WINE PRODUCTION AND GEOLOGY OF THE OKANAGAN VALLEY OF BRITISH COLUMBIA

The Okanagan Valley of British Columbia, 250 km inland from Vancouver, lies in the same latitudinal belt as many great wine regions of the world. The Coast Mountains to the west protect it from humid Pacific air and mountain belts to the east protect it from cold air from the Canadian Prairies. During the past 15 years wine grape cultivation has been the fastest growing industry in this valley.

Bedrock in the valley varies from high grade metamorphic rocks to fresh basalt. Structures are oriented in a general north-south direction and the valley lies on the boundary between the Omenica and Intermontane structural belts of the Canadian Cordilla. Glacial and nonglacial Quaternary aged sediments overlie bedrock in most lower valley areas. The majority of this material consists of post glacial alluvial deposits, and outwash and lake sediments deposited at the end of the last glaciation.

Local climate is a major determinant of where wine grapes can be successfully grown. Geomorphology plays a major role in influencing local climate. Other factors controlling wine grape production in the Okanagan Valley are texture and thickness of unconsolidated materials. These influence drainage of the soil and techniques required to manage soil moisture. These factors can be used to define three distinct wine-grape growing areas: 1) Okanagan River Region, in the south, underlain by glacial fluvial sand and gravel, and alluvial fan deposits; 2) Southern Okanagan Lake Region, extending from Okanagan Falls to Peachland, underlain primarily by glacial lake silt, and 3) Central Okanagan Lake Region (in the vicinity of Kelowna) which is underlain by a mixture of sand and gravel, diamicton, and glacial lake silt.

The unconsolidated materials on which soils are developed consist of a heterogeneous mixture of the bedrock types found throughout the valley. Consequently, their chemical composition varies little from one part of the valley to an other. Hence, variation in soil composition can not be used to explain variation in grape or wine quality. Probably the greatest controlling factors on wine character and quality are the experience and capabilities of the viticulturalists and of the wine makers.