中国の水資源政策は，アジア地域において決定的な影響力を持っている。なぜなら利用可能な水資源の主要を占めるにおいて，その大半で中国が上流に位置するからである。本稿では，における中国の水資源外交政策について，カザフスタン，ロシア，インド，メコン川流域諸国の4カ国・地域との関係を「紛争防止メカニズム」の観点からその要因を比較した。中国とこれら4カ国・地域の間に構築されたメカニズムの共通点としては，「常設の共同機関」の存在がある。そこでは，定期会合の開催や「情報・データの交換」を通して信頼の醸成が意図され，国際水資源をめぐる紛争の防止を目指してきた。しかし，中国の北方に位置するカザフスタン・ロシアと，南方に位置するインド・メコン川流域諸国とでは，中国は異なるメカニズムを取っていることが判明した。その理由を考察すると，中国の領域主権原則から現れていることや，中国のにおける問題認識の違いがあるとみられる。特に関係が進展しているカザフスタンに対しては，水資源以外の要素が関係を定めていることが指摘される。いずれにしても中国の紛争防止メカニズムの構築は，主に「二国間アプローチ」を取っている所に特徴があり，流域における関係諸国を全て含んだ「多国間アプローチ」は取っておらず，その展開は今後の研究課題の一つとして挙げられる。

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An international water body has territories of more than one nation in its basin. Centuries-long conflicts among basin countries of some international water bodies have been recorded. As water resources become more precious resources for basin countries in the future, conflicts among basin countries are expected to intensify. Such renowned people as Former Secretary General of the United Nations, Mr. Gahli and King Hussein I of Jordan once hinted at the possibility of observing “water wars” in this century. This mainly stems from the fact that water resources are closely connected with the security of nations in the Middle East. Existing conflicts among basin countries in semi-arid and arid regions are likely to intensify. Traditionally, basin countries downstream of an international water body accuse basin countries in upstream areas of abusing shared water resources. While upstream countries seldom compromise with those downstream, traditional upstream-downstream relations are changing, with increasing interactions among basin countries in non-water sectors. This implies that agreements among upstream and downstream countries might be established in some international water bodies, in which relations among basin countries have been “conflictive” in the past with little hope of having an agreement. International organizations are expected to be instrumental in abating or resolving conflicts among basin countries in international water bodies, while international organizations might be more instrumental in elaborating a collaborative mechanism for riparian countries rather than serving as a mediator to solve conflicts among basin countries.

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This study considers the conflict-prevention mechanisms over international rivers between India and its neighboring countries (Pakistan, Bangladesh, and Nepal). India is a country where three important international rivers flow. The discussion concerns the Indus, the Ganges and the Mahakali rivers. Conflicts have taken place in the past over water resources between India and its neighboring countries, but India has presently signed treaties and Memorandum of Understandings and established mutually acceptable mechanisms for the development and management of the rivers. Furthermore, they have put in place permanent joint organizations, exchange of data, and river inspections.

Previous studies have analyzed how the conflict-prevention mechanisms were established in the process; however, no one has examined their effectiveness and weaknesses. In addition, there are no studies comparing policies and diplomatic efforts for all three rivers.

India and its neighbors have instituted permanent joint organizations to manage the water resources and have kept these organizations far from another politics. The role of mechanism’s factor is important and thus it was also investigated. For example, in the case of the Indus River, the mechanism does not specify the quantity of water allocated as shown in the Ganges River, but it effectively provides for a territorial type of sharing. It does not change the bounders between India and Pakistan, but traces a fictitious line that divides the basin and limits the sovereign rights of use of each state. In the case of the Mahakali River,which is at the border of India and Nepal, both countries benefited equally from the instituted irrigation and flood management policies.

Finally, this study examined the weaknesses of the conflict-prevention mechanisms. In the case of the Indus River, Pakistan has filed complaints against India to the Permanent Court of Arbitration concerning water resources for India to resolve the conflict. The court favored Pakistan on three out of four points, namely the restriction on India to maintain the minimum flow of the River, environmental protection and the diversion of water. However, the court ruled against and maintained that the instituted mechanisms function well.

In conclusion, while water supply and demand across the world is tight, considering mechanisms to prevent conflicts over water resources between countries will be significant. Especially, water demand in Asia is even sharply increasing compared to the world. Among them, India is a unique example of a country that shares waterways with more than one country.

