Author(s): Hiroshi Yajima; Hideo Otani; Miho Akiyoshi

Linked Author(s): Hiroshi Yajima

Keywords: Lake Koyama; Littoral zone; Macrophytes

Abstract: Recently we began to make use of the natural purification system for the preservation of a lake environment. One of the methods is to restore the macrophytes in a water body. To clarify the physical conditions for the existence of macrophytes, we conducted field surveys in Lake Koyama, which is a small, shallow and brackish lake. We studied the existing area of macrophytes, the water depth, the grain size of the bottom sediment and lakefront condition around the shoreline. Moreover we measured wave height at two stations in the lake and conducted wave analysis using a wave simulation model named SWAN developed and maintained by Delft University of Technology as many research suggested that wave condition might have a great impact on the growth of macrophytes. In Lake Koyama most of the emergent plants were seen where the water depth was less than 1m and the lakefront was not concrete revetment. The results of SWAN suggested that strong wave prevented the emergent plants from growing even if the depth was shallower than 1 m. As to the submerged plants, we could find very little of them in the lake. The low transparency was considered to be the main reason for this and we need further study about the light condition to clarify the scarcity of the submerged plants.

DOI:

Year: 2010