Pond Boss Forums AERATION Systems questions Dissolved oxygen questions

How quickly will dissolved oxygen levels in a pond fall under adverse weather conditions? In a worst case scenario of extremely hot weather with no wind, how quickly can dissolved oxygen levels in a healthy pond go from a high level to a level which is detrimental to the pond environment? If a pond is stable with fish population, beneficial plants, etc; how quickly can dissolved oxygen levels fall based only on weather conditions?

Wow, thats a loaded question. Its like asking if I hold my breath, how long until I pass out. That depends if you are a runner or a person who does not exercise.

There are many veribles to oxygen concentration in a water body. Oxygen is concentration and temperature dependent.

During the day the oxygen will build to saturation levels at temperature. Another words, freshwater at a temperature of 22 deg C, (72 F) the saturation level would be 8.7 mg/l in the middle of the day with no wind.

Once the sun falls, the hypothetical pond in your question with a stable fish population and plant life will begin to consume that oxygen. If there is no stratification and good oxygen from top to bottom, then the pond is able to support the oxygen demand.

The next morning shows to be bad weather with very little sunlight and nutrients washing in from heavy rain storms. The plants did not produce as much oxygen as they did the day before. Now night falls again and the plants, fish and now anarobic digestion begin to consume oxygen the smaller amount of 02 availble. There is not as much to consume as there was the night before. Therefore the Biochemical Oxygen Demand is higher than the night before.

So you see the above examples are just a few of the many dynamics that happen in the water. To be able to give you even a rough number of how quickly a pond will be lacking healthy oxygen levels without having more water chemistries like Biochemical Oxygen Demands and Oxygen Reduction Potentials done is not likely. It depends on how healthy you hypothetical lake is, how much plant biomass it contains and the amount and type of watershead washing in.

I have seen a pond go from healthy 02 to below 2mg/l overnight, but that was due to sever stratification.

I wish I had an answer that is standard for you but it just does not exsist.

Embarrassing! I did not check my spelling before posting that reply.

Please excuse my posting before proof reading!