In a body of fresh water, a dissolved oxygen concentration of 0.262 mm or higher is usually needed to maintain a healthy aquatic ecosystem. for a lake to maintain this concentration, what is the maximum water temperature?

We are given that

DO = 0.262mM O2

And since 1mM = 32mg/L

Converting to mg/L:

DO = 32mg/L * 0.262mM

DO = 8.4 mg/L = 8.4ppm

Using the nomograph to identify the maximum temperature to maintain 8.4 ppm of DO concentration:

Max water temp is 26 ˚C.