 Filtering and purification: Certain types of rocks, like limestone and sandstone, have porous properties that allow water to filter through them. This natural filtration process helps remove impurities, sediment, and pollutants, resulting in cleaner water.  pH balance: The rocks' mineral content can also influence the pH levels of the water. Acidic rocks, such as granite, can lower the water's pH, making it more acidic. On the other hand, limestone, with its alkaline properties, can increase the water's pH. Fluctuations in pH can impact aquatic life, affecting the survival and reproduction of different species.  Mineral leaching: Rocks contain minerals that can dissolve and leach into the water. This leaching process can add essential minerals to the water, benefiting aquatic life. However, excessive mineral leaching, such as high levels of heavy metals, can be harmful and lead to water pollution.  Nutrient availability: The composition of rocks can affect the availability of nutrients in the water. Some rocks may release nutrients such as phosphorus or nitrogen, which can contribute to eutrophication if present in excess. Conversely, certain rocks may have low nutrient levels, affecting the overall fertility and productivity of the river ecosystem.  Habitat creation: Different rock formations, such as boulders, gravel beds, or rocky ledges, provide habitats for various aquatic organisms. They offer hiding places, nesting sites, and areas for algae and aquatic plants to attach and thrive. The presence of rocks can enhance biodiversity, acting as critical habitats for fish, invertebrates, and other species.  Sediment accumulation: The characteristics of rocks can influence sedimentation patterns in rivers. Smooth rocks can facilitate the movement of sediment downstream, preventing excessive build-up and maintaining a healthy river channel. Conversely, rough or jagged rocks can cause sediment deposition and alter water flow dynamics, potentially impacting water quality and ecosystem health.  Thermal regulation: Rocks can absorb and retain heat from the sun, modifying water temperature in rivers. Shaded areas with rocks can create cooler microhabitats that provide refuge for sensitive species, while sun-exposed rocks can contribute to warmer water temperatures. Temperature variations play a crucial role in determining the distribution and behaviour of aquatic organisms.