The world's 261 international river basins, covering 45 percent of Earth's land surface (excluding Antarctica), are shared by more than one nation.*Even the most cordial and cooperative of neighboring nations have found it difficult to achieve mutually acceptable arrangements to govern their transboundarysurface waters, even in relatively humid regions where fresh water usually is found in sufficient abundance to satisfy most or all needs. When nations are located inaridregions, conflicts become endemic and intense despite otherwise friendly relations or even membership in a federal union. Little wonder the English language derives the word "rival" from the Latin word"rivalis,"meaning persons who live on opposite banks of a river used forirrigation.

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