what affects dissolved oxygen levels in water

The amount of dissolved oxygen (DO) in water is affected by both natural and anthropogenic factors. Naturally, water conditions such as temperature, salinity, and the presence of too many aquatic organisms can affect DO levels. Higher water temperatures result in decreased oxygen solubility, while cooler waters have greater oxygen solubility. The capacity of water to hold DO also decreases as the salinity increases. Water bodies at higher altitudes will have lower oxygen levels than water closer to sea level, as atmospheric O2 is less dense at higher altitudes. Water flow also affects DO levels, with more turbulent water containing more oxygen. Anthropogenic factors that affect DO levels include clearing land, runoff, and sewage waste. Physical alteration of the stream channel, through impoundments or channel alterations, can also contribute to low dissolved oxygen concentrations.