These odors in your water may come from natural organic matter found in river water. Natural organic matter from river water can sometimes produce a swampy or musty taste and odor during the summer and fall months. This organic matter will not harm you at all, and the water is safe for you to drink.
The more likely cause of these smells is hair, soap, and food waste that accumulates over time on the walls of a sink drain. Bacteria can grow on these deposits. As the bacteria grow and multiply, they produce gases that can smell musty or moldy. These gases accumulate in the drain until the water is turned on. As the water runs down the drain, the gases are expelled into the air around the sink. It is natural to assume the bad odor is coming from the water because the smell is noticeable only when the water is on. However there is nothing wrong with the water, but the drain may need to be disinfected.