Dissolved oxygen refers to the amount of free, non-compound oxygen present in water and is one of the most important indicators of water quality in natural and engineered aquatic systems. It originates primarily from two sources: diffusion of atmospheric oxygen into water and photosynthetic activity of aquatic plants, algae, and phytoplankton. The concentration of dissolved oxygen is usually expressed in milligrams per liter (mg/L) and varies with physical, chemical, and biological conditions of the water body. Temperature plays a critical role in determining dissolved oxygen levels, as the solubility of oxygen decreases with increasing temperature. Cold water can hold more dissolved oxygen than warm water, which is why high-altitude streams and cold-water ecosystems generally have higher DO levels. Salinity also affects oxygen solubility; freshwater can dissolve more oxygen than saline water. Turbulence and water movement, such as waves, waterfalls, and flowing streams, enhance