River

Thecharacteristics of a river vary in a predictable fashion from the headwaters, along the middle and lower courses to themouth, and so constitute an ecological continuum.

This longitudinal gradient has important implications for the distribution of the flora and fauna along a river.

Lower Course

In the lower course, regular inundation of the floodplain creates a lateral dimension to the river system, and there are important interactions between land and water during the flood cycle.

The long ribbon-like character of streams and rivers gives them a high surface to volume ratio and long edges (banks) compared with lakes or the oceans.

As a result of these physical features, the river environment interacts strongly with the surrounding land, and ecological processes in the drainage basin have major implications for river ecology.

By contrast lakes, and especially oceans, are much less affected by terrestrial processes.