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More than 200 river basins in the world are shared by two or more countries. These basins account for about 47 percent of the earth's land area. In international watercourses, national interests among countries are likely to diverge because of externalities. Coordinated management of international river basins is still rare, resulting in economic losses, environmental degradation, and international conflict.

International conferences such as the 1992 UNCED have stressed the need for comprehensive management of water resources using the river basin as the focus of analysis. Cooperation and goodwill among riparian countries are essential for efficient development and utilization of international rivers.

Four cases, all in major international river basins, were analysed in this study with a view to identifying some prerequisites, which are indispensable to secure mutual agreement among riparian countries upon construction of hydraulic works. Of four cases, agreements have been reached among basin countries in three cases (Nile River, Indus River and Danube River), while discussion between riparian nations has encountered an impasse in the Ganges River basin.

The lessons of experience with agreements and joint actions between riparian, such as the World Bank's effort to facilitate the 1960 Indus Water Treaty between India and Pakistan, suggest that external assistance and encouragement are valuable and sometimes essential ingredients in establishing international water agreements.

The presence of third parties can facilitate dispute resolution, guide complex bargaining towards acceptable outcomes, and help maintain balance and commitment by riparian countries to the negotiating process. The international organizations have many advantages as a third party since it can (1) act as independent broker, (2) provide leadership inherent in its international role in donor coordination, and (3) catalyze the mobilization of both official and private funding.

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メコン河委員会は, 95年に調印された 「メコン河流域の持続可能な開発に関わる協力協定」 に基づいて, カンボジァ, ラオス, タイ, ベトナム4力国の政府機関として発足した。同委員会は, 57年に設立された旧メコン委員会を引き継いではいるものの, 旧メコン委員会とは目的, 組織, 活動方針, 活動内容等が異なる。発足以来, メコン河委員会は持続可能な開発を達成するため, 何を成すべきかの議論とともに, 流域機構としての戦略作り, 水利用規則, 流域開発計画策定等の業務を行ってきた。本報では, 他の流域機構に先駆けて持続可能な開発を目指すことを宣言したメコン河委員会の発足以来の活動について述べる。

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 「国際水路の非航行的利用に関する条約」が，国連総会での採択から17年を経て，2014年8月に発効した．この条約は国境をまたぐ河川，湖沼，地下水を含む淡水資源の開発や管理に関する国際基準を示したもので，国際社会に大きな影響を及ぼすものと考えられる．特に，条文上最も重要視される「衡平利用原則」については，水資源をめぐる当事国間で紛争があった場合の一つの解決基準として用いられると期待され，事実，発効前にもかかわらず，これまで国際司法裁判所の判決でも引用されてきた．条約は当事国のみを規律するのが原則であるが，締約国以外にも当該条文が適用できるか，いわゆる国際慣習法化されているかは，条約発効後の国家実行や裁判例を待つ必要があろう．

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流域は，各流域国の間で農業，工業，生活，環境用水をめぐる争い（越境水紛争）の舞台となってきた．多くは流域国同士の話し合いにより解決する努力がなされてきたが，武力行使による軍事衝突が20世紀の間にアフリカと中東にて7件報告されている．人口増加や気候変動により世界規模での将来の水逼迫が深刻化した場合，稀少となった水資源を確保するために，国家間で政治的対立や武力衝突が頻発するリスクは否定できないため，水逼迫と水紛争の関係性を定量的に分析することは大変重要な課題であると言える．そこで，本研究では全球水資源モデルから推定された水逼迫指標を用いた過去の水逼迫状態や考えられる過去の水紛争要因から流域における越境水紛争生起確率モデルを構築した．構築されたモデルは概ね良好な予測性能を有すると言える結果となった．しかし，モデル構築に関して仮説の設定や説明変数の選出にはまだまだ検討の必要な課題があり，今後も情報収集を進めて，モデルの改良に取り組む予定である．

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Trans-boundary river basins have been affected by flow variability caused by water use. Down-stream countries are often forced to face water shortage and sometimes dispute and compete with up-stream countries for shared water resources. To avoid future water conflict, the basin at risk should be identified by hydrological variability and institutional mechanisms which agreements contains. This paper investigates the potential risk for trans-boundary water conflict in the future. This risk can be estimated with two components. One is water stress level projected by a global water resource model and the other is vulnerability level defined by both trans-boundary freshwater agreement and river basin organization. As a result, the potential risk for trans-boundary water conflict in Africa and Central Asia is found.

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