PUBLIC interest and concern regarding water-supply, expressed in Parliament, in the Press and in the debates of various professional bodies, has never been so general, or so generally well informed, as it is to-day. Interest increases primarily because of almost chronic threats of shortage, which only the foresight of water engineers has usually prevented from becoming actual. The threats themselves occur because the ever-growing demand outstrips provision. Growth of population in ‘new’ centres is an obvious problem; but in general it is of far less importance than the rise in standards of living. Populations which were satisfied fifty years ago with a daily supply of ten or fifteen gallons a head are now barely served with thirty. Even less generally appreciated is the ever-growing demand of industry. The concern increasingly felt has been stimulated by a recent succession of serious droughts. Finally, the feeling that something is wrong has almost certainly been brought to a climax by the war-time experience that demands can be met ‘when the devil drives’. The stupendous requirements of camps, aerodromes and factories have been surprisingly fulfilled, mainly by resort to underground water.