To improve water quality for agricultural use, it is needed to introduce the natural and low-cost
self-purification system. It is also necessary to develop the water purification facilities for more efficient and
convenient design, construction, operation and management. This study aims to develop the practical facilities to
improve water quality for agricultural use. The practical detention pond system, which uses artificial floating island
and shield skirts with bio-media, enhanced removal efficiencies of SS, TN and TP more particularly than the
detention pond using an auxiliary dam. The removal efficiencies SS, TN and TP for the practical detention pond
were 55.7%, 61.0% and 55.9%, respectively. The facilities of the practical detention pond has a lot of disadvantages
such as the low-cost and high efficiency as well as uncountable impacts regarding ecology and landscape. However,
an auxiliary dam is recommended to be installed in shallow depth due to low efficiency.