Algae simulation in water quality module

EFDC_Explorer
1

Dear all,

I am currently facing some challenges while using EFDC to simulate water quality in stormwater pond sites, particularly in the algae simulation part. I have simplified the system by selecting only one group of algae in the biota tab. Initially, I inputted some reference values into the model, but I noticed that the algae concentration kept decreasing, almost reaching zero levels. In attempts to address this issue, I made various adjustments, including increasing the growth rate, decreasing the metabolism rate and predation rate, increasing the settling velocity and so on. However, none of these changes seem to prevent the algae concentration from declining, and it has become even more pronounced.

My field data indicates that the Chla concentration is relatively stable around the same level with fluctuations, but the simulation results are not even close to capturing this trend. I have tried adjusting almost every parameter in the biota tab, and it is becoming frustrating to see the algae concentration continue to decrease. I am confident in the hydrodynamic model as it has been validated, so the issue seems to be related to the water quality module.

I am reaching out for assistance and hoping that someone can provide me with feasible combinations of parameters that can at least maintain the algae growth in the simulation. I have all the water quality data from the sites, and I believe resolving this problem will significantly improve the accuracy of my simulation results. Thank you all for your time and support.

Best regards,
Alwyn

2

Hi I had a similar problem, did you solve it?

3

Hi,

In the new version, I set a minimum algae threshold to prevent it from dropping below a certain value. I also calibrated the model by adjusting the optimal temperature for algae growth (if you notice peaks in the algae plot, try matching them with the temperature preference). This approach helped improve my model, though sometimes the calibrated values can be unrealistic (e.g., a 5°C optimal temperature for algae growth). I apologize that this isn’t a perfect solution, but it’s what I’ve found effective so far.