Evaluation of river improvement works based on benthic animal fauna

根据岩手县Yukiya河和宫森河的水质和水虫情况，对河流整治工程进行了评价。河道整治后，水生昆虫的个体数量和类群数量都很少，以穴居型昆虫为主，其次为织网型昆虫。结果表明，在河床条件、支流流入和水虫涌流条件安排合理的情况下，水虫群落结构可在几个月内恢复。结果表明，河道整治工程造成的高浑浊水对水生昆虫的生物群损害并不严重。位于宫森河中上游的河岸林增加了流动有机质通量和河床有机质量，导致水生昆虫的个体和类群数量增加。碎纸机个体数与粒径大于3.35 mm的流动有机质通量具有良好的相关性，水虫Shannon多样性指数升高。河岸林对河流水环境的重要性得到了明确的说明。

Evaluation of river improvement works was conducted based on the water quality and water insects obtained in the River Yukiya and the River Miyamori in Iwate prefecture. Immediately after the river improvement work the number of individuals and taxa of aquatic insects was very small and the burrowing type of insects was predominant and then the net-spinning type. It was found that the community structure of aquatic insect could recover in several months if the condition of riverbed, inflow of tributary and runup of aquatic insects were arranged well. It was shown that the high turbidity water caused by river improvement works did not damage the biota of aquatic insects seriously.The riparian forest located in the upper and middle water regions in the River Miyamori increased the flux of flowing organic matter and the amount of organic matter in the riverbed, resulting in an increase in the number of individuals and taxa of aquatic insects. The individual number of shredder and the flux of flowing organic matter with a size of more than 3.35 mm had a good correlation and the value of Shannon Diversity Index of aquatic insect was increased. The importance of riparian forest on river water environment was clearly shown.