Storage Area Connections

Storage Area connections are used to link two storage areas together with a hydraulic structure. Storage area connections can consist of a weir; culverts and a weir; gated spillways and a weir; or a linear routing option. To establish a hydraulic connection between two storage areas, press the “Storage Area Conn” button at the top of the geometric data window. Once the storage area connection drawing tool is invoked, the user simple presses the left mouse button one time while over the from storage area, then double click the left mouse button while over the too storage area. This establishes the connection between the storage areas, as well as what is considered to be the positive flow direction.

Once a connection is made between two storage areas, the user must enter information describing the hydraulics of the connection. This is accomplished by pressing the Storage Area Conn editor button on the left hand side of the geometric data editor. When this button is pressed, the following window will appear:

Figure 6.38 Storage Area Connection Editor

As shown in the figure above, the user should first enter a description for the storage area connection. Next the type of routing connection must be selected from the drop down box. As mentioned previously, the user has the choice of a weir only; weir and gates; weir and culverts; or linear coefficient routing between storage areas. Once a routing type is selected, the window will place editor buttons specific to that type of routing onto the left side of the editor. In this example, because a weir and culverts was selected, the weir, culverts, and hydraulic table parameters buttons show up on the window. The user must enter data for each of the buttons shown on the window. In this example it is required to enter a weir/embankment, culvert information, and hydraulic table parameters. When the weir/embankment editor is selected, the following window will appear:

Figure 6.39 Weir/Embankment Editor for Storage Area Connections

To complete the data for the weir/embankment between two storage areas, the user enters a Weir Width (used only for drawing the schematic); a Weir Coefficient (used in the weir flow calculations); a Weir Crest Shape (used to assist in the calculation of the weir coefficient, as well as defining submergence criteria); and the Station/Elevation Points that describe the top of the weir/embankment profile. The weir/embankment can have up to 500 points to describe the profile. The program will use all of the information entered by the user for calculating weir flow between the two storage areas. After all of the data is entered, simply press the OK button to have the data accepted by the program.

If the user has selected the weir and culverts routing type, then culvert information must be entered also. When the culvert editor button is selected, the following window will appear:

Figure 6.40 Culvert Editor for Storage Area Connections

The culvert editor shown above has exactly the same information as the normal culvert editor used at a river crossing. For detailed information about this editor, please review the section on culverts found earlier in this chapter.

Whenever the user selects a weir, or a weir and culvert routing type, and additional button will appear on the editor labeled “Htab Param”. This editor is used to define the limits of the family of rating curves that will be developed for the storage area connection. When this button is pressed, the following editor will appear:

Figure 6.41 Hydraulic Properties Table Editor

As shown in Figure 6.41, the user must enter a number of points for the free flow curve (default is 40, max 50); number of submerged curves (default is 40, max 50); number of points on the submerged curves (default is 10, max 20); and head water maximum elevation. Additionally, the user can enter a tailwater maximum elevation; maximum swell head (difference between headwater and tailwater); and a maximum flow rate. All of these parameters are used to define the limits of the family of rating curves that get created when the geometric pre-processor runs.

If the user has selected the Weir and Gates option, an editor for gated spillways will show up on the left hand side of the window. Pressing this button will bring up the window shown in Figure 6.42. As shown in the figure, this editor is the same gate editor that is used for inline and lateral gated spillways. For information about this editor, please review the sections on inline and lateral gated spillways found earlier in this chapter.

Figure 6.42 Gated Spillway Editor for Storage Area Connections

The final option for Storage Area Connections is to model the connection as a Linear Routing Method. This option uses a coefficient times the difference in available storage between the two storage areas, divided by the time step. When this option is pressed, the following window will appear:

Figure 6.43 Simple Spillway Data Editor

As shown in the Linear Routing editor, the user must enter a linear routing coefficient for both the positive and negative flow directions. Additionally, the minimum elevation of the spillway crest must be entered. If both water surfaces go below the spillway crest, no flow is passed between the storage areas.

Pump Stations