National Geographic : 1896 Apr
HYDROGRAPHY IN THE UNITED STATES of the stream, in order that the central office of the district or that at Washington may be informed in time to issue predictions or warnings as to impending disaster. The operations of this bureau, as far as they relate to the hydrography of the rivers and of the lake and seacoast navigation, are for the exclusive purpose of issuing prompt notices, which shall be of immediate value to the farmer or other resident upon the lowlands and to the sailor. Coming next in the scheme of the study of the waters of the country is the work of the Geological Survey, which, taking the facts relating to precipitation and moisture given by the Weather Bureau and utilizing the data as to river heights as far as possi ble, expands these into a general study of the occurrence of water within the United States, tracing out the causes, especially those of topographic and geologic character, which lead to variations in distribution and fluctuations in supply, and in short bringing together material by which the water resources of the country may be known as thoroughly as its mineral wealth. From the time, therefore, that the rain reaches the ground the Geological Survey endeavors to trace its course on or below the surface and to ascertain the laws governing its circulation and its reappear ance by seepage or through natural outlets in springs or in arti ficial openings, such as artesian or other wells. This Survey, as incidental to the preparation of the great map of the United States, examines in detail the surface of the country, determines the age and character of the rocks, their structure and position with relation to each other, their permeability or im perviousness to water, and the probabilities of their being able to yield a supply at points not yet penetrated by the well-digger. As in all scientific work, the ultimate object is that of prediction, of revealing that which is now unknown or but partly under stood. Such extension of knowledge rests upon a thorough ex amination and understanding of the history of the past and of the conditions in the present. Before questions can be answered as to what is the probable supply of water at this or that point, for power, for irrigation, or for municipal supply, it is necessary that long-continued and accurate work be done. The work of the United States Geological Survey relating to water resources is carried on by the Division of Hydrography. The field operations of this division consist of the measurement at selected points of the flowing waters of springs, creeks, and rivers, the estimation of the discharge of artesian wells, and of the quantities of water which can be obtained by other means.