work, paying to the Survey, through transfer of funds in the Treasury Department, the actual cost of the investigations. During the last year 152 stations have been maintained under this cooperative agreement.

OFFICE OF INDIAN AFFAIRS.

Cooperation has also been effected with the Office of Indian Affairs in connection with ground-water investigations. At the request of the Commissioner of Indian Affairs a study of ground-water supplies was undertaken in the Moki and Navajo reservations of Arizona, New Mexico, and southern Utah, $3,000 being set aside for this purpose by the Indian Office. A report, with recommendations, based on this study and intended for the guidance of representatives of the Indian Office who are responsible for water development in this region, has been transmitted to the Commissioner.

Stream-flow investigations on Indian reservations have also been placed in charge of the Geological Survey by the Commissioner of Indian Affairs. The work during the last year has been performed on the following reservations:

Indian reservations on which investigations of stream flow have been made.

The cost of this work has been paid by transfer in the United States Treasury from the Indian Office appropriation.

FOREST SERVICE.

At the request of the Forester a geologist was detailed to the Paulina district, in eastern Oregon, to advise the local forest officials as to the possibility of developing underground waters in that area for domestic and stock purposes and, further, to assist in determining the depths of wells for which contracts are to be let in the future. The amount set aside by the Forest Service and expended in this work was approximately $400.

PUBLICATIONS.

The work of the water-resources branch is represented in the following publications issued during the year: Professional Paper 65;

Water-Supply Papers 232 to 236, 238, 239, 241 to 245, 247 to 250, and 252. Titles and brief summaries of these publications are given on pages 15, 21-23. Seven other papers were in press at the close of the year, 3 have been submitted for publication, and 34 are in different stages of preparation.

CHARACTER OF INVESTIGATIONS.

The investigation of water resources in the United States involves work of three kinds. One is the determination of river flow, which is the basis for the development of storage, water power, irrigation, flood prevention, and land drainage. Another is the determination of the occurrence, location, and amount of underground waters. The third is the study of the quality of water, both surface water and that occurring underground, and its fitness for the various industrial and domestic uses. The problems involved are of engineering, geologic, and chemical character and wide fields are covered in each of these branches of science.

MEASUREMENTS OF RIVER FLOW.

DISTRICTS AND GAGING STATIONS.

The methods followed in gaging streams are discussed in detail in the printed annual progress reports of the work. (See Water-Supply Papers 241-252.) For administrative purposes the country is divided into districts, each in charge of a district engineer, as follows:

New England district: Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut. T. W. Norcross, district engineer, 6 Beacon street, Boston, Mass. District engineer in subdistrict of Maine, C. C. Babb, state capitol, Augusta, Me.

New York district: New York, New Jersey, and northern Pennsylvania. C. C. Covert, district engineer, Federal Building, Albany, N. Y.

Middle Atlantic district: Southern Pennsylvania, Maryland, Delaware, Virginia, and the eastern part of West Virginia. R. H. Bolster, district engineer, Washington, D. C.

Southeastern district: North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Louisiana, and Tennessee. M. R. Hall, district engineer, Federal Building, Atlanta, Ga.

Ohio Valley district: Ohio, Indiana, Illinois, Michigan, middle Missouri, and Arkansas. A. H. Horton, district engineer, Federal Building, Newport, Ky.

Upper Mississippi district: Minnesota, Wisconsin, and Iowa. Robert Follansbee, district engineer, Old Capitol Building, St. Paul, Minn.

Denver district: Southern Wyoming, Colorado, and New Mexico. W. B. Freeman, district engineer, Commonwealth Building, Denver, Colo.

Upper Missouri district: Northern Wyoming, Montana, North Dakota, and South Dakota. W. A. Lamb, district engineer, Helena, Mont.

59394°-10-7

Great Basin district: Utah, Idaho, and Nevada. E. C. La Rue, district engineer, Brooks Arcade, Salt Lake City, Utah.

Columbia River district: Oregon and Washington. J. C. Stevens, district engineer, Tilford Building, Portland, Oreg.

California district: California and Arizona. W. B. Clapp, district engineer, Federal Building, Sacramento, Cal.

The results of the work performed in these districts are compiled and computed for publication by the computing section in the Washington office, under the charge of R. H. Bolster, assistant engineer. The distribution of the gaging stations by States is as follows:

NEW FEATURES OF THE WORK.

Special attention has been given during the year to raising the standard of the progress report on stream measurements. The methods of computation have been revised so as to insure much greater accuracy in the results than heretofore. This work has been under the direct supervision of R. II. Bolster, who has had many years' experience in work of this class. He has been assisted by a corps of trained men, who, under his direction, make up a computing section that is to be a permanent feature of the water-resources branch.

In order to insure the greatest accuracy in the data, they are carefully reviewed by the field men before being transmitted to this office. These data, with full notes on all special points, form the basis for the work in the computing section, where the final estimates are made. These estimates are then submitted to the district engineers for inspection, so that all published results have a double check. All the descriptive matter in the progress reports has been carefully revised and all nonessential material eliminated.

The physical conditions governing the work of stream gaging are such that the data for the different stations can not be of the same standard of accuracy. In order that the engineer using the report may know what reliance to place on the results given, a column has been added to the monthly estimate table for each station, showing the probable error.

The increased demand for water for municipal supply, irrigation, and other uses has forced the utilization of many small sources of supply which heretofore have not been considered important. This has created a demand for data on the small streams, and every effort has been made to meet this demand.

During the year the instruments for determining stream flow have been greatly improved, with the result both of facilitating the work and of increasing the accuracy of the results. A new automatic gage, which gives a printed record of the time and stage of the river for every fifteen minutes, has been developed by Gurley & Co., of Troy, N. Y., from preliminary plans and suggestions given by the engineers of the water-resources branch. It is believed that this instrument will be a large factor in future stream-gaging work, as the diurnal fluctuations in most streams, due to natural and artificial conditions, require a continuous record of stage in order to obtain accurate results.

To facilitate the use of government reports relating to water supply, climate, etc., the United States has, by agreement between the Survey and the Weather Bureau, been divided into twelve areas and the progress report of stream gaging has been divided into

twelve parts, each part covering one of these areas. The areas and the numbers of the corresponding reports giving the results for 1907-8 and for 1909 are as follows:

Preliminary river-profile surveys in advance of topographic mapping have been made during the year in Maine, Minnesota, and Oregon. The work in Minnesota was done at the expense of the State, but under the direction of the Geological Survey. Certain reservoir-site surveys formed a part of these examinations. The localities of the work are given in the following table: