400
A frequent cause of musty, earthy odors, especially toward the end of the summer, is naturally occurring organic compounds derived from the decay of plant material in lakes and reservoirs. The odors can be objectionable, but generally are not harmful to health. However, odors can be caused by other constituents as well, so you may want to call your local Health Department and mention the odor to them.
What can cause our water to have an earthy odor or to smell like rotten eggs?