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Hello all
I want to calculate the tracer residence time in my domain in which tide and wind are affecting the area with reasonable velocity and water depth results.
I tried after that to calculate the residence time. I have initial value of tracer= 100mg/l in the whole domain with no prescribed tracer value.i have three boundaries in which (LITBOR=4) for all three boundaries.
I used law of tracer degradation = 1
the problem is how to choose value for coefficient 1 for law of tracer degradation??
I tried to put it for about 5 hrs as first trial but the average tracer value decreases by 0.8 mg/l every 4days so the tracer may take more than 1year to go out of the tracer... is this reasonable?

Hello,

My first question is what kind of tracer do you study? Is it a tracer that follows a 1st order kinetic degradation law or no degradation?

The current degradation law implemented in WAQTEL is a 1st order kinetic law with a T90 parameter, as for bacteria. T90 is the duration to obtain 90% mortality. The COEFFICIENT 1 FOR LAW OF TRACERS DEGRADATION keyword has the to be set at this T90 value (in hours).

The hydrodynamic of your area may have much more influence on the residence time.

Hope this helps,

Chi-Tuan