4 BULLETIN 1017, U. S. DEPARTMENT OF AGRICULTURE. 



PHYSICAL CHARACTERISTICS. 



Lake Traverse, the Bois de Sioux River, and the Red River form a 

 continuous natural watercourse from Browns Valley, Minn., to the 

 international boundary, a distance of 456 miles. From the outlet 

 of Lake Traverse the stream follows a winding course through the 

 center of a flat valley, the general direction of flow being almost due 

 north (see fig. 1). The fall in general is slight and diminishes to- 

 ward the north (see fig. 2). The surface altitudes above sea level 

 are: 980 feet at Lake Traverse; 963 feet at Wahpeton; 900 feet at 

 Fargo ; 830 feet at Grand Forks ; 789 feet at the international bound- 

 ary ; and 755 feet at Winnipeg, 62 miles north of the boundary. 



TOPOGEAPHY. 



The watershed of that part of the river above the international 

 boundary has an area of 35,895 square miles (fig. 1). It consists of 

 a broad plain flanked on the east and west by higher land. This 

 central plain has a width of from 15 to 30 miles. To the eye the land 

 appears level but it has a certain degree of natural drainage so that 

 it can in no sense be classed as swamp land. The bordering land rises 

 more or less sharply to the higher parts, which are from 300 to 700 

 feet above the central portion of the basin. 



The eastern part of the watershed originally was forested and 

 contained extensive swamps and many lakes. Much of the timber 

 has been cut and the land cleared, so that at present it is estimated 

 that not more than one-tenth of the whole watershed is forested. 

 Probably 80 per cent of the prairie and cleared lands are now culti- 

 vated, the remainder being utilized in raising grasses and for town 

 and building sites, drainage channels, highways, and railroads. 



GEOLOGICAL ORIGIN. 



Geologists state that during the glacial period the entire central 

 portion of the valley was covered by glaciers which were deepest 

 near the center of the valley. The glaciers moved toward the south 

 and the water from them flowed to the south. As the glaciers melted 

 and their southern edges receded, a barrier of earth, sand, gravel, 

 and bowlders formed to the south of Lake Traverse. Water from 

 the melting glaciers accumulated behind this barrier and formed a 

 lake that has since disappeared, which the geologists call Lake Agas- 

 siz. There was not, however, sufficient water to erode the barrier 

 south of the lake. The glaciers continued to melt away until finally 

 the water in the lake was enabled to drain away to the north into 

 Lake Winnipeg. Water from the melting glaciers, and that which 

 has been flowing off since the glacial period, eroded and formed the 

 channels of the present watercourses. 



