Table of Contents

• Reservoir # 1 Geometry

• Reservoir # 2 Geometry

• River Geometry

• Data Stations in Lower Bull Run System

• Reservoir # 3

• Bull Run River Geometry Between Reservoir #1 and # 3

CE-QUAL-W2 requires that for each model cell a width in meters be specified. Hence, a cross-section is divided into a series of cell widths as a function of the vertical grid resolution.

For the reservoirs the following procedure was performed:

1. x, y, z bathymetry data files for each reservoir from DEA (1991) and surrounding topography data from USGS Digital Elevation Maps were entered into SURFER (a 3-D topographical plotting package)
2. Area-elevation volume curves were generated using SURFER
3. A center-line file was created and digitized for each reservoir following the channel bottom
4. A program was written to determine the location of segment centers based on known grid spacing
5. Polygons were created for each segment
6. Area-Volume-Elevations were determined for each segment based on a given vertical grid of 1 m and cell widths at each elevation were computed by preserving volume

1. x, y, z data file for the river was entered into SURFER
2. A center-line file was created and digitized
3. A program was written to create perpendicular slices to the channel at a set spacing
4. A program was written to interpolate these cross-sectional slices to a grid based on a prescribed layout of the channel slopes and segment lengths.

Table 48 summarizes the grid statistics for the Lower Bull Run River and Reservoirs #1 to #3 model gridss. The bathymetry grids used in the model can be found in Appendices E through I.

Reservoir #1 Geometry

Figure 90 and Figure 91 show the Reservoir #1 topographic map based on the field surveys by DEA(1991) with the digitized centerline. The layout of the model grid is shown in

Figure 92. Reservoir #1 Model Grid Layout with Segment Numbers Shown
and summarized in Table 49. A comparison of the model volume-elevation and the model area-elevation curves determined by SURFER for the topography in Figure 90 compared with data from the Water Bureau (1920s) and the CE-QUAL-W2 grid are shown in Figure 93 and Figure 94, respectively. Figure 95 shows the segment orientation of Reservoir #1 model segments.

Reservoir #2 Geometry

Figure 96 and Figure 97 show the Reservoir #2 topographic map based on the field surveys by DEA (1991) with the digitized centerline. Figure 98 shows the model segments for the two branches up to an elevation of 292 m NGVD. Figure 98 is summarized in Table 51. A comparison of the model volume-elevation and the model area-elevation curves determined by SURFER for the topography in Figure 96 compared with data from the Water Bureau (1962) and the CE-QUAL-W2 grid are shown in Figure 99 and Figure 100, respectively.

The spillway area was incorporated into Segment 36 at the dam because this spillway section had negligible volume below 262 m NGVD, the active uppermost operating region of the reservoir, Figure 101.

Figure 102 shows the segment orientation for the Reservoir #2 grid.

River Geometry

The Bull Run River, as shown below in Figure 103, is a very steep stream with an average slope over 1%. The channel bottom variation with distance from the Sandy River is shown in Figure 104. This section describes the set-up of the CE-QUAL-W2 model for the Bull Run River below Reservoir #2.

Cross-sections were "sliced" from the revised river bathymetry in SURFER, Figure 105, and then interpolated onto a grid that is described below in Table 53 and shown in Figure 106. A close-up view of the segments near the Plunge Pool is shown in Figure 107.

Table 54 describes the inflows and tributaries to the Bull Run River model. Figure 108 shows the vertical-longitudinal grid, and Figure 109 shows the model segment orientation.

Figure 110 and Figure 111 show the plan view of the river temperature and velocity at a flow rate greater than 350 cfs as predicted by the model, respectively.
 
 

Data Stations in Lower Bull Run System

Table 55 summarizes the temperature and water quality stations for both the Lower Bull Run River and the Reservoirs. Station name, data type, and location are given. The segment numbers in which these stations are located is also provided.
 
 

Reservoir #3 Geometry

The reservoir was divided into 6 branches, 53 longitudinal segments (lengths varying from 68 m to 204 m), and 114 vertical layers (1 m vertical spacing). This is shown in Figure 112. The model grid was compared with the SURFER computed volume and surface area in Figure 113 and Figure 114. The volume of the grid matches exactly to the SURFER topography since the computation of the segment widths was based on preserving volume, rather than surface area.

Table 56 and Table 57 show the model grid segment layout and the inflows to the Reservoir #3 model, respectively.
 

Bull Run River Geometry between Reservoir #1 and Reservoir #3

The Bull Run River below Reservoir #3 consists of 39 model segments with an average length of 204 m (a total distance of about 7.5 km) and an average slope of 2.3%. The topography of the area was used to generate an approximate model grid. The centerline and distance from the headwaters of Reservoir #1 are shown in Figure 115. Figure 116 shows the grid for the river segments.

Table 58 and Table 59 show the model grid segment layout and the inflows to the river model below Reservoir #3, respectively.