(This material is from the Harrison Fagg Browning-Blackfeet Comprehensive Plan.)
The Blackfeet Reservation lies in two continental drainage patterns -- the Hudson Bay and the Gulf of Mexico. Water falling on the eastern slopes of the the continental divide in the northern portion of the reservation flows north into Hudson Bay, and the southern portion, south into the Gulf of Mexico. St. Mary’s Divide and Divide Mountain separate the two drainage basins. [Those of us who call this mountain “Triple Divide” know that the third drainage basin is to the west, towards the Columbia River and Pacific Ocean.] West of St. Mary’s Divide the drainage is chiefly into the St. Mary’s River, but east and south of the divide it is into such streams as the forks of the Milk River, Cut Bank, Two Medicine and Badger which unite to form several large streams before entering the Missouri River. The reservation drainage was not greatly influenced by the mountain and continental ice sheets. The streams were locally diverted, but most of them returned to their pre-glacial valleys after the ice receded.
St. Mary’s River, a tributary of Saskatchewan River in Canada, heads on the continental divide in the west-central part of Glacier County. It extends in a northeasterly direction and south of Babb emerges from several long finger lakes, such as Upper and Lower St. Mary’s, onto an outwash gravel flat about one mile in width north of Kennedy Creek. It flows through a drift-covered basin between the mountains and a high bench south of the Canadian line. The larger streams entering St. Mary’s River are Swift Current and Kennedy creeks. These streams are fed by mountain glaciers on the continental divide and flow east through deep valleys. Between Many Glaciers and the park boundary the valley of Swift Current Creek and its branches flow through a number of finger lakes, of which the Sherburne Lakes are storage reservoirs for the Milk River Irrigation Project. [Now in bad shape, this system supplies water for much of the High-Line.] East of the park line the stream enters an enclosed canyon above the gravelly flat.
Forks of Milk River: the North Fork of Milk River heads in the morainic sag north of St. Mary’s Divide and flows northeast into Canada. It is a small perennial stream flowing through a deep, narrow valley entrenched in a wide stony basic between the high benches. South of the Canadian line the supply canal of the Milk River Irrigation Project enters it and during the summer months its volume is greatly increased.
The South Fork of Milk River heads on Milk River Ridge east of Divide Mountain. It is a larger stream than the North Fork and also flows northeast, crossing the international line. The bottom of this stream above the mouth of the Middle Fork is a flat, wet meadow, but below it varies from poorly alkaline clays to sandy gravelly terraces. Toad, Fox, and Livermore creeks are small perennial streams, heading on St. Mary’s Divide and entering the stream from the west. The bottom of these streams are narrow and poorly drained. The intermittent streams entering the river from the south head within 2 to 5 miles of the river. A few of them have perennial springs along their courses.
The Middle Fork of Milk River neads on St. Mary’s Divide and flows east, and enters the South Fork. It is a small perennial stream, flowing through a flat swampy bottom one-fourth to one-half mile wide below the plateau. A narrow gravel-capped bench forms the divide between North and South Forks.
Several other branches of Milk River and its forks head in the northern Blackfeet Reservation and flow northeast into Canada. Willow Creek heads in Spider Lake, located in a gap east of St. Mary’s River, below the high bench. It flows through an open poorly drained valley, in which are located several small lakes. Red River rises in the northwestern reservation. It is an intermittent stream draining a drift-covered upland above a heavy basin along the branches of the stream.
Cut Bank Creek is one of the larger streams that heads on the continental divide in the west-central reservation and takes an easterly course until it turns sharply to the south, leaving the reservation near Cut Bank. It has eroded a valley 1,000 to 1,500 feet deep through the stony plateau, which rises above the stream as the Milk River and Cut Bank ridges.
The larger perennial steams entering Cut Bank Creek from the north in the central Blackfeet Reservation are Greasewood, Trail Cabelle, and Powell. These streams drain a rather sharply rolling area, characterized by gravel-capped hills and ridges east of the high benches and by sandstone riddges and buttes in the central part. Trail and Powell creeks are enclosed in narrow valleys, while Greasewood and Cabelle creeks have more open valleys. The bottoms of Greasewood and Cabelle creeks widen out locally to one-fourth to one-half mile. All streams have heavy alkaline bottoms. Little Rocky Coulee is a perennial stream except in very dry seasons. It heads on the eastern slopes of Red Buttes and flows southwest, entering Cut Bank Creek about 6 miles northwest of Cut Bank. Its bottom is heavy and alkaline along most of its course. Rocky Creek heads in the morainic ridges east of the South Fork of Milk River and flows south, entering Cut Bank Creek a few miles east of the mouth of Little Rocky Coulee. It is a small perennial stream enclosed in a deep sandstone canyon below the moraines. It drains a drift-covered area in the northeastern Blackfeet Reservation. One branch of this stream heads in the gap connecting the South Fork of Milk River with Rocky Creek. Snake Creek is an intermittent stream heading below the sandstone excarpment south of Hay Lake. It flows southwest and enters Cut Bank Creek north of Cut Bank. It drains a gently sloping outwash section below the sandstone escarpment and the stony moraines to the east.
(To be continued)