TOPOGRAPHY, GEOLOGY AND FORESTATION.

The entire area is covered with glacial drift which takes the form of till in Benton County, and of washed sand and gravel in Sherburne County. Beneath the drift are granites. The range of altitude is from 860 to 1,150 feet.

The basin contains about 20 small lakes, chiefly in the lower por-. tion, and these comprise less than 1 per cent of the area.

The greater part of the drainage basin was originally covered with timber, but most of this has been cut off as the land is nearly all under cultivation.

RAINFALL.

The mean annual rainfall for the Elk River basin is about 28 inches, as shown by records just outside the basin-there being none within the basin itself. Of this amount 3 inches fall as snow. Th nearest record is that at St. Cloud, which is continuous since 1893. In that period the wettest year was 1897 when the rainfall was 41.9 inches. The driest year was 1910, when the precipitation was 14.6 inches.

DRAINAGE AREAS.

The following drainage areas have been measured in this basin:

Location. At the highway bridge 4 miles east of Big Lake and one-half mile east of Bailey station on the Northern Pacific Railway; in Sec. 23, T. 33 N., R. 27 W., one-half mile above Tibbetts Brook, and 4 miles below mouth of St. Francis River.

Records available.-April 15, 1911, to December 31, 1912.

Drainage area.-615 square miles.

Gage.-Vertical staff.

Channel.-Probably permanent, as small rapids a short distance below are the control point.

Discharge measurements.-Made from the highway bridge at all stages except low, when wading measurements are made nearby. Regulation. The flow of the river above the station is entirely uncontrolled as the only dam on the river is located near the mouth about 8 miles below.

Winter flow. From December to March the relation between gage heights and discharge is affected by ice, and during that period measurements are made to determine the winter discharge.

Daily discharge, in second-feet, of Elk River near Big Lake.

Day.

Jan. Feb. Mar. Apr. May. June. July. Aug. Sept. Oct. Nov. Dec.

discharges 100 and 1,300 second-feet and fairly well defined between 1,300 and

NOTE-Daily discharge computed from a rating table well defined between

4,000

second-feet.

Estimated from three measurements made during the winter months, semiweekly gage heights and climatological data.

· ELK RIVER NEAR ELK RIVER.

Location. At the Hastings foot bridge in Sec. 31, T. 33 N., R. 26 W., 3 miles above the mouth of the river. The nearest tributary is Tibbetts

Brook which enters 3 miles above. This station was maintained by the U. S. Engineer Corps.

Records available.-October 15, 1896, to September 14, 1897. These records have been compiled from unpublished data in the U. S. Engineer Office at St. Paul. As the drainage area at this point is only 9 per cent larger than that of the station near Big Lake, the records are very nearly comparable.

Drainage area.-670 square miles.

Gage. -No data. This was not of great importance as very frequent discharge measurements were made, on which the estimates were largely based.

Winter flow. The river was frozen over during the winter months, but frequent measurements were made to determine the flow.

Daily discharge, in second-feet, of Elk River near Elk River.

Day.

Jan. Feb. Mar. Apr. May. June. July. Aug. Sept. Oct. Nov.

Dec.

126

The only power developed on Elk River is that of the Elk River Milling Co. whose dam at Elk River gives an 11-foot head used in generating 150 horsepower by means of two turbines, one of 125 horsepower capacity and the other of 25 horsepower. The power is used in operating the flour mill.

SANITARY CONDITION.

No settlement of any considerable size is situated on Elk River or its tributaries, and therefore no urban sewage enters the river. The rural population is 21.6 per square mile.

CROW RIVER.

SOURCE, COURSE AND TRIBUTARIES.

The area drained by Crow River lies in Stevens, Kandiyohi, Meeker, Renville, McLeod, Wright and Hennepin counties between the basins of the Sauk and the Minnesota. Crow River proper is a short stream, being formed by the junction of the North and South forks 2 or 3 miles above Rockford. Throughout its course it forms the boundary between Hennepin and Wright counties, and it discharges into the Mississippi at Dayton. The North Fork, which is the longer of the two, rises in McLeod and Grove lakes, in the eastern part of Pope County. These lakes together are about 4 miles long and average one-third mile wide. From the outlet of the lakes the general course of the North Fork is southeastward through Rice and Cedar lakes, both of which are of considerable size. At Manannah it receives the Middle Fork, which