of the field is specified. For simulation purposes within WEPS, fields that are circles or partial circles (i.e., half or quarter circle) are approximated as a square or rectangular filed with an area equal to that specified in the Simulation Region Information panel. Field shapes that can be selected include Rectangle, Square, Circle, Half Circle VE (vertical east), Half Circle VW (vertical west), Half Circle HS (horizontal south), Half Circle HN (horizontal north), Quarter Circle NE (northeast), Quarter Circle SE (southeast), Quarter Circle SW (southwest), and quarter Circle NW (northeast). For a square, enter either the X-Length or the area. If area is entered, the field side length will be calculated and displayed. For rectangular fields enter either the X-Length and Y-Length or the area and one length. For circles or partial circles, enter the radius or the area. If area is entered, the radius is calculated and displayed.

Special shapes or configurations such as circles and strip cropping are further discussed under the "Special Field Configurations" section of the chapter titled "Using WEPS for Conservation Planning" in the WEPS User Manual. Strip cropping is further discussed in detail in the "WEPS How To Guide" for Strip Cropping. The orientation of tillage direction is specified within the Management Crop Rotation Editor for WEPS (MCREW).

The Simulation Region must be considered carefully. The boundaries of this region are assumed to be non-erodible. This is assumed so that unknown quantities of material will not be entering from a neighboring area. Typically, stable boundaries do not allow creep and saltation sized material to pass through and include barriers or a surface at lease 15 feet wide that has vegetation sufficient to stop erosion. However there are situations where one may want to simulate a field with erodible boundaries such as an area within an erodible field. In these situations the user should consult their agency's policy for simulating such areas.