The location of water resources played a role in determining the post-World War I Palestine–Syrian border and presumably will play a part in future negotiations with Syria. Although Syria and Lebanon are upstream riparians on the Jordan basin, the two countries have alternative water resources and are therefore less dependent on the Jordan basin for their water supply. For Israel, Jordan and the Palestinians, however, the Jordan basin offers a primary source of water. The Johnston Plan served as a basis of understanding between Jordan and Israel but without explicit references to international law. The Israel–Jordan peace treaty and the bilateral interim arrangements reached between Israel and the Palestinians deal with allocations of specified quantities of water and not with legal principles. Future negotiations between Israel and the Palestinians will have to find a compromise between two basic tenets of international law, the rule of not causing appreciable harm to existing uses and the inherently contradictory rule of equitable allocations.