SURFACE WATER MODULE

DIMENSIONS TAB

WW-VELOC--Flow velocity at constituent entry point
Units: feet per second (m/s)
Range: greater than 0.0

The river flow velocity should be determined for the location where constituents from the release site enter the river. The river flow velocity is based on the average annual stream discharge. Depending on the data available, the flow velocity can be estimated in a number of ways. The following techniques are suggested, in order of preference:

1. Published information: If the average annual flow velocity has been published for the stream or river, use this value.

2. USGS Water Resources Data Report or USACOE Stage-Discharge Reports, and Discharge Summary Measurement Sheets: the first step (1) is to locate the U.S. Geological Survey (USGS) gaging station that is closest to the facility and within the reach of the river of interest. The gaging station can be identified from the USGS Water Resources Data reports for the appropriate states or from stage and discharge reports for selected rivers published by the U.S. Army Corps of Engineers (Figure 2.25). An example map showing locations of USGS gaging stations is presented in Figure 2.26. From these reports, water-discharge records are available for each of the gaging stations. USGS gaging stations are also available via the internet (http://water.usgs.gov/).

The second step (2) is to obtain the average annual discharge from a table similar to the example shown in Figure 2.27. The average annual discharge is listed under the heading titled "Average Discharge" on the USGS Water Resources Data Report (see Figure 2.27). USGS discharge data is also available via the internet (http://water.usgs.gov/).

The third step (3) is to develop a relationship between velocity and discharge, which can be determined from data in the USGS Discharge Measurement Summary Sheets; i.e., Form 9-207 (Figure 2.28). Correlated pairs of discharge and mean flow velocity data are available from Form 9-207. Form 9-207 is associated with each station; it describes the width, cross-sectional area, height, and flow velocity for various discharges. Using data from this form and the other reports, velocity versus discharge, depth versus discharge, and/or width versus discharge can be plotted on log-log graph in a spreadsheet. Example plots of velocity versus discharge and width versus discharge are illustrated in Figure 2.29. The points plotted may be somewhat scattered; a best-fit curve will have to be estimated.

3. USGS Water Resources Data Report or USACOE Stage-Discharge Reports, and USGS 7.5' Topographic Maps: If Discharge Summary Measurement Sheets (i.e., Form 9-207) for a gage (within the reach of the river that is of interest) is unavailable, the average flow velocity can be calculated using an USGS Water Resources Data Report or U.S. Army Corps of Engineers (USACOE) Stage-Discharge Reports, field data, and/or USGS 7.5-min topographic maps. In this case, the average annual velocity is estimated using the average annual discharge, flow width, and flow depth in the following equation:

Flow Velocity = Average Annual Discharge/Flow Depth/Flow Width
The average annual discharge is obtained as described above in Step 2. The flow width and depth can be measured during site visit(s) or estimated with the help of someone who has visited the site. If field measurements of the depth are unavailable, the depth can be estimated as follows. The USGS topographic maps can be used to locate the gaging station and estimate the bed elevation of the stream at that location. The USGS or USACOE reports are used to identify gage height versus discharge. To convert gage height to flow depth for flow depth-discharge plots (Figure 2.29), use the following equation:

Flow Depth = Gage Elevation + Gage Height - Bed Elevation
The elevation of the gage can usually be obtained from the USGS or USACOE report under the heading "Gage." The gage height is recorded for various discharges in these reports. The bed elevation is obtained from the USGS topographic map. The flow depths and the discharges can be plotted on a log-log graph which is similar to one illustrated in Figure 2.29. The flow depth corresponding to the average annual discharge can be obtained from this plot.

4. Site Inspection: If some of the recorded information is unavailable for the stream in question, a site visit may be required, or correspondence with appropriate government agencies may be appropriate.

5. First available gaging station: If no information is available, use data from the first gaging station downstream.

WW-DEPTH--Depth at constituent entry point
Units: feet (m)
Range: greater than 0.0

The river flow velocity should be determined for the location where constituents from the release site enter the river. An analogous procedure as that outlined in Section WW-VELOC can be used. In step (3), use flow depth from Form 9-207 and plot flow depth versus discharge.

