# Simulation problem involving two tracers in Telemac2d? **URL:** \ **Category:** TELEMAC-2D\ **Created:** [August 11, 2025, 10:21am UTC](https://opentelemac.org/forum/t/simulation-problem-involving-two-tracers-in-telemac2d/8038 "2025-08-11T10:21:20Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![user\_16418](https://opentelemac.org/forum/letter_avatar_proxy/v4/letter/u/e0b2c6/32.png) [@user\_16418](https://opentelemac.org/forum/u/user_16418)\ **Post date:** [August 11, 2025, 10:21am UTC](https://opentelemac.org/forum/t/simulation-problem-involving-two-tracers-in-telemac2d/8038/1 "2025-08-11T10:21:20Z")
Hello [name removed], Could you please help me identify the problem in the .cas file? I ran a simulation with Telemac2D to study the dispersion of two tracers at the pollution source: nitrate (10 mg/l) and phosphate (20 mg/l). I have three (3) pollution sources, each with a flow rate of 5.0 m³/s. The hydrodynamic calculations are correct in the .slf file, but I am not getting any results for the dispersion. For all three sources, I noticed that the tracer concentrations remain at 0. I cannot figure out the cause of the problem. The .cas file is attached. Thank you very much for your help and cooperation. [name removed] [Dispersion\_t2d.cas](https://opentelemac.org/forum/uploads/short-url/vDSktuC4IEbgyz3bDVeUTLdVGF6.cas) (4.13 KB) ---
**Author:** ![user\_438](https://opentelemac.org/forum/letter_avatar_proxy/v4/letter/u/c77e96/32.png) [@user\_438](https://opentelemac.org/forum/u/user_438)\ **Post date:** [October 20, 2025, 5:48pm UTC](https://opentelemac.org/forum/t/simulation-problem-involving-two-tracers-in-telemac2d/8038/2 "2025-10-20T17:48:45Z")
Hello, To define sources, you have to declare as many sources as the size of array WATER DISCHARGE OF SOURCE. In your case, if commenting this keyword, no punctual source is defined. Hope this helps, [name removed]