The severe downpours that hit northern Greece and neighboring Bulgaria in recent days caused the Evros River to burst its banks, causing crop damage and loss of livestock. Efforts to tackle the chronic flood threat, however, are complicated by the past prejudices underlying the trilateral ties linking Greece, Turkey and Bulgaria. Talks with Ankara on the issue in the early 1950s, for example, collapsed in 1955 because of rising bilateral tensions caused by developments in Cyprus and Istanbul. The Evros River is not the only transboundary water resource that Greece has to manage in cooperation with its neighbors. The Nestos, Strymonas and Axios rivers that flow on the plains of the Macedonia region as well as the Prespes and Doirani lakes, which impact thousands of households across national borders, must be high on the agenda of Greek foreign policy. Existing international agreements determine the quantity and quality of the water that reaches Greece. But these have become outdated as the Balkans have changed. Downstream Balkan states will be tempted to exploit their shared water resources at Greece’s expense. The case of the Nestos River is indicative of the challenges ahead. According to existing agreements, Greece receives 29 percent of the water flowing across the border; for the time being, this is enough to water the eastern Macedonia-Thrace plain. Should Bulgaria go ahead with plans to divert the river to water its own plains, Greece will continue to get the same share – but out of a smaller total amount. The issue of transboundary waters is too serious to be left to local decision making. Water, a life-giving commodity, is likely to become of source of conflict in water-scarce regions. Greece must hammer out a national water strategy to ward off future tension with its neighbors.