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Negative heterograde oxygen curve in place of clinograde curve

Wed, 09/23/2015 - 3:01pm — Seyoum
Hello, I am calibrating CE-QUAL-W2 version 4 lake model for a moderately productive lake. Lake volume and temperature fitted observation date quite well but the model is showing consistently very low DO right below thermocline (negative heterograde curve) beginning in April. The DO minima spreads to the bottom with the season contrary to observed DO minima that begins from the bottom and spreads upward in the fall to generate a clinograde curve. Any input to fix this is greatly appreciated. Thank you, Seyoum
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Water Quality
Tue, 09/29/2015 - 10:50am — Scott

Seyoum: It appears your inflow organic matter and/or algae are coming as an interflow and causing depletion below the thermocline and this is probably dominant. If the SOD were higher, the bottom DO depletion would be larger. Good success, Scott
Thu, 10/29/2015 - 5:17pm — Seyoum

Scot: Thank you for pointing me in the right direction. I have dissolved silica measurements (SiO2) that I added to the input file as is without converting it to Si (elemental). Untimely DO depletion was automatically disappeared and the model started to compute DO profiles closely resembling observations when this error was corrected, underscoring how the model was sensitive to silica concentrations in influent water.