Greetings from oikos !
 

Diversity within riverine or instream habitats manifests itself within the river channel or stream channel. Life bursts out in the waterfalls, rapids, pools, riffles, fords, ripples, pot holes, sand bars, rootwads, islands and such other places. It changes with the changing physical nature of the river. It is different in the source, plains and delta. The gradient and velocity of water shapes various habitats, and the temperature, depth and turbidity of the water influences the distribution of biota across these habitats.

Rapids are stretches of river characterized by small falls and turbulent, high-velocity water. They are responsible for the mixing of oxygen in the water. Riffles and pools are the other important features of a river. They occur alternatively in sequence, repeating over long stretches. A Riffle, Rift or Ford is characterized by shallow, fast-moving water broken by the presence of cobbles or rocks and boulders. On the other hand, pools are characterized by shallow, low-velocity water and a smooth surface. Riffles provide a shelter to a majority of fast stream inhabitants. They find protection under the rubble and gravel, which shelters them from the current. Nymphs of mayflies, caddisflies, alderflies, stoneflies and the larva and pupae of true flies all live in harmony here. In pools, the dominant insects are burrowing mayfly nymphs, dragonflies, damselflies and water striders and water beetles. Deep pools (डोह) and large pot holes are excellent habitats for fishes, especially in case of seasonal rivers. Rootwads are a mass of roots associated with a tree adjacent to, or in a stream that provides refuge for fish and other aquatic life.

Most natural riverine systems are relatively stable over long periods of time as long as there is no human interference. However, interventions such as dams, dredging or channel straightening, alter these habitats, and consequently their inhabitants. This in turn, alters the functioning of the ecosystem.
 

Regards,

Ketaki & Manasi

With Team oikos !