game-jp mailing list の皆さま: 沖です。
IGBP/BAHC 会議で来日中の New Hanpshire 大学の Charles Vorosmarty 氏に
講演していただくことになりました。どなたでもご参加できますので、ご興
味のある方はどしどしご参加ください。グローバル0.5度グリッド河道網を使
った水質や物質循環に関連した話になると思います。ちなみに、明日は、GAME-T
に参加しているハワイ大学の T. Giambelluca 教授の講演が同じ場所で14:30〜
15:30に行なわれます。そちらの方もどうぞよろしく。
日時: 1999年5月21日(金) 15:00〜16:00
場所: 東京大学生産技術研究所(六本木旧キャンパス)第五会議室
講演者: Charles J. Vorosmarty
所属: ニューハンプシャー大学地球海洋宇宙研究所 助教授
講演題目: 大貯水池による大陸規模の河川流量の時系列変化と加齢
講演概要:
世界の総貯水容量のほぼ60%を占める633の大貯水池情報をグローバルな30分分解能デジタル
河川網で結び、個々の貯水池や河道、そして流域全体における滞留時間を算定した。その結果
ならびにこうした大規模貯水池が土砂輸送に及ぼす将来的な影響などについて講演する。
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The Distortion and Aging of Continental Runoff by Large
Impoundments: A Global-scale Effect
by
Charles J. Vorosmarty
Research Associate Professor
Institute for the Study of Earth, Oceans, and Space
University of New Hampshire
Durham, New Hampshire 03824 (USA)
ABSTRACT
In this presentation I analyze the scope and potential impact
of reservoir construction on the world's river systems. The study links
information on 633 of the world's largest reservoirs (LRs) (=84 0.5 km3
maximum storage capacity) to a digitized river network at 30-minute
spatial resolution. This sub-set represents approximately 60% of the
global impoundment by registered dams. A residence time is computed
for individual reservoirs, river segments, and entire drainage basins.
Water storage behind the global population of large dams represents a
700% increase in the standing stock of natural river water, with
residence times for individual impoundments spanning less than one day
to several years. The discharge-weighted mean residence time for
individual LRs distributed worldwide is 0.21 years. The imprint of such
storage persists downstream. The mouths of several large rivers show a
reservoir-induced aging of continental runoff that exceeds three
months. From both case studies and global synthesis this aging can be
shown to lead to significant changes in net water balance, flow regime,
and reoxygenation of surface waters. I go on to assess the potential
impact of global reservoir construction on sediment transport from the
continental land mass. It can be demonstrated that more than 40% of
global river discharge is intercepted by the large impoundments
analyzed and that a significant proportion (=89 70%) of this discharge
maintains a theoretical sediment trapping efficiency in excess of 50%.
For regulated drainage basins the global, discharge-weighted residence
time is 0.09 years, representing a 30% potential sediment trapping.
For all river systems, an estimate of 16% sediment trapping by LRs can
be given. The interception of suspended sediment flux due to all size
classes of reservoirs is likely to exceed 25% at the global scale.
From the standpoint of sediment retention, the most heavily-regulated
drainage basins reside in Europe. North America, Africa, Australia /
Oceania are also strongly affected. The pandemic construction of large
reservoirs represents an important component of the terrestrial water
cycle and one that merits due consideration in future global change
studies.