Model Geometry

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

For the mainstem Lower Bull Run River from Reservoir #1 to Reservoir #3 the following procedure was performed:

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.

In conducting the reservoir bathymetry analysis, the data obtained from DEA were found to offset by approximately 200 ft vertically downward from the known position of Reservoir #2. As a result, the reservoir bathymetry data were adjusted vertically and then converted to the coordinate system and units to be used by the model.

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.

Parameter | Bull Run River – below Reservoir #2 | Reservoir #2 | Reservoir #1 | Reservoir #3
Number of branches | 15 | 2 | 2 | 6
Channel slope range [-] | 0.000 to 0.022 | 0.0 | 0.0 | 0.0
Segment length, D x, range, m | 67-210 | 167-211 | 101-225 | 68-201
Vertical grid Dz, m | 2 | 1 | 1 | 1
IMP (number of segments) | 95 | 46 | 38 | 53
KMP (number of layers) | 20 | 65 | 83 | 114
ELBOT (elevation of top of lowermost vertical layer, m NGVD) | 74.2 | 228.5 | 266.5 | 498.5

Table 48. River and Reservoir Model Grids

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.

Figure 90. Reservoir #1 Topography and Centerline.

Figure 91. Reservoir #1 Topography - 3-D View.

Figure 92. Reservoir #1 Model Grid Layout with Segment Numbers Shown

Figure 93. Elevation-Volume Curves for Reservoir #1 Comparing Model Grid, SURFER, and Water Bureau Historical Data.

Figure 94. Elevation-Area Curve Comparison of Model Grid and SURFER, Reservoir #1

Branch # | Number of segments | Total branch length, m | Upstream Branch Segment | Downstream Branch Segment | Upstream BC | Downstream BC | Segment lengths, m
1 | 29 | 6514.2 | 2 | 30 | flow | flow | 224.63
2 | 5 | 504 | 33 | 37 | flow | Internal | 100.81

Table 49. Branch Grid Description, Reservoir #1

Tributary number | Tributary name | Inflow tributary segment
1 | Fir Creek | 10
2 | North Fork | 11
3 | Deer Creek | 22
4 | Cougar Creek | 21
Inflow number |  |
1 | Bull Run River | 2
2 | Inflow from Bear Creek | 33

Table 50. Location of Inflows and Tributaries for Reservoir #1

Figure 95. Reservoir #1 Segment Orientation in Degrees.

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.

Figure 96. Reservoir #2 Topography with Centerline.

Figure 97. Reservoir #2 Topography - 3-D View.

Figure 98. Reservoir #2 Model Grid

Figure 99. Elevation-Volume Curves for Reservoir #2 Comparing Model Grid, SURFER, and Water Bureau Historical Data

Figure 100. Elevation-Area Curve Comparison of Model Grid and SURFER, Reservoir #2

Figure 101. Elevation-Volume Curve for the Spillway and Reservoir

Figure 102. Reservoir #2 Segment Orientation, in Degrees

Branch # | Number of segments | Total branch length, m | Upstream Branch Segment | Downstream Branch Segment | Upstream BC | Downstream BC | Segment lengths, m
1 | 35 | 7373.8 | 40 | 74 | flow | flow | 210.68
2 | 7 | 1166.5 | 77 | 83 | flow | internal | 166.64

Table 51. Branch Grid Description, Reservoir #2

Tributary number | Tributary name | Inflow tributary segment
1 | Five Mile Creek | 43
2 | Camp Creek | 55
Inflow number |  |
1 | Inflow from Reservoir #1 | 40
2 | Inflow from South Fork | 77
Withdrawal number |  | Withdrawal segment
1 | Spillway outflow | 74
2 | North Tower | 74
3 | South Tower | 74

Table 52. Location of Inflows and Tributaries for Reservoir #2

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.

Figure 103. Bull Run River below Reservoir #2.

Figure 104. Channel Bottom as a Function of Distance from Confluence with Sandy River.

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.

Branch # | Number of segments | Total branch length, m | Upstream Branch Segment | Down-stream Branch Segment | Up-stream BC | Down-stream BC | Segment lengths, m | Slope [-]
1 | 3 | 191.9 | 2 | 4 | Flow from Res 1 | Flow* | 63.97 | 0.00000
2 | 3 | 137.5 | 7 | 9 | Flow 4 | Flow | 45.83 | 0.01782
3 | 3 | 280 | 12 | 14 | Flow 9 | Flow | 93.33 | 0.02232
4 | 3 | 257.5 | 17 | 19 | Flow 14 | Flow | 85.83 | 0.00000
5 | 3 | 135 | 22 | 24 | Flow Spillway | 19 | 45.0 | 0.00000
6 | 3 | 355 | 27 | 29 | Flow 19 | Flow | 118.3 | 0.02154
7 | 3 | 225 | 32 | 34 | Flow 29 | Flow | 75.0 | 0.00000
8 | 3 | 292.5 | 37 | 39 | Flow 34 | Flow | 97.5 | 0.01949
9 | 8 | 1520 | 42 | 49 | Flow 39 | Flow | 190.0 | 0.00641
10 | 6 | 1187.5 | 52 | 57 | Flow 49 | Flow | 197.92 | 0.01305
11 | 6 | 1310 | 60 | 65 | Flow 57 | Flow | 218.33 | 0.01160
12 | 3 | 460 | 68 | 70 | Flow 65 | Flow | 153.33 | 0.00000
13 | 10 | 2235 | 73 | 82 | Flow 70 | Flow | 223.5 | 0.01422
14 | 7 | 1367.5 | 85 | 91 | Flow 82 | Flow | 195.36 | 0.01024
15 | 6 | 1282.5 | 94 | 99 | Flow 91 | Flow | 213.75 | 0.00663
* most of the flow boundaries are treated as spillways within the river model

