Calculator
Use manual saturation data or estimate saturation from temperature, altitude, and salinity.
Example data table
| Case | Actual DO (mg/L) | Saturation DO (mg/L) | Deficit (mg/L) | Percent Deficit |
|---|---|---|---|---|
| River Morning | 7.80 | 9.20 | 1.40 | 15.22% |
| Pond Noon | 6.10 | 8.70 | 2.60 | 29.89% |
| Lake Edge | 9.40 | 10.10 | 0.70 | 6.93% |
| Outlet Mix | 4.80 | 8.40 | 3.60 | 42.86% |
Formula used
Primary deficit formula:
D = Cs − C
Where:
- D = dissolved oxygen deficit in mg/L
- Cs = saturation dissolved oxygen in mg/L
- C = actual dissolved oxygen in mg/L
Percent deficit:
Percent Deficit = (D ÷ Cs) × 100
Percent saturation:
Percent Saturation = (C ÷ Cs) × 100
Estimated saturation option:
Cs,sea level = 14.652 − 0.41022T + 0.007991T² − 0.000077774T³
Pressure Ratio = (1 − 2.25577 × 10−5h)5.25588
Salinity Factor ≈ 1 − 0.005S
Cs = Cs,sea level × Pressure Ratio × Salinity Factor
This estimated path is an engineering approximation. Use measured saturation values when field data is available.
How to use this calculator
- Select manual entry when saturation dissolved oxygen is already known.
- Select estimate mode when you want the tool to approximate saturation.
- Enter the actual dissolved oxygen reading in mg/L.
- Provide saturation directly, or enter temperature, altitude, and salinity.
- Set a critical dissolved oxygen target for your review.
- Press Calculate Deficit to show the result above the form.
- Review deficit, percent deficit, percent saturation, and target gap.
- Use the CSV or PDF buttons to save the result summary.
Why dissolved oxygen deficit matters
Dissolved oxygen deficit shows how far current oxygen conditions are from saturation. A larger deficit often signals higher oxygen stress, stronger organic loading, or weaker mixing. This metric helps compare sites, track changes, and assess whether water conditions are moving toward a risky range.
Manual saturation values are best when you have measured data. Estimated saturation helps when temperature, altitude, and salinity are available but direct saturation results are missing. Comparing actual oxygen against a critical target also helps screening for aquatic habitat concerns and process control limits.
FAQs
1) What is dissolved oxygen deficit?
Dissolved oxygen deficit is the difference between saturation dissolved oxygen and actual dissolved oxygen. It shows how much oxygen is missing relative to equilibrium conditions in the water.
2) What does a higher deficit mean?
A higher deficit usually means the water has less oxygen available than expected at saturation. That can point to stronger biological demand, pollution, warmer water, or weak aeration.
3) Can the deficit be negative?
Yes. A negative result means actual dissolved oxygen is above the saturation estimate or entered saturation value. That condition is often called supersaturation.
4) When should I use manual saturation input?
Use manual saturation input when you already have a trusted saturation value from field measurements, laboratory work, or a separate validated model.
5) Is the estimated saturation exact?
No. The estimate is practical and useful, but it is still an approximation. Direct measured saturation is better when precision matters.
6) Why are temperature and altitude included?
Temperature changes oxygen solubility, and altitude changes air pressure. Both factors affect the maximum oxygen water can hold under equilibrium conditions.
7) Why is a critical oxygen target useful?
A critical target gives you a benchmark. It helps show whether current oxygen conditions are acceptable or whether additional oxygen is needed to reach a chosen operating or habitat threshold.
8) What units should I enter?
Enter dissolved oxygen values in mg/L, temperature in degrees Celsius, altitude in meters, and salinity in parts per thousand.