HEC 4.0 model for irrigation scheme

[Anonymous]

Hi everyone. I was wondering if HEC could be used to study an irrigation scheme, composed by a dendritic layout of a few canals, connected by flap gates. The inlets of the irrigation scheme also depend on the tide in the river, so there are also a few inlets with tide/flap gates.

I would like to develop just a easy model, where I could enter the boundary conditions (levels upstream of the flap gates which are the inlets of the system), and also the outflows for irrigation.

It is possible to develop such a model in HEC RAS?

Thank you very much

[Lonnie A]

Use unsteady and should have no issues doing this.

[Chris G.]

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Subject: Re: HEC 4.0 model for irrigation scheme
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Definitely. I’ve done it myself a number of times.=20

Sent from my iPhone

> On Jun 17, 2015, at 9:58 AM, John Clark [via HEC-RAS Help] wrote:
>=20
> Hi everyone. I was wondering if HEC could be used to study an irrigation s=
cheme, composed by a dendritic layout of a few canals, connected by flap gat=
es. The inlets of the irrigation scheme also depend on the tide in the river=
, so there are also a few inlets with tide/flap gates.=20
>=20
> I would like to develop just a easy model, where I could enter the boundar=
y conditions (levels upstream of the flap gates which are the inlets of the s=
ystem), and also the outflows for irrigation.=20
>=20
> It is possible to develop such a model in HEC RAS?=20
>=20
> Thank you very much=20
>=20
> If you reply to this email, your message will be added to the discussion b=
elow:
> http://hec-ras-help.1091112.n5.nabble.com/HEC-4-0-model-for-irrigation-sch=
eme-tp1738.html
> To unsubscribe from HEC-RAS Help, click here.
> NAML

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Definitely. I’ve done it myself a number of times. 

Sent from my iPhone

On Jun 17, 2015, at 9:58 AM, John Clark [via HEC-RAS Help] <[email protected]> wrote:

Hi everyone. I was wondering if HEC could be used to study an irrigation scheme, composed by a dendritic layout of a few canals, connected by flap gates. The inlets of the irrigation scheme also depend on the tide in the river, so there are also a few inlets with tide/flap gates.

I would like to develop just a easy model, where I could enter the boundary conditions (levels upstream of the flap gates which are the inlets of the system), and also the outflows for irrigation.

It is possible to develop such a model in HEC RAS?

Thank you very much

---

If you reply to this email, your message will be added to the discussion below:

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To unsubscribe from HEC-RAS Help, click here.
NAML

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[Anonymous]

Oh great! Thank you both Lonnie and Chris for your responses.

Actually I will try to develop the model in HEC-RAS running with conditions introduced by used in EXCEL (like the initial level at the irrigation canals, the tide level at the inlet, among others). That it is possible right?

Another question that I have is:

In order to control the total inflow volume entering the main irrigation canal (from the tide gates) for a certain time interval the better/easiest way to do it is to create a storage area (representing the river) connected with the main irrigation canal by a tide gate right?

[Anonymous]

Hi everyone.

I would like to simulate a flap gate between 2 river reaches.

I tried a lateral structure with a diversion rating curve, but how can I define the relation between the levels of the 2 river reaches?

[Anonymous]

Assuming that both sides of the weir are modeled, RAS will recognize the differential between the water surface elevations and (based on the lateral weir characteristics) compute the flow at any time over the weir. The direction of flow is based on which side has the higher water surface. The lateral structure can either connect to a storage area or another reach.

[Anonymous]

Actually I am trying to simulate a tide gate (with only 1 direction) connecting one inlet channel to the main channel. It is possible to do that with a diversion RC? Or should I specify the culvert characteristics?

And what boundary condition should I have in the last section of the inlet channel. It should work like a reservoir.

[Anonymous]

Lateral structures can contain culverts that have flap gates. You can find the data entry from: Geometric Data > Lateral Structures > All culverts. Under the culvert description there is an entry for the type of gate. Under flap gates, the direction of flow can be chosen.
Hope this helps,
Michael

[Anonymous]

Thank you very much.

What is the best DS boundary condition for the channel act as a “reservoir” i.e., with no flow leaving the DS cross section. When the flap gate is closed, the level in the channel should rise until the level is high enough to open the flap gate.

I tried Rating curve with 2 values near 0 but it is impossible.

[Anonymous]

If the downstream area is not a RAS reach or storage area; suggest that you use a stage hydrograph for the D/S BC. Commonly use this for situations that have tidal or reservoir connections downstream. For these applications, the D/S connecting cross section should be large enough so that the velocity head is negligible.
Michael

[Anonymous]

Actually it will connect with the main reach, but as I am using a lateral structure as a flap gate, I need some DS boundary condition for the last section.

However, I think stage hydrograph is not aplicable because the level in the reach may depend only the inflow (given by the tidal level upstream) and the outflow from the lateral flap gate. Am I correct?

This stream acts like a reservoir in order to provide inflow for other channel by a flap gate. I hope that my explication is clear enought.

[Anonymous]

A schematic of your system would be useful to look at to figure out what BC’s are appropriate.
Michael

[John Clark]

Hi Michael. You are right a schematic overview always help!

In my simulation, the inlet channel is not connect with the main channel (as you can see by the image cross section 1 is the last cross section). In cross section 1 I have a BC of a rating curve with almost zero flow, in order to avoid the inlet channel to lose water when both tidal gates are closed.

In my simulation the tidal gate 1 is simulated as a lateral structure flag gate avoiding negative flow (from main channel to the inlet channel). I have not yet the tidal gate 2. I would like to set the levels in the river as a time series. It is possible to do with a storage area? And then connect with a flap gate to the first cross section of the inlet channel?

Sorry for all my questions and long post

Thank you very much for your help.

[Anonymous]

I would model this situation by connecting the inlet channel to the main channel. A couple of cross sections would be needed between the flap gate and the main channel. Those sections should be large enough that the velocity is negilible.
If you want to model the main channel as a storage area, the inlet channel still needs to be connected to it. Think that you can prescribe a stage time history for a storage area in RAS.

Michael

[John Clark]

Sorry I did not get it. If I connect the inlet channel with the main channel, there will be 2 “connections” between the 2 channels (the flap gate and the junction).
How can I avoid flow leaving the main channel into the inlet channel through the junction, even with a very wide cross section?
Actually I want to model the inlet channel as reservoir (storage area).

I did not find a boundary condition for the time series level for a storage area.

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