rises in Crow Lake, in the southwestern part of Stevens County, and flows southward through Green Lake (area several square miles) and then eastward to its junction with the North Fork. Below the Middle Fork it receives one or two small tributaries which also head in the lakes. The South Fork heads in a number of lakes in the southeastern part of Kandiyohi County, from which it takes a general easterly course, flowing through Otter Lake.

TOPOGRAPHY, GEOLOGY AND FORESTATION.

The valley of the North Fork lies 40 to 50 feet below the general surface level-that of the South Fork is from 30 to 40 feet below the surface and one-fourth to one-half mile wide. The basin of the North Fork contains about 70 lakes, comprising approximately 3 per cent of its drainage area-that of the South Fork contains 120 lakes, comprising 2 per cent of the total area drained. Many of these lakes are small and have no apparent outlet. Altitudes range from 900 to 1,300 feet above sea level.

The entire basin is covered by blue till, of glacial origin, and scattered through it, especially in the western portion, are deposits of modified drift composed of sand and gravel. These deposits being porous form ground water reservoirs which give rise to springs, though such springs are not of great importance in the Crow River Basin. In the western part of the area the drift rests on cretaceous rocks-in the eastern part it is underlain by Archean granites and Upper Cambrian sandstones. Rock outcrops are found nowhere in the basin.

The lower part of the area, east of the west line of Wright County, lies in the district that was originally forested-the upper part is in the prairie region. Very little of the area is forested at the present time. The land is nearly all under cultivation.

RAINFALL AND RUNOFF.

The upper portion of the basin lies in a small area of low rainfall as shown by the records at 3 stations. The mean rainfall for this area is 23 inches. The remainder of the basin has an annual precipitation of 27.5 inches which is the normal amount for the center of the State. In the upper portion of the basin, the wettest year since 1895 was 1896, when the rainfall was 33 inches. The driest year was 1910, when it was 14 inches. For the lower portion of the basin continuous records are available since 1866. In that period the wettest year was 1868, when the rainfall was 41.6 inches. The driest year was 1910, when the precipitation was 11.6 inches.

Runoff records of Crow River have been maintained since 1909. Since that time the runoff has varied from 0.83 to 1.51 inches or from 2.7 to 11.5 per cent of the rainfall.

DRAINAGE WORK.

Much of the basin is so flat that ditching is necessary to secure the proper drainage. The following table compiled from the report of the State Drainage Commission shows the amount of drainage work done in the basin :

The following drainage areas have been measured in the basin of Crow River:

NORTH FORK CROW RIVER NEAR ROCKFORD.

Location. At highway bridge in Sec. 1, T. 118 N., R. 25 W., 3 miles west of Rockford, and 11⁄2 miles above the junction of the South Fork. There are no tributaries within several miles of the station.

Records available.-June 15, 1909, to June 30, 1910. Owing to unsatisfactory conditions no estimates of daily discharge were made and only the base data are available.

Drainage area.-
a.-1,310 square miles.

Gage. Vertical staff which remained permanent.

Channel. The station was within the influence of the dam at Rockford and conditions remained constant as long as the dam was not opened nor the water level below the crest. From July 27 to August 10, 1909, the dam was open for repairs.

Discharge measurements.-Made from the bridge.

Winter flow.-Observations were discontinued during the winter months because of ice.

Discharge measurements of North Fork of Crow River near Rockford.

Daily gage height, in feet, of North Fork of Crow River near Rockford. (Observer, Miss Grace Wandersee.)

Day.

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

Dec.

Daily gage height, in feet, of North Fork of Crow River near Rockford-Contd.

Day. Jan. Feb.

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

Location.

SOUTH FORK CROW RIVER NEAR ROCKFORD.

At highway bridge 31⁄2 miles southwest of Rockford in Sec. 1,

T. 118 N., R. 25 W.; no tributaries within several miles.

Records available.-June 15, 1909, to March 31, 1912.

Drainage area.-1,160 square miles.

Gage.-Vertical staff; datum unchanged since established.

Channel. Slightly shifting.

Discharge measurements.-Made from the bridge, except at low stages when they are made by wading a short distance upstream.

Regulation. The nearest dam is that at Delano which is merely used as a diversion dam by the Great Northern Railway Co. The control for the station is determined by the dam at Rockford. From July 27 to August 10, 1909, and from June 1, 1911 to March 31, 1912, the dam at Rockford was open and the control was temporarily changed.

Winter flow.-During the winter periods of 1911 and 1912 the flow was based on discharge measurements; prior to that time the station was discontinued during the frozen periods.

Accuracy.-Conditions at this station are favorable for good results and the records therefore should be reliable.

Daily discharge, in second-feet, of South Fork of Crow River near Rockford.

Day.

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