MOHID Water forum. Questions and discussion around MOHID Water
MOHID Beginner
Posts: 12
Joined: Thu Jan 01, 1970 00:00


Postby » Tue Nov 30, 2010 19:55

Hi Mohiders,

I need to simulate the 3-dimensional hydrodynamic and water quality (temperature, phosphorous cycle, nitrogen cycle, chlorophyll, BOD, DO…) of some freshwater reservoirs. I am working with curvilinear grid and I will use harmonic coordinates. My questions are:

1-It’s not possible to create the digital terrain at Mohid GIS with a polygon circulating all the reservoir area in the option land points. So, I need to impose at least one open boundary? I created a digital terrain without any polygon, but I think it will not work.

2-If I choose the option FLOW_OVER:1 in the Discharges Module to simulate the spillway, the flow will be calculated with the Bernoulli equation?

3-In the water quality module, phytoplankton is described in terms of carbon concentration. But in the formulation of the light extinction factor chlorophyll concentration is used. How the chlorophyll concentration is obtained? With a constant reason?

4-The model CE-QUAL-W2 is 2D laterally averaged. In Mohid, CEQUALW2 module uses the same ecological formulations, but can be 3D, right? In what version of the model CE-QUAL-W2 the module of Mohid is based? Where I find the keywords for this module?

5-I am spending a lot of time doing the curvilinear grids in some big reservoirs thinking that I will save some time later in the simulations. I would like to know if someone have some experience working with curvilinear grids and if it worth.

Thank you for your help.

Posts: 151
Joined: Thu Jan 01, 1970 00:00
Location: Technical University of Lisbon


Postby » Thu Dec 02, 2010 10:45

Dear Guilherme,

ansers to some of your questions:

1. You can specify more then one polygon for Land areas, in this way it´s possible to surround the reservoir by land. You don't need a open boundary.

2. Yes, simplified equation based weir length, crest height, discharge coeficient and water level inside the reservoir.

3. I'm not sure, but I think in the water quality module a constant redfield ration is used.

4. Yes to your first answer. But Ce-QUAL-W2 in MOHID has not been used very often, so don't expect that it works right from the scratch.

5. Curvilinear grids are suitable for reservoirs and I have used them once. Only be carefull for not getting very small cells in a specific place which will affect your stablility. PS: It's also not yet possible to generate curvelinear grids with MOHID Studio.

Hope this helps,
In order to understand recursivity you must first understand recursivity.
MOHID Beginner
Posts: 12
Joined: Thu Jan 01, 1970 00:00

Postby » Tue Dec 21, 2010 16:01


Thank you for your answer.

About the curvilinear grids, my experience is that`s not a good idea use curvilinear grids in dentritic reservoirs, only in reservoirs with simple geometry.

Happy new year.

Return to “MOHID Water”

Who is online

Users browsing this forum: No registered users and 3 guests