The attenuant water in the first rice crop is more than the second rice crop, because the first rice crop in 2001 is dry reason and the water quality in the river becomes bad.

• 其中一期作之稀释水量远高于二期作，其原因在九十一年一期作适逢乾旱，雨水稀少造成河水水质劣化所致。