The international law of transboundary groundwater resources Introduction : groundwater at the global level Understanding groundwater resources and aquifers Groundwater resources in a transboundary context Early legal treatment of groundwater resources Groundwater and aquifers under the UN Watercourses Convention Groundwater and aquifers under the UN Draft Articles on the Law of Transboundary Aquifers Trends in the evolution of international law of transboundary aquifers Gaps in the law of transboundary aquifers