In preparing the report of the Committee on Underground Waters of the Section of Hydrology for the final year of the triennium, it becomes evident that the collection of fundamental data relating to the hydrology of underground waters continues at a rate comparable to that maintained in the past few years, and perhaps even at an accelerated rate. Almost every extensive practical investigation of ground‐water supplies offers some opportunity for study of fundamental problems, in fact many of them require such fundamental study. With a larger number of investigations in progress, and with fairly liberal appropriations much new and valuable information is being discovered. Some idea of the increase in ground‐water studies since the organization of the Section of Hydrology may be given by a few statistics on the work of the Division of Ground‐Water of the Federal Geological Survey, which does the largest amount of ground‐water work in the United States. In 1932 the Division worked on about 50 projects in 25 States, in 15 of which and in Hawaii the investigations were made in cooperation with States, or other local Governmental agencies. During the current fiscal year work has been completed, or is in progress, on about 100 investigations in 35 States, Hawaii, and the Virgin Islands. The number of States cooperating on the work has increased to 24. During the current fiscal year about \$375,000 will be spent for ground‐water investigations by the Federal Geological Survey and cooperating organizations, as compared to about $175,000 spent during the fiscal year ended June 30, 1932.