Upland streams run with fast, clear water. This water is low in nutrients but high in oxygen and flows over rock and gravel stream beds. A number of dragonflies and other insects are well suited to this environment and can be seen over the summer months flying up and down the streams, looking for smaller insects to eat. These streams are dotted with waterfalls and rocks, where the spray and shade keeps the banks cool and moist and they have developed a thick cover of mosses and ferns.

As the streams reach the lowlands the water slows down picks up material washed in from the surrounding land. There are more nutrients, and with the slower water flow, reeds can take root and fringe the river margins. Gravel beds collect in some places and are important spawning grounds for fish and river lampreys.

Much of the Usk has tree-lined banks that provide cover for the elusive otter and form important flight-lines for bats. The rivers and their banks are natural corridors in the landscape that help wildlife move around. The river Usk is a protected site in both UK and European law as it is almost entirely natural, having seen little engineering like flood banks and straightening that have impoverished the habitat in other UK rivers.

Use the navigation bar on the left to explore other wetland habitats or go back to Biodiversity in the National Park.