Paraphrase Excercise

The first effect of a dam is to alter the pattern of disturbances that the plants and animals of a river have evolved for. Many aquatic animals coordinate their reproductive cycles with annual flood seasons. Every flood is valuable in that it takes nutrients from the land and deposits them in the river, providing food for the stream's residents. Floods also provide shallow backwater areas on vegetated and shaded riversides; the young of many animals depend on these backwaters to protect them from large predators.

The construction of a dam essentially regulates the flow of the river, eliminating the natural patterns of a free flowing water stream. This includes a rivers flood patterns and, while this control seems desirable for us, it is very disruptive to countless creatures for which flooding proves crucial in the process of reproduction because of the creation of an excess of nutrients and new shallows, which serve as safe harbors for many species’ offspring. (Cave)