Conditions may become especially serious during a period of hot, calm weather, resulting in the loss of many fish. Water near the surface of the lake– the epilimnion– is too warm for them, while water near the bottom–the hypolimnion– has too little oxygen. Thus, excess organic material in lakes and rivers can cause eutrophic conditions, which is an oxygen-deficient situation that can cause a water body to 'die.' Aquatic life can have a hard time in stagnant water that has a lot of rotting, organic material in it, especially in summer (the concentration of dissolved oxygen is inversely related to water temperature), when dissolved-oxygen levels are at a seasonal low. Bacteria in water can consume oxygen as organic matter decays. Rapidly moving water, such as in a mountain stream or large river, tends to contain a lot of dissolved oxygen, whereas stagnant water contains less. Algal blooms can occur under such conditions. This dissolved oxygen is breathed by fish and zooplankton and is needed by them to survive.Ī eutrophic lake where dissolved-oxygen concentrations are low. Oxygen enters a stream mainly from the atmosphere and, in areas where groundwater discharge into streams is a large portion of streamflow, from groundwater discharge. A small amount of oxygen, up to about ten molecules of oxygen per million of water, is actually dissolved in water. Another common measurement often taken is dissolved oxygen (DO), which is a measure of how much oxygen is dissolved in the water - DO can tell us a lot about water quality.Īlthough water molecules contain an oxygen atom, this oxygen is not what is needed by aquatic organisms living in natural waters. Some measurements, such as temperature, pH, and specific conductance are taken almost every time water is sampled and investigated, no matter where in the U.S. The USGS has been measuring water for decades.

USGS scientist is measuring various water-quality conditions in Holes Creek at Huffman Park in Kettering, Ohio.

Oxygen not included germs in water