In the foreseeable future there will be two legal framework instruments covering transboundary water issues in force at the global level: the 1997 United Nations (UN) Watercourses Convention and the 1992 UN Economic Commission for Europe Water Convention. This development raises questions about the compatibility of both instruments, and how they might be implemented in a coordinated manner. A comparative analysis of the text of both instruments demonstrates that there are both similarities and differences between them, but that they are complementary. There is therefore significant benefit in promoting and implementing the conventions as a package. Three basic institutional options can be envisaged to support this ‘package approach’, each with their strengths and weaknesses. Ultimately, whichever option is chosen, the ‘package approach’ to the implementation of both conventions offers the best means by which to strengthen the law of international watercourses.