[5] In the upper reaches of the watershed, the Kruzgamepa and Grand Central rivers form one stream but are known by different names, and their physical features vary somewhat.

The Kruzgamepa flows to the northeast and, sweeping around the east end of the range, reaches the head of Imuruk Basin by a northwesterly course.

Near its mouth, this stream flows through a small rock canyon about 50 feet (15 m) deep, above which is a bench on either side covered with gravel.

The bed rock consists of limestones with interbedded quartz schists of sedimentary origin and with intruded greenstones.

A high gravel bench on the east side of the Kruzgamepa, between Slate and Willow creeks, was prospected in 1904 by a company proposing to bring water for hydraulicking from Salmon Lake.