When computing a model, it fails with a user notification like one of the below:.
"Number out of range. Looking for value that is less than lowest table value. Looking for ### ft. Lowest table value ### ft."
"Number out of range. Looking for headwater elevation value that is greater than highest table value. Looking for ### cfs. Highest table value ### cfs."
"The vortex valve with the id '#####' is out of range. If using Downstream Channel tailwater type, make sure the channel has enough capacity."
This type of issue can occur when a pond or outlet experiences a calculated flow or head which does not exist on the respective rating table. In short, the lookup tables to determine the head/flow relationship do not cover the appropriate range needed. This can happen with pond outlet structures as well as outfall rating curves.
First, check all of your outfall elements to see if any are configured to use a rating table such as Elevation-Flow. If any of them do, ensure that the maximum flow on the table is higher than the maximum flow that could possibly reach that outfall. For example if the rating table only goes up to 100 CFS but the upstream flow that reaches the outfall exceeds 100 CFS, the error will occur because it cannot find a lookup value for the headwater resulting from such a flow. Add more points to the rating table to resolve this.
For an outlet structure, this issue can happen when a component (such as an orifice, culvert, weir, or vortex valve) has elevations set that do not match up with the headwater elevation range used for the composite outlet structure itself (pond). This most often occurs with the composite outlet structure noted in the user notification itself, although it can sometimes be more general and be referring to a different composite outlet structure.
First, note the name of the outlet structure that is causing the issue in the list of User Notifications. Next, go to Components > Composite Outlet Structures and find the composite outlet structure associated with the outlet structure in the User Notification.
Next, review the elevations for the headwater range of the Composite Outlet Structure and make sure that they match up with the elevations of the pond associated with the Composite Outlet Structure.
If the outlet link element has "Use Elevation-Flow-Tailwater Table" set to "Yes", then check the selected EQT table to make sure the headwater range matches the upstream pond elevation range, and that the tailwater range matches the downstream pond's elevation range. For example, if the pond elevation is from 10 feet to 20 feet, then the headwater portion of the EQT table needs to range from 10 to 20 feet.
If using a composite outlet structure, the elevations for the Composite Outlet Structure may be outside of the range of the pond elevations, and will need to be resolved before the model will compute. This can happen for example if the wrong pond is selected in the "Pond" field of the headwater range, when the headwater type is set to "Use pond for headwater range".
Next, check the elevations in the outlet structure components (weirs, orifices, etc) and ensure that they are within range of the pond. One common confusion is with irregular weirs - the elevations in the irregular weir cross section table are added to the "elevaiton" field in the weir properties.
The maximum value on the vortex valve curve is 6 ft. at 0.29 cfs., but if you look in the screen shot below the total difference in headwater range is 6.24 ft., which is not covered by the curve. If you add in one valve of 6.24 ft. with a flow of about 0.30 cfs this problem would be resolved and the model would run.
On rare occasions, this user notification may be related to a different outlet structure than the one referenced in the User Notification. If the headwater range in the Composite Outlet Structure is the same as the pond for the outlet structure element referenced in the user notification, please do a careful review of the other outlet structures in the model to make sure that the headwater range of the associated Composite Outlet Structure matches that of the referenced pond. It is possible that the incorrect Composite Outlet Structure is being used for a given outlet structure.
Fatal error when using Downstream Channel option for outlet structure tailwater