Land use effects on lowland lakes
The diagrams below show a lowland lake before and after development in its catchment.
The diagram below shows a lake in its natural state, before development of the surrounding catchment. Native forest covers the hills, and native vegetation surrounds the lake margin. The water is clear, and the lake supports many native birds, fish and aquatic plants.
After development of the surrounding catchment the condition of the lake has changed markedly.
The forested hills have been cleared for pasture. Nutrient-rich runoff from fertiliser, animal wastes and sediment has washed in from surrounding farms. These nutrients have boosted the growth of water weeds and algae in the lake, which have competed with native plant species and reduced the clarity of the water.
The native aquatic plants have died off, and native bird and fish numbers have declined. Pest fish, such as koi carp and rudd, are now present.
Find out more about how land use affects peat and riverine lakes in the Waikato region: