Multipond systems: A sustainable way to control diffuse phosphorus pollution

Diffuse pollution from agricultural land is one of the main causes for lake eutrophication. Multipond systems, an ancient invention in China, are comp osed of many tiny ponds and ditches, scattered in agricultural fields. Afte r a long period of research in an experimental watershed in Liuchahe, it wa s found that multipond systems constitute diffuse pollution control. They h ave a large capacity for water storage and serve to control the export of w ater, suspended matter, and phosphorus. Multipond systems significantly red uce runoff velocity. Sediments and phosphorus retained in the Liuchahe wate rshed were 14.38 . 10(6) and 7016 kg yr(-1), respectively (area 691.6 ha). Irrigation provides an effective way to recycle and remove phosphorus. The use of multipond systems is a sustainable way to recycle valuable nutrients and reduce their discharge and thus pollution of downstream lakes.