Table 53. River Model Branch Layout

Tributary number | Tributary or inflow name | Inflow tributary segment
1 |  | 7
2 |  | 19
3 | Spillway Creek | 28
4 |  | 34
5 |  | 39
6 |  | 44
7 |  | 46
8 | Gage Creek | 47
9 |  | 48
10 |  | 52
11 |  | 53
12 |  | 55
13 |  | 56
14 | Little Sandy River | 69
15 | Devils Backbone Creek | 78
16 |  | 79
17 | Laughing Water Creek | 82
18 |  | 89
19 | Deer Creek | 90
Inflow number |  |
1 | Flow from Reservoir #2 | 2

Table 54. Location of Inflows and Tributaries for the Lower Bull Run River

Figure 105. Cross-Sectional Slice Required for the River Geometry

Figure 106. River Model Segment Locations and Orientation.

Figure 107. Lower Bull Run River Grid in Vicinity of Spillway Pool

Figure 108. Lower Bull Run River Vertical Grid.

Figure 109. River Segment Orientation, in Degrees

Figure 110. Plan View of River Segments and Format for River Animations

Figure 111. Bull Run River Model Showing Velocities along the River System for a Flow of 350 cfs

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.

Station Name | Date Type | Water Body | River Mile | Segment Number
S2P | Water Temp | Lower river | 6.42 | 13
120 | Water Temp | Lower river | 6.06 | 28
121 | Water Temp | Lower river | 6.0 | Not Available*
122 | Water Temp | Lower river | 6.13 | 27
130 | Water Temp | Lower river | 4.82 | 48
131 | Water Temp | Lower river | 4.9 | Not Available*
140 | Water Temp | Lower river | 3.88 | 60
141 | Water Temp | Lower river | 3.93 | 60
145 | Water Temp | Lower river | 3.06 | 69
146 | Water Temp | Lower river | 3.0 | Not Available*
148 | Water Temp | Lower river | 3.13 | 68
149 | Water Temp | Lower river | 3.02 | 70
150 | Water Temp | Lower river | 2.48 | 76
160 | Water Temp | Lower river | 1.69 | 82
161 | Water Temp | Lower river | 1.9 | Not Available*
59P0 | Water Quality | Res#1 | 14.15 | 8
59M0 | Water Quality | Res#1 | 13.64 | 12
59H0 | Water Quality | Res#1 | 12.46 | 21
59G0 | Water Quality | Res#1 | 12.34 | 22
59-1 | Water Quality | Res#1 | 11.29 | 30
60O0 | Water Quality | Res#2 | 9.88 | 50
60N0 | Water Quality | Res#2 | 9.38 | 55
60G0 | Water Quality | Res#2 | 8.12 | 82
60-1 | Water Quality | Res#2 | 7.16 | 73
60B0 | Water Quality | Res#2 | 6.97 | 74
*Stations represent tributaries entering the Lower Bull Run River

Table 55. Temperature and Water Quality Stations in the Lower Bull Run System

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.

Branch # | Number of segments | Total branch length, m | Upstream Branch Segment | Down-stream Branch Segment | Up-stream BC | Down-stream BC | Segment lengths, m | Slope [-]
1 | 25 | 5014.3 | 2 | 26 | Flow | Flow | 200.57 | 0
2 | 3 | 300 | 29 | 31 | Flow | Internal - 23 | 100.01 | 0
3 | 3 | 242.7 | 34 | 36 | Flow | Internal - 23 | 80.91 | 0
4 | 4 | 812.3 | 39 | 42 | Flow | Internal - 19 | 203.09 | 0
5 | 3 | 204.2 | 45 | 47 | Flow | Internal- 13 | 68.08 | 0
6 | 3 | 289.9 | 50 | 52 | Flow | Internal- 5 | 96.62 | 0

Table 56. Reservoir #3 Model Branch Layout

Inflow number to Branch | Tributary or inflow name | Inflow tributary segment
1 | Flow from Basin 7, 10, 11* | 2
2 | Flow from Basin 4 | 29
3 | Flow from Basin 3 | 34
4 | Flow from Basin 5 (Main Stem) | 39
5 | Flow from Basin 2 | 45
6 | Flow from Basin 8 and 9 | 52
Tributary number |  |
1 | Flow from Basin 1 and 6 | 25
*Basins are described in Figure 81

Table 57. Location of Inflows and Tributaries for Reservoir #3

Figure 112. Reservoir #3 Model Grid

Figure 113. Elevation-Volume Curves for Reservoir #3 Comparing Model Grid and SURFER

Figure 114. Elevation-Area Curve Comparison of Model Grid and SURFER, Reservoir #3

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.

Branch # | Number of segments | Total branch length, m | Upstream Branch Segment | Down-stream Branch Segment | Up-stream BC | Down-stream BC | Segment lengths, m | Slope [-]
1 | 39 | 7564.3 | 2 | 38 | Flow | Flow | 204.44 | 0.02115

Table 58. Model Branch Layout for River Model below Reservoir #3.

Inflow number to Branch | Tributary or inflow name | Inflow tributary segment
1 | Flow from Reservoir #3 | 2
Distributed Tributary # |  |
1 | Flow from drainage basin along river | All segments based on surface area

Table 59. Location of Inflows and Tributaries for River Model below Reservoir #3

Figure 115. Channel Centerline for the River Model below Reservoir #3

Figure 116. Model Grid for River below Reservoir #3 Proposed Dam