東京大学愛知演習林および千葉演習林の山地小流域における基底流出量と流域面積の関係の差異について Relationship between Base Flow and Basin Area of Small Mountainous Basins at the Tokyo University Forest in Aichi and in Chiba

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Abstract

降雨流出過程の相違を明らかにする目的で,異なる基盤地質における流域面積と比流量の関係を解析した。解析対象流域を新第三紀層堆積岩の千葉演習林内鳥居沢流域と風化花崗岩地帯の愛知演習林内白坂流域とし,鳥居沢流域内で4地点(12.0~39.4ha),白坂流域内で9地点(2.6~88.5ha)渓流流量を測定した。比流量比を,流域出口での比流量で流域内の各比流量を除して計算したところ,比流量比の値は鳥居沢流域で0.25~1.0,白坂流域で0.83~1.31であった。また,鳥居沢流域内では流域面積が増大するに従い比流量も増加するが,白坂流域内では流域面積に関わらず比流量は比較的差が無いという特徴が見られた。電気伝導度の調査でも同様の傾向が見られ,鳥居沢流域内では流域面積の増大に伴い電気伝導度の値が増加することが分かった。これらのことは,上流の流域で基岩への深部浸透が多くあり,これが下流の河道に湧出しているという新第三紀層流域の基底流出形成機構の特徴を示している。

We investigated the relationship between basin area and specific discharge of base flow at two basins underlaid by different types of geological bedrock to find the differences in discharge characteristics. We selected the Toriisawa basin at the Tokyo University Forest in Chiba, a Tertiary sedimentary rock, and the Shirasaka basin at the Tokyo University Forest in Aichi, a weathered granite basin. We measured discharge quantities at 4 (12.0-39.4 ha) and 9 (2.6-88.5 ha) points respectively. The ratios of specific discharge, which were calculated by dividing each specific discharge value by the specific discharge value at the basin outlet, varied from 0.25 to 1.0 at the Tertiary basin and from 0.83 to 1.31 at the granite basin. At the Tertiary basin, the specific discharge increased with an increase in basin area, whereas there was relatively little difference between the specific discharges at the granite basin. The electrical conductivity showed the same tendencies as specific discharge. At the Tertiary basin, the electrical conductivity increased with an increase in the basin area while it remained almost constant at the weathered granite basin. These results indicate that much water infiltrates into bedrock at the upstream basin and this infiltrated water containing much dissolved material re-emerges through bedrock at the downstream area in the Tertiary basin.

Journal

  • Bulletin of the Tokyo University Forests

    Bulletin of the Tokyo University Forests (111), 49-57, 2004-06

    東京大学大学院農学生命科学研究科附属演習林

Cited by:  1

Codes

  • NII Article ID (NAID)
    120001092957
  • NII NACSIS-CAT ID (NCID)
    AN00162451
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • Journal Type
    大学紀要
  • ISSN
    03716007
  • NDL Article ID
    7124022
  • NDL Source Classification
    ZR21(科学技術--農林水産--林産)
  • NDL Call No.
    Z18-548
  • Data Source
    CJPref  NDL  IR 
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