Okanagan Lake is called a fjord lake as it has been carved out by repeated glaciations. Although the lake contains numerous lacustrine terraces, it is not uncommon for the lake to be 100m deep only 10m offshore.[6] Major inflows include Mission, Vernon, Trout, Penticton, Equesis, Kelowna, Peachland and Powers Creeks.[7] The lake is drained by the Okanagan River, which exits the lake's south end via a canal through the city of Penticton to Skaha Lake, whence the river continues southwards into the rest of the South Okanagan and through Okanogan County, Washington to its confluence with the Columbia.
The lake's maximum depth is 232 metres near Grant Island (Nahun Weenox). There is one other island known as Rattlesnake Island, much farther south by Squally Point. Some areas of the lake have up to 750 metres of glacial and post-glacial sediment fill which were deposited during the Pleistocene Epoch.[1]
Notable features of the Okanagan Valley include terraces which were formed due to the periodic lowering of the lake's predecessor, glacial Lake Penticton. These terraces are now used extensively for agriculture such as fruit cultivation.