WW-WIDTH--Width at constituent entry point
Units: feet (m)
Range: greater than 0.0

The river flow velocity should be determined for the location where constituents from the release site enter the river. An analogous procedure as that outlined in Section WW-VELOC can be used. In step (3), use flow width from Form 9-207 and plot flow width versus discharge (see Figure 2.29).

WW-DIST--Distance from source to location
Units: feet (m)
Range: greater than or equal to 0.0

Identify the distance from the surface-water source to the downstream usage location from the USGS topographic maps. A usage location is where water is withdrawn from the river for domestic or agricultural uses or where receptors are directly exposed to river water. Usage locations are always assumed to be on the same side of the river as the constituent source entering the river. Identify the distance from the center of the source entering the river to the downstream usage locations. Figures 2.30 and 2.31 present examples that illustrate WW-DIST: 1) downstream receptor (e.g., water intake structure) is located near the river source or on the straight river, and 2) it is on the meandering river, respectively.

WW-DISCHG--Average annual discharge at location
Units: cubic feet per second (m³/s)
Range: greater than 0.0

Discharge is a function of distance and may change from one usage location to the next. To determine the average annual discharge, follow the guidelines outlined in WW-VELOC. If a usage location lies between two gaging stations, interpolate linearly to estimate the discharge. Note that the discharge is not necessarily the same as that used to determine the flow velocity, river depth, or river width where constituents enter the river (WW-VELOC, WW-DEPTH, or WW-WIDTH).

WW-Y--Georeferenced northing coordinate
Units: meters (m)
Range: real number

A mapable northing coordinate. When combined with the easting coordinate, the coordinate pair shall represent a point on a map where the surface water concentrations are located. It is assume that the user will supply all coordinates on the same basis, such as Nad87, UTM zone 11. This value is not used to compute the concentrations.

WW-X--Georeferenced easting coordinate
Units: meters (m)
Range: real number

A mapable easting coordinate. When combined with the northing, the coordinate pair shall represent a point on a map where the surface water concentrations are located. It is assume that the user will supply all coordinates on the same basis, such as Nad87, UTM zone 11. This value is not used to compute the concentrations.

WW-Z--Elevation
Units: meters (m)
Range: real number, probably greater than zero.

The elevation at the point represented by northing and easting coordinate pair. This value is not used to compute the concentrations.

CONSTITUENT PROPERTIES TAB

FS-CNAME--Name of constituent(s) for current transport scenario

This field shows the constituents that are selected for the scenario. Use the arrow buttons to scroll through the list of constituents and enter an adsorption coefficient and water solubility for each one, and a degradation/decay half-life for non-radionuclides. If a constituent has decay products, they will be shown on the bottom part of this screen.

WW-SOL--Water solubility
Units: milligrams per liter (mg/l) or picocuries per milliliter (pCi/ml)
Range: greater than or equal to 0.0

Enter the aqueous solubility for the constituent. For most organic constituents, this value is available in the constituent database or in chemical property books. For inorganic constituents, this value will have to be estimated based on the geochemistry of the waste zone. If a value is available in the constituent database, it will be used as an initial default value. If a database value is not available, the solubility is set to 0, which is used as an indicator meaning an unknown solubility. The vadose zone module only uses the water solubility for a comparison with the concentration of constituent entering the layer. If that concentration exceeds the solubility, a warning message is written to a warning message file (casename.WRN). If the solubility is 0, this comparision is not performed.

WW-SHALF--Half-life in surface water
Units: years
Range: greater than 0.0

This parameter is the half-life of the constituent in the aquifer. For radionuclide and non-radionuclide constituents, this value defaults to the data in the constituent database, but the value can be changed to a site-specific value. This parameter can be used to implement other degradation rates (e.g., biodegradation, photo degradation, etc...) when they are converted to equivalent half-lives.