1 0 0 0 OA 〈報文〉霞ヶ浦におけるヨシ原の分布と低地の成り立ち
- 著者
- 関 智弥 池田 宏 SEKI Tomoya IKEDA Hiroshi
- 出版者
- Terrestrial Environment Research Center, the University of Tsukuba
- 雑誌
- 筑波大学陸域環境研究センター報告 = Bulletin of the Terrestrial Environment Research Center,the University of Tsukuba (ISSN:13463381)
- 巻号頁・発行日
- vol.4, pp.75-88, 2003-10
Lake Kasumigaura is a coastal lake, the second largest lake in Japan. There is the lacustrine lowland with a width of 0.5 - 1.0km, around Lake Kasumigaura. The lacustrine lowland consists of "Terrace I", "Terrace II" and "developing Lowland". It has been known that the lacustrine lowland formed at present, however the mechanisms and processes of formation have not been well understood. Thus, in this study, geomorphic characters and mechanism of developing lowland are revealed by distributions of reed community and grain size analysis and analysis of wave energy.Developing lowland is low and flat topography, and its relative height is 0 - 0.5m from mean water level. And its structure materials are mainly fine grains especially "very fine sand" and "silt". In addition distributions of the developing lowland and reed community have close correlation. And these distributions are determined mainly by wave energy.These results lead to the conclusion that developing lowland was formed with deposition of sands by the wave and capture of fine grains by reeds.
1 0 0 0 OA 〈報文〉栃木県那須扇状地における地下水と河川水の交流
- 著者
- 山中 勤 田中 正 浅沼 順 濱田 洋平 YAMANAKA Tsutomu TANAKA Tadashi ASANUMA Jun HAMADA Yohei
- 出版者
- Terrestrial Environment Research Center, the University of Tsukuba
- 雑誌
- 筑波大学陸域環境研究センター報告 = Bulletin of the Terrestrial Environment Research Center,the University of Tsukuba (ISSN:13463381)
- 巻号頁・発行日
- vol.4, pp.51-59, 2003-10
Water levels were measured for 34 wells in the Nasu Fan, Tochigi prefecture, in the end of October, 2002. Water quality of groundwater (34 samples), river water (6 samples) and spring water (3 samples) were also analyzed. Local relief of groundwater table is considerably low, and the typical value of its gradient is approximately 1/100. At an elevation between 220m and 250m, groundwater table approaches to the ground surface. Revival of interrupted stream of the Sabi River and the Houki River can recharge groundwater. These facts indicate that there is active interaction between groundwater and surface streams. Groundwater level fell over most part of the fan in recent 10 years. The maximum reduction of the groundwater level exceeds 3m. Increase in electric conductivity of groundwater was detected in some areas including urban areas.