<P> Rivers have been a source of food since pre-history . They are often a rich source of fish and other edible aquatic life, and are a major source of fresh water, which can be used for drinking and irrigation . Most of the major cities of the world are situated on the banks of rivers . Rivers help to determine the urban form of cities and neighbourhoods and their corridors often present opportunities for urban renewal through the development of foreshoreways such as river walks . Rivers also provide an easy means of disposing of waste water and, in much of the less developed world, other wastes . </P> <P> Fast flowing rivers and waterfalls are widely used as sources of energy, via watermills and hydroelectric plants . Evidence of watermills shows them in use for many hundreds of years, for instance in Orkney at Dounby Click Mill . Prior to the invention of steam power, watermills for grinding cereals and for processing wool and other textiles were common across Europe . In the 1890s the first machines to generate power from river water were established at places such as Cragside in Northumberland and in recent decades there has been a significant increase in the development of large scale power generation from water, especially in wet mountainous regions such as Norway . </P> <P> The coarse sediments, gravel, and sand, generated and moved by rivers are extensively used in construction . In parts of the world this can generate extensive new lake habitats as gravel pits re-fill with water . In other circumstances it can destabilise the river bed and the course of the river and cause severe damage to spawning fish populations which rely on stable gravel formations for egg laying . </P> <P> In upland rivers, rapids with whitewater or even waterfalls occur . Rapids are often used for recreation, such as whitewater kayaking . </P>

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