河川純一次生産力に基づく全球月別環境流量必要量の推定  [in Japanese] GLOBAL MONTHLY ENVIRONMENTAL FLOW REQUIREMENT BASED ON THE NET PRIMARY PRODUCTIVITY OF RIVERS  [in Japanese]

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Abstract

流量変動に支えられた河川生態系の保全のためには一定の環境流量必要量(EFR)では不十分であり,一年の内に最大でどの程度のEFRがどの季節に必要かを知ることが重要である.本研究では,河川植物の純一次生産力から河川生態系の質と脆弱性を指標化するモデルを用いて,月別に全球環境流量必要量を計算した.その結果,全球年平均のEFRの45%に対し,最大月のEFRは149%と3倍にもなった.特に雨季乾季が明瞭なサバナなど一次生産力や流量の季節変動が大きい場所では最大月を加味したEFRを設定する必要がある.検証の結果,本モデルは個別設定されたEFRと最も一致率が高く,既往の全球モデルで評価の難しかった低緯度地域や流況変動の大きな地域でも精度よく評価できることを確認した.

 A constant environmental flow requirement (EFR) is insufficient to protect river ecosystems supported by seasonal flow fluctuations. The objective of this research is to estimate global monthly environmental flow requirements using a fluvial plant biomass model to highlight the timing and magnitude of the maximum flow requirements. The average global EFR estimated by this model was 45% of mean annual discharge. In contrast, the maximum monthly EFR was 149% which was tripled to the average EFR. The maximum monthly EFR is larger in the area where the primary productivity as well as seasonal fluctuation of flow are large. For such regions, not only base flow but also maximum EFR should be considered. In order to validate this model, we compared the EFR calculated by three global models and 28 places in 17 countries. The verification indicated that our model has the highest accuracy among the compared global models.

Journal

  • Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research)

    Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research) 74(6), II_85-II_92, 2018

    Japan Society of Civil Engineers

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