Effects of high flows to organic matters and organisms in the agricultural canals

Abstract

Concrete and earth canals were used to examine the effects of high flows on organic matters and organisms. The two high flows were done during the high-flow season from 3 June to 23 September 2008. The high flows could transport only particulate organic matters, and the discharge and coefficient of variation were higher in the concrete canal than in the earth canal. The total number of taxa and the densities of invertebrates were higher in the concrete canal than in the earth canal. Before the high-flow season, the responses of invertebrates to the current velocity differed among the life cycle characteristics. During the high-flow season, the concrete canal was more affected by high flows than the earth canal, and the reduction of densities of invertebrates was higher in the concrete canal than in the earth canal. After the high-flow season, the recovery for the reduction was influenced by the life cycle of invertebrates and the flow refugia of the paddy field in both canals. This study suggested the importance of considering the physical environments of canals connecting paddy fields and the life cycle of invertebrates in assessing the effects of agricultural